Magnetic pole position detection method and control of a brushless DC servomotor with incremental encoder

Abstract

AbstractOn start‐up of a brushless DC servomotor, it is necessary to detect its magnetic pole position in order to generate the torque effectively. Numerous brushless DC servomotors contain a high angle resolution encoder for the speed control and position control. It can also be used in magnetic pole position detection. There are absolute encoders and incremental encoders. If a brushless DC servomotor contains the absolute encoder, the motor can be started since its absolute position can be detected using magnetic pole position detection. However, the absolute encoder is not used except where high accuracy is required because it is expensive. The incremental encoder generally cannot detect the magnetic pole position during motor start‐up, which is why an exclusive magnetic pole position sensor is required until a standard signal output of the encoder is established.This paper describes a method of magnetic pole position detection of a brushless DC servomotor with an incremental encoder used without an exclusive magnetic pole position sensor. The feature of this method is that it allows detection of the magnetic pole position with very few revolutions in a matter of seconds during motor start‐up. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(4): 64–77, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10219