Finding a decay scheme that works for a stepper motor system is time-consuming and involves trade-offs. The right setting depends on various factors such as supply voltage, current being regulated, motor characteristics, motor speed and back electromotive force (BEMF). The fixed-decay scheme selected can become suboptimal over time as the battery supply voltage lowers, motor characteristics change, and so on, and does not handle BEMF well. This paper introduces smart tune, a plug-and-play decay scheme implemented in Texas Instruments stepper motor drivers. The scheme works in real time and automatically selects the optimal decay setting. By constantly adapting to changes in the system, this scheme results in quieter, smoother and more efficient motor operation, eliminating the need for any tuning.
Stepper motor operation
Stepper motors are very common in applications needing position control without requiring feedback sensors (open loop control). Automated teller machines (ATMs), surveillance cameras, printers, scanners, robotics and office automation are just a few applications using stepper motors A stepper motor has electromagnets to control its movement. To make the motor shaft turn, the electromagnets are energized in a controlled manner using a driver integrated circuits (IC). Figure 1 shows a stepper motor with two coils being driven by a stepper motor driver.