Hybrid force/velocity discrete event controller synthesis for assembly tasks with friction

A discrete event controller synthesis methodology for the successful convergence of assembly tasks is presented. The modelling of an assembly process as a hybrid dynamic system has been shown to be a very effective strategy to incorporate both the continuous and discrete natures of the interaction between the workpiece and its environment. Prior works have presented separate controller synthesis methodologies for both velocity- and force-controlled systems and here we present the next step, a hybrid force/velocity controller. Force control is a natural paradigm for assembly as it is fundamentally compliant and velocity control is used to ensure that frictional forces are overcome during sliding motions. Experimental results for a four degree of freedom assembly task are presented, demonstrating the robustness of the system to very large positioning and orientation errors