Brushless DC motor control

DETAILED DESCRIPTION In accordance with the present invention, a control for a brushless DC motor according to the present invention permits a brushless DC motor to be operated in a simple fashion according to a desired operational characteristic.
Broadly, there is disclosed herein a control for a brushless DC motor that includes a permanent magnet rotor and a stator having stator coils which are energized in accordance with a commutation angle command signal and a voltage command signal for imparting rotation to the rotor.
The control comprises first means for developing a motor performance command signal representing a desired operational characteristic of the motor, second means for developing a motor feedback signal representing an actual operational characterictis of the motor and means coupled to the first and second developing means for deriving the commutation angle command signal and the voltage command signal from the motor performance command signal and the motor feedback signal so that the motor exhibits the desired operational characteristic.
Specifically, in the preferred embodiment of the invention, the motor control includes a motor system controller coupled to a motor electronic control circuit.
The motor system controller develops a motor performance command signal in response to an input command signal and a feedback signal from the motor.
The motor performance command signal may represent, for example, a command for constant torque or a command for torque as a function of motor speed.
The function generator is responsive to the motor performance command signal and the motor feedback signal and develops both a commutation angle command signal and a voltage command signal therefrom.
The commutation angle command signal and the voltage command signal are utilized by the motor electronic control circuit to drive the motor in the commanded fashion.
The function generator is implemented either by software in a microprocessor or by hardware.
In the peferred embodiment, the function generator utilizes mathematical models of the motor operation which correlate voltage and commutation angle commands with torque commands as a function of motor speed