This thesis considers two issues related to impedance control, which is a unified approach to controlling motion and force of a manipulator either in free space or when mechanically coupled with its environment. The first of these issues involves developing a robust impedance control scheme which imposes a desired relationship (impedance) between position and force on the end-effector of a manipulator. The second issue involves developing a force regulation scheme applicable to an impedance controlled manipulator.

A system error (reflecting the difference between desired and actual impedance) has been defined for implementing a desired impedance. Using this system error, the author has formulated a new robust sliding mode-based impedance control scheme.

The proposed impedance control scheme consists of two parts. One part is used to partially compensate for the non-linearities of the dynamic model of the manipulator;​ the other is a system error compensator. Three different compensators-Switching compensator, Saturation compensator, and PI (Proportional and Integral) with Saturation compensator-have been investigated to assess their effects on the system performance. Stability of the proposed impedance control scheme with different error compensators has been verified using Variable Structure System (VSS) theory and Lyapunov’s method.

The force regulation scheme is formulated based on impedance control. It involves finding an input command as a function of the desired force and model of the environment so that contact force of a manipulator will track the desired force. As well, a method for obtaining the model of the environment is proposed in this context.

Experiments were performed to test the proposed impedance control and force regulation schemes. Two such experiments with the impedance control scheme involved implementing Saturation, and PI with Saturation compensations. Because of its known chattering and consequent instability, the Switching compensator was not implemented. These experiments have confirmed the theoretical results.

Finally, the practical application of the proposed impedance control scheme was demonstrated through a grinding experiment. Problems in determining the desired impedance to properly perform grinding tasks have been investigated.