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Vortrag

- Roland Platz

Uncertainty Quantification for Passive and Active Vibration Isolation used in Structural Dynamic Systems

In: Deggendorfer Wissenschaftliches Kolloquium

Technische Hochschule Deggendorf Deggendorf

- 17.11.2022 (2022)

- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- M. Schaeffner
- Roland Platz
- T. Melz

Active buckling control of compressively loaded beam-columns and trusses (Chapter 5.4.7)

In: Mastering Uncertainty in Mechanical Engineering. null (Tracts in Mechanical Engineering book series (STME)) pg. 343-347.

Berlin

- (2021)

- Maschinenbau und Mechatronik
- NACHHALTIG

Beitrag in Sammelwerk/Tagungsband

- J. Lenz
- B. Götz
- T. Melz
- Roland Platz

Vibration attenuation in beam truss structures via (semi-)active piezoelectric shunt-damping (Chapter 5.4.6)

In: Mastering Uncertainty in Mechanical Engineering. null (Tracts in Mechanical Engineering book series (STME)) pg. 338-343.

Berlin

- (2021)

- Maschinenbau und Mechatronik
- NACHHALTIG

Beitrag in Sammelwerk/Tagungsband

- S. Kersting
- Roland Platz
- M. Kohler
- T. Melz

Data Uncertainty (Chapter 2.1)

In: Mastering Uncertainty in Mechanical Engineering. null (Tracts in Mechanical Engineering book series (STME)) pg. 31-34.

Berlin

- (2021)

- Maschinenbau und Mechatronik
- NACHHALTIG

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- J. Lenz

Analysis of data uncertainty using the example of passive and active vibration isolation (Chapter 4.1.1)

In: Mastering Uncertainty in Mechanical Engineering. null (Tracts in Mechanical Engineering book series (STME)) pg. 119-123.

Berlin

- (2021)

- Maschinenbau und Mechatronik
- NACHHALTIG

Vortrag

- Roland Platz

Approach to Assess Data and Model Form Uncertainty when Predicting and Comparing the Dynamic Behavior in Passive and Active Vibration Isolation via Numerical and Experimental Simulation

In: Engineering Mechanics Institute Conference 2021 and Probabilistic Mechanics & Reliability Conference 2021

Online

- 25.-28.05.2021 (2021)

- Maschinenbau und Mechatronik
- NACHHALTIG

Beitrag in Sammelwerk/Tagungsband

- Roland Platz

Approach to Assess Basic Deterministic Data and Model Form Uncertainty in Passive and Active Vibration Isolation

pg. 208-223.

Cham

- (2021)

This contribution continues ongoing own research on uncertainty quantification in structural vibration isolation in early design stage by various deterministic and non-deterministic approaches. It takes into account one simple structural dynamic system example throughout the investigation: a one mass oscillator subject to passive and active vibration isolation. In this context, passive means that the vibration isolation only depends on preset inertia, damping, and stiffness properties. Active means that additional controlled forces enhance vibration isolation. The simple system allows a holistic, consistent and transparent look into mathematical modeling, numerical simulation, experimental test and uncertainty quantification for verification and validation. The oscillator represents fundamental structural dynamic behavior of machines, trusses, suspension legs etc. under variable mechanical loading. This contribution assesses basic experimental data and mathematical model form uncertainty in predicting the passive and enhanced vibration isolation after model calibration as the basis for further deterministic and non-deterministic uncertainty quantification measures. The prediction covers six different damping cases, three for passive and three for active configuration. A least squares minimization (LSM) enables calibrating multiple model parameters using different outcomes in time and in frequency domain from experimental observations. Its adequacy strongly depends on varied damping properties, especially in passive configuration.

- Maschinenbau und Mechatronik
- NACHHALTIG

Zeitschriftenartikel

- C. Ehrett
- D. Brown
- C. Kitchens
- X. Xu
- Roland Platz
- S. Atamturktur

Simultaneous Bayesian Calibration and Engineering Design With an Application to a Vibration Isolation System

In: Journal of Verification, Validation and Uncertainty Quantification vol. 6

- (2021)

DOI: 10.1115/1.4050075

Calibration of computer models and the use of those design models are two activities traditionally carried out separately. This paper generalizes existing Bayesian inverse analysis approaches for computer model calibration to present a methodology combining calibration and design in a unified Bayesian framework. This provides a computationally efficient means to undertake both tasks while quantifying all relevant sources of uncertainty. Specifically, compared with the traditional approach of design using parameter estimates from previously completed model calibration, this generalized framework inherently includes uncertainty from the calibration process in the design procedure. We demonstrate our approach to the design of a vibration isolation system. We also demonstrate how, when adaptive sampling of the phenomenon of interest is possible, the proposed framework may select new sampling locations using both available real observations and the computer model. This is especially useful when a misspecified model fails to reflect that the calibration parameter is functionally dependent upon the design inputs to be optimized.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- C. Gehb
- Roland Platz
- T. Melz

Load redistribution via semi-active guidance elements in a kinematic structure (Chapter 5.4.8)

In: Mastering Uncertainty in Mechanical Engineering. null (Tracts in Mechanical Engineering book series (STME)) pg. 347-351.

Berlin

- (2021)

- Maschinenbau und Mechatronik
- NACHHALTIG

Beitrag in Sammelwerk/Tagungsband

- C. Gehb
- T. Melz
- Roland Platz

Bayesian inference based parameter calibration for a mathematical model of a load-bearing structure (Chapter 4.1.2)

In: Mastering Uncertainty in Mechanical Engineering. null (Tracts in Mechanical Engineering book series (STME)) pg. 123-128.

Berlin

- (2021)

- Maschinenbau und Mechatronik
- NACHHALTIG

Beitrag in Sammelwerk/Tagungsband

- A. Matei
- Roland Platz
- S. Ulbrich
- M. Schaeffner

Model Uncertainty (Chapter 2.2)

In: Mastering Uncertainty in Mechanical Engineering. null (Tracts in Mechanical Engineering book series (STME)) pg. 35-39.

Berlin

- (2021)

- Maschinenbau und Mechatronik
- NACHHALTIG

Beitrag in Sammelwerk/Tagungsband

- J. Lenz
- Roland Platz

Quantification and Evaluation of Parameter and Model Uncertainty for Passive and Active Vibration Isolation

In: Model Validation and Uncertainty Quantification, Volume 3. Proceedings of IMAC–XXXVII A Conference and Exposition on Structural Dynamics (Jan. 28–31, 2019; Orlando, FL, USA) (Conference Proceedings of the Society for Experimental Mechanics Series) pg. 135-147.

Cham

- (2020)

DOI: 10.1007/978-3-030-12075-7_14

Vibration isolation is a common method used for minimizing the vibration of dynamic load-bearing structures in a region past the resonance frequency, when excited by disturbances. The vibration reduction mainly results from the tuning of stiffness and damping during the early design stage. High vibration reduction over a broad bandwidth can be achieved with additional and controlled forces, the active vibration isolation. In this context, “active” does not mean the common understanding that the surroundings are isolated against the machine vibrations. Also in this context, “passive” means that no additional and controlled force is present, other than the common understanding that the machine is isolated against the surroundings. For active vibration isolation, a signal processing chain and an actuator are included in the system. Typically, a controller is designed to enable a force of an actuator that reduces the system’s excitation response. In both passive and active vibration isolation, uncertainty is an issue for adequate tuning of stiffness and damping in early design stage. The two types of uncertainty investigated in this contribution are parametric uncertainty, i.e. the variation of model parameters resulting in the variation of the systems output, and model uncertainty, the uncertainty from discrepancies between model output and experimentally measured output. For this investigation, a simple one mass oscillator under displacement excitation is used to quantify the parameter and model uncertainty in passive and active vibration isolation. A linear mathematical model of the one mass oscillator is used to numerically simulate the transfer behavior for both passive and active vibration isolation, thus predicting the behavior of an experimental test rig of the one mass oscillator under displacement excitation. The models’ parameters that are assumed to be uncertain are mass and stiffness as well as damping for the passive vibration isolation and an additional gain factor for the velocity feedback control in case of active vibration isolation. Stochastic uncertainty is assumed for the parameter uncertainty when conducting a Monte Carlo Simulation to investigate the variation of the numerically simulated transfer functions. The experimental test rig enables purposefully adjustable insertion of parameter uncertainty in the assumed value range of the model parameters in order to validate the model. The discrepancy between model and system output results from model uncertainty and is quantified by the Area Validation Metric and an Bayesian model validation approach. The novelty of this contribution is the application of the Area Validation Metric and Bayes’ approach to evaluate and to compare the two different passive and active approaches for vibration isolation numerically and experimentally. Furthermore, both model validation approaches are compared.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Zeitschriftenartikel

- C. Gehb
- S. Atamturktur
- Roland Platz
- T. Melz

Bayesian Inference Based Parameter Calibration of the LuGre-Friction Model

In: Experimental Techniques vol. 44 pg. 369-382.

- (2020)

DOI: 10.1007/s40799-019-00355-7

Load redistribution in smart load bearing mechanical structures can be used to reduce negative effects of damage or to prevent further damage if predefined load paths become unsuitable. Using controlled friction brakes in joints of kinematic links can be a suitable way to add dynamic functionality for desired load path redistribution. Therefore, adequate friction models are needed to predict the friction behavior. Possible models that can be used to model friction vary from simple static to complex dynamic models with increasing sophistication in the representation of friction phenomena. The LuGre-model is a widely used dynamic friction model for friction compensation in high precision control systems. It needs six parameters for describing the friction behavior. These parameters are coupled to an unmeasurable internal state variable, therefore, parameter identification is challenging. Conventionally, optimization algorithms are used to identify the LuGre-parameters deterministically. In this paper, the parameter identification and calibration is formulated to achieve model prediction that is statistically consistent with the experimental data. By use of the R2 sensitivity analysis, the most influential parameters are selected for calibration. Subsequently, the Bayesian inference based calibration procedure using experimental data is performed. Uncertainty represented in former wide parameter ranges can be reduced and, thus, model prediction accuracy can be increased.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- J. Lenz
- M. Schäffner
- Roland Platz
- T. Melz

Selection of an Adequate Model of a Piezo-Elastic Support for Structural Control in a Beam Truss Structure

In: Model Validation and Uncertainty Quantification, Volume 3. null (Conference Proceedings of the Society for Experimental Mechanics Series) pg. 41-49.

