07 Fakultät Konstruktions-, Produktions- und Fahrzeugtechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/8
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Item Open Access Inverse fuzzy arithmetic for the quality assessment of substructured models(2015) Iroz, Igor; Carvajal, Sergio; Hanss, Michael; Eberhard, PeterThe dynamical analysis of complex structures often suffers from large computational efforts, so that the application of substructuring methods has gained increasing importance in the last years. Substructuring enables dividing large finite element models and reducing the resulting multiple bodies, yielding a reduction of, in this case, complex eigenvalue calculation time. This method is used to predict the appearance of friction-induced vibrations such as squeal in brake systems. Since the method is very sensitive to changes in parameter values, uncertainties influencing the results are included and identified. As uncertain parameters, standard coupling elements are considered and modeled by so-called fuzzy numbers, which are particularly well suited to represent epis- temic uncertainties of modeled physical phenomena. The influence of these uncertainties is transferred to undamped and damped eigenfrequencies of a substructured model by means of direct fuzzy analyses. An inverse fuzzy arithmetical approach is applied to identify the uncertain parameters that optimally cover the undamped reference eigenfrequencies of a non-substructured, full model. If a validity criteria is defined, a positive decision in favor of the most adequate model can be performed.Item Open Access Comparison of local and global approaches for parametric model order reduction for systems with distributed moving loads(2017) Fröhlich, Benjamin; Eberhard, PeterIn order to ensure a numerically efficient simulation of elastic multibody systems, model order reduction has to be employed for reducing the complexity of the underlying Finite-Element-Models. Elastic multibody systems with moving loads can be modeled as parameter dependent systems for which methods from parametric model order reduction have to be applied. In this contribution, two local and a global approach from parametric model order reduction are investigated. A comparison is made with respect to their approximation quality in frequency domain and time domain and their numerical cost in transient simulations. As a numerical example, a linear drive with a distributed moving load is considered.Item Open Access Investigation of chip jamming in deep-hole drilling(2023) Baumann, Andreas; Eberhard, PeterIn this paper, we show the recent progress and first insights in modeling chip jamming in the deep-hole drilling process. Chip jamming is a significant problem when chips wrap around the tool, leading to marks on the borehole wall and an increased drilling torque causing sudden tool failure. Recent investigations focused on chip evacuation and fluid distribution along the cutting edge. This work extends the existing models by adding an artificial barrier in the chip flute. This barrier approximates a chip jammed between the drill shaft and the borehole wall. In the first approach, this barrier blocks the complete chip flute but allows fluid to pass, only blocking the chips from their evacuation. In the second approach presented, a non-permeable artificial barrier partially blocks the chip flute. Furthermore, we show the validation of the model and evaluate the assumption of rigid chips for the chip evacuation as they are applied in earlier investigations. Finally, we show the deformation of the chip as it blocks the fluid from its evacuation and the impact on the fluid flow during the process.Item Open Access Integrated modeling, simulation, and optimization of multibody systems(1994) Eberhard, Peter; Bestle, DieterDesign of nonlinear dynamic systems is a challenging task. Computers may help to analyze and optimize virtual prototypes in an earl design phase, but there is a lack of design tools. In this paper, a design concept on the basis of a multibody system approach is described. Programs for modeling, simulation, sensitivity analysis, optimization, and animation are operating under a common administration which ensures model consistency. The designer is supported by a graphical user interface, distributed computation improves efficiency.Item Open Access Ride Comfort Transfer Function for the MAGLEV Vehicle Transrapid(2018) Zheng, Qinghua; Dignath, Florian; Eberhard, Peter; Schmid, PatrickIn order to predict the ride comfort for the MAGLEV vehicle Transrapid TR09 for various scenarios, e.g. for higher vehicle speeds than hitherto travelled, a transfer function from the excitations given by the guideway position to the relevant car body acceleration is calculated by two different methods. Method A is based on a mechatronic simulation model of the Transrapid TR09 which describes a two- dimensional lateral cross section of the vehicle. The simulation model consists of a 2D multibody system describing the mechanical part, four network models of the electro-magnets - two levitation magnets and two guidance magnets - and a signal model of each magnet controller. These signal models contain a representation of the authentic C-Code of the control law used within the actual magnet control units within the vehicle TR09. The overall model can be exploited to calculate the accelerations of the car body for given excitations at the interfaces between guideway and vehicle. Moreover, it is possible to generate a model-based transfer function in the frequency domain from the guideway excitations to the car body accelerations. For method B, measurement results of test runs of the Transrapid TR09 at the test track TVE in Northern Germany are exploited which were recorded for vehicle dynamics analysis and ride comfort evaluation in 2009. From these measurement results two characteristic