Model-Free Based Back-Stepping Sliding Mode Control for Wearable Exoskeletons

In this paper, a model-free back-stepping sliding mode control strategy for wearable exoskeletons through a second order ultra-local model and the time delay estimation technique is proposed. First, a second order ultra-local model is developed to take place of the dynamics model with parameter uncertainties and disturbance. Then, a sliding mode control law is designed by the second order ultra-local model, and time delay estimation is used to estimate the lumped uncertain term. In addition, a back-stepping controller is employed to improve the control accuracy. Finally, a virtual prototype is realized in SolidWorks and then transferred to MATLAB/Simulink as a platform, visual simulation program is implemented to validate the correctness and effectiveness of the proposed strategy.