Hybrid PD sliding mode control of a two degree-of-freedom parallel robotic manipulator

One of the most important tasks in robotic applications is trajectory tracking. For such applications it is inherently important that the system obtains a high tracking performance. A widespread control method for trajectory tracking is PD control, which is well-known for its ease of implementation and acceptable tracking performance. However, for tasks that require high precision some advanced methods may be considered that provides higher tracking performance. One such a control method is sliding mode control (SMC), which provides robustness and low tracking errors. In this paper, using the hybridization concept, a new control law is formulated which combined the ease of implementation that PD control provides and the high tracking performance of SMC, while avoiding the inherent drawback of both. The so-called hybrid PD-SMC law provides model-free nonlinear feedback control. The effectiveness of the proposed hybrid control method is investigated through various simulation experiments that provide a comparison in both tracking performance and robustness with stand PD and SMC methods.