Control of industrial robots that have transmission elasticity

A multiloop control scheme for electrically driven industrial robots is presented. Previous works have used the inner loop to cancel the elastic coupling torque, and the outer loop for the control of the arm position. A modification of this control scheme is presented. It is shown that exact cancellation of the elastic torque is not necessary; the elasticity effects in some robots can be adequately controlled by using only a damping term proportional to the different speed. The analysis yields design guidelines for selecting the control gains; encouraging experimental results are presented