由于超声电机压电材料、摩擦材料、接触界面的非线性, 速度平稳性和位置控制精度不高, 这在一定程度上制约了它在高端精密装备中的应用。本文介绍了一种实现超声电机速度、位置高精度控制的方法。从连续运动与步进运动两个维度分析了超声电机的速度调控机理, 阐明了速度波动的误差来源, 建立了以幅值、频率为输入量, 融合稳态环节与动态环节的速度模型。为了准确预测步进位移量, 建立并辨识了启动-关断两段式二阶速度模型; 接着采用双环复合控制算法实现了高平稳性速度控制, 并通过驱动参数优化实现了电机的高分辨率位置控制。最后, 运用分段逼近策略实现了高精度定位。实验结果表明, 在速度控制方面, 采用双环复合方法控制的速度平稳性为0.44%, 相比单速度环的控制效果提升了一倍; 在位置控制方面, 超声电机的开环位置分辨率达到了0.375 μrad, 定位精度达到了1.7 μrad。本文提出的控制方法综合了不同参数及不同环路的调控特点, 有效提高了超声电机的速度与位置控制精度, 为超声电机在精密装备中的拓展应用奠定了基础。

In order to improve speed/position control accuracy and overcome nonlinearity accompanied by a multivariable coupling effect, the targeted speed and position control of the ultrasonic motor was proposed in this paper. Firstly, the control mechanism of the ultrasonic motor was demonstrated from the perspectives of continuous macroscopic motion and microscopic stepwise motion. Then, the sources of velocity fluctuation errors were clarified, and a multiparameter speed control model was established; the amplitude and frequency were integrated into the model by combining steady and dynamic links. In order to predict stepwise displacements, a two-stage second-order speed model was also constructed from the microscopic dimension. Then, the double-loop compound control algorithm was used to realize high-stability speed control, while high-resolution position control could be achieved through driving parameter optimization. Finally, a piecewise approximation strategy was adopted to combine the continuous and stepwise motion for high-precision positioning. The experimental results show that speed stability under dual-loop compound control is 0.44%, which is two times better than that of single-loop control. In terms of position control, the open-loop position resolution of the ultrasonic motor reached 0.375 μrad, and a positioning accuracy of 1.7 μrad is achieved. The proposed control strategy integrates the control characteristics of different parameters and loops, which effectively improves the speed and position control accuracy of the ultrasonic motor. This work lays the foundation for extended applications in advanced precision equipment.