Time-optimal stepper motor motion profile through a novel load-angle-based step-command optimization

Abstract

Nowadays, stepper motors are extensively used in positioning applications due to excellent open-loop accuracy and a relatively simple control principle. Every time the controller sends a step-command pulse to the motor, the rotor will move for a known discrete angle. By subsequently counting the number of pulses, the rotor angle is known at all times. Nevertheless, due to the control principle's nature, as a matter of safety, the bulk of stepper motors are often not driven at their full potential to prevent so-called step-losses. Typically, this results in low energy efficiency and an over-dimensioned motor. As a solution, maximizing the motor's load potential through intelligent algorithms contributes to smaller motors and increases efficiency since higher motion speeds are reachable. Until now, in search of optimal motor usage for point-to-point motion profiles, literature mainly focused on finding time-optimal motion profiles using simplified models with a complicated analytical approach rather than developing an easily executable methodology that optimizes at the fundamental control level. Therefore, this paper presents a novel optimization methodology, solely based on the motor's load angle, of which the resulting puls commands' timings can be easily deployed in commercial stepper motor drives. Results show a significant improvement in time-saving of 36,45% compared to a reference 5th-order polynomial point-to-point trajectory.