Sensorless motor braking system
An electric motor control system includes a motor control circuit for generating a motor control signal and a braking mechanism for adjusting the motor control signal to augment motor losses when the motor control circuit is in a braking mode. The braking mechanism includes a difference component for receiving a first signal containing motor reference speed information, for receiving a second signal containing actual speed information, and for generating a third signal containing information indicating a difference between the reference speed and the actual speed. An integrating component integrates the third signal and generates a fourth signal representing the integrated third signal. The fourth signal may augment a voltage control signal in a voltage-based control circuit or may augment a flux-producing component of a current control signal in a current-based control circuit. The electric motor control circuit may include multiple braking mechanisms for use in different modes of operation.
1. A braking mechanism for use with an electric motor control system, the braking mechanism comprising:
a difference component for receiving a first signal corresponding to a change in a reference motor speed over time, for receiving a second signal corresponding to a change in an actual motor speed over time, and for generating a third signal containing information indicating a difference between the change in reference motor speed and the change in actual motor speed; and
an integrating component for integrating the third signal and generating a fourth signal based on the integrated third signal.
2. The braking mechanism of claim 1 , the integrating component being an integral controller.
3. The braking mechanism of claim 1 , further comprising a switch for selectively engaging the integrating component.
4. A control system for an electric motor, the system comprising:
a motor control circuit for generating a motor control signal, the motor control circuit configured to generate a motor driving waveform according to a target current;
a braking mechanism for adjusting the motor control signal to augment motor losses when the motor control circuit is operating in a braking mode, the braking mechanism including—a difference component for receiving a first signal containing motor reference speed information, for receiving a second signal containing actual speed information, and for generating a third signal containing information indicating a difference between the reference speed and the actual speed, the braking mechanism configured to augment a flux producing component of the target current when the motor control circuit is operating in the braking mode; and
an integrating component for integrating the third signal and for generating a fourth signal representing the integrated third signal.
5. The control system of claim 4 , the motor control circuit configured to generate a motor driving waveform according to a target voltage.
6. The control system of claim 5 , the braking mechanism configured to augment the target voltage when the motor control circuit is operating in the braking mode.
7. The control system of claim 4 , further comprising a regulator for limiting an amount of voltage induced by the motor during braking by regulating a slip frequency of the motor.