Cham

- (2020)

DOI: 10.1007/978-3-030-47638-0_4

Axial and lateral loads of lightweight beam truss structures e.g. used in automotive engineering may lead to undesired structural vibration that can be reduced near a structural resonance frequency via resonant piezoelectric shunt-damping. In order to tune the electrical circuits to the desired structural resonance frequency within a model-based approach, an adequate mathematical model of the beam truss structure is required. Piezo-elastic truss supports with integrated piezoelectric stack transducers can transfer the axial and lateral forces and may be used for vibration attenuation of single beams or whole beam truss structures. For usage in a single beam test setup, the piezo-elastic support’s casing is clamped rigidly and is connected to the beam via a membrane-like spring element that allows for rotation as well as axial and lateral displacements of the beam. In this contribution, the piezo-elastic support is integrated into a two-dimensional beam truss structure comprising seven beams, where its casing is no longer clamped rigidly but is subject to axial, lateral and rotational displacements. Based on the previously verified and validated model of the single beam test setup, two different complex mathematical models of the piezo-elastic support integrated in the two-dimensional beam truss structure are derived in this contribution. The two mathematical models differ in their number of degrees of freedom for the piezo-elastic support as well as in the assumption of rigid or compliant casing. By comparing numerically and experimentally determined structural resonance frequencies and vibration amplitudes, the model that more adequately predicts the truss structure’s vibration behavior is selected on basis of the normalized root mean squared error. For future works, the more adequate model will be used to tune electrical circuits for resonant piezoelectric shunt-damping in a three-dimensional truss structure.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- R. Feldmann
- M. Schäffner
- C. Gehb
- Roland Platz
- T. Melz

Analyzing Propagation of Model Form Uncertainty for Different Suspension Strut Models

In: Model Validation and Uncertainty Quantification, Volume 3. null (Conference Proceedings of the Society for Experimental Mechanics Series) pg. 255-263.

Cham

- (2020)

DOI: 10.1007/978-3-030-47638-0_28

Model form uncertainty often arises in structural engineering problems when simplifications and assumptions in the mathematical modelling process admit multiple possible models. It is well known that all models incorporate a model error that is captured by a discrepancy due to missing or incomplete physics in the mathematical model. As an example, this discrepancy can be modelled as a function based upon Gaussian processes and its confidence bounds can be seen as a measure of adequacy for the respective model. Assessment of model form uncertainty can be conducted by comparing the confidence bounds of competing discrepancy functions. In this paper, a modular active spring-damper system is considered that was designed to resemble a suspension strut as part of an aircraft landing gear and is excited by dynamic drop tests. In previous research about the suspension strut, different mathematical system models with respect to different linear and non-linear assumptions for damping and stiffness properties to describe the dynamic system behaviour of the suspension strut were compared by means of the confidence intervals of their discrepancy functions. The results indicated that the initial conditions used for exciting the system model were inadequate. The initial conditions themselves constitute a mathematical model, so that model form uncertainty inherent to the initial condition model can effect the system model. The propagation of model form uncertainty within the model will be analysed in this paper by considering two cases: In the first case, the system model is excited with an inadequate initial condition model, while in the second case, experimentally measured initial conditions will be employed that represent the true value except for measurement errors. The comparison of both shows how model form uncertainty propagates through the model chain from the initial condition model to the system model.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- C. Gehb
- Roland Platz
- T. Melz

BAYESIAN Inference Based Parameter Calibration of a Mechanical Load-Bearing Structure’s Mathematical Model

In: Model Validation and Uncertainty Quantification, Volume 3. null (Conference Proceedings of the Society for Experimental Mechanics Series) pg. 337-347.

Cham

- (2020)

DOI: 10.1007/978-3-030-47638-0_37

Load-bearing structures with kinematic functions like a suspension of a vehicle and an aircraft landing gear enable and disable degrees of freedom and are part of many mechanical engineering applications. In most cases, the load path going through the load-bearing structure is predetermined in the design phase. However, if parts of the load-bearing structure become weak or suffer damage, e.g. due to deterioration or overload, the load capacity may become lower than designed. In that case, load redistribution can be an option to adjust the load path and, thus, reduce the effects of damage or prevent further damage. For an adequate numerical prediction of the load redistribution capability, an adequate mathematical model with calibrated model parameters is needed. Therefore, the adequacy of an exemplary load-bearing structure’s mathematical model is evaluated and its predictability is increased by model parameter uncertainty quantification and reduction. The mathematical model consists of a mechanical part, a friction model and the electromagnetic actuator to achieve load redistribution, whereby the mechanical part is chosen for calibration in this paper. Conventionally, optimization algorithms are used to calibrate the model parameters deterministically. In this paper, the model parameter calibration is formulated to achieve a model prediction that is statistically consistent with the data gained from an experimental test setup of the exemplary load-bearing structure. Using the R2 sensitivity analysis, the most influential parameters for the model prediction of interest, i.e. the load path going through the load-bearing structure represented by the support reaction forces, are identified for calibration. Subsequently, BAYESIAN inference based calibration procedure using the experimental data and the selected model parameters is performed. Thus, the mathematical model is adjusted to the actual operating conditions of the experimental load-bearing structure via the model parameters and the model prediction accuracy is increased. Uncertainty represented by originally large model parameter ranges can be reduced and quantified.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- M. Schaeffner
- Roland Platz
- T. Melz

Adequate Mathematical Beam-Column Model for Active Buckling Control in a Tetrahedron Truss Structure

In: Model Validation and Uncertainty Quantification, Volume 3. null (Conference Proceedings of the Society for Experimental Mechanics Series) pg. 323-332.

Cham

- (2020)

DOI: 10.1007/978-3-030-47638-0_35

Active buckling control of compressively loaded beam-columns provides a possibility to increase the maximum bearable axial load compared to passive beam-columns. Reliable mathematical beam-column models that adequately describe the lateral dynamic behavior are required for the model-based controller synthesis in order to avoid controller instability for real testing and application. This paper presents an adequate mathematical beam-column model for the active buckling control in a tetrahedron truss structure. Furthermore, it discusses model form uncertainty arising from model simplification of the global tetrahedron model to three local beam-column models. An experimental tetrahedron truss structure that comprises three passive beams and three active beam-columns with piezo-elastic supports for active buckling control is investigated. The tetrahedron is clamped at the three base nodes and free at the top node. In the two piezo-elastic supports of each active beam-column, integrated piezoelectric stack actuators compensate lateral deflections due to increasing axial compressive loads and may, thus, prevent buckling. In previous works, active buckling control was investigated for a single beam-column that was clamped rigidly in an experimental test setup. A verified and validated single beam-column model with compliant boundary conditions was used to represent the piezo-elastic supports for active buckling control. The mathematical model of the active beam-columns is calibrated with experimental data from all three nominally identical active beam-columns to account for uncertainty in manufacturing, assembly or mounting. Subsequently, they are compared with respect to the transfer functions and the first eigenfrequencies. It is shown that the boundary conditions of the single beam-column model may be calibrated to adequately describe the boundary conditions within the tetrahedron truss structure. Thus, it will be used for the model-based controller synthesis in future investigations on the active buckling control of the tetrahedron truss structure.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- R. Locke
- S. Kupis
- C. Gehb
- Roland Platz
- S. Atamturktur

Applying uncertainty quantification to structural systems: Parameter reduction for evaluating model complexity

In: Model Validation and Uncertainty Quantification, Volume 3. Proceedings of IMAC–XXXVII A Conference and Exposition on Structural Dynamics (Jan. 28–31, 2019; Orlando, FL, USA) (Conference Proceedings of the Society for Experimental Mechanics Series) pg. 241-256.

Cham

- (2020)

Different mathematical models can be developed to represent the dynamic behavior of structural systems and assess properties, such as risk of failure and reliability. Selecting an adequate model requires choosing a model of sufficient complexity to accurately capture the output responses under various operational conditions. However, as model complexity increases, the functional relationship between input parameters varies and the number of parameters required to represent the physical system increases, reducing computational efficiency and increasing modeling difficulty. The process of model selection is further exacerbated by uncertainty introduced from input parameters, noise in experimental measurements, numerical solutions, and model form. The purpose of this research is to evaluate the acceptable level of uncertainty that can be present within numerical models, while reliably capturing the fundamental physics of a subject system. However, before uncertainty quantification can be performed, a sensitivity analysis study is required to prevent numerical ill-conditioning from parameters that contribute insignificant variability to the output response features of interest. The main focus of this paper, therefore, is to employ sensitivity analysis tools on models to remove low sensitivity parameters from the calibration space. The subject system in this study is a modular spring-damper system integrated into a space truss structure. Six different cases of increasing complexity are derived from a mathematical model designed from a two-degree of freedom (2DOF) mass spring-damper that neglects single truss properties, such as geometry and truss member material properties. Model sensitivity analysis is performed using the Analysis of Variation (ANOVA) and the Coefficient of Determination R2. The global sensitivity results for the parameters in each 2DOF case are determined from the R2 calculation and compared in performance to evaluate levels of parameter contribution. Parameters with a weighted R2 value less than .02 account for less than 2% of the variation in the output responses and are removed from the calibration space. This paper concludes with an outlook on implementing Bayesian inference methodologies, delayed-acceptance single-component adaptive Metropolis (DA-SCAM) algorithm and Gaussian Process Models for Simulation Analysis (GPM/SA), to select the most representative mathematical model and set of input parameters that best characterize the system’s dynamic behavior.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Zeitschriftenartikel

- S. Mallapur
- Roland Platz

Uncertainty quantification in the mathematical modelling of a suspension strut using Bayesian inference

In: Mechanical Systems and Signal Processing vol. 118 pg. 158-170.

- (2019)

DOI: 10.1016/j.ymssp.2018.08.046

In the field of structural engineering, mathematical models are utilized to predict the dynamic response of systems such as a suspension strut under different boundary and loading conditions. However, different mathematical models exist based on their governing functional relations between the model input and state output parameters. For example, the spring-damper component of a suspension strut is considered. Its mathematical model can be represented by linear, nonlinear, axiomatic or empiric relations resulting in different vibrational behaviour. The uncertainty that arises in the prediction of the dynamic response from the resulting different approaches in mathematical modelling may be quantified with Bayesian inference approach especially when the system is under structural risk and failure assessment. As the dynamic output of the suspension strut, the spring-damper compression and the spring-damper forces as well as the ground impact force are considered in this contribution that are taken as the criteria for uncertainty evaluation due to different functional relations of models. The system is excited by initial velocities that depend on a drop height of the suspension strut during drop tests. The suspension strut is a multi-variable system with the payload and the drop height as its varied input variables in this investigation. As a new approach, the authors present a way to adequately compare different models based on axiomatic or empiric assumptions of functional relations using the posterior probabilities of competing mathematical models. The posterior probabilities of different mathematical models are used as a metric to evaluate the model uncertainty of a suspension strut system with similar specifications as actual suspension struts in automotive or aerospace applications for decision making in early design stage. The posterior probabilities are estimated from the likelihood function, which is estimated from the cartesian vector distances between the predicted output and the experimental output.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Zeitschriftenartikel

- C. Gehb
- Roland Platz
- T. Melz

Two control strategies for semi-active load path redistribution in a load-bearing structure

In: Mechanical Systems and Signal Processing vol. 118 pg. 195-208.

