Precise slow motion control of a direct-drive robot arm with velocity estimation and friction compensation

Abstract

Precise low speed motion control of a robot manipulator calls for precise position and velocity measurement and joint friction compensation, as well as robustness and adaptability of the control scheme. However, precise velocity measurement and friction compensation remain challenging research tasks, especially for very slow motions. In the present work, a simple and efficient method is proposed to estimate velocity from a sampled incremental encoder pulse train, which is then utilized in the experimental investigation on a proposed robust decomposition-based friction compensation method. The experimental results on a direct drive robot arm have demonstrated precise motion control at very slow speeds and in the presence of significant joint friction.