System and method for determining position or speed of a commutaded DC motor with error correction

摘要

A motor control system (10) and method (100) are provided for detecting current ripple in a commutatcd DC motor (14) and further determining position and speed of the motor (14) based on the detected ripple current. Ripples in the motor current (I a ) are detected and a ripple frequency is calculated based on the time between successive ripples. A ripple count between successive frequencies is determined and the ripple count is compared to a threshold value, and an estimated ripple frequency is determined from a motor model (28) when the ripple count exceeds the threshold value. A corrected ripple count is calculated from a ratio of the calculated ripple frequency and the estimated ripple frequency, and motor position and motor speed are determined based on the corrected ripple count.