Active noise control system for attenuating engine generated noise

• US 5,222,148 A
• Filed: 04/29/1992
• Issued: 06/22/1993
• Est. Priority Date: 04/29/1992
• Status: Expired due to Fees

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Yuan, Yi
• Primary Examiner(s): Isen, Forester W.
• Application Number:
  US07/875,893
• Time in Patent Office: 419 Days
• Field of Search: 381/71, 381/94
• US Class Current: 381/71.9
• CPC Class Codes: F01N 1/065 by using an active noise source, e.g. speakers
• CPC Class Codes: F16L 55/0333 by means of an active system
• CPC Class Codes: G10K 11/17823 Reference signals, e.g. ambient acoustic environment
• CPC Class Codes: G10K 11/17825 Error signals
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17857 Geometric disposition, e.g. placement of microphones
• 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 2210/3032 Harmonics or sub-harmonics
• CPC Class Codes: G10K 2210/3039 Nonlinear, e.g. clipping, numerical truncation, thresholding or variable input and output gain
• CPC Class Codes: G10K 2210/3046 Multiple acoustic inputs, multiple acoustic outputs
• CPC Class Codes: G10K 2210/3053 Speeding up computation or convergence, or decreasing the computational load
• CPC Class Codes: G10K 2210/501 Acceleration, e.g. for accelerometers

Abstract

An active noise control (ANC) system is disclosed for attenuating engine generated noise that contains at least one sinusoidal noise component having an amplitude and frequency that vary with changes in engine rotational speed. The ANC system includes a means for generating an input signal that contains one or more sinusoidal signal components, where each signal component has a frequency corresponding to that of a respective one of the noise components. The input signal is filtered with an adaptive filter having adjustable filtering characteristics to produce a filter output signal. Noise canceling waves are generated by a noise canceling actuator in response to the filter output signal, and the canceling waves are superimposed with the undesirable noise generated by the engine. The level of residual noise resulting from this superposition is sensed and a corresponding error signal is developed. The filtering characteristics of the adaptive filter are adaptively adjusted in accordance with the error signal and sensed indications for the engine rotational speed and acceleration. In the preferred embodiment, the characteristics of the adaptive filter are adjusted according to an algorithm having a convergence factor and a leakage factor, where the value of the convergence factor is scaled as a function of engine acceleration and the value of the leakage factor is scaled as a function of engine speed and acceleration.

Claims

1. A system for attenuating undesirable noise generated by an internal combustion engine, wherein the undesirable noise contains at least one sinusoidal noise component having an amplitude and frequency that vary in accordance with engine rotational speed, the system comprising:

means for generating an input signal containing at least one sinusoidal signal component having a frequency corresponding to the frequency of a respective sinusoidal noise component;

means for sensing engine rotational acceleration;

an adaptive filter having adjustable filtering characteristics for filtering the input signal to produce an output signal;

actuator means for generating noise canceling waves in response to the output signal and for superimposing the generated noise canceling waves with the undesirable noise;

means for sensing a residual noise level resulting from the superposition of the noise canceling waves and the undesirable noise and for developing an error signal representative of the residual noise level; and

means for adaptively adjusting the filtering characteristics of the adaptive filter based upon the error signal and the sensed engine rotational acceleration to reduce the sensed residual noise level.

2. The system of claim 1, wherein the filtering characteristics of the adaptive filter are adaptively adjusted in accordance with an algorithm having a convergence factor and the value of the convergence factor is scaled as a function of the sensed engine rotational acceleration.

3. A system for attenuating undesirable noise generated by an internal combustion engine, wherein the undesirable noise contains at least one sinusoidal noise component having an amplitude and a frequency that vary in accordance with engine rotational speed, the system comprising:

means for generating an input signal containing at least one sinusoidal signal component having a frequency corresponding to the frequency of a respective sinusoidal noise component;

means for sensing engine rotational speed;

means for sensing engine rotational acceleration;

an adaptive filter having adjustable filtering characteristics for filtering the input signal to produce an output signal;

actuator means for generating noise canceling waves in response to the output signal and for superimposing the generated noise canceling waves with the undesirable noise;

means for sensing a residual noise level resulting from the superposition of the noise canceling waves and the undesirable noise and for developing an error signal representative of the residual noise level; and

means for adaptively adjusting the filtering characteristics of the adaptive filter in accordance with the error signal and the sensed engine rotational speed and acceleration to reduce the sensed residual noise level.

