Method and system for motor oscillatory state detection

1. A method for controlling an electric motor, the method comprising:

providing power to energize coils of the electric motor for a first time period;

subsequent to providing the power, removing the power;

subsequent to removing the power, monitoring a signal for a second time period, the signal being associated with rotation of a rotor of the motor;

resume providing power to energize the coils when the signal indicates the rotor was rotating during the second time period, and

performing an error process when the signal indicates the rotor was not rotating during the second time period.

2. The method of claim 1 wherein the error process comprises:

providing power to the electric motor for a third time period after a predetermined time has elapsed;

monitoring the signal for a fourth time period, the fourth time period being after the third time period; and

determining whether the rotor was rotating or not based on the signal monitored during the fourth time period.

3. The method of claim 2 wherein the predetermined time period is at least 5 seconds.

4. The method of claim 1 wherein the error process comprises sending an error signal.

5. The method of claim 1 wherein the electric motor comprises a brushless DC motor.

6. The method of claim 1 further comprising:

monitoring the signal for a third time period, the third time period being after the second time period;

providing power to the electric motor when the signal indicates the rotor was not rotating during the second time period.

7. The method of claim 1 wherein the signal is an output of a Hall effect device.

8. The method of claim 7 the signals are characterized by rising and falling edges.

9. The method of claim 1 further comprising:

monitoring the movements of the rotor using an optical motion detection module;

generating the signal based on the movements of the rotor.

10. The method of claim 1 wherein the electric motor is in a power off mode during the second time period.

11. The method of claim 1 wherein the first time period is associated with a pre-drive stage.

12. The method of claim 1 wherein the second time period is associated with an actual driver stage.

13. The method of claim 12 wherein the actual driver stage is bipolar.

14. An electric motor system comprising:

a rotor, the rotor including energize coils;

a driving module, the driving module being adapted to provide a commutation signal to the energize coils;

a sensor module, the sensor module being configured to output a signal; and

a control module, the control module being adapted to:

control the driving module to output the commutation signal for a first period of time;

control the driving module to cease outputting the communication signal;

monitor the signal output by the sensor module during a second period of time;

control the driving module to output the commutation signal when the signal indicates the rotor was rotating during the second period of time; and

perform an error process when the signal indicates the rotor was not rotating during the second period of time.

15. The system of claim 14 wherein the control module includes a timer.

16. The system of claim 14 wherein the sensor module comprises a Hall effect sensor.

17. The system of claim 14 wherein the sensor module comprises an optical sensor.

18. The system of claim 14 wherein the signal comprises Hall effect edges.

19. A method for controlling an electric motor, the method comprising:

providing power to the electric motor for a first time period, the power being used to cause a rotor of the electric motor to rotate;

subsequent to providing the power, removing the power;

subsequent to removing the power, monitoring a signal for a second time period, the signal being associated with movements of the rotor;

determining whether the rotor is in an oscillation state based on the signal, the rotor being in the oscillation state if the signal is less than a predetermined threshold level for the second time period;

if the rotor is in an oscillatory state:

generating a signal indicating the oscillatory state;

stopping providing power to the rotor for a third time period;

monitoring the signal for a fourth time period.