- (2019)

DOI: 10.1016/j.ymssp.2018.08.044

In this paper, a two mass oscillator, a translatoric moving mass connected to a rigid beam by a spring-damper system, is used to numerically and experimentally investigate the capability of load path redistribution due to controlled semi-active guidance elements with friction brakes. The mathematical friction model will be derived by the LuGre approach. The rigid beam is embedded on two supports and is initially aligned with evenly distributed loads in beam and supports by the same stiffness condition. With the semi-active auxiliary guidance elements it is possible to provide additional forces to relieve one of the beam’s supports. Two control strategies are designed and tested to induce additional forces in the auxiliary guidance elements to bypass a proportion of loading away from the spring-damper system towards the now kinetic auxiliary guidance elements. The control strategies I and II depend on the different control inputs: I beam misalignment and II desired reaction force ratio in the supports. The beam’s misalignment and the supports’ reaction forces are calculated numerically and measured experimentally for varying stiffness parameters of the supports and are compared with and without semi-active auxiliary kinematic guidance elements. The structure’s moving mass is loaded with a force according to a step-function. Thus, undesired misalignment caused by varying stiffness as well as undesired load distribution in the structure’s supports can be reduced by redistributing load between the supports during operation.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Zeitschriftenartikel

- M. Schäffner
- Roland Platz

Gain-Scheduled H∞ Buckling control of a Circular Beam-Column Subject to Time-Varying Axial Loads

In: Smart Materials and Structures vol. 27 pg. 065009.

- (2018)

Smart Materials and Structures
Paper
Gain-scheduled ${{\mathscr{H}}}_{\infty }$ buckling control of a circular beam-column subject to time-varying axial loads
Maximilian Schaeffner1
and Roland Platz2
Published 3 May 2018 • © 2018 IOP Publishing Ltd
Smart Materials and Structures, Volume 27, Number 6 Citation Maximilian Schaeffner and Roland Platz 2018 Smart Mater. Struct. 27 065009
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Author affiliations
1 Technische Universität Darmstadt, System Reliability, Adaptronics and Machine Acoustics SAM, Magdalenenstraße 4, D-64289 Darmstadt, Germany
2 Fraunhofer Institute for Structural Durability and System Reliability LBF, Bartningstraße 47, D-64289 Darmstadt, Germany
ORCID iDs
Maximilian Schaeffner
https://orcid.org/0000-0002-0957-7725
Dates
Received 12 January 2018
Accepted 13 March 2018
Published 3 May 2018
Check for updates using Crossmark
Peer review information
Method: Single-anonymous
Screened for originality? Yes
DOI
https://doi.org/10.1088/1361-665X/aab63a [Titel anhand dieser DOI in Citavi-Projekt übernehmen]
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Abstract
For slender beam-columns loaded by axial compressive forces, active buckling control provides a possibility to increase the maximum bearable axial load above that of a purely passive structure. In this paper, an approach for gain-scheduled ${{\mathscr{H}}}_{\infty }$ buckling control of a slender beam-column with circular cross-section subject to time-varying axial loads is investigated experimentally. Piezo-elastic supports with integrated piezoelectric stack actuators at the beam-column ends allow an active stabilization in arbitrary lateral directions. The axial loads on the beam-column influence its lateral dynamic behavior and, eventually, cause the beam-column to buckle. A reduced modal model of the beam-column subject to axial loads including the dynamics of the electrical components is set up and calibrated with experimental data. Particularly, the linear parameter-varying open-loop plant is used to design a model-based gain-scheduled ${{\mathscr{H}}}_{\infty }$ buckling control that is implemented in an experimental test setup. The beam-column is loaded by ramp- and step-shaped time-varying axial compressive loads that result in a lateral deformation of the beam-column due to imperfections, such as predeformation, eccentric loading or clamping moments. The lateral deformations and the maximum bearable loads of the beam-column are analyzed and compared for the beam-column with and without gain-scheduled ${{\mathscr{H}}}_{\infty }$ buckling control or, respectively, active and passive configuration. With the proposed gain-scheduled ${{\mathscr{H}}}_{\infty }$ buckling control it is possible to increase the maximum bearable load of the active beam-column by 19% for ramp-shaped axial loads and to significantly reduce the beam-column deformations for step-shaped axial loads compared to the passive structure.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- S. Mallapur
- B. Götz
- Roland Platz

Bayesian Multivariate Validation Approach to Quantify the Uncertainty in the Finite Element Model of a Suspension Strut (Paper No. 248)

- (2018)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Zeitschriftenartikel

- S. Mallapur
- Roland Platz

Quantification of Uncertainty in the Mathematical Modelling of a Multivariable Suspension Strut Using Bayesian Interval Hypothesis-Based Approach

In: Applied Mechanics and Materials vol. 885 pg. 3-17.

- (2018)

Mathematical models of a suspension strut such as an aircraft landing gear are utilized by engineers in order to predict its dynamic response under different boundary conditions. The prediction of the dynamic response, for example the external loads, the stress and the strength as well as the maximum compression in the spring-damper component aids engineers in early decision making to ensure its structural reliability under various operational conditions. However, the prediction of the dynamic response is influenced by model uncertainty. As far as the model uncertainty is concerned, the prediction of the dynamic behavior via different mathematical models depends upon various factors such as the model's complexity in terms of the degrees of freedom, material and geometrical assumptions, their boundary conditions and the governing functional relations between the model input and output parameters. The latter can be linear or nonlinear, axiomatic or empiric, time variant or time-invariant. Hence, the uncertainty that arises in the prediction of the dynamic response of the resulting different mathematical models needs to be quantified with suitable validation metrics, especially when the system is under structural risk and failure assessment. In this contribution, the authors utilize the Bayesian interval hypothesis-based method to quantify the uncertainty in the mathematical models of the suspension strut.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Zeitschriftenartikel

- B. Götz
- Roland Platz
- T. Melz

Effect of static axial loads on the lateral vibration attenuation of a beam with piezo-elastic supports

In: Smart Materials and Structures vol. 27 pg. 035011.

- (2018)

In this paper, vibration attenuation of a beam with circular cross-section by resonantly shunted piezo-elastic supports is experimentally investigated for varying axial tensile and compressive beam loads. The beam's first mode resonance frequency, the general electromechanical coupling coefficient and static transducer capacitance are analyzed for varying axial loads. All three parameter values are obtained from transducer impedance measurements on an experimental test setup. Varying axial beam loads manipulate the beam's lateral bending stiffness and, thus, lead to a detuning of the resonance frequencies. Furthermore, they affect the general electromechanical coupling coefficient of transducer and beam, an important modal quantity for shunt-damping, whereas the static transducer capacitance is nearly unaffected. Frequency transfer functions of the beam with one piezoe-elastic support either shunted to an RL-shunt or to an RL-shunt with negative capacitance, the RLC-shunt, are compared for varying axial loads. It is shown that the beam vibration attenuation with the RLC-shunt is less influenced by varying axial beam loads and, therefore, is more robust against detuning.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- D. Mayer
- G. Stevens

Approach in Uncertainty Quantification to Predict the Vibration Control Performance of Tuned Absorbers in Early Design Stage (Paper No. 262)

- (2018)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Zeitschriftenartikel

- M. Kohler
- A. Krzyżak
- S. Mallapur
- Roland Platz

Uncertainty Quantification in Case of Imperfect Models: A Non‐Bayesian Approach

In: Scandinavian Journal of Statistics vol. 45 pg. 729-752.

- (2018)

DOI: 10.1111/sjos.12317

The starting point in uncertainty quantification is a stochastic model, which is fitted to a technical system in a suitable way, and prediction of uncertainty is carried out within this stochastic model. In any application, such a model will not be perfect, so any uncertainty quantification from such a model has to take into account the inadequacy of the model. In this paper, we rigorously show how the observed data of the technical system can be used to build a conservative non-asymptotic confidence interval on quantiles related to experiments with the technical system. The construction of this confidence interval is based on concentration inequalities and order statistics. An asymptotic bound on the length of this confidence interval is presented. Here we assume that engineers use more and more of their knowledge to build models with order of errors bounded by urn:x-wiley:sjos:media:sjos12317:sjos12317-math-0001. The results are illustrated by applying the newly proposed approach to real and simulated data.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Zeitschriftenartikel

- B. Götz
- Roland Platz
- T. Melz

Consistent approach to describe and evaluate uncertainty in vibration attenuation using resonant piezoelectric shunting and tuned mass dampers

In: Mechanics & Industry vol. 18 pg. 108.

- (2017)

DOI: 10.1051/meca/2016011

Undesired vibration may occur in lightweight structures due to low damping and excitation. For the purpose of vibration attenuation, tuned mass dampers (TMD) can be an appropriate measure. A similar approach uses resonantly shunted piezoelectric transducers. However, uncertainty in design and application of resonantly shunted piezoelectric transducers and TMD can be caused by insufficient mathematical modeling, geometric and material deviations or deviations in the electrical and mechanical quantities. During operation, uncertainty may result in detuned attenuation systems and loss of attenuation performance. A consistent and general approach to display uncertainty in load carrying systems developed by the authors is applied to describe parametric uncertainty in vibration attenuation with resonantly shunted piezoelectric transducers and TMD. Mathematical models using Hamilton’s principle and Ritz formulation are set up for a beam, clamped at both ends with resonantly shunted transducers and TMD to demonstrate the effectiveness of both attenuation systems and investigate the effects of parametric uncertainty. Furthermore, both approaches lead to additional masses, piezoelectric material for shunt damping and compensator mass of TMD, in the systems. It is shown that vibration attenuation with TMD is less sensitive to parametric uncertainty and achieves a higher performance using the same additional mass.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- M. Schäffner
- Roland Platz

Linear Parameter-Varying (LPV) Buckling Control of an Imperfect Beam-Column Subject to Time-Varying Axial Loads

In: Proceedings of the 35th IMAC, a Conference and Exposition on Structural Dynamics 2017 (30 Jan - 2 Feb, 2017; Garden Grove, CA, USA). null (Conference Proceedings of the Society for Experimental Mechanics Series) pg. 103-112.

