Neuro Sliding Mode Control for Exoskeletons with 7 DoF

In this work, a novel neuro-sliding mode controller (NSMC) is developed for a 7 degree of freedom (DoF) upper limb exoskeleton. Even though the regular sliding mode controller (SMC) is very sufficient tool when the unknown dynamics of the system is time invariant, variation in the unknown dynamics cannot be handled by regular SMC. Therefore, two-layer neural network (NN) is used to approximate the exoskeleton dynamics in the structure of the SMC. Stability of the NSMC is developed by using Lyapunov stability criteria. To validate our theoretical claims and to compare NSMC with regular SMC, simulation results are provided at the end of the paper. In the simulation section, advantage of the NSMC over regular SMC is presented in the presence of time-varying unknown exoskeleton dynamics.