quantities are generated for several different velocities of the vehicle: Firstly, the position of the guideway is reconstructed by using an integration of the absolute accelerations of the magnets and the signals of the magnet's sensors for the air gap. Secondly, the relation between the accelerations at the car body of the vehicle and the guideway position is calculated as a transfer function in the frequency domain. For this, the measurement data and the reconstructed guideway position are both transformed into the frequency domain by a Fast Fourier Transformation (FFT). The resulting transfer function gives the relevant accelerations for the ride comfort for given excitations of the vehicle as calculated by Method A above. The two transfer functions from Method A and B are compared for validation. Then, a smoothed version of the validated transfer function is applied for estimating the ride comfort for travelling scenarios which have not yet been measured in practical operation, e.g. for higher velocities of the vehicle.Item Open Access Sensitivity computation for uncertain dynamical systems using high-dimensional model representation and hierarchical grids(2015) Walz, Nico-Philipp; Burkhardt, Markus; Hanss, Michael; Eberhard, PeterGlobal sensitivity analysis is an important tool for uncertainty analysis of systems with uncertain model parameters. A general framework for the determination of sensitivity measures for fuzzy uncertainty analysis is presented. The derivation is founded on the high-dimensional model representation, which provides a common basis with Sobol indices, illustrating the similarities and differences of fuzzy and stochastic uncertainty analysis. For the numerical calculation, a sparse-grid approach is suggested, providing an efficient realization due to the direct relationship between hierarchical grids and the sensitivity measures.Item Open Access Simulation of a micro shift valve with impact actuation(2011) Eberhard, Peter; Fischer, ChristianA new concept of an impact actuated micro shift valve is presented. The impacts are transmitted to the interior of the valve through the casing. In order to predict the energy transmitted into the valve, the most important effects are discussed and two elastic multibody models using the Hertzian contact law are introduced and compared to a full finite element simulation. A simpler model with one degree of freedom for an elastic plate as transmission element proves to be too crude. But a more sophisticated model with axisymmetric finite elements for the plate shows good agreement. The simulations are compared to experiments performed with a scaled model for two different cases. The experiments show that so far neglected effects like plastic deformation occur and must be considered in the simulation if accurate predictions are required.Item Open Access Comparison of distributed model predictive control approaches for transporting a load by a formation of mobile robots(2017) Ebel, Henrik; Sharafian Ardakani, Ehsan; Eberhard, PeterThis paper investigates and discusses two different distributed formation control approaches based on model predictive control (MPC). Specifically, the presented control schemes are used to govern the motion of omnidirectional mobile robots that shall maintain a given formation shape while following a path through a previously unknown environment. The setup of the control schemes accounts for the requirements of transporting an elastic plate purely by normal and friction forces. The intricacy of this task motivates the choice of model predictive control since it allows to explicitly constrain the movements of the robots. The two schemes analyzed in this contribution are fundamentally different in their optimization and communication strategies. The performance of the schemes is carefully examined in various simulations. These include situations in which the robots have to shrink the formation in order to squeeze through narrow passages. An exemplary experimental result involving real robot hardware is also presented.Item Open Access Modeling of the Transrapid’s electromagnets and the application to large mechatronic vehicle models(2022) Schmid, Patrick; Schneider, Georg; Kargl, Arnim; Dignath, Florian; Liang, Xin; Eberhard, PeterThis work gives an overview of a general approach for modeling the electromagnets of a magnetic levitation (Maglev) vehicle based on electromagnetic suspension. The method intends to map the magnets’ static and dynamic behavior in a frequency range relevant for use in mechatronic simulation models and Maglev control or observer design. The methodology starts with setting up the equivalent magnetic circuit considering magnetic reluctances, fringing and leakage flux, magnetic saturation, and eddy currents. Then, the resulting equations are coupled with the magnet’s electric circuits using Ampère’s law and Faraday’s law of induction. Further, a numerical model reduction technique is sketched, which yields a simplified version of the previously derived magnet model with nearly the same input-output structure and input-output behavior, suitable for large simulation models and control design. The approach’s capabilities and strengths are shown by the agreement to measurements and by implementing the resulting models in large mechatronic vehicle models of the Transrapid.Item Open Access Experimental investigations on impact transmission through a plate(2013) Fischer, Christian; Eberhard, PeterThe concept of an impact actuated shift valve is presented. This valve concept can be actuated by different kinds of actuators, such as piezo stack actuators. A simplified model for the investigation of the impact process is created. The model consists of a plate, two spheres and a fluid-filled tank. Experiments are presented with and without fluids and different plates. The results are compared to simulations.