Cham

- (2017)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- B. Götz

Non-probabilistic Uncertainty Evaluation in the Concept Phase for Airplane Landing Gear Design

In: Proceedings of the 35th IMAC, a Conference and Exposition on Structural Dynamics 2017 (30 Jan - 2 Feb, 2017; Garden Grove, CA, USA). null (Conference Proceedings of the Society for Experimental Mechanics Series) pg. 161-169.

Cham

- (2017)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- B. Götz
- Roland Platz
- T. Melz

Lateral Vibration Attenuation of a Beam with Piezo-Elastic Supports Subject to Varying Axial Tensile and Compressive Loads

In: Proceedings of the 35th IMAC, a Conference and Exposition on Structural Dynamics 2017 (30 Jan - 2 Feb, 2017; Garden Grove, CA, USA). null (Conference Proceedings of the Society for Experimental Mechanics Series) pg. 1-8.

Cham

- (2017)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- B. Götz
- Roland Platz
- T. Melz

Global Load Path Adaption in a Simple Kinematic Load-Bearing Structure to Compensate Uncertainty of Misalignment Due to Changing Stiffness Conditions of the Structure's Supports

In: Proceedings of the 35th IMAC, a Conference and Exposition on Structural Dynamics 2017 (30 Jan - 2 Feb, 2017; Garden Grove, CA, USA). null (Conference Proceedings of the Society for Experimental Mechanics Series) pg. 133-144.

Cham

- (2017)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- S. Mallapur
- Roland Platz

Quantification and Evaluation of Uncertainty in the Mathematical Modelling of a Suspension Strut Using Bayesian Model Validation Approach

In: Proceedings of the 35th IMAC, a Conference and Exposition on Structural Dynamics 2017 (30 Jan - 2 Feb, 2017; Garden Grove, CA, USA). null (Conference Proceedings of the Society for Experimental Mechanics Series) pg. 113-124.

Cham

- (2017)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Zeitschriftenartikel

- S. Li
- Roland Platz

Observations by Evaluating the Uncertainty of Stress Distribution in Truss Structures Based on Probabilistic and Possibilistic Methods

In: Journal of Verification, Validation and Uncertainty Quantification vol. 2

- (2017)

DOI: 10.1115/1.4038486

Load-bearing mechanical structures like trusses face uncertainty in loading along with uncertainty in stress and strength, which are due to uncertainty in their development, production, and usage. According to the working hypothesis of the German Collaborative Research Center SFB 805, uncertainty occurs in processes that are not or only partial deterministic and can only be controlled in processes. The authors classify, compare, and evaluate four different direct methods to describe and evaluate the uncertainty of normal stress distribution in simple truss structures with one column, two columns, and three columns. The four methods are the direct Monte Carlo (DMC) simulation, the direct quasi-Monte Carlo (DQMC) simulation, the direct interval, and the direct fuzzy analysis with α-cuts, which are common methods for data uncertainty analysis. The DMC simulation and the DQMC simulation are categorized as probabilistic methods to evaluate the stochastic uncertainty. On the contrary, the direct interval and the direct fuzzy analysis with α-cuts are categorized as possibilistic methods to evaluate the nonstochastic uncertainty. Three different truss structures with increasing model complexity, a single-column, a two-column, and a three-column systems are chosen as reference systems in this study. Each truss structure is excited with a vertical external point load. The input parameters of the truss structures are the internal system properties such as geometry and material parameters, and the external properties such as magnitude and direction of load. The probabilistic and the possibilistic methods are applied to each truss structure to describe and evaluate its uncertainty in the developing phase. The DMC simulation and DQMC simulation are carried out with full or “direct” sample sets of model parameters such as geometry parameters and state parameters such as forces, and a sensitivity analysis is conducted to identify the influence of every model and state input parameter on the normal stress, which is the output variable of the truss structures. In parallel, the direct interval and the direct fuzzy analysis with α-cuts are carried out without altering and, therefore, they are direct approaches as well. The four direct methods are then compared based on the simulation results. The criteria of the comparison are the uncertainty in the deviation of the normal stress in one column of each truss structure due to varied model and state input parameters, the computational costs, as well as the implementation complexity of the applied methods.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Zeitschriftenartikel

- G. Enss
- M. Kohler
- A. Krzyzak
- Roland Platz

Nonparametric Quantile Estimation Based on Surrogate Models

In: IEEE Transactions on Information Theory vol. 62 pg. 5727-5739.

- (2016)

Nonparametric estimation of a quantile q m(X),α of a random variable m(X) is considered, where m : ℝ d → ℝ is a function, which is costly to compute and X is an ℝ d -valued random variable with known distribution. Monte Carlo surrogate quantile estimates are considered, where in a first step, the function m is estimated by some estimate (surrogate) m n , and then, the quantile q m(X),α is estimated by a Monte Carlo estimate of the quantile qm n(X),α . A general error bound on the error of this quantile estimate is derived, which depends on the local error of the function estimate m n , and the rates of convergence of the corresponding Monte Carlo surrogate quantile estimates are analyzed for two different function estimates. The finite sample size behavior of the estimates is investigated in simulations.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Zeitschriftenartikel

- M. Schaeffner
- Roland Platz

Active buckling control of an imperfect beam-column with circular cross-section using piezo-elastic supports and integral LQR control

In: Journal of Physics: Conference Series vol. 744 pg. 012165.

DOI: 10.1088/1742-6596/744/1/012165

For slender beam-columns loaded by axial compressive forces, active buckling control provides a possibility to increase the maximum bearable axial load above that of a purely passive structure. In this paper, the potential of active buckling control of an imperfect beam-column with circular cross-section using piezo-elastic supports is investigated numerically. Imperfections are given by an initial deformation of the beam-column caused by a constant imperfection force. With the piezo-elastic supports, active bending moments in arbitrary directions orthogonal to the beam-column's longitudinal axis can be applied at both beam- column's ends. The imperfect beam-column is loaded by a gradually increasing axial compressive force resulting in a lateral deformation of the beam-column. First, a finite element model of the imperfect structure for numerical simulation of the active buckling control is presented. Second, an integral linear-quadratic regulator (LQR) that compensates the deformation via the piezo-elastic supports is derived for a reduced modal model of the ideal beam-column. With the proposed active buckling control it is possible to stabilize the imperfect beam-column in arbitrary lateral direction for axial loads above the theoretical critical buckling load and the maximum bearable load of the passive structure.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Zeitschriftenartikel

- C. Gehb
- Roland Platz
- T. Melz

Active load path adaption in a simple kinematic load-bearing structure due to stiffness change in the structure's supports

In: Journal of Physics: Conference Series vol. 744 pg. 012168.

- (2016)

DOI: 10.1088/1742-6596/744/1/012168

Load-bearing structures with kinematic functions enable and disable degrees of freedom and are part of many mechanical engineering applications. The relative movement between a wheel and the body of a car or a landing gear and an aircraft fuselage are examples for load-bearing systems with defined kinematics. In most cases, the load is transmitted through a predetermined load path to the structural support interfaces. However, unexpected load peaks or varying health condition of the system's supports, which means for example varying damping and stiffness characteristics, may require an active adjustment of the load path. However, load paths transmitted through damaged or weakened supports can be the reason for reduced comfort or even failure. In this paper a simplified 2D two mass oscillator with two supports is used to numerically investigate the potential of controlled adaptive auxiliary kinematic guidance elements in a load-bearing structure to adapt the load path depending on the stiffness change, representing damage of the supports. The aim is to provide additional forces in the auxiliary kinematic guidance elements for two reasons. On the one hand, one of the two supports that may become weaker through stiffness change will be relieved from higher loading. On the other hand, tilting due to different compliance in the supports will be minimized. Therefore, shifting load between the supports during operation could be an effective option.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Zeitschriftenartikel

- B. Götz
- M. Schaeffner
- Roland Platz
- Mendeley Open Access Data Set

Lateral vibration attenuation of a beam with circular cross-section by a support with integrated piezoelectric transducers shunted to negative capacitances

In: Smart Materials and Structures vol. 25 pg. 095045.

- (2016)

DOI: 10.1088/0964-1726/25/9/095045

Undesired vibration may occur in lightweight structures due to excitation and low damping. For the purpose of lateral vibration attenuation in beam structures, piezoelectric transducers shunted to negative capacitances can be an appropriate measure. In this paper, a new concept for lateral vibration attenuation by integrated piezoelectric stack transducers in the elastic support of a beam with circular cross-section is presented. In the piezoelastic support, bending of the beam in an arbitrary direction is transformed into a significant axial deformation of three stack transducers and, thus, the beam's surface may remain free from transducers. For multimodal vibration attenuation, each piezoelectric transducer is shunted to a negative capacitance. It is shown by numerical simulation and experiment that the concept of an elastic beam support with integrated shunted piezoelectric stack transducers is capable of reducing the lateral vibration of the beam in an arbitrary direction.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Zeitschriftenartikel

- G. Enss
- Roland Platz

Evaluation of uncertainty in experimental active buckling control of a slender beam-column with disturbance forces using Weibull analysis

In: Mechanical Systems and Signal Processing vol. 79 pg. 123-131.

- (2016)

DOI: 10.1016/j.ymssp.2016.02.066

Buckling of slender load-bearing beam-columns is a crucial failure scenario in light-weight structures as it may result in the collapse of the entire structure. If axial load and load capacity are unknown, stability becomes uncertain. To compensate this uncertainty, the authors successfully developed and evaluated an approach for active buckling control for a slender beam-column, clamped at the base and pinned at the upper end. Active lateral forces are applied with two piezoelectric stack actuators in opposing directions near the beam-column' clamped base to prevent buckling. A Linear Quadratic Regulator is designed and implemented on the experimental demonstrator and statistical tests are conducted to prove effectivity of the active approach. The load capacity of the beam-column could be increased by 40% and scatter of buckling occurrences for increasing axial loads is reduced. Weibull analysis is used to evaluate the increase of the load capacity and its related uncertainty compensation.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- C. Melzer

Uncertainty quantification for decision making in early design phase for passive and active vibration isolation

pg. 4501-4513.

- (2016)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- S. Mallapur
- Roland Platz

Description and evaluation of uncertainty in the early development phase of a beam-column system subjected to passive and active buckling control

pg. 269-280.

Oldenbourg

- (2016)

DOI: 10.1515/9783110469240-024

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- B. Götz
- O. Heuss
- Roland Platz
- T. Melz

Optimal tuning of shunt parameters for lateral beam vibration attenuation with three collocated piezoelectric stack transducers (Paper No. 149)

- (2016)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Patentschrift

- M. Schäffner
- Roland Platz
- S. Ondoua
- T. Melz
- B. Götz
- C. Gehb
- G. Enss

Solid State Support

- 28.07.2016 (2016)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- B. Götz
- T. Melz

Approach to Evaluate and to Compare Basic Structural Design Concepts of Landing Gears in Early Stage of Development Under Uncertainty

In: Model Validation and Uncertainty Quantification, Volume 3. (IMAC-XXXIV Conference and Exposition on Structural Dynamics; January 25-28, 2016; Orlando, FL, USA) (Conference Proceedings of the Society for Experimental Mechanics Series) pg. 167-175.

