Application of flexible multibody modelling for control synthesis in mechatronics

The models used in the conceptual phase of the mechatronic design should not be too complicated, yet they should capture the dominant system behaviour. This includes the computation of natural frequencies and mode shapes in a relevant frequency range. For the control system synthesis the low frequent behaviour up to the cross-over frequency needs to be known. Furthermore, the closed-loop system can be unstable due to parasitic modes at somewhat higher frequencies. In this paper we demonstrate the applicability of a multibody modelling approach based on non-linear finite elements for the mechatronic design of a compliant six DOF manipulator. A kinematic analysis is applied to investigate the exact constrained design of the system. From dynamic models the natural frequencies and mode shapes are predicted and a state-space model is derived that describes the system’s input-output relations. The models have been verified with experimental identification and closed-loop motion experiments. The predicted lowest natural frequencies and closed-loop performance agree sufficiently well with the experimental data.