Hybrid analog/digital vibration control system

• US 5,841,876 A
• Filed: 11/15/1996
• Issued: 11/24/1998
• Est. Priority Date: 04/07/1993
• Status: Expired due to Fees

• Current Assignee: Noise Cancellation Technologies, Inc. (NCT Group, Inc.)
• Original Assignee: Noise Cancellation Technologies, Inc. (NCT Group, Inc.)
• Inventors: Trinder, Michael Charles John, Gifford, Carl S., Jones, Owen
• Primary Examiner(s): Kuntz, Curtis A.
• Assistant Examiner(s): LEE, PING
• Application Number:
  US08/749,718
• Time in Patent Office: 739 Days
• Field of Search: 381/71.14, 381/71.13, 381/71.11, 381/71.9, 381/71.8, 381/71.1, 381/71.2
• US Class Current: 381/71.14
• CPC Class Codes: F16F 13/26 characterised by adjusting or regulating devices responsive to exterior conditions F16F13/101 takes precedence
• CPC Class Codes: F16F 15/002 characterised by the control method or circuitry control of mechanical oscillations per se G05D19/00
• CPC Class Codes: F16F 15/02 Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems F16F15/005 takes precedence ; layered products B32B; suppression of vibration in ships B63; relieving load on bearings, using magnetic means F16C39/06
• CPC Class Codes: G10K 11/17825 Error signals
• CPC Class Codes: G10K 11/17833 by using a self-diagnostic function or a malfunction prevention function, e.g. detecting abnormal output levels
• CPC Class Codes: G10K 11/17853 of the filter
• CPC Class Codes: G10K 11/17875 using an error signal without a reference signal, e.g. pure feedback
• CPC Class Codes: G10K 11/17883 the reference signal being derived from a machine operating condition, e.g. engine RPM or vehicle speed
• CPC Class Codes: G10K 2210/121 Rotating machines, e.g. engines, turbines, motors; Periodic or quasi-periodic signals in general
• CPC Class Codes: G10K 2210/1282 Automobiles
• CPC Class Codes: G10K 2210/129 Vibration, e.g. instead of, or in addition to, acoustic noise
• CPC Class Codes: G10K 2210/1291 Anti-Vibration-Control, e.g. reducing vibrations in panels or beams
• CPC Class Codes: G10K 2210/3013 Analogue, i.e. using analogue computers or circuits
• CPC Class Codes: G10K 2210/30232 Transfer functions, e.g. impulse response
• CPC Class Codes: G10K 2210/3026 Feedback
• CPC Class Codes: G10K 2210/3027 Feedforward
• CPC Class Codes: G10K 2210/3032 Harmonics or sub-harmonics
• CPC Class Codes: G10K 2210/3037 Monitoring various blocks in the flow chart
• CPC Class Codes: G10K 2210/3042 Parallel processing
• CPC Class Codes: G10K 2210/3045 Multiple acoustic inputs, single acoustic output
• CPC Class Codes: G10K 2210/3211 : Active mounts for vibrating structures with means to actively suppress the vibration, e.g. for vehicles
• CPC Class Codes: G10K 2210/3213 : Automatic gain control [AGC]
• CPC Class Codes: G10K 2210/501 : Acceleration, e.g. for accelerometers
• CPC Class Codes: G10K 2210/503 : Diagnostics; Stability; Alarms; Failsafe
• CPC Class Codes: G10K 2210/511 : Narrow band, e.g. implementations for single frequency cancellation

Abstract

A vibration control system includes a processor-based circuit which monitors and controls an analog vibration control circuit. The system include, a sensor to detect the undesirable vibrations and a synchronous pulse generator for determining the fundamental frequency of the vibrations emitted by the source. An actuator produces anti-noise to counter unwanted vibrations. The processor circuit tests the system, monitors system functions, and adjusts various parameters to provide optimal performance.

Claims

1. An active feedback noise cancellation system, comprising:

a sensor for detecting a residual vibration having a periodic component, said residual vibration comprising the sum of an unwanted vibration to be canceled and a canceling vibration which operates to cancel the unwanted vibration, and generating a residual signal according to said detected residual vibration;

a control circuit connected to said sensor for receiving said residual signal from said sensor, wherein said control circuit includes a plurality of narrow bandpass filters connected in parallel that filter said residual signal to produce an electrical canceling signal, wherein each narrow bandpass filter of the plurality of narrow bandpass filters has an adjustable center frequency responsive to the frequency of said periodic component and adjusted to maintain within its passband a frequency related to said periodic component of said residual signal in order to achieve stability of said active feedback noise cancellation system over a wide range of harmonic frequency components;

an actuator connected to said control circuit for receiving said filtered electrical canceling signal and generating the canceling vibration according to said filtered residual signal; and

a means for testing said noise cancellation system connected to said sensor;

wherein each said filter is tuned to the frequency of said periodic component so that said periodic component of said residual signal is transmitted to said actuator.

2. An active noise cancellation system according to claim 1, wherein each said filter is a tunable bandpass filter, and wherein said filter is tuned so as to maintain within its passband a selected frequency related to said periodic component of said residual signal.

3. An active noise cancellation system according to claim 1, wherein a first narrow bandpass filter of said plurality of narrow bandpass filters is tuned to a different frequency than a second narrow bandpass filter of said plurality of narrow bandpass filters.

4. An active noise cancellation system according to claim 3, including means for dynamically varying the -3 dB frequency of said second narrow bandpass filter as a function of a preselected frequency of said periodic component of said residual signal.