Cham

- (2016)

DOI: 10.1007/978-3-319-29754-5_16

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Zeitschriftenartikel

- M. Schaeffner
- B. Götz
- Roland Platz

Active buckling control of a beam-column with circular cross-section using piezo-elastic supports and integral LQR control

In: Smart Materials and Structures vol. 25

- (2016)

DOI: 10.1088/0964-1726/25/6/065008

Buckling of slender beam-columns subject to axial compressive loads represents a critical design constraint for light-weight structures. Active buckling control provides a possibility to stabilize slender beam-columns by active lateral forces or bending moments. In this paper, the potential of active buckling control of an axially loaded beam-column with circular solid cross-section by piezo-elastic supports is investigated experimentally. In the piezo-elastic supports, lateral forces of piezoelectric stack actuators are transformed into bending moments acting in arbitrary directions at the beam-column ends. A mathematical model of the axially loaded beam-column is derived to design an integral linear quadratic regulator (LQR) that stabilizes the system. The effectiveness of the stabilization concept is investigated in an experimental test setup and compared with the uncontrolled system. With the proposed active buckling control it is possible to stabilize the beam-column in arbitrary lateral direction for axial loads up to the theoretical critical buckling load of the system.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- S. Ochs
- K. Pitz
- T. Melz
- Roland Platz

Quantitative Description and assessment of uncertainty for a load-bearing system

In: Tagungsband zur 27. VDI-Fachtagung Technische Zuverlässigkeit TTZ 2015. null (VDI-Berichte) pg. 29-44.

- (2015)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- B. Götz
- M. Schäffner
- Roland Platz
- T. Melz

Model verification and validation of a piezo-elastic support for passive and active structural control of beams with circular cross-section

pg. 67-77.

- (2015)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Patentschrift

- M. Schäffner
- Roland Platz
- S. Ondoua
- T. Melz
- B. Götz
- C. Gehb
- G. Enss

Load Transmitting Device

- 19.11.2015 (2015)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- C. Melzer
- M. Krech
- L. Kristl
- T. Freund
- A. Kuttich
- M. Zocholl
- P. Groche
- M. Kohler
- Roland Platz

Methodical Approaches to Describe and Evaluate Uncertainty in the Transmission Behavior of a Sensory Rod, Applied Mechanics and Materials

pg. 205-217.

- (2015)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- C. Melzer
- Roland Platz
- T. Melz

Comparison of Methodical Approaches to Describe and Evaluate Uncertainty in the Load-Bearing Capacity of a Truss Structure

In: Proceedings of the Fourth International Conference on Soft Computing Technology in Civil, Structural and Environmental Engineering. null (Civil-Comp Proceedings)

Stirlingshire, UK

- (2015)

DOI: 10.4203/ccp.109.26

Load bearing mechanical structures like trusses face uncertainty in loading along with uncertainty in stress and strength due to uncertainty in their development, production and usage. According to the working hypothesis of the German Collaborative Research Centre SFB 805, uncertainty occurs in processes that are not, or only partial deterministic, and can only be controlled in processes. The authors classify and compare different methodical approaches to describe and to evaluate uncertainty in the development phase of three simple two-dimensional linear mathematical truss structure models in a consistent way. The truss structures are assumed to be mounted statically determined. They are each loaded by a vertical static force at a similar node. The criteria to compare the methodical approaches for uncertainty analysis are the limit load condition in one of the columns in the truss structure due to that load. For that, the authors distinguish between stochastic and non-stochastic or, respectively, probabilistic and non-probabilistic evaluation methods, depending on the quality of information of the internal system properties such as geometry and material, and external properties such as magnitude and direction of loading. As a probabilistic approach, direct Monte-Carlo simulation with full sample sets of internal and external property values are conducted exemplarily. Furthermore, the relation between the number of columns in a truss structure and the number of samples through the criteria of convergence is presented. Examples of interval and fuzzy analysis will give information about non-probabilistic uncertainty. The effectiveness and confidence intervals of the different methods will be evaluated by means of the uncertain limit load condition in one column of the truss structure due to uncertainty in internal and external system properties. Additionally, uncertainty of the safety factor for the three trusses is analysed by varying the radii of the columns and by evaluating the probability of failure.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- C. Gehb
- Roland Platz
- T. Melz

Approach to prevent locking in a spring-damper system by adaptive load redistribution in auxiliary kinematic guidance elements

In: Industrial and Commercial Applications of Smart Structures Technologies 2015. null (SPIE Proceedings) pg. 94330G.

- (2015)

DOI: 10.1117/12.2086491

In many applications, kinematic structures are used to enable and disable degrees of freedom. The relative movement between a wheel and the body of a car or a landing gear and an aircraft fuselage are examples for a defined movement. In most cases, a spring-damper system determines the kinetic properties of the movement. However, unexpected high load peaks may lead to maximum displacements and maybe to locking. Thus, a hard clash between two rigid components may occur, causing acceleration peaks. This may have harmful effects for the whole system. For example a hard landing of an aircraft can result in locking the landing gear and thus damage the entire aircraft. In this paper, the potential of adaptive auxiliary kinematic guidance elements in a spring-damper system to prevent locking is investigated numerically. The aim is to provide additional forces in the auxiliary kinematic guidance elements in case of overloading the spring-damper system and thus to absorb some of the impact energy. To estimate the potential of the load redistribution in the spring-damper system, a numerical model of a two-mass oscillator is used, similar to a quarter-car-model. In numerical calculations, the reduction of the acceleration peaks of the masses with the adaptive approach is compared to the Acceleration peaks without the approach, or, respectively, when locking is not prevented. In addition, the required force of the adaptive auxiliary kinematic guidance elements is calculated as a function of the masses of the system and the drop height, or, respectively, the impact energy.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- C. Melzer
- Roland Platz
- T. Melz

Consistent Comparison of Methodical Approaches to Describe and Evaluate Uncertainty in the Load-Carrying Capacity of a Truss Structure (Paper No. D10)

- (2015)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- G. Enss

Comparison of Uncertainty in Passive and Active Vibration Isolation

In: Model Validation and Uncertainty Quantification, Volume 3. null (Conference Proceedings of the Society for Experimental Mechanics Series) pg. 15-25.

Cham

- (2015)

DOI: 10.1007/978-3-319-15224-0_2

In this contribution, the authors discuss a clear and comprehensive way to deepen the understanding about the comparison of parametric uncertainty for early passive and active vibration isolation design in an adequate probabilistic way. A simple mathematical one degree of freedom linear model of an automobile’s suspension leg, excited by harmonic base point stroke and subject to passive and active vibration isolation purpose is used as an example study for uncertainty comparison. The model’s parameters are chassis mass, suspensions leg’s damping and stiffness for passive vibration isolation, and an additional gain factor for velocity feedback control when active vibration isolation is assumed. Assuming the parameters to be normally distributed, they are non-deterministic input for Monte Carlo-Simulations to investigate the dynamic vibrational response due the deterministic excitation.
The model parameters are assumed to vary according plausible assumptions from literature and own works. Taking into account three different damping levels for each passive and active vibration isolation approach, the authors investigate the numerically simulated varying dynamical output from the model’s dynamic transfer function in six case studies in frequency and time domain. The cases for the output in frequency domain are (i) varying maximum vibration amplitudes at damped resonance frequencies for different passive and active damping levels, (ii) varying vibration amplitudes at the undamped resonance frequency, (iii) varying isolation frequency, (iv) varying amplitudes at the excitation frequency beyond the passive system’s fixed isolation frequency, and (v) vibration amplitudes for −15 dB isolation attenuation. In time domain, case (vi) takes a closer look at the varying decaying time until steady state vibration is reached.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- B. Götz
- Roland Platz
- T. Melz

Lateral vibration attenuation of a beam with circular cross-section by supports with integrated resonantly shunted piezoelectric transducers

- (2015)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- C. Gehb
- Roland Platz
- T. Melz

Influence of varying support stiffness on the load path in a 2D-truss for structural health control

pg. 3067-3074.

- (2014)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- G. Enss
- S. Ondoua
- T. Melz

Active stabilization of a slender beam-column under static axial loading and estimated uncertainty in actuator properties

pg. 235-245.

- (2014)

Buckling of load-carrying beam-columns is a severe failure scenario in light-weight structures. The authors present an approach to actively stabilize a slender beam-column under static axial load to prevent it from buckling in its first buckling mode. For that, controlled active counteracting forces are applied by two piezoelectric stack actuators near the column's fixed base, achieving a 40% higher axial critical load and leaving most of the column's surface free from actuation devices. However, uncertain actuator properties due to tolerances in characteristic maximum free stroke and blocking force capability have an influence on the active stabilization. This uncertainty and its effect on active buckling control is investigated by numerical simulation, based on experimental tests to determine the actual maximum free stroke and blocking force for several piezoelectric stack actuators. The simulation shows that the success of active buckling control depends on the actuator's variation in its maximum free stroke and blocking force capability.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- S. Ondoua
- G. Enss
- T. Melz

Approach to Evaluate Uncertainty in Passive and Active Vibration Reduction

In: Topics in Modal Analysis I, Volume 7. (Proceedings of IMAC–XXXII A Conference and Exposition on Structural Dynamics; Feb. 3-6, 2014; Orlando, FL, USA) (Conference Proceedings of the Society for Experimental Mechanics Series) pg. 345-352.

Cham

- (2014)

Uncertainty is an important design constraint when configuring a dynamic mechanical system that is subject to passive or active vibration reduction. Uncertainty can be divided into the categories unknown, estimated and stochastic uncertainty depending on the amount of information, e.g. of the principal mechanical parameter’s deviation in inertia, energy dissipation, compliance and today more and more with active energy feeding to enhance damping. In this paper, these uncertainty categories as well as solutions for uncertainty control in the early design phase will be described and evaluated analytically in a simple but consistent and transparent way on the basis of a mathematical dynamic linear model. The model is a one degree of freedom mass-damper-spring system representing a suspension leg supporting a vehicle’s chassis that is subject to passive and active damping. The amplitude and phase responses in frequency domain are shown analytically in case studies for different assumptions of the effective uncertainty. Amongst others, sample tests are conducted by Monte Carlo Simulations when stochastic uncertainty is considered. The uncertainty examinations on vibration reduction for the selected dynamical model show promising results indicating the predominance of active damping vs. passive damping statistically.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- G. Enss
- Roland Platz

Statistical approach for active buckling control with uncertainty

In: Topics in Modal Analysis I, Volume 7. (Proceedings of IMAC–XXXII A Conference and Exposition on Structural Dynamics; Feb. 3-6, 2014; Orlando, FL, USA) (Conference Proceedings of the Society for Experimental Mechanics Series) pg. 291-297.

