Numerical system simulation plays an important role in vehicle engineering. Virtual prototyping of mechanical systems can accelerate the development process enormously and reduces costs. For the numerical simulation of vehicle multiobody systems input signals are needed. Convenient examples of such input data are wheel forces, cylinder displacements of a virtual test-rig or a digital road profile used for driving simulation of a vehicle. With these input data, the equations of motion can be integrated numerically and some output quantities can be calculated from the simulation results. In this work we consider the corresponding inverse problem: We assume that some reference output signals are available, typically gained by measurement and focus on the task to derive the input signals that produce the desired reference output in a suitable sense. However output quantities which are typically measured in an experiment, e.g., wheel forces or relative displacements, are often not invariant but highly dependent on the specific vehicle variant that was used for the measurement. Therefore, they cannot be transferred and used as excitation signal for other vehicle-model variants. If the input data is invariant, i.e., independent of the specific system, it can be transferred and used to excite other system variants. This problem can be formulated as optimal control problem. We discuss two solution approaches from optimal control theory and give some simulation results. An indirect approach (Riccati-approach) and a direct discretization method is discussed. The first is a suitable choice for linear systems of moderate size, whereas the latter is applicable to general full non-linear MBS, which can be modeled in a commercial MBS software tool. For that case, the indirect method can provide a starting point for the iterative optimization process, if it is applied to a linearization of the MBS.
Optimal control of multibody systems for the calculation of invariant input loads
2010
10 Seiten, 5 Bilder, 11 Quellen
Aufsatz (Konferenz)
Englisch
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