초록 ▼

A drive circuit for a brushless motor utilizing both phase shift and current shaping to provide for efficient operation of a brushless motor in a servo control system. The circuit includes circuitry for altering the phase of the drive signal as a function of motor velocity to compensate for increase

A drive circuit for a brushless motor utilizing both phase shift and current shaping to provide for efficient operation of a brushless motor in a servo control system. The circuit includes circuitry for altering the phase of the drive signal as a function of motor velocity to compensate for increased current phase lag due to inductance of the motor at high commutation frequencies corresponding to high motor velocities. In addition to altering the phase shift of the drive signal, the circuitry also alters the commutation signal waveform to compensate for a non-sinusoidal field distribution to produce a nearly sinusoidal torque from each of the brushless motor windings. The compensation of both phase shift and commutation signal waveform is accomplished using digital circuitry. The phase commutation is a non-linear function of motor velocity. The waveform compensation is selected to compensate for a trapezoidal magnetic field distribution in the motor air gap.

대표청구항 ▼

A motor control system for driving at a constant speed a multiple phase brushless DC motor, including at least two stator windings, a permanent magnet rotor and a position indicator for indicating the angular position of the rotor, the system comprising: (a) excitation current generating circuit mea

A motor control system for driving at a constant speed a multiple phase brushless DC motor, including at least two stator windings, a permanent magnet rotor and a position indicator for indicating the angular position of the rotor, the system comprising: (a) excitation current generating circuit means connected for providing excitation current to the stator windings in response to a current command vector signal; (b) computing means coupled to the position indicator for receiving information therefrom concerning the position of the rotor and for providing a control signal for each axis having values selected from a stored table of values in accordance with the calculated rotational speed and the instantaneous angular position of the rotor, the values being selected to correct the amplitude of the current vector command to compensate for non-sinusoidal variation of the magnetic field in the air gap as a function of the angular position of the rotor; and (c) control circuit means responsive to a velocity error signal indicative of the difference between the calculated rotational speed and the commanded rotational speed and the control signal provided by the computing means and for providing a current vector command signal to the excitation current generating means which is adjusted in magnitude to provide a substantially sinusoidal tongue distribution for each phase.