OPTIMAL HYBRID POSITION FORCE TRACKING CONTROL OF A CONSTRAINED ROBOT

In this paper, a global tracking control problem of a constrained robot is considered to be formulated by the hybrid coordinate frames of the joint-space coordinate for the motion of the robot's joints, and the task-space coordinate for the constraint forces on the robot's end-effector. After model reduction and a proper change of control variable, reduced state-space error dynamics are explicitly obtained and used to derive the nonlinear quadratic optimal tracking controller for the constrained robot. The advantage of the controller is that is provides an asymptotic tracking solution to minimize, simultaneously and systematically, the tracking error about the desired position and velocity of the joint-space motion, with a minimum of applied torques which affect the kinetic energy only. In addition. it is interesting that our controller can achieve the exponential tracking of the task-space constraint force.