Prescribed performance model-free adaptive sliding mode control of a shape memory alloy actuated system

This paper concentrates on a simple and robust control method for the discrete time nonlinear systems to fulfill the requirement of predefined accuracy. A sliding mode control method is designed by introducing equivalent dynamic linearization technique according to the input/output (I/O) information merely. A square-root type error transformation method is presented for the tracking error to be restricted within a preassigned zone. The performance of presented control method is demonstrated through experiments on a nonlinear system. Experiment results show that the presented control method has a superior tracking accuracy compared with PID controller and model-free adaptive control (MFAC). •A novel prescribed performance function is proposed to convert the restricted tracking error into an unrestricted one.•A novel sliding mode control framework with a unconstrained variable is investigated to ensure the tracking error in a prescribed region according to I/O data.•This control method is presented for the discrete-time system, which is easily implemented on the hardware system without numerical approximation.•An experiment is conducted on the SMA system to verify a good performance of this control method.