基于PI迟滞模型的单压电变形镜开环控制

压电非线性迟滞导致压电变形镜的开环控制精度及闭环工作带宽降低,限制了其在自适应光学系统中的应用。为克服迟滞影响,提出采用PI迟滞模型描述单压电变形镜的迟滞非线性特性,实现单压电变形镜的高精度开环控制。首先建立PI迟滞数学模型,利用最小二乘法辨识PI迟滞模型的权值,计算出PI逆模型的权值和阈值,从而获得消除迟滞后的变形镜控制电压;接着搭建了基于哈特曼波前传感器的自适应光学测试平台,采用单压电变形镜的环形致动器进行离焦面形的开环控制实验。实验结果表明,经过迟滞消除后变形镜的电压-变形迟滞由9.3%降低到1.2%,离焦面形的开环重构精度提高70%以上,证明该迟滞模型可有效应用于单压电变形镜的开环控制。

Open loop control of unimorph piezoelectric deformable mirror based on PI hysteresis model

Nonlinear piezoelectric hysteresis reduces the open loop control precision and closed loop operation bandwidth of the piezoelectric deformable mirror (DM), which limits its applications in adaptive optics (AO) system. In order to overcome the hysteresis influence of the piezoelectric deformable mirror, the PI hysteresis model was adopted to describe the nonlinear hysteresis behavior of a unimorph piezoelectric deformable mirror and achieve the high precision open loop control of the unimorph piezoelectric deformable mirror. Firstly, the mathematical model of PI hysteresis was established. The least square method was used to identify the weight value of the PI hysteresis model. The weight value and threshold value of the PI inverse model were calculated. The control voltage of the unimorph piezoelectric deformable mirror after hysteresis elimination was obtained. Then, an adaptive optical test platform based on Hartmann wavefront sensor was built. The open loop control experiment of the defocus wavefront using a ring actuator of the unimorph piezoelectric deformable mirror was carried out. The experiment results show that the voltage deformation hysteresis of the unimorph piezoelectric deformable mirror is reduced from 9.3% to 1.2% after hysteresis elimination. The open loop reconstruction accuracy of the defocus wavefront is improved by more than 70%, which proves that the proposed PI hysteresis model can be effectively applied in the open loop control of the unimorph piezoelectric deformable mirror.