Gait tracking for lower extremity exoskeleton based on sliding mode control with CMAC compensation

There is an increasing trend in using exoskeleton to walk or carry payload. In the process of human-exoskeleton interaction, since the user's intention is required accurately, an important problem is human-robot collaborative control. A precise position control strategy will significantly enhance collaboration between the exoskeleton and the user. This paper proposes a novel method combining sliding mode control (SMC) with Cerebellar model articulation controller (CMAC). The proposed method is applied in a lower extremity exoskeleton to track a desired trajectory. The switching surface in sliding mode control was determined by tracking error. A CMAC was designed as a compensator which considers uncertainty of the dynamical model. The dynamic of the lower extremity is derived by using Euler-Lagrange Equation. The proposed control strategy was proved stable with Lyapunov analysis and used for trajectory tracking in comparison with a conventional sliding mode control. Results with Matlab simulation shows that the proposed controller can achieve better tracking capability and robust performance.