Detecting rotation of an encoder with short or missing teeth

摘要

An apparatus (200) configured to detect rotation of a shaft includes a sensor (104) cooperating with an encoder having a plurality of teeth (107,108) located circumferentially on a rotating shaft (106). A processor is configured to detrmine whether the current tooth is located within the vicinity of a position reference gap defined by at least one missing tooth (M). In this case, shaft position data and shaft rotation speed data are not directly based on the timing of the current tooth. The speed in the vicinity of the reference gap is derived from timing data determined from teeth outside the vicinity of the reference gap. The reference position is no derived from a tooth adjacent the reference gap but rather from the N-th tooth following the gap. In this way, measurement errors caused by signal distortion in the vicinity of the reference gap due to the missing teeth can be avoided.