基于DSP与光栅的步进电机速度与位置复合控制

Velocity and Position Control of Step Motor Based on DSP and Raster

鉴于相机调焦过程中频繁变步长、频繁启停,粗调焦时快速性好、精调焦时位置控制精度高的工作需求,提出了基于DSP与光栅的步进电机速度与位置复合控制方法。通过对步进电机矩频特性曲线的分析,速度控制采用指数曲线升降法。离线计算出升降频表格,运行中采用查表方式改变定时器周期寄存器装载值,从而改变输出PWM脉冲的频率以实现电机升降速控制。位置控制利用光栅尺进行位置测量实现位置的闭环控制,实验表明重复定位误差小于2μm。速度与位置复合控制使系统同时具备了稳定性、高速性和高精度性。

To meet the demand that frequently step length changing, startup and stop of movement when focusing a camera, high speed when cursorily focusing a camera, high precision of position control when accurately focusing a camera, this paper introduced a new composite approach for controlling the velocity and position of a step motor based on DSP and raster. Based on the analysis of moment-frequency curve of step motor, exponential curve was applied to control the velocity. Intended to accomplish the accelerating and decelerating of a motor, a table contains the up-down frequencies is computed offline and stored at first, the loaded data of timer period register was changed according to the table to adjust the frequency of PWM pulse when needed. Rater was applied to build a closed loop of position and experiments proved that the position error is smaller than 2μm. Due to the composite control approach, the step servo system processed the characteristics of stability, high speed and high precision.