5. An active noise cancellation system according to claim 1, further comprising means connected to said plurality of narrow bandpass filters for dynamically determining the frequency of said periodic component of said residual signal and dynamically tuning said plurality of narrow bandpass filters according to said dynamically determined frequency.

6. An active noise cancellation system according to claim 1, wherein said center frequencies of said plurality of narrow bandpass filters are tuned to integer multiples of the frequency of said periodic component.

7. An active noise cancellation system according to claim 1, wherein said control circuit includes means for dynamically varying the operating parameters of said plurality of narrow bandpass filters to maintain stable operations of said system over a predetermined range of frequencies.

8. An active noise cancellation system according to claim 7, wherein said operating parameter varying means includes a microprocessor connected to said residual vibration sensor and said plurality of narrow bandpass filters for receiving said residual signal, calculating a current transfer function of said system, and adjusting said filtered residual signal according to said calculated current transfer function.

9. An active noise cancellation system according to claim 8, wherein said operating parameter varying means further comprises an equalizer connected in series with said plurality of narrow bandpass filters, said sensor, and said actuator for adjusting said signal, wherein said microprocessor is connected to said equalizer for receiving said residual signal, calculating a current transfer function of said system based on said equalizer processed residual signal and said residual signal sensed by said sensor, and adjusting said equalizer according to said calculated current transfer function.

10. An active noise cancellation system according to claim 7, wherein said operating parameter varying means includes a microprocessor connected to said plurality of narrow bandpass filters and said sensor, wherein said microprocessor receives said residual signal from said sensor, processes said residual signal, and adjusts the portion of said residual signal transmitted by said plurality of narrow bandpass filters according to said processed residual signal.

11. An active noise cancellation system according to claim 10, wherein said microprocessor selects a predetermined number of frequency components of said residual signal based at least partially on the amplitudes of said frequency components, and adjusts said residual signal transmitted by said plurality of narrow bandpass filters according to said selected frequency components.

12. An active noise cancellation system according to claim 11, wherein at least one of said selected frequency components is a constant frequency component of said residual signal.

13. An active noise cancellation system according to claim 7, wherein said operating parameter varying means includes means for adjusting the gain of said noise cancellation system.

14. An active noise cancellation system according to claim 7, wherein said operating parameter varying means includes means for adjusting the quality factor Q of said plurality of narrow bandpass filters.

15. An active noise cancellation system according to claim 7, wherein:

said residual vibration includes a periodic component; and

said each narrow bandpass filter of said plurality of narrow bandpass filters is tuned to the frequency of said periodic component so that said periodic component of said residual signal is transmitted to said actuator.

16. An active noise cancellation system according to claim 15, wherein said operating parameter varying means includes a microprocessor connected to said residual wave sensor and said plurality of narrow bandpass filters for receiving said residual signal, calculating transfer function of said system, and adjusting said filtered residual signal according to said calculated current transfer function.

17. An active noise cancellation system according to claim 16, wherein said operating parameter varying means further comprises an equalizer connected in series with said plurality of narrow bandpass filters, said sensor, and said actuator for adjusting said signal, wherein said microprocessor is connected to said equalizer for receiving said residual signal, calculating a current transfer function of said system based on said equalizer processed residual signal and said residual signal sensed by said sensor, and adjusting said equalizer according to said calculated current transfer function.

18. An active noise cancellation system according to claim 15, wherein said operating parameter varying means includes a microprocessor connected to said filter and said sensor, wherein said microprocessor receives said residual signal from said sensor, processes said residual signal, and adjusts the portion of said residual signal transmitted by said plurality of narrow bandpass filters according to said processed residual signal.

19. An active noise cancellation system according to claim 18, wherein said microprocessor selects a predetermined number of frequency components of said residual signal based at least partially on the amplitudes of said frequency components, and adjusts the portion of said residual signal transmitted by said plurality of narrow bandpass filters according to said selected frequency components.

20. An active noise cancellation system according to claim 19, wherein at least one of said selected frequency components is a constant frequency component of said residual signal.

21. An active noise cancellation system according to claim 15, wherein said operating parameter varying means includes means for adjusting the gain of said noise cancellation system.

22. An active noise cancellation system according to claim 15, wherein said operating parameter varying means includes means for adjusting the quality factor Q of said filter.

23. An active noise cancellation system according to claim 1, wherein said testing means comprises a microprocessor for providing a test signal over a range of frequencies to said actuator, receiving said residual signal in response to said test signal provided to said actuator, and analyzing amplitude and phase components of said residual signal to determine the operational status of said cancellation system.

24. An active noise cancellation system according to claim 23, wherein said testing means comprises:

a test signal generator connected to said actuator for providing said test signal to said actuator;

a receiver for receiving said residual signal from said sensor in response to said test signal; and

a testing circuit for testing said amplitude and phase components of said received residual signal.

25. The system of claim 1, wherein said plurality of narrow bandpass filters is a plurality of switched capacitor bandpass filters and each narrow bandpass filter of said plurality of narrow bandpass filters is a switched capacitor bandpass filter.

26. An active noise cancellation system according to claim 25, wherein said control circuit includes an anti-aliasing filter connected in series with said plurality of switched capacitor bandpass filters and a compensating filter connected in series with said plurality of switched capacitor bandpass filters for adjusting said plurality of switched capacitor bandpass filters to correct the effects of said anti-aliasing filter, wherein the compensating filter has a phase characteristic that is complementary to a phase characteristic of the anti-aliasing filter and reduces delay in the active noise cancellation system.