Active noise control system for attenuating engine generated noise

• US 5,321,759 A
• Filed: 04/29/1992
• Issued: 06/14/1994
• Est. Priority Date: 04/29/1992
• Status: Expired due to Fees

• Current Assignee: General Motors Corporation (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Yuan, Yi
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): LEE, PING
• Application Number:
  US07/875,897
• Time in Patent Office: 776 Days
• Field of Search: 381/71, 381/94, 381/86, 381/72
• US Class Current: 381/71.9
• CPC Class Codes: F01N 1/065 by using an active noise source, e.g. speakers
• 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 2210/1282 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 2210/3042 Parallel processing
• CPC Class Codes: G10K 2210/3046 Multiple acoustic inputs, multiple acoustic outputs
• 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 2210/3212 Actuator details, e.g. composition or microstructure
• CPC Class Codes: G10K 2210/511 Narrow band, e.g. implementations for single frequency cancellation

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 at least one generator output signal that contains one or more sinusoidal signal components, where the frequency of each signal component corresponds to the frequency of a respective noise component. A separate control signal having an amplitude that varies with engine rotational speed is generated to correspond with each generator output signal. Each generator output signal is then multiplied by its respective control signal to produce a corresponding filter input signal. Each filter input signal passes to a respective adaptive filter, where it is filtered to produce a corresponding filter output signal according to the adjustable filtering characteristics of the adaptive filter. Noise canceling waves are generated by a noise canceling actuator in response to each 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 an error signal is developed to represent the residual noise level. The filtering characteristics of each adaptive filter are adaptively adjusted based upon the error signal to minimize the residual noise level. In the preferred embodiment, each control signal has its amplitude determined in accordance with a respective predetermined function based upon the sensed engine rotational speed, and each predetermined function is correlative of the amplitude behavior of those noise components corresponding to the signal components contained in the generator output signal that is multiplied by the respective control signal.

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 sensing engine rotational speed;

means responsive to said engine rotational speed for generating a generator output signal containing at least one sinusoidal signal component, where each sinusoidal signal component has a predetermined constant amplitude, and a frequency corresponding to the frequency of a respective sinusoidal noise component;

means for producing a control signal having an amplitude that varies as a function of the sensed engine rotational speed;

means for multiplying the generator output signal with the control signal to produce a filter input signal;

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

actuator means for generating noise canceling waves in response to the filter 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 to reduce the sensed residual noise level.

2. 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 relation to the time rate of change of engine angular rotational position in an engine operating cycle, the system comprising:

means for sensing the engine angular rotational position in the operating cycle;

means for deriving engine rotational speed by determining the time rate of change of the angular rotational position of the engine in the operating cycle;

means responsive to said engine rotational speed for generating a generator output signal containing at least one sinusoidal signal component, where each sinusoidal signal component has a predetermined constant amplitude, and a frequency corresponding to the frequency of a respective sinusoidal noise component, wherein the generator output signal is derived from predetermined schedule of values based upon the sensed angular rotational position of the engine in the operating cycle;

means for producing a control signal having a varying amplitude that is obtained from a look up table based upon the derived engine rotational speed;

means for multiplying the generator output signal with the control signal to produce a filter input signal;

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

actuator means for generating noise canceling waves in response to the filter 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 to reduce the sensed residual noise level.

3. 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;

signal generating means responsive to said engine rotational speed for producing a plurality of generator output signals, where each generator output signal contains at least one sinusoidal signal component with each sinusoidal signal component having a predetermined constant amplitude and a frequency corresponding to a respective one of the sinusoidal noise components;

means for producing a plurality of control signals each control signal having a varying amplitude determined in accordance with a respective predetermined function based upon the sensed engine rotational speed;

means for multiplying each generator output signal with a respective one of the control signals to produce a corresponding filter input signal;

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

summing means for adding one 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 to reduce the sensed level of residual noise.

4. The system of claim 3, wherein the signal components contained in the generator output signals are partitioned according to the amplitude behavior of their corresponding noise components with respect to engine rotational speed, and the respective predetermined function for each control signal is correlative with the amplitude behavior of those noise components corresponding to the signal components contained in the generator output signal that is multiplied by the resepective control signal.

5. A system for attenuating undesirable noise generated by an internal combustion engine, wherein the undesirable noise contains multiple sinusoidal noise components having amplitudes and frequencies that vary in relation to the time rate of change of engine angular rotation position in an engine operating cycle, the system comprising;

means for sensing the engine angular rotational position in the engine operating cycle;

means for sensing the engine angular rotational position in the engine operating cycle;

means for deriving engine rotational speed by determining the time rate of change of the sensed angular rotational position of the engine in the operating cycle;

means for producing a plurality of generator output signals, where each generator output signal contains at least one sinusoidal signal component, with at least one generator output signal containing multiple sinusoidal signal components, and each sinusoidal signal component having a constant predetermined amplitude and a frequency corresponding to the frequency of a respective one of the sinusoidal noise component, and with each generator output signal being derived from respective predetermined schedule of values based upon the sensed angular rotational position of the engine in the operating cycle;

means for producing a plurality of control signals, each control signal having a varying amplitude determined in accordance with a respective predetermined function based upon the derived rotational speed of the engine;

means for multiplying each generator output signal with a respective one of the control signals to produce a corresponding filter input signal;

a plurality of adaptive filters, each adaptive filter having adjustable filtering characteristics for filtering a respective one of the filter input 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 to reduce the sensed level of residual noise.

6. The system of claim 5, wherein multiple signal components contained in any generator output signal is selected so that the amplitude behavior of their corresponding noise components behave similarly with respect to engine rotational speed, and the respective predetermined function for each control signal is correlative with the amplitude behavior of those noise components corresponding to the signal components contained in the generator output signal that is multiplied by the respective control signal.