Cham

- (2014)

DOI: 10.1007/978-3-319-04753-9_30

Buckling of load-carrying column structures is an important failure scenario in light-weight structures as it may result in the collapse of the entire structure. If the actual loading is unknown, stability becomes uncertain. To investigate uncertainty, a critically loaded beam-column, subject to buckling, clamped at the base and pinned at the upper end is considered, since it is highly sensitive to small changes in loading. To control the uncertainty of failure due to buckling, active forces are applied with two piezoelectric stack actuators arranged in opposing directions near the beam-column’s base to prevent it from buckling. In this paper, active buckling control is investigated experimentally. A mathematical model of the beam-column is built and a model based Linear Quadratic Regulator (LQR) is designed to stabilize the system. The controller is implemented on the experimental test setup and a statistically relevant number of experiments is conducted to prove the effect of active stabilization. It is found that the load bearing capacity of the beam-column could be increased by more than 40% for the experimental test setup using different controller parameters for three ranges of axial loading.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- S. Ondoua
- Roland Platz

Numerical and experimental investigation of parameter uncertainty in the working diagram and in use of a single piezoelectric stack actuator to stabilize a slender beam column against buckling

In: Eurodyn 2014. Proceedings of the 9th International Conference on Structural Dynamics (30 June - 2 July 2014; Porto, Portugal) (EURODYN) pg. 2713-2719.

Porto

- (2014)

Uncertainty in the use of a single piezoelectric stack actuator for stabilization purposes of a slender beam column is described and assessed via the working diagram to estimate the stack actuator’s force and stroke levels. Deviations in the blocking force, in the maximum free stroke of the actuator, in the mechanical prestress load on the actuator and in the stiffness of the host structure are considered as uncertain parameters. Worst Case analyses in the working diagram are performed to assess the influence of the uncertain parameters on the actuator’s force and stroke levels. Real measurements of the force and stroke levels generated by a single piezoelectric stack actuator working against a cantilever beam are performed in an experimental set up. Uncertainty in the experimental measurements of the actuator’s force an stroke levels are described an discussed. It is seen that a high discrepancy between numerical and experimental results with respect to uncertainty can be quantified.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Patentschrift

- A. Hanselka
- T. Koch
- T. Melz
- Roland Platz

Device capable of self-propulsion along a supporting structure

- 15.05.2014 (2014)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- M. Schaeffner
- G. Enss
- Roland Platz

Mathematical modeling and numerical simulation of an actively stabilized beam-column with circular cross-section

In: Active and Passive Smart Structures and Integrated Systems 2014. null (SPIE Proceedings) pg. 90572H.

- (2014)

DOI: 10.1117/12.2044666

Buckling of axially loaded beam-columns represents a critical design constraint for light-weight structures. Besides passive solutions to increase the critical buckling load, active buckling control provides a possibility to stabilize slender elements in structures. So far, buckling control by active forces or bending moments has been mostly investigated for beam-columns with rectangular cross-section and with a preferred direction of buckling. The proposed approach investigates active buckling control of a beam-column with circular solid cross-section which is fixed at its base and pinned at its upper end. Three controlled active lateral forces are applied near the fixed base with angles of 120° to each other to stabilize the beam-column and allow higher critical axial loads. The beam-column is subject to supercritical static axial loads and lateral disturbance forces with varying directions and offsets. Two independent modal state space systems are derived for the bending planes in the lateral y- and z-directions of the circular cross-section. These are used to design two linear-quadratic regulators (LQR) that determine the necessary control forces which are transformed into the directions of the active lateral forces. The system behavior is simulated with a finite element model using one-dimensional beam elements with six degrees of freedom at each node. With the implemented control, it is possible to actively stabilize a beam-column with circular cross-section in arbitrary buckling direction for axial loads significantly above the critical axial buckling load.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- M. Schäffner
- G. Enss
- Roland Platz

Influence of uncertain support boundary conditions on the buckling load of an axially loaded beam-column

pg. 4675–4686.

- (2014)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- B. Götz
- Roland Platz
- T. Melz

Consistent Approach to describe and evaluate uncertainty in vibration attenuation using resonant piezoelectric shunting and tuned mass dampers

pg. 51-64.

- (2014)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Zeitschriftenartikel

- G. Enss
- B. Götz
- M. Kohler
- A. Krzyżak
- Roland Platz

Nonparametric estimation of a maximum of quantiles

In: Electronic Journal of Statistics vol. 8 pg. 3176 - 3192.

- (2014)

DOI: 10.1214/14-EJS970

A simulation model of a complex system is considered, for which the outcome is described by m(p,X), where p is a parameter of the system, X is a random input of the system and m is a real-valued function. The maximum (with respect to p) of the quantiles of m(p,X) is estimated. The quantiles of m(p,X) of a given level are estimated for various values of p from an order statistic of values m(pi,Xi) where X,X1,X2,… are independent and identically distributed and where pi is close to p, and the maximal quantile is estimated by the maximum of these quantile estimates. Under assumptions on the smoothness of the function describing the dependency of the values of the quantiles on the parameter p the rate of convergence of this estimate is analyzed. The finite sample size behavior of the estimate is illustrated by simulated data and by applying it in a simulation model of a real mechanical system.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- B. Götz
- Roland Platz
- T. Melz

Effect of uncertain boundary conditions and uncertain axial loading on lateral vibration attenuation of a beam with shunted piezoelectric transducers

pg. 4495–4508.

- (2014)

Undesired vibration may occur in lightweight structures due to excitation and low damping. For the purpose of vibration attenuation, resonantly shunted piezoelectric transducers can be an appropriate measure. In this paper, uncertainty in design and application of resonantly shunted piezoelectric patch transducers to attenuate the vibration of a beam due to uncertain rotational support stiffness and uncertain static axial loading is investigated. A linear mathematical model of a beam with piezoelectric patch transducers using RITZ formulation is used to calculate the vibration attenuation potential under uncertainty. Variation in the support stiffness and variation static axial loading lead to detuning and cause the resonant shunt to work off the desired frequency, resulting in higher vibration amplitudes. For a beam that is pinned or fixed at both ends, the attenuation effect is less sensitive to uncertainty in the support stiffness than in case of an elastic support that is neither fully pinned nor fully fixed at both ends. A beam fixed at both ends is most robust against uncertainty in static axial loading.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- G. Enss
- Roland Platz
- H. Hanselka

Uncertainty in passive and active stabilisation of critically loaded columns

pg. 61-67.

Stuttgart

- (2013)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- S. Ondoua
- Roland Platz
- H. Hanselka

Unsicherheit im Arbeitsdiagramm eines piezoelektrischen Aktuators für die aktive Stabilisierung von Stäben (Uncertainty in the working diagram of a piezoelectric actuator to stabilize rods)

In: 26. VDI-Fachtagung Technische Zuverlässigkeit 2013: Entwicklung und Betrieb zuverlässiger Produkte (Leonberg bei Stuttgart, 23.-24. April 2013). null (VDI-Berichte) pg. 261-270.

Düsseldorf

- (2013)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Zeitschriftenartikel

- G. Enss
- Roland Platz
- A. Hanselka

Uncertainty in Loading and Control of an Active Column Critical to Buckling

In: Shock and Vibration vol. 19

- (2012)

Buckling of load-carrying column structures is an important design constraint in light-weight structures as it may result in the collapse of an entire structure. When a column is loaded by an axial compressive load equal to its individual critical buckling load, a critically stable equilibrium occurs. When loaded above its critical buckling load, the passive column may buckle. If the actual loading during usage is not fully known, stability becomes highly uncertain.This paper presents an approach to control uncertainty in a slender flat column structure critical to buckling by actively stabilising the structure. The active stabilisation is based on controlling the first buckling mode by controlled counteracting lateral forces. This results in a bearable axial compressive load which can be theoretically almost three times higher than the actual critical buckling load of the considered system. Finally, the sensitivity of the presented system will be discussed for the design of an appropriate controller for stabilising the active column.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- H. Hanselka
- P. Groche
- Roland Platz

Uncertainty in Mechanical Engineering

- (2012)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- G. Enss
- Roland Platz
- H. Hanselka

Mathematical modelling of postbuckling in a slender beam column for active stabilisation control with respect to uncertainty

In: Active and Passive Smart Structures and Integrated Systems 2012 (12-15 March 2012; San Diego, CA, USA). null (Proceedings of SPIE) pg. 834119.

Bellingham, WA, USA

- (2012)

Buckling is an important design constraint in light-weight structures as it may result in the collapse of an entire structure. When a mechanical beam column is loaded above its critical buckling load, it may buckle. In addition, if the actual loading is not fully known, stability becomes highly uncertain. To control uncertainty in buckling, an approach is presented to actively stabilise a slender flat column sensitive to buckling. For this purpose, actively controlled forces applied by piezoelectric actuators located close to the column's clamped base stabilise the column against buckling at critical loading. In order to design a controller to stabilise the column, a mathematical model of the postcritically loaded system is needed. Simulating postbuckling behaviour is important to study the effect of axial loads above the critical axial buckling load within active buckling control. Within this postbuckling model, different kinds of uncertainty may occur: i) error in est imation of model parameters such as mass, damping and stiffness, ii) non-linearities e. g. in the assumption of curvature of the column's deflection shapes and many more. In this paper, numerical simulations based on the mathematical model for the postcritically axially loaded column are compared to a mathematical model based on experiments of the actively stabilised postcritically loaded real column system using closed loop identification. The motivation to develop an experimentally validated mathematical model is to develop of a model based stabilising control algorithm for a real postcritically axially loaded beam column.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- G. Enss
- Roland Platz
- H. Hanselka

Parameter study on an actively stabilised beam column

pg. 17-25.

- (2011)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- G. Enss
- T. Eifler
- M. Haydn
- L. Mosch
- Roland Platz
- H. Hanselka

Prozessmodell zur systematischen Beschreibung und Verkettung von Unsicherheit (Process model for systematic description and linking uncertainty) . Poster

- (2011)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- G. Enss
- Roland Platz
- H. Hanselka

A survey on uncertainty in the control of an active column critical to buckling (Paper No. 17)

- (2011)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- S. Ondoua
- Roland Platz
- J. Nuffer
- H. Hanselka

A study of uncertainties in active load carrying systems due to scatter in specifications of piezoelectric actuators

pg. 2114-2120.

