Adaptive robust force tracking impedance control of redundant manipulators based on sliding mode control

In this paper, a sliding mode control method using the force signal and its integral for redundant manipulators is presented. In the proposed method, a continuous control signal is produced to compensate the effect of null space control signal on the task space control performance as well as other system uncertainties. In addition, an adaptive method for determining the desired impedance is presented. Gain of the force error in the impedance relation is adjusted through a direct adaptive method. The important fact is that, the proposed adaptive scheme does not require force derivative or delayed force signal. Also, the environment position does not appear in the force error dynamic and the impedance adapts with the environment stiffness. The desired impedance is realized by a sliding mode control method. The system stability is proved via an appropriate Lyapanov function. The simulation results show the merits of this method.