Real-time implementation of a super twisting control algorithm for an upper limb wearable robot

This paper proposes a robust nonlinear controller for an active orthosis. The system is composed of the upper limb orthosis worn by the arm, which can be represented by a nonlinear second-order dynamical model. A robust control strategy is developed to guarantee an accurate and precise movement that encounter important issues such as unknown disturbance torque, inertial and viscous and the parameter uncertainties. A novel control strategy is proposed based on the Super Twisting Algorithm (STW). The stability analysis is performed based on the Lyapunov theory. For further dissemination of the proposed method, a wearable robot arm was built and the exoskeleton building process includes the following parts: mechanical design, mechanical components, electronic circuit design, robot assembly, programming of closed-loop control algorithms in the microprocessor. Hardware-in-the-loop is being implemented by a DAQ-Advantech, PCI-1716 AE, and PC to test the super twisting control algorithm. An experimental prototype, including the arm wearable exoskeleton, is designed and implemented. Experimental results indicate the proposed controller is able to reach high tracking accuracy.