London

- (2011)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Zeitschriftenartikel

- T. Eifler
- G. Enss
- M. Haydn
- L. Mosch
- Roland Platz
- H. Hanselka

Approach for a Consistent Description of Uncertainty in Process Chains of Load Carrying Mechanical Systems

In: Applied Mechanics and Materials vol. 104 pg. 133-144.

- (2011)

DOI: 10.4028/www.scientific.net/amm.104.133

Uncertainty in load carrying systems e.g. may result from geometric and material deviations in production and assembly of its parts. In usage, this uncertainty may lead to not completely known loads and strength which may lead to severe failure of parts or the entire system. Therefore, an analysis of uncertainty is recommended. In this paper, uncertainty is assumed to occur in processes and an approach is presented to describe uncertainty consistently within processes and process chains. This description is then applied to an example which considers uncertainty in the production and assembly processes of a simple tripod system and its effect on the resulting load distribution in its legs. The consistent description allows the detection of uncertainties and, furthermore, to display uncertainty propagation in process chains for load carrying systems.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- S. Ondoua
- Roland Platz
- H. Hanselka

A study on scatter in piezoelectric stack actuator characteristics as an uncertainty criterion in usage process of a load-carrying system (Paper No. 41)

- (2011)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- J. Koenen
- Roland Platz
- H. Hanselka

General approach and possibility to evaluate uncertainty in estimating loads acting on a beam (Paper No. 25)

- (2011)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Zeitschriftenartikel

- J. Koenen
- G. Enss
- S. Ondoua
- Roland Platz
- H. Hanselka

Evaluation and Control of Uncertainty in Using an Active Column System

In: Applied Mechanics and Materials vol. 104 pg. 187-195.

- (2011)

DOI: 10.4028/www.scientific.net/amm.104.187

Uncertainty in usage of load-carrying systems mainly results from not fully knownloads and strength. This article discusses basic approaches to control uncertainty in usage ofload-carrying systems by passive and active means. An active low damped column system critical to buckling is presented in which a slender column can be stabilised actively by piezo stackactuators at one of its ends only. Uncertainty may be controlled in the active column systemby temporarily enhancing the bearable axial load theoretically up to three times compared to the passive column system in case of critical loading. However, in the implementation of theseapproaches, system-speci c uncertainty may also occur. In numerical examinations it is shown, that small deviations in measured axial loading may increase the active force signi cantly to achieve stabilisation. The increase of applied active force might affect lifetime of the piezo stackactuators and thus the stabilising capability of the active column system.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- S. Ondoua
- Roland Platz
- J. Nuffer
- H. Hanselka

Unsicherheit in der Zuverlässigkeitsbewertung von aktiven Komponenten am Beispiel eines piezoelektrischen Stapelaktuators für eine aktive Knickstabilisierung (Uncertainty in evaluating reliability of active components in active buckling control)

In: Tagungsband zur 25. VDI-Fachtagung Technische Zuverlässigkeit TTZ 2011: Entwicklung und Betrieb zuverlässiger Produkte. null (VDI-Berichte) pg. 145-158.

Düsseldorf

- (2011)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Zeitschriftenartikel

- Roland Platz
- C. Stapp
- H. Hanselka

Statistical approach to evaluating reduction of active crack propagation in aluminum panels with piezoelectric actuator patches

In: Smart Materials and Structures vol. 20 pg. 1-11.

- (2011)

DOI: 10.1088/0964-1726/20/8/085009

Fatigue cracks in light-weight shell or panel structures may lead to major failures when used for sealing or load-carrying purposes. This paper describes investigations into the potential of piezoelectric actuator patches that are applied to the surface of an already cracked thin aluminum panel to actively reduce the propagation of fatigue cracks. With active reduction of fatigue crack propagation, uncertainties in the cracked structure's strength, which always remain present even when the structure is used under damage tolerance conditions, e.g. airplane fuselages, could be lowered. The main idea is to lower the cyclic stress intensity factor near the crack tip with actively induced mechanical compression forces using thin low voltage piezoelectric actuator patches applied to the panel's surface. With lowering of the cyclic stress intensity, the rate of crack propagation in an already cracked thin aluminum panel will be reduced significantly. First, this paper discusses the proper placement and alignment of thin piezoelectric actuator patches near the crack tip to induce the mechanical compression forces necessary for reduction of crack propagation by numerical simulations. Second, the potential for crack propagation reduction will be investigated statistically by an experimental sample test examining three cases: a cracked aluminum host structure (i) without, (ii) with but passive, and (iii) with activated piezoelectric actuator patches. It will be seen that activated piezoelectric actuator patches lead to a significant reduction in crack propagation.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- G. Enss
- Roland Platz
- H. Hanselka

An Approach to Control the Stability in an Active Load-Carrying Beam-Column by One Single Piezoelectric Stack Actuator

pg. 535-546.

- (2010)

Euler buckling of column structures is an important design constraint in slender light-weight structures as it may result in the collapse of an entire structure. Thus, uncertainties in the usage of technical products, that result from unforeseen incidents or misuse, shall be identified, assessed and controlled. The main objective of this research is to develop and validate a concept to stabilise a column structure by the use of a lateral active force, induced by a piezoelectric stack actuator. A slender flat beam-column, built in vertically at the base, pinned at the upper end and loaded by an axial compressive force equal to its buckling load is examined numerically and experimentally. The active stabilisation is based on the fact that the initial minimal deflection will be superimposed with the deflection, caused by an actively controlled actively controlled counteracting force. This leads the structure into its approximate second bending deflection mode. With the concept shown, a simple beam-column critical to buckling is stabilised on demand.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- S. Ondoua
- Roland Platz
- J. Nuffer
- H. Hanselka

Uncertainties in active stabilization of buckling

University Park, PA; Red Hook, NY

- (2010)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- J. Koenen
- Roland Platz
- H. Hanselka

An Approach to Quantify the Influence of Uncertainties in Model-based Usage-Monitoring of Load-Carrying Systems

pg. 857-866.

- (2010)

In this study, a method to estimate uncertainties in a model-based usage-monitoring of a load-carrying system to determine mechanical loading condition online during operation is discussed. Generally, uncertainties in the determination of the loading condition occur. As an example, uncertainties in identifying a single external force on a simple cantilever beam depending on scattering input and process parameter, for example derivations of material properties or in sensor position, are investigated with Monte Carlo Simulations. These influences of scattering properties are evaluated by estimating the correlation between uncertain input as well as process parameters and the standard deviation of error in force estimation. For this application it will be shown, that uncertainty in the assumptions on structural damping and uncertainty in measured signals due tovarying sensor position has a high influence to the accuracy of the force estimation. With the method shown,measures to reduce uncertainties in usage monitoring could be derived and rated.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- C. Stapp

Investigating the Potential of Piezoelectric Actuator Patches for the Reduction of Fatigue Crack Propagation in Aluminum Panels

University Park, PA; Red Hook, NY

- (2010)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- G. Enss
- Roland Platz
- H. Hanselka

An Enhanced Approach to Control Stability in an Active Column Critical to Buckling

University Park, PA; Red Hook, NY

- (2010)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- S. Ondoua
- K. Habermehl
- T. Bedarff
- T. Hauer
- S. Schmitt
- H. Hanselka

Approach to validate the influences of uncertainties in manufacturing on using load-carrying structures

pg. 5319-5333.

- (2010)

This paper gives an example of a new approach to display systematically uncertainties within the processchain to manufacture, to assemble and to use load-carrying structures to, eventually, control them in the future. By controlling uncertainties, safety margins between external loading and internal strength of a load carrying structure could be lowered, oversizing will be reduced, resources will be preserved, range of application will be widened and economic advantages will be achieved. In this work, the influences of uncertainties in manufacturing as well as assembling processes on the usage processes with respect to load distribution in a simple tripod is examined. If equal load distribution is desired, this equality highly depends on the quality of drilling holes for a leg connecting device. The holes vary in diameters, so the legs may be assembled differently. It will be shown exemplary, how deviations due to manufacturing may change the load distribution. Monte Carlo Simulation and real experiments on a simple tripod are conducted for validation.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Zeitschriftenartikel

- H. Hanselka
- Roland Platz

Ansätze und Maßnahmen zur Beherrschung von Unsicherheit in lasttragenden Systemen des Maschinenbaus . Controlling uncertainties in load carrying systems

In: Konstruktion (Zeitschrift für Produktentwicklung und Ingenieur-Werkstoffe) pg. 55-62.

- (2010)

In diesem Beitrag werden neue Ansätze zur Beherrschung von Unsicherheiten in lasttragenden Systemen vorgestellt. Werden Unsicherheiten beherrscht, können z. B. Sicherheitsbeiwerte zwischen Beanspruchbarkeit und Beanspruchung minimiert, Überdimensionierung vermieden, Ressourcen geschont, Einsatzbereiche erweitert und damit wirtschaftlicher Vorteil ermöglicht werden. Um diese Ziele zu erreichen, werden im seit Anfang 2009 bestehenden und von der Deutschen Forschungsgemeinschaft DFG geförderten Sonderforschungsbereich SFB 805 zunächst bekannte Methoden und Technologien zur Entwicklung, Produktion und Nutzung bis zur Wiederverwendung lasttragender Systeme hinsichtlich ihres Unsicherheitspotenzials untersucht. Auf dieser Basis werden dann die Unsicherheiten systematisch beschrieben und beurteilt, um sie schließlich zu beherrschen.
This paper shows a new approach for controlling uncertainties in load carrying systems in mechanical engineering. By controlling uncertainties, for example, safety margins between mechanical loading and strength will be lowered, oversizing will be reduced, resources will be preserved, range of application will be widened and economic advantages will be achieved. To reach these goals, the new german collaborative research centre (SFB 805), funded by the Deutsche Forschungsgemeinschaft DFG and started in January 2009, examines in the first step the potential of uncertainties of well known methods and technologies to develop, to fabricate and to use as well as to reuse load carrying systems. On this basis and in the second step, uncertainties will be described and evaluated systematically to, eventually, control them.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- J. Koenen
- Roland Platz
- H. Hanselka

A survey to control uncertainties by comprehensive monitoring of load-carrying structures

In: Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2010. null (SPIE Proceedings) pg. 76471R1–76471R9.

