Determination of the absolute angular position of an electric motor rotor, using an array or reflecting surfaces arranged around the inner surface of a rotor to generate a light signal whose brightness varies with angular position

摘要

A device for determining the angular position of a rotor (11) forming part of an electric motor (10) has a number of planar, slightly inclined, reflecting surfaces (31) arranged on the rotor surface (20) and a light source (32) for illumination of the reflecting surfaces with a light beam (33). The reflected light is detected by a sensor element (34). The invention also relates to a corresponding method for determining the rotational position of a rotor with the position of the rotor determined from the detected brightness of the reflected light beam. A row type sensor, especially a CCD sensor, is used for detection of the reflected light. A comparator is incorporated in the sensor for determining brightness or light intensity information. Optimally the reflection surfaces can coincide with the rotor pole pairs.