Design and Control of a Large Direct-Drive Arm for Practical Industrial Applications

Abstract

A direct-drive robot of a comparatively large size has been developed for practical applications in industry, such as laser cutting. It was designed based on the semi-direct-drive concept, and has 5 degrees of freedom with a 700 mm-long shoulder arm, and a 1050 mm-long forearm, covering a working range as large as a car body.
In this paper, control strategies for the full scale model are proposed through basic analysis. Unfavorable behavior of the arm due to its flexibility was supressed by using the pole-cancellation to obtain high servo-stiffness of the arm. Furthermore, feedforward control was applied to a conventional controller to practically remove its tracking-error.