4. The system of claim 3, wherein the filtering characteristics of the adaptive filter are adaptively adjusted in accordance with an algorithm having a leakage factor and the value of the leakage factor is scaled as a function of the sensed engine rotational speed and acceleration.

5. The system of claim 3, wherein the filtering characteristics of the adaptive filter are adaptively adjusted in accordance with an algorithm having a convergence factor and a leakage factor, where the value of the convergence factor is scaled as a function of the sensed engine rotational acceleration and the value of the leakage factor is scaled as a function of the sensed engine rotational speed and acceleration.

6. A system for attenuating undesirable noise generated by an internal combustion engine, wherein the undesirable noise contains multiple sinusoidal noise components each having an amplitude and a frequency that vary in accordance with engine rotational speed, the system comprising:

means for sensing engine rotational acceleration;

signal generating means for producing a plurality of generator output signals, each generator output signal containing at least one sinusoidal signal component having a frequency corresponding to a respective one of the sinusoidal noise components;

a plurality of adaptive filters, each adaptive filter having adjustable filtering characteristics for filtering a respective one of the generator output signals to produce a corresponding filter output signal;

summing means for adding each filter output signal to produce an output canceling signal;

actuator means for generating noise canceling waves in response to the output canceling signal and for superimposing the canceling waves with the undesirable noise;

means for sensing a residual noise level resulting from the superposition of the canceling waves and the undesirable noise and for developing an error signal indicative of the residual noise level; and

means for adaptively adjusting the filtering characteristics of each one of the adaptive filters in accordance with the error signal and the sensed rotational acceleration of the engine to reduce the sensed level of residual noise.

7. The system of claim 6, wherein the filtering characteristics of at least one adaptive filter are adaptively adjusted in accordance with an algorithm having a convergence factor and the value of the convergence factor for each adaptive filter is scaled as a function of the sensed engine rotational acceleration.

8. The system of claim 6, wherein the sinusoidal signal components contained in the generator output signals are partitioned according to the behavior of the amplitudes of the corresponding sinusoidal noise components with changes in engine rotational speed.

9. A system for attenuating undesirable noise generated by an internal combustion engine, wherein the undesirable noise contains multiple sinusoidal noise components each having an amplitude and a frequency that vary in accordance with engine rotational speed, the system comprising:

means for sensing engine rotational speed;

means for sensing engine rotational acceleration;

signal generating means for producing a plurality of generator output signals, each generator output signal containing at least one sinusoidal signal component having a frequency corresponding to a respective one of the sinusoidal noise components;

a plurality of adaptive filters, each adaptive filter having adjustable filtering characteristics for filtering a respective one of the generator output signals to produce a corresponding filter output signal;

summing means for adding each filter output signal to produce an output canceling signal;

actuator means for generating noise canceling waves in response to the output canceling signal and for superimposing the canceling waves with the undesirable noise;

means for sensing a residual noise level resulting from the superposition of the canceling waves and the undesirable noise and for developing an error signal indicative of the residual noise level; and

means for adaptively adjusting the filtering characteristics of each one of the adaptive filters in accordance with the error signal and the sensed rotational speed and acceleration of the engine to reduce the sensed level of residual noise.

10. The system of claim 9, wherein the filtering characteristics of each adaptive filter are adaptively adjusted in accordance with an algorithm having a leakage factor and the value of the leakage factor for at least one adaptive filter is scaled as a function of the sensed engine rotational speed and acceleration.

11. The system of claim 9, wherein the filtering characteristics of each adaptive filter are adaptively adjusted in accordance with an algorithm having a convergence factor and a leakage factor, where the value of the convergence factor for at least one adaptive is scaled as a function of the sensed engine rotational acceleration and the value of the leakage factor for at least one adaptive filter is scaled as a function of the sensed engine rotational speed and acceleration.

12. The system of claim 9, wherein the signal components contained in the generator output signals are partitioned according to the amplitude behavior of the corresponding noise components as engine rotational speed changes, so that the adaptive adjustment of the filtering characteristics of each adaptive filter can be tailored in accordance with the amplitude behavior of those engine noise components corresponding to the signal components contained in the respective generator output signal for the adaptive filter.