Modeling of Overactuated Closed-Loop Mechanisms With Singularities: Simulation and Control
Abstract The modeling and control of redundantly actuated closed-loop mechanical systems is considered in the present work an illustrated with a planar four-bar mechanism and a 3-D parallel manipulator. A specific trajectory involving singular configurations is generated and then followed using the overactuation. To generate the trajectory, four-degree polynomial functions are considered. The loop constraint equations are solved by means of the Newton-Raphson numerical algorithm. In order to describe the dynamics of the systems, the Lagrange multiplier technique is used. The multipliers are eliminated via the coordinate partitioning method. To overcome the underdetermined state of the system induced by the overactuation, additional equations that represent a specific condition for smoothly passing through the singularities are applied. Further, to control the redundantly actuated mechanisms a feed-forward controller is chosen. The robustness of the controller is investigated through several cases of simulation including random noise applied to the controller input and instantaneous loading.