Active Disturbance Rejection Control for Precise Position Tracking of Shape Memory Alloy Actuators

An active disturbance rejection control (ADRC) method for accurate position tracking of shape memory alloy actuators (SMAAs) with uncertain dynamics and disturbances is presented in this paper. It is difficult to achieve precise positioning of SMAAs because of its strong nonlinear characteristics due to its solid phase transition mechanism. To solve the problem that the SMAAs mechanism modeling is difficult and the nonlinear characteristics have adverse effect on the precise position control, a second order transfer function model is established through step response system identification. Furthermore, nonlinear active disturbance rejection controller (NLADRC) are used for accurate position tracking of SMAAs. The overshoot of step signal tracking is effectively inhibited by using a tracking differentiator (TD), and the uncertain dynamics and disturbances are estimated by a designed third order extended state observer (ESO). position tracking accuracy and response speed of the SMAA servo systems are improved by nonlinear error feedback controller (NEFC). The experimental results demonstrate that the present NLADRC scheme for SMAA servo systems can improve the control performance in the accurate position tracking.