Composite control of direct-drive manipulators under motion constraints

Develops a singularly perturbed model of a direct-drive manipulator operating under motion constraints. The electrical subsystem is feedback linearized and made a fast subsystem via high gain current feedback. A slow control is then developed for the manipulator´s mechanical subsystem which consists of a corrective control to compensate for the fast motor dynamics and a computed torque control developed for a single n-joint nonredundant manipulator constrained by a rigid environment. Using models of the robot dynamics and environmental constraints, reduced order dynamic equations are obtained for the mechanical subsystem with respect to a user defined set of constraint variables. A feedback linearising control which yields simultaneous position and force tracking is then formulated for the reduced order manipulator dynamics. This control assumes exact model knowledge and requires measurement of the robot joint positions, joint velocities, end-effector contact forces, and motor currents. Simulation results show that compensating for the electrical motor dynamics provides a dramatic increase in force tracking performance