Frequency domain study of the relative effect of microstepping on the vibration spectra of stepping motors

The design of a microprocessor-based programmable current source is described for application in the microstepping control of stepping motors. Tests were carried out to measure motor vibration in the time domain as a function of speed, step mode and current control. Two types of vibration sensor were designed and evaluated. In order to decouple the sensor from the motor, a unit was developed, based on optical coupling, which provides an output proportional to displacement. A second sensor utilized a micromachined silicon device to yield an output signal proportional to acceleration. A dual integrator/amplifier circuit was designed for use with the latter system to provide displacement, velocity, and acceleration outputs. The results are digitized and transformed into the frequency domain for further analysis. Frequency spectra are compared for variations in the motor control parameters. The results are of interest in stepping motor applications which require very delicate control of vibrations.<>