Implementation of a High-speed Sinusoidal Encoder Interpolation System

In order to meet higher performance demands on brushless motor controllers, motor feedback signals must meet correspondingly higher standards. Brushless motor controllers require angular feedback for motor commutation, and generally for one or more of the following: torque, velocity or position regulation. These feedback categories impose different requirements on the control system. In many brushless motor applications, sinusoidal encoders have significant advantages over square-wave encoders. Signal processing techniques for sinusoidal encoder feedback signals are considered in the context of a brushless motor positioning system. In particular, a method is presented for correcting gain and offset measurement errors based on ellipse-fitting techniques.