Design of motion control systems with positive force/torque feedback using μ synthesis

Positive force/torque feedback (PFF) can compensate for the detrimental effects of load dynamics and exogenous force/torque disturbances on the tracking performance of motion control systems. With real world non-ideal force/torque actuators, a force/torque feedback controller can be designed to accommodate the actuator´s dynamics or external force/torque disturbances upon the motion tracking loop. This paper shows that PFF is an effective method for many practical control problems. It is also shown that the analysis and design of motion control systems with PFF can be put into the μ framework, and thus the tracking controller and the force/torque feedback controller can be synthesized simultaneously using commercially available μ tools. Experimental results with a UW hexapod strut show that the μ design method for PFF is promising.