Force control command synthesis for constrained hybrid dynamic systems with friction

A new hybrid dynamic controller synthesis methodology for the successful co nvergence of force-controlled assembly tasks with friction is presented. Hy brid dynamic modeling has been shown to be a very effective strategy to inc orporate both the continuous-time and discrete event natures of an assembly task. Previously hybrid dynamic controllers have used velocity control. Th is paper develops a hybrid dynamic controller that uses force control, the accepted paradigm for constrained motion systems such as assembly tasks. Fr ictional forces present a significant problem for force control and cannot be neglected in the development of a controller. Constraints on the control command are developed for each type of single-contact transition, and then further constraints are developed to ensure that superposition can be used for multicontact situations. Experimental results are presented for the ne w controller synthesis method performing an assembly task with a 0.8 mm tol erance and requiring four degrees of freedom for completion. These experime nts demonstrate the effectiveness of the combination of hybrid dynamic cont rol and force control for assembly tasks, successfully completing the assem bly with positioning errors of up to 50 mm and orientation errors of up to 10 degrees.