Unified predictive control of contact force in flexible link manipulators

Using the modal expansion method the dynamics of a flexible link for constrained and unconstrained motion is modeled, assuming stiff contact. The noncolocated actuator/sensor configuration and the dispersive behavior of the link lateral vibrations produce nonminimum phase (NMP) transfer function. The class of model-based predictive controllers (MBPC) have been quite successful at overcoming many of the well-known difficulties inherent to NMP systems, and among the various model-based predictive controllers, unified predictive control(UPC) was selected in this paper. Simulation results suggest that the UPC designed for the system in contact with its environment, will perform well even in presence of serious joint stiction and contact discontinuity. The results also show a very good improvement in performance and command following of the controlled system over conventional approaches