Hybrid Impedance Force Tracking Control of a Robot Manipulator under Non-model Dynamics and Nonlinear Uncertianties

Hybrid force control regulates a contact force directly by specifying a desired force to form the force error and minimize it without knowing the environment, which is a big advantage over impedance force control. However, this can be a disadvantage to yield a large contact force overshoot. When a robot manipulator moves from free space to contact space, the contact force overshoot occurs and may get damages on both the environment and the end-effector of a robot. In this paper, impedance function is added to the hybrid force control loop to minimize the contact overshoot of a robot manipulator, which forms hybrid impedance force control. Addition of impedance function reduces the contact overshoot and force tracking performance under a non-model based control frame is improved by the time-delayed control method. Simulation studies of force tracking tasks with a 3 link rotary robot manipulator are conducted to confirm the proposal.