LAUSR

Abstract Stepping motors are used in numerous applications because of their low manufacturing cost and simple open-loop position control capabilities. The bulk of the widely used full-step open-loop stepping motor drive algorithms are driven at maximum current to avoid step loss. This non-optimal way of control leads to low efficiency. In order to use stepping motors in a more optimal way, closed-loop control is needed. A previously described sensorless load angle estimation algorithm, solely based on voltage and current measurements, is used to provide the necessary feedback without using a mechanical position sensor. In this paper, an adaptive PI controller which optimizes the current level based on the feedback of the estimated load angle is introduced. Although the current - load angle dynamics are highly non-linear, an adaptive PI controller with the settling time of the current reduction as design constraint is worth considering. Especially because few tuning parameters are required. The described method is complimentary to the popular methodology used to drive a stepper motor, which is based on step command pulses. Measurements validate the proposed approach.