Commutation

The Magnetic Encoder System (MES) serves as feedback for linear motors of the AL8xxx series. It is to be used exclusively for operation on a servo drive.

Linear feedback systems are required for the commutation and the detection of the velocity and position of brushless linear motors. Such feedback systems consist of a reader head and a scale installed parallel to the travel path. The AL8200 works directly on the magnetic plates of the linear motor, eliminating the need for an additional scale. It detects the magnetic field of the permanent magnets of the magnetic plates and supplies the encoder signals to the servo drive. Since the MES is a part-absolute feedback system, no wake & shake is required in order to determine the commutation angle at machine start-up. The MES supplies one sine oscillation per logical motor revolution. A logical motor revolution is equivalent to the distance between two homopolar magnets, i.e. between two north poles. The attainable accuracy of ±0.1 mm is sufficient for simple positioning tasks and depends to a large extent on the mechanical accuracy and position of the magnets along the travel path. Since no scale has to be installed, the MES is an inexpensive feedback solution for linear motors.

Detailed information on the commutation of the AL8000 linear motor in conjunction with the AL8200 MES can be found in chapter 9.6.2 of the AX5000 System Manual.