CN111724761A - Vehicle-mounted active noise control device and method - Google Patents
Vehicle-mounted active noise control device and method Download PDFInfo
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- CN111724761A CN111724761A CN202010433500.XA CN202010433500A CN111724761A CN 111724761 A CN111724761 A CN 111724761A CN 202010433500 A CN202010433500 A CN 202010433500A CN 111724761 A CN111724761 A CN 111724761A
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- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
- G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
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- G10K11/17879—General system configurations using both a reference signal and an error signal
- G10K11/17883—General system configurations using both a reference signal and an error signal the reference signal being derived from a machine operating condition, e.g. engine RPM or vehicle speed
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
- G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
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Abstract
The invention discloses a vehicle-mounted active noise control device and method. The device includes: the rotating speed measuring module is used for acquiring a rotating speed signal of a vehicle engine; the shaping module is used for shaping the rotating speed signal; the clock signal generating module is used for generating a clock signal according to the shaped rotating speed signal; the processing unit is used for generating a reference signal according to the clock signal and filtering the reference signal to generate a control signal; the power amplification module is used for driving a loudspeaker to sound according to the control signal; the microphone is used for acquiring an acoustic response signal of the loudspeaker; and the processing unit is further used for calculating the power of the residual noise in the current clock cycle according to the acoustic response signal, and comparing the power of the residual noise with the power of the residual noise in the previous clock cycle to correspondingly adjust the coefficient of the filter. The invention has less calculation amount and obviously reduces the consumption of calculation resources.
Description
Technical Field
The invention belongs to the technical field of vehicle-mounted noise reduction, and relates to a vehicle-mounted active noise control device and method.
Background
With the increase of the degree of vehicle intelligence, the requirements of drivers and passengers on the acoustic environment in the vehicle are more and more strict. The noise in the automobile can reduce the comfort of drivers and passengers, and cause the dysphoria and fatigue of the passengers in the automobile; the definition of communication and even the perception of the driver to the signal sound outside the vehicle can be influenced, and the traffic hidden trouble is increased. Automotive NVH (Noise, vision, Harshness) is an important concern for automotive plants. The noise is reduced by modifying the structural design and adding damping materials or using devices such as damping springs and the like, the devices are collectively called passive noise control, and the control mode has a good noise reduction effect on middle and high frequency noise. However, such control methods have a poor effect on low frequencies, particularly noise of an engine in a vehicle cabin, road noise caused by collision friction between a road surface and tires, and even airflow wind noise, which are often concentrated on low frequencies. The main sources of noise in the vehicle that are of major concern to the driver and passengers are engine noise, intake and exhaust noise, road tire noise and noise caused by wind excitation. In addition, passive noise control requires a long training time and is difficult to control cost. On the contrary, the scheme of actively reducing noise utilizes the vehicle-mounted audio system, effectively reduces the noise in the carriage, but hardly adds extra balance weight to the automobile, is favorable for reducing exhaust emission, and is a green energy-saving solution.
At present, there are patent documents disclosing vehicle-mounted active noise reduction methods, which are listed as follows:
CN107600011A discloses an active control noise reduction system and method for automobile engine noise, which receives the rotating speed signal of the engine, and filters the square wave signal to obtain the fundamental wave as the reference signal; the reference signal needs to be convoluted with a transfer function, and a general FxLMS algorithm is applied; the way in which the reference signal is constructed is relatively easy to implement.
CN101473370B discloses active noise reduction with adaptive filter leakage adjustment, the active noise reduction system receiving a high delay signal of the engine speed, providing a signal at a reference frequency related to the engine speed, generating an audio signal at a frequency corresponding to a predetermined multiple of the reference frequency; or receiving an engine speed signal from a bus associated with the audio entertainment system; a sine wