Integral Control with Torque Limitation

The behaviour of a basic remote-position-control system with velocity-feedback stabilization and integral-of-error control is investigated, taking torque limitation of the servo motor into account. It is shown that the transient response deteriorates as the magnitude of the input signal is increased and becomes unstable above a critical value. Both phase-plane analysis and describing-function techniques are employed. The experimental behaviour to random input signals is observed. The effect of other non-linear elements added to eliminate the possibility of amplitude-dependent instability is discussed.