Improving motion tracking of servomotor-driven closed-loop mechanisms using mass-redistribution

This paper proposes a new design methodology for the improvement of motion tracking performance of single-freedom closed-loop mechanisms (actuated by controlled servomotors) under the operation conditions of robot manipulators. In particular, this design methodology suggests a mass redistribution scheme (prior to designing controllers), which follows the principle of a full shaking force balancing scheme, for the modification of an existing mechanism, with the aim to obtain a “simple” system dynamic model and thus to facilitate controller design. By taking a four-bar mechanism as example, the paper will show that motion-tracking performance of the mechanism is significantly improved by simply applying a conventional proportional-plus-derivative control algorithm. Simulation studies on cases of velocity tracking and trajectory tracking verify the effectiveness of the proposed methodology.