Using back-EMF of a motor, StallGuard and CoolStep add increased functionality and efficiency to your applications without requiring additional components. Enjoy state-of-the-art technologies and develop devices with sensorless homing and stall protection that are optimized for efficiency.
Electric motors such as steppers and BLDCs rotate using magnetic fields. From the rotor point of view, the electromagnetic field of the stator pulls or pushes the rotor. This causes a phase shift between the magnetic field of the rotor and the direction of the rotating field of the stator. This phase shift is the load-angle, or the angle between the two magnetic field directions of the motor’s rotor and stator. Under normal load-conditions the load-angle is low and part of the energy flowing into the motor also flows back to the power supply, resulting in back-EMF. This back-EMF indicates the mechanical load on the motor, meaning it can be used to monitor actual load-conditions of a drive system without using additional components.
A sensorless load measurement for stepper motors, StallGuard gives cost-effective feedback on the load-angle. The StallGuard sensitivity can be adjusted to fit the applications need, making it ideal for sensorless homing, self-calibration, distance measurement, or to verify all mechanics still function within the safety margins. Implemented in a standard stepper motor driver, the sensorless load detection eliminates the need for reference or limit switches and reduces cost and complexity of applications where precise referencing is required.
Normally, open-loop stepper drives lose step count in overload situations as they stall, for example when an axis is obstructed. StallGuard technology prevents step loss, keeping step count integrity by stopping the motor when the set load-value is reached. The sensorless technology can detect up to 1024 different load-levels, allowing for high-resolution feedback for continuous monitoring of the system.
CoolStep offers dynamic current control based on StallGuard values. Originally developed for medical devices and lab automation, the sensorless load-dependent current control always drives the motors at the minimum amount required for the actual load condition. By doing so, the technology reduces the motor energy consumption by up to 90% and reduces heat generation. Furthermore, by eliminating the current safety margin and allowing for temporary current boosts, CoolStep allows for smaller motors since less torque reserve is required.