Infinite-impulse-response periodic-disturbance observer for harmonics elimination with wide band-stop bandwidths

Repetitive motions of automatic machines induce a periodic disturbance, and the periodic disturbance deteriorates precision of motion control of the machines. A periodic-disturbance observer (PDOB) was proposed to suppress the periodic disturbance, but variation of the periodic disturbance frequency deteriorates the periodic disturbance suppression because its band-stop bandwidths in the sensitivity function for harmonics elimination are narrow. This paper proposes an infinite impulse response (IIR)-PDOB. The IIR-filter realizes wider frequency bandwidths in the sensitivity function than the PDOB, which achieves robustness against the variation of the periodic disturbance frequency. We confirmed that the IIR-PDOB was robust against the variation of the periodic disturbance frequency using a parallel robot.