- (2010)

DOI: 10.1117/12.847303

This paper gives a general view on some aspects of the influence of uncertainty in model-based monitoring of loadcarrying structures. The advantages and relevance of monitoring for the prediction of reliability will be clarified and the difference between uncertainty and reliability is discussed. Solving inverse Problems is a particular challenge in monitoring systems. Therefore, different categories of inverse problems are discussed. A generally valid extended difference equation, which describes the transfer behavior of the structure, will be derived as the basis for digital signal processing of model-based monitoring. This equation also considers changes in the structures dynamic properties, e.g due to damage or temperature. With this equation, the influence of uncertainty due to measurement noise to the functionability of monitoring is discussed and some possibilities are shown to control this uncertainty when determining ideal sensor-positions for monitoring.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- R. Engelhard
- G. Enss
- J. Koenen
- A. Sichau
- Roland Platz
- H. Kloberdanz
- H. Birkhofer
- H. Hanselka

A Model to Categorise Uncertainty in Load-Carrying Systems

pg. 53-64.

- (2010)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- E. Janssen

Mechatronische Stabilisierung knickgefährdeter Stäbe in lasttragenden Systemen des Maschinenbaus (Mechatronic stabilisation of beams critical to buckling)

pg. 323-328.

- (2009)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- M. Matthias
- Roland Platz
- J. Bös

Lärm- und Schwingungsminderung im Schiffbau durch adaptronische/mechatronische Lösungsansätze (Acoustic and vibration reduction in ship building with mechatronic solutions)

pg. 384-399.

- (2009)

Maßnahmen zur technischen Lärm- und Schwingungsminderung basieren idealerweise auf der Vermeidung der Entstehung, der Verringerung der Abstrahlung oder der Beeinflussung der Ausbreitung und Übertragung von Vibrationen und (Körper-) Schall am oder möglichst nahe dem Entstehungsort sowie an Koppelstellen. Die Technologie der Adaptronik/Mechatronik verfolgt dazu den Ansatz, an entsprechenden Stellen (z.B. Lagerstellen, Verbindungselemente, schwingende Flächen) eine in Frequenz, Phase und Amplitude angepasste Kraft derart einzuleiten, dass sie die störenden Schwingungen destruktiv überlagert und somit eine Schwingungsreduktion erzielt wird. Die erreichbare Schwingungsreduktion und der dafür notwendige Aufwand (Entwicklungs- und Systemkosten) hängen dabei stark von der jeweiligen Zielanwendung ab. Anhand von unterschiedlichen Beispielen werden in diesem Beitrag das Potenzial und die Einsatzmöglichkeiten dieser Technologie für schiffbauliche Anwendungen dargestellt.
Technical measures for noise and vibration reduction are usually based on the reduction of vibration generation, of sound radiation, or of the transmission of vibrations, air-borne, and structure-borne sound at (or as closely as possible to) the source, as well as at coupling points. The technology of adaptronics/mechatronics (i.e., smart structure technology) applies the concept of using additional forces that are adjusted with respect to frequency, phase, and amplitude at appropriate locations (e.g., bearings, fasteners, vibrating surfaces) in such a way that they counteract the unwanted vibrations in order to significantly reduce the overall vibrations. The achievable vibration reduction and the required expenses (e.g., development and system costs) depend strongly on the particular target application. This paper demonstrates the potential and possibilities of this technology for ship building applications.

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- R. Markert
- H. Hanselka

Modellgestützte Diagnose von Unwuchten und Wellenrissen in Rotorsystemen (Model based diagnose of unbalances and shaft cracks in rotor systems)

In: VDI-Schwingungstagung 2007: Schwingungsüberwachung und Diagnose von Maschinen. null (VDI-Berichte) pg. 205-223.

Düsseldorf

- (2007)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz

Examination of Reliability of Piezoelectric Cantilever Beams . Poster

pg. 1-4.

- (2007)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- D. Mayer
- J. Nuffer
- M. Thomaier
- K. Wolf

FMEA for qualitative measurement of the reliability of an active interface for vibration reduction in passenger cars

In: Proceedings der 23. Tagung Technische Zuverlässigkeit TTZ 2007. null (VDI-Bericht) pg. 317-328.

- (2007)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- A. Sekhar
- Roland Platz
- R. Markert

Health Monitoring and Crack Identifikation in a Rotor System

pg. 217-225.

Monza

- (2006)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Zeitschriftenartikel

- Roland Platz
- A. Büter
- D. Mayer
- H. Hanselka

Schadensüberwachung mit Wandlermaterialien . Health Monitoring with Smart Materials

In: Thema Forschung (Technische Universität Darmstadt) pg. 20-27.

- (2006)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- J. Nuffer
- A. Friedmann
- Roland Platz
- M. Matthias
- T. Melz

Zuverlässigkeitsbewertung einer Strukturschnittstelle zur aktiven Schwingungsminderung (Evaluation of reliability of an interface for active vibration control)

In: Tagungsband zur 1. Tagung DVM - Arbeitskreis Zuverlässigkeit mechatronischer und adaptronischer Systeme. null (DVM-Bericht) pg. 7-16.

- (2006)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- K. Wolf
- J. Nuffer
- Roland Platz

Zuverlässigkeitsuntersuchungen an resonant erregten piezoelektrischen Biegeaktoren: Experiment und Analyse zur Degradation und Schädigung von Piezoventilatoren . Reliability studies on resonantly stimulated piezoelectrical bending actuators: Experiment and analysis on the degradation and damage of piezo fans

In: Proceedings der 22. Tagung Technische Zuverlässigkeit TTZ 2005. null (VDI-Bericht) pg. 163-173.

- (2005)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- J. Nuffer
- Roland Platz
- T. Melz

Zuverlässigkeit aktiver Systeme: experimentelle und theoretische Methoden (Reliability of active Systems: experimental and theoretical methods)

pg. 19.1-19.7.

- (2004)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Monographie

- Roland Platz

Untersuchungen zur modellgestützten Diagnose von Unwuchten und Wellenrissen in Rotorsystemen . Dissertation

In: Fortschrittberichte VDI : Reihe 11, Schwingungstechnik vol. Nr. 325

VDI-Verlag Düsseldorf

- (2004)

- TSZ Weißenburg
- Maschinenbau und Mechatronik

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- R. Markert

Untersuchungen zur Rißidentifikation in Rotoren

pg. 173-181.

Braunschweig

- (2003)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- A. Sekhar
- Roland Platz
- R. Markert

Model based crack identification and monitoring in a rotor system passing the critical speed

pg. 877-884.

- (2002)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- R. Markert
- J. Jayesh
- A. Sekhar

Model Based Unbalance and Fatigue Crack Identification in Rotor Systems

pg. 41.

- (2002)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- R. Markert

Model Based Fatigue Crack Identification in Rotor Systems

pg. 145.

- (2002)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Zeitschriftenartikel

- R. Markert
- Roland Platz
- M. Seidler

Model Based Fault Identification in Rotor Systems by Least Squares Fitting

In: International Journal of Rotating Machinery vol. 7 pg. 311-321.

- (2001)

DOI: 10.1155/S1023621X01000264

In the present paper a model based method for the on-line identification of malfunctions in rotor systems is proposed. The fault-induced change of the rotor system is taken into account by equivalent loads which are virtual forces and moments acting on the linear undamaged system model to generate a dynamic behaviour identical to the measured one of the damaged system.By comparing the equivalent loads reconstructed from current measurements to the pre-calculated equivalent loads resulting from fault models, the type, amount and location of the current fault can be estimated. The identification method is based on least squares fitting algorithms in the time domain. The quality of the fit is used to find the probability that the identified fault is present.The effect of measurement noise, measurement locations, number of mode shapes taken into account etc., on the identification result and quality is studied by means of numerical experiments. Finally, the method has also been tested successfully on a real test rig for some typical faults.

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- R. Markert

Fault Models for On-line Identification of Malfunctions in Rotor Systems

pg. 435-446.

- (2001)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- R. Markert
- Roland Platz
- M. Seidler

Model Based Fault Identification in Rotor Systems by Least Squares Fitting

pg. 901-907.

- (2000)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

Beitrag in Sammelwerk/Tagungsband

- Roland Platz
- R. Markert
- M. Seidler

Validation of Online Diagnostics of Malfunctions in Rotor Systems

pg. 581-590.

- (2000)

- Maschinenbau und Mechatronik
- TSZ Weißenburg
- DIGITAL

Hochschulschrift

- Roland Platz

Ermittlung des Dynamischen Verhaltens eines Verkehrsflugzeug-Fußbodens im Hinblick auf die Reduzierung von Schallabstrahlung in die Kabine . Masterarbeit in Kooperation mit Airbus Industries in Hamburg

Technische Universität Berlin Berlin

- 1998 (1998)

- TSZ Weißenburg
- Maschinenbau und Mechatronik
- DIGITAL

- Bewegungsdynamik und Konstruktion
- Maschinen- und Strukturdynamik, Rotordynamik
- Schwingungstechnik, Experimentelle Modalanalyse
- Mathematische Modellierung, numerische Simulation, experimenteller Test
- Model Verifikation und Validierung, probabilistische und nicht-probabilistische Quantifizierung der Unsicherheit
- Aktive/adaptive Zustandskontrolle, StructuralHealth Monitoring und Kontrolle in mechatronischen dynamischen Systemen.
- Quantifizierung Systemzuverlässigkeit und Unsicherheit in früher Entwicklungsphase
- Lehre und Betreuung/Beratung Studierender

- 2004 Dr.-Ing., Rotordynamik, ehem. Fachbereich Mechanik, TU Darmstadt
- 1998 Dipl.-Ing.,Maschinenbau, Technische Universität Berlin

- 2019 – 2021 Visiting Scholar for Structural Dynamics and Uncertainty Quantification, Architectural Engineering, College of Engineering, Penn State University, State College
- 2017 – 2019 Forschungsgruppenleiter, Systemzuverlässigkeit Future Mobility, Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF, Darmstadt
- 2008 – 2019 Wissenschaftlicher Fachgruppenleiter und Geschäftsführer sowie Teilprojektleiter im SFB 805 „Beherrschung von Unsicherheit in lasttragenden Systemen des Maschinenbaus“, Fraunhofer LBF, Darmstadt
- 2016 – 2017 Adjunct Professor, Department of Civil Engineering, College of Engineering & Science, Clemson University, Clemson
- 2004 – 2008 Wissenschaftlicher Mitarbeiter, Geschäftsführung des Forschungsschwerpunkts für Funktionale Werkstoffe am Fachgebiet Systemzuverlässigkeit, Adaptronik und Maschinenakustik SAM an der sowie am Fraunhofer LBF
- 1998 – 2004 Wissenschaftlicher Mitarbeiter, Arbeitsgruppe Rotordynamik, ehem. Fachbereich Mechanik, Technische Universität Darmstadt
- 1997 – 1998 Structural Engineer/Stress Analyst, Boeing Commercial Airplane Group, Seattle

https://scholar.google.com/citations?user=IGJZsR8AAAAJ&hl=en