Patent ID: 7321801

Claim:
An automatic gain adjustment device of a feedback control system that uses a phase difference between an output signal obtained from a controlled object and an input signal while controlling the object based on the input signal, the automatic gain adjustment device comprising: a disturbance generator for generating the input signal; the input signal being a sine wave of a predetermined frequency; phase shifting means connected to an input stage of the feedback control system for shifting a phase of the input signal such that a phase shift amount of the phase shifting means is set so that a frequency of the input signal to be supplied to a closed loop coincides with a crossover frequency at which an open loop gain of the feedback control system becomes 0 db; a band-pass filter for filtering the output signal to extract a component signal of the predetermined frequency; a multiplier for multiplying the phase-shifted input signal from the phase shifting means and the component signal from the band-pass filter; an integrator for integrating product results of the multiplier over one cycle at the predetermined frequency and outputting integrated product results; and a gain setting unit for adjusting a gain of the feedback control system based on a sign of the integrated product results from the integrator so that the open loop gain converges to 0 dB.