TRAJECTORY TRACKING CONTROL OF A HYDRAULIC PARALLEL ROBOT MANIPULATOR WITH LUMPED DISTURBANCE OBSERVER

Xuan-yin Wang and Yang-jun Pi

Keywords

Parallel robot manipulator, lumped disturbance, hydraulic, Gough–Stewart platform

Abstract

This paper addresses the trajectory tracking problem of a hydraulic parallel robot manipulator. High-precision tracking control of a hydraulic parallel robot manipulator is hardly achieved due to the existence of modelling error such as uncertain parameters and external disturbances. Sliding mode control (SMC) and adaptive control are always used to deal with these problems, but some problem remained unsolved. To overcome the drawbacks of conventional sliding mode control and adaptive control, a lumped disturbance which synthesized both parametric uncertainties and un-modelled dynamics is first defined. An adaptive disturbance observer is then constructed to estimate and compensate the lumped disturbance. Therefore, designers do not need to know in advance the bounds of uncertainties, which are required in conventional sliding mode control. Moreover, a linearly parameterized dynamics model is also not required in this approach. Finally, simulation and experimental results performed with a Stewart-typed parallel robot manipulator demonstrate the effectiveness of the proposed control scheme.

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