Stability enhancement of admittance control with acceleration feedback and friction compensation

This paper presents an experimental investigation of a new position control scheme that enhances the stability of admittance control by using: (a) PDD2 (proportional, derivative, and second derivative) feedback, (b) dither-based friction compensation and (c) sliding-mode-based noise filter with a variable gain. The PDD2 structure and the friction compensation are for expanding the bandwidth of the internal position-controlled subsystem. The sliding-mode-based filter is for the attenuation of noise in the acceleration signal without producing a large phase lag. The variable gain of the filter is for suppressing acceleration-measurement noise at low velocity. The proposed controller is validated by employing a 1-DOF device.