Dynamic Modelling and Control of Flexible-Link Multibody Systems

Multibody systems are mechanisms of interconnected bodies with application in many areas of engineering. There is a need to optimize such systems for, among others, the minimization of the torque demand of the system motion, and also for maximization of the velocity of the systems. The integration of lightweight flexible bodies in multibody systems makes sense as the lower weight would imply an overall lighter systems and faster system; but this also comes with vibrations that in turn affect the system dynamics. It is necessary to have a control system for the motion of the system such that the torque and velocity targets are met and keeping vibrations low. This work focuses on a four-bar linkage multibody system. Moreover, the four-bar linkage system in this case includes two extra links in the middle of the structure symmetrically dividing the system. This architecture is based on the horizontal-to-vertical and vertical-to-horizontal target motion of the system’s coupler link. For the study, different configurations of lightweight flexible body integration are modeled and observed for nature of the system performance in terms of the speed, torque and vibration. From the foregoing, a most suitable configuration is selected and following this, a control architecture is proposed for the system such that the torque demand is kept below the set limit, link vibrations are lowered and the system is fast. In this work, Matlab/SimscapeMultibody is used to model and study the system. Using the Simulink environment, the controller is designed to satisfy the performance requirement and to follow the reference motion path. Simulation results are presented, which show that the controller can control the system motion and keep vibrations low. The dynamic modeling and control approach presented can be applied to other cases of multibody systems other than the four-bar linkage mechanism.