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

05 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.

Nanotec says that its sensorless technology allows stepper motors to be operated like servomotors

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.

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