The stabilization of control systems with backlash using a high-frequency on-off loop

The paper introduces a method of stabilizing control systems which have backlash in their control sequence. The technique described employs an auxiliary loop to drive the motor across the backlash whenever the motor and load tend to separate. Requirements of the auxiliary loop are deduced and a phase-plane analysis is developed for a second-order position-control system with this loop operative. Analysis shows that the system with backlash is effectively linearized. It is also shown that impacts between motor and load are avoided. To establish the feasibility of the method an analogue computer study is presented. Results from the analogue show that the technique leads to considerable improvement in the step-function response. Variation of the system damping and of the ratio of inertias is also investigated. It is found that the system stabilized by the technique behaves essentially as a linear system.