形状记忆合金执行机构的精确位移控制研究

To address the control difficulties caused by severe nonlinearities such as large hysteresis in shape memory alloy (SMA) actuators, a closed-loop displacement control method combining inverse hysteresis feedforward compensation and sliding mode control-proportional integral derivative (SMC-PID) was proposed based on the self-sensing characteristics of SMA. First, a forward model of the actuator was established based on the working principle of SMA, and the inverse model was obtained by inverting the forward model of each module. Second, the resistance-displacement self-sensing model of the SMA actuator was established by experimental method based on the analysis of the resistance characteristics of SMA, thereby realizing displacement feedback without external sensors. Third, a composite control method combining inverse model feedforward and adaptive SMC-PID feedback was designed. The feedforward control was used to compensate for the nonlinearity and hysteresis of SMA, while the feedback control employed an adaptive SMC-PID controller with online parameter tuning to approximate the sliding mode equivalent control signal, and the stability of the system was proved. Simulation and experimental results demonstrate that the proposed method outperforms traditional control approaches in tracking sinusoidal commands, continuous step commands during heating contraction and natural cooling process. For step command tracking, the settling time of step command signal tracking is no more than 17 s, and the displacement tracking error is no more than 0. 2 mm. This realizes precise closed-loop displacement control of SMA actuators with strong robustness against system hysteresis and parameter uncertainties.