Modelling, identification and robust control of 6-DOF parallel manipulators

Abstract

The majority of publications noticeably claim that parallel robots or manipulators are supposed to perform better than their serial counterparts. However, in practice these mechanisms suffer from many problems, such that the theoretically provided potentials are difficult to exploit. Focusing on the issue of dynamics and control, this paper gives a self-contained methodology to achieve accurate control for parallel manipulators. The general case of a 6-DOF (degrees of freedom) mechanism is chosen as the case study to substantiate the approach by experimental results. First, accurate and computational efficient modelling of the dynamics is discussed, followed by presenting appropriate and optimal design of experimental parameter identification. The development of the control scheme is based on the compensation of the non-linear dynamics by using the desired motion. Moreover, a robust design of controller-observer combination for the actuators is proposed. The success of the developed strategy is demonstrated by experimental results.