Development and control of an upper extremity exoskeleton robot for rehabilitation

This chapter presents a new integral second-order terminal sliding mode control incorporating quasi-time delay estimation (TDE) applied to passive and active rehabilitation protocols of an exoskeleton robot with dynamics’ uncertainties, unknown bounded disturbances, and without velocity measurement. The employment of the second-order sliding mode is because of its appealing features of precision, attenuation of chattering, and quick convergence. However, the dilemma is that the unknown dynamics of the exoskeleton robot and external disturbances prompted by its different wearers can be amplified by the second derivative of the sliding surface, which leads to instability of the exoskeleton system. Using quasi-TDE will estimate the uncertain dynamics while overcoming the foremost limitation of the second-order sliding mode. The stability analysis of the system is formulated and proved based on the Lyapunov function. Experimental results with a healthy subject confirm the effectiveness of the proposed control. The active motion is achieved by estimating the desired motion intentions of the exoskeleton’s wearers, and a virtual environment is used which permits the stimulation of the subject to complete the active treatment.