Sensorless control for stepper motors is ‘world’s first’

5 January 2015  

The German motors and drives manufacturer Nanotec, claims to have developed the first sensorless control for stepper motors. It uses a “virtual encoder” to determine the speed of the rotor, allowing the stepper motor to be operated as a servomotor, with no lost steps, no resonance and no risk of overheating.

A setup routine measures the motor’s characteristics and determines all of the required parameters automatically. Depending on the type of motor, speed and positioning information is obtained at a speed of 25­–250 rpm with an accuracy said to be comparable to that of a conventional optical encoder with 500 or 1,000 increments.

According to Nanotec, this allows a level of control to be achieved as good as – and with the same torque as – a motor controlled using an encoder. To operate at lower speeds and for positioning purposes, it is possible to switch automatically to open-loop mode.

The company says that the new closed-loop mode is suitable for applications where traditional closed-loop set-ups with encoders cannot be used due to cost constraints. The new sensorless control system is available as a firmware update for Nanotec’s N and C series controllers.