Torque ripple sensor and mitigation mechanism

• US 20040079173A1
• Filed: 10/28/2002
• Published: 04/29/2004
• Est. Priority Date: 10/28/2002
• Status: Active Grant

• Current Assignee: Curators of the University of Missouri (University of Missouri)
• Original Assignee: Curators of the University of Missouri (University of Missouri)
• Inventors: Pekarek, Steven D., Neely, Jason, Banaskavich, Jason M., Stutts, Daniel S.
• Granted Patent: US 7,117,754 B2
• Time in Patent Office: Days
• US Class Current: 73/862.333
• CPC Class Codes: H02P 6/10 Arrangements for controlling torque ripple, e.g. providing reduced torque ripple

Abstract

A torque ripple sensor and method for torque ripple sensing and/or mitigation. A piezoelectric sensor is positioned relative to a motor so that torque fluctuations due to torque ripple of the motor are transmitted to the sensor, resulting in strain of a piezoelectric element. A resulting signal can be amplified and conditioned for determining a magnitude of the torque ripple and/or fed into a feedback loop for applying current control or a counter-torque to the motor for torque ripple mitigation.

Claims

1. An apparatus for sensing fluctuations in torque from a permanent magnet machine, the permanent magnet machine being contained in a housing, the apparatus comprising:

a piezoelectric sensor coupled to said permanent magnet machine to receive transmitted vibration produced by the fluctuations of the permanent magnet machine, said piezoelectric sensor producing a sensor signal corresponding to an amplitude of said vibration.

2. An apparatus for sensing fluctuations in torque for a motor, the apparatus comprising:

a piezoelectric sensor disposed relative to said motor to receive a transmitted reaction force from the motor, said piezoelectric sensor producing a sensor signal corresponding to an amplitude of said reaction force.

3. The apparatus of claim 2 wherein said piezoelectric sensor is positioned relative to a housing of the motor and a fixed point relative to the motor to receive said reaction force.

4. The apparatus of claim 3 wherein said fixed point comprises a mount attached to a fixed substrate.

5. The apparatus of claim 3 wherein said fixed point is a fixed substrate, and wherein said piezoelectric sensor is sandwiched between a mount fixed to the motor and said fixed substrate.

6. The apparatus of claim 3 wherein said mount comprises a bracket.

7. The apparatus of claim 3 wherein said piezoelectric sensor comprises a plate-type sensor.

8. The apparatus of claim 2 wherein said piezoelectric sensor comprises an annular piezoelectric element, and wherein said annular piezoelectric element is disposed between a housing of the motor and a substrate mounted to the housing.

9. The apparatus of claim 3 wherein said piezoelectric sensor is attached to a motor housing and stretched between the motor housing and said fixed point, whereby rotation of the motor caused by the fluctuations stretches and releases said piezoelectric sensor to create strain.

10. The apparatus of claim 2 wherein said piezoelectric sensor includes a piezoelectric element insulated by a plurality of non-conducting elements.

11. The apparatus of claim 10 wherein said plurality of non-conducting elements comprises a coating on opposing surfaces of said piezoelectric element.

12. The apparatus of claim 10 wherein at least one of said plurality of nonconductive elements comprises a ceramic substrate.

13. The apparatus of claim 10 wherein said piezoelectric element comprises a poled thin-film of at least one of lead zirconate titanate (PZT) and polyvinylidene fluoride (PVDF).

14. The apparatus of claim 2 wherein said piezoelectric sensor produces a signal linearly proportional to reaction forces of the motor.

15. An apparatus for mitigating fluctuations in torque for a motor, the apparatus comprising:

a piezoelectric sensor that receives a transmitted reaction force from the motor, said piezoelectric sensor producing a sensor signal corresponding to an amplitude of said reaction force;

a feedback mechanism coupled to said sensor for receiving said sensor signal and to said motor, said feedback mechanism supplying a current control signal to the motor based on said sensor signal.

16. The apparatus of claim 15 wherein said feedback mechanism comprises:

a controller that receives said sensor signal from said piezoelectric sensor and produces said current control signal to said motor.

17. The apparatus of claim 16 wherein said feedback mechanism is coupled to said motor for receiving a rotor position and phase signal for the motor.

18. The apparatus of claim 16 wherein said feedback mechanism is an active vibration noise canceling actuator used to reduce vibration transmitted to the motor mount based on said signal from said piezoelectric sensor.

19. The apparatus of claim 16 wherein said feedback mechanism further comprises:

a signal amplifier and conditioner coupled to said piezoelectric sensor for amplifying said sensor signal to produce an amplified signal, which is coupled to said controller.

20. The apparatus of claim 16 wherein said feedback mechanism further comprises:

a multiplication element for acquiring values for harmonics of the torque fluctuations.

21. The apparatus of claim 20 wherein said feedback mechanism further comprises:

a low-pass filter coupled to said convolution element for filtering an output of said convolution element.

22. The apparatus of claim 16 wherein said controller further comprises:

a gain matrix that defines a cost function in terms of torque ripple of the motor.

23. The apparatus of claim 16 wherein said controller reaches steady state when a predetermined cost function involving elements of torque vectors are minimized.

24. The apparatus of claim 16 wherein said current controller substantially eliminates at least one of the sixth and twelfth harmonics of torque ripple.

25. A method of reducing torque ripple in a motor, the method comprising the steps of:

providing a piezoelectric sensor in a position relative to the motor to receive rotational reaction forces transmitted by the motor due to torque ripple and generate a sensor signal correlating to an amplitude of said rotational reaction forces;

processing said sensor signal to produce a control signal including commanded current harmonics;

supplying said control signal to a current controller of the motor to reduce the torque ripple.

26. The method of claim 25 wherein said providing step comprises placing said piezoelectric sensor relative to the motor and a fixed point.

27. The method of claim 25 wherein said processing step comprises the steps of:

correlating said sensor signal with functions of harmonics to create torque values;

filtering said torque values;

defining a cost function in terms of torque ripple based on said filtered values;

minimizing said cost function to produce current for minimizing the torque ripple.