Novel Adaptive Reaching Law for Sliding Mode Control of an Upper Limb Exoskeleton Robot∗

In this research, we propose a novel sliding mode controller (SMC) to control the nonlinear systems. The proposed control approach includes a modification of the reaching law that overcomes the major limitations of the SMC. The proposed reaching law, unlike the existing ones, provide high trajectory tracking performance by effectively reducing the undesirable chattering problem and faster converging the system trajectories to zero. Thus the proposed reaching law allows benefiting from its advantages (faster convergence, reduced chattering, and high trajectory tracking), as well as overcome the limitations of both conventional sliding mode control (SMC) and the exponential reaching law (ERL). To evaluate the performance of the proposed controller and validate our propositions in real-time, experiments have been carried out with a wearable upper extremity exoskeleton robot named ETS-MARSE. Further, the experimental results were compared to the results with the conventional SMC and ERL to demonstrate the better performance of the proposed controller.