DA转换器在电机转动轨迹测量中的应用

Application of the DA Conversion in Displaying the Motor Turning Track

光电编码器的输出是两列相位差1/4周期的方波信号,该信号直接被DSP的正交编码脉冲输入电路(QEP)捕获并进行计数。通过DSP的XINTF总线把采样到的光电编码器计数发送到DA转换器上,DA转换器把该计数转换成模拟电压,从而实时地显示电机轴的运动轨迹。DSP写XINTF总线时间、DA转换时间都是纳秒级,比采样时间小很多,所以对于高采样率的数字控制系统,该方法仍能实时地显示电机的轨迹。该方法误差主要取决于DA芯片的相对转换误差。在实例中,电机作变速转动,最大转速5 r/min,控制系统采样率为33 kHz,DA转换器实时地显示出电机的运动轨迹。

The output signals of a raster coder were two periodic square waves that differ one quarter period in phase degree, which were counted directly by the QEP circuits in a DSP chip. The counts sampled were transferred to a DA conversion through the XINTF BUS in the DSP chip, and were converted to analog voltages. The voltages represented the motor real - time turning track which was displayed in an oscillograph. The time spent on writing to the XINTF BUS and the converting time cost by the DA conversion were in nanosecond scale which were much smaller than the sampling time, so this method was suitable for high - frequency sampling control systems. The display error was determined mainly by the relative accuracy of the DA conversion. As an example, the real - time track of a motor was shown as the motor turned in a variety speed and the fast speed was 5 r/s and the sampling frequency of the controlling system was 33 kHz.