Control of a Direct-Drive Arm Using Novel Repetitive Control.

Abstract

A direct-drive (DD) arm system is one of the most attractive and interesting research subjects in the field of robot engineering. Up till now, many DD robot arm systems with vertical axis have been adopted for industrial applications, but very few systems with horizontal axis because of the difficulty to reduce the speed fluctuation caused by the arm weight. The PID control without any additional control process has very poor response characteristics because of the continuous load fluctuation and the time delay in the system, The accuracy is consequently, not satisfactory. Therefore, we proposed a repetitive control with learning process (position-memory type) to drive the horizontal axis robot arm with constant speed, which is based on the periodicity of the arm action.