A comparative study of backlash compensation methods

This paper describes three different approaches to compensation of backlash influence in a position-controlled system. The influence of backlash in a cascade structured position controller (method 1) with inner torque control loop is compensated by utilizing a fast linear torque controller, at the expense of having to measure the torque on shaft. Defining the model of backlash (method 2) allows for compensation of backlash influence by superposition of compensation signal. However, this method is more sensitive to measurement noise. Variable structure controller (method 3) (one for linear, and the other for nonlinear regime) proved well, with constraints on input signal. These methods were chosen because they were judged most appropriate with respect to constructional and computational constraints in the controlled system. Excellent system behaviors had been experimentally verified on a laboratory model, when proposed control concepts were utilized.