METHOD AND APPARATUS FOR FINE RESOLUTION BRUSHLESS MOTOR CONTROL

摘要

A motor controller (30) includes three analog Hall-effect sensors (42, 44, 46) for forming continuous-time signals proportional to the sine and cosine of the position of the rotor (24) of a motor (20). The sine and cosine signals are differentiated to obtain signals proportional to the 4 rotor rate times the sine and cosine values. These integrated values are then multiplied by the cosine and inverse of the sine values, respectively, to obtain values equal to the rotor rate times 6 the square of the cosine and the rotor rate times the square of the sine. These latter two values 7 are summed to obtain an output signal proportional to the rotor rate based on the trigonometric identity sin<2>(x) + cos<2>(x) = 1. Since the motor controller (30) derives a high-resolution value for the rotor rate, it may be used for fine resolution control of brushless motors and the like.