Mechanical Systems and Signal Processing vol:9 issue:1 pages:15-29
This paper describes a new approach to control flexible robots. Many control schemes for flexible robots have been developed and published in robotics research literature. All of them assume the use of torque controlled actuators (DC-motors), while most commercially available robots have velocity controlled actuators. It is possible to extend a traditional controller, which uses velocity controlled actuators and which is designed to control rigid robots, to a controller for flexible robots. However, it is shown that the high gain velocity loop introduces a controllability problem.
The proposed control approach is based on state feedback, built around a high gain velocity controlled actuator. The total dynamic model consists of a parallel combination of the models relating the differential velocity input to the joint position on the one hand and relating the differential velocity input to the flexible deformation on the other. This structure is proven to solve the controllability problem. By state feedback together with feedforward, accurate tracking, proper positioning and oscillation suppression during and after positioning of the end point are achieved. Test results on a bread board model prove the applicability of the proposed control scheme.