基于PI-Lead控制的永磁同步电机双环位置伺服系统

Permanent Magnet Synchronous Motor Dual-Loop Position Servo System Based on PI-Lead Control

为提高位置伺服系统轨迹跟踪精度及极限带宽,该文研究了一种位置-电流双环伺服结构,其位置控制采用结合相位超前环节的比例积分控制器(PI-Lead)。首先,探讨了P-PI-PI和PI-P-PI两种传统三环位置控制结构在轨迹跟踪精度上存在的局限,研究了速度前馈提升精度的机理及问题;然后,证明了PI-Lead双环结构相位超前环节对维持系统稳定的意义,详细分析了低通滤波器对系统性能的影响及其参数设计方法,给出了PI-Lead双环位置伺服系统基于闭环频域指标的参数整定策略;最后,对比分析了双环结构与传统三环结构的特点,推导了三种结构的位置极限带宽。实验结果表明,PI-Lead双环结构无需任何前馈补偿即可基本消除系统动态跟踪误差,并具有更高的位置环极限带宽。此外,由于减少了速度控制环节,其无需速度测量且参数整定更加简单。

AC position servo system has been widely used in the industrial field,and how to improve the tracking accuracy and dynamic response performance of the position servo system has become one of the focuses and difficulties of the research.Although the position-speed-current three-loop nested structure is commonly used in position servo systems,for some occasions with strict position tracking accuracy requirements,on the one hand,the speed loop will introduce a large inertia delay link to the system,which will affect the dynamic response performance;on the other hand,the speed quantization error introduced by the encoder accuracy and speed measurement method will also directly affect the tracking accuracy of the system.In order to improve the position tracking accuracy and dynamic response performance of the servo system,this paper studies a position-current dual-loop servo control structure with speed loop free and analyzes characteristics of the dual-loop servo control structure and the traditional position-speed-current three-loop structure,thus providing a theoretical basis for the selection and choice of different position servo control structures in practical applications.Firstly,the paper discusses the limitations of two traditional three-loop structures in tracking accuracy,gives the mechanism of speed feedforward to equivalently improve the system type number and the position tracking accuracy by configuring appropriate feedforward coefficients,and points out that the tracking accuracy is sensitive to the feedforward coefficients.Then the significance of the phase-leading link is proved that it can maintain the stability of the dual-loop structure.Besides,the influence of the second-order low-pass filter in each frequency band of the studied dual-loop control structure is analyzed in detail.The cut-off frequency design range of the low-pass filter is obtained under the trade-off between high-frequency noise suppression capability and stability requirements.Finally,the parameter tuning strategy of dual-loop control structure based on closed-loop frequency domain index is given.In order to provide a theoretical basis and guideline for the selection and choice of the speed loop’s existence in practical application,this paper analyzes the characteristics of the dual-loop structure with speed loop free and the traditional position-speed-current three-loop structure in low-frequency band,middle-frequency band,and high-frequency band.Then,the position limit bandwidth of the three structures is derived,and the relationship between the current loop bandwidth and the position loop limit bandwidth is given.Finally,the experimental verification is carried out on a 750 W commercial permanent magnet synchronous motor and its matched motor driver.The experimental results show that the dual-loop structure with speed loop free can eliminate the dynamic tracking error of the system without any feedforward compensation under multiple position trajectories.It has higher limit bandwidth of the position loop and a stronger ability to suppress high-frequency noise than three-loop structures.In addition,because the speed control loop is reduced,the speed measurement link is unnecessary,and the parameter adjusting procedure is simpler.