Performance enhancing adaptive friction compensation for uncertain systems

A regulator design technique for uncertain motor drive systems severely affected by nonlinear friction is presented in this paper. The regulator includes an internal adaptive loop to compensate for the nonlinear friction torque. The adaptive loop is based on a simple friction model, and is adapted with respect to the measure of performance. A new, simple search algorithm for the adaptation is proposed. The friction compensation allows the design of a lower gain robust linear controller for prescribed performance specifications. The closed loop is analyzed with respect to stability and performance. A quantitative comparison is made between robust control with and without friction compensation. Experimental results are presented.