精密气浮转台励磁电流矢量控制

Vector control of excitation current for precision air flotation turntable

为实现精密气浮转台精准定位和低速平稳运行的同时降低硬件成本,针对精密气浮转台轻载、低摩擦的特点,提出了一种无需电流反馈的励磁电流矢量控制策略。该策略基于矢量控制思想,令d-q坐标系下转矩电流趋于零,转台电机旋转动力主要依靠励磁电流;设计了速度观测器,通过观测转速变化对转矩电流进行力矩补偿,以提高伺服系统动态响应能力和扩大低速控制范围。对比常规三环伺服系统,该策略没有电流闭环回路,无需高精度电流反馈,节约了硬件成本。理论研究表明:励磁电流越大,转台抗扰性越强;实验结果表明:在低成本硬件平台上,力矩补偿后转台运动跟踪误差≤2.87″,均方根误差≤1.51″。该方法能在低成本硬件平台上,实现精密气浮转台定位精度高、速度平稳性好的要求。

To achieve precise positioning and low-speed smooth operation of the precision air floatation turntable while reducing hardware costs, an excitation current vector control strategy without current feedback is proposed for the light load and low friction characteristics of the precision air floatation turntable. This strategy is based on the vector control idea. To be specific, the torque current in the d-q coordinate system is approximately equal to zero, and the rotating power of the turntable motor mainly depends on the excitation current. A speed observer is designed to compensate the torque current by observing the speed change. In this way, the dynamic response capability is improved and the low-speed control range of the servo system is expanded. Compared with the conventional three-loop servo system, this strategy does not have a current closed-loop and does not require high-precision current feedback. Therefore, the hardware costs can be saved. Theoretical research shows that the higher the excitation current, the stronger the immunity of the turntable. Experimental results show that on a low-cost hardware platform, the motion tracking error of the turntable after torque compensation is not larger than2.87″, and the root mean square error is not larger than 1.51″. The method can meet the requirements of high positioning accuracy and good speed stability of the precision air float turntable on a low-cost hardware platform.