A hybrid PID control scheme for flexible joint manipulators and a comparison with sliding mode control

Abstract

The article focuses on the issues of dynamic modelling and control of manipulators which have elastic joints. An adaptive hybrid PID (proportional, integral, derivative) control scheme is proposed. For each joint two PID controllers have been implemented. The first is to cope with the joint elasticity and the second is used to deal with the rigid links motion. Simple adaptive mechanism is introduced to eliminate the need of continual tuning the PID gains and a comparison is made with a previously published sliding mode controller (SMC). For both controllers, the desired joint trajectories are computed online. This approach is necessary to overcome the influence of joint flexibility on the tracking performance. The proposed hybrid PID controller and the SMC are compared based on simulation tests. Results demonstrate the effectiveness and usefulness of the proposed hybrid PID control method. Keywords: Flexible joint manipulators (FJM), Adaptive PID controller, Sliding mode control (SMC), Parameter bounds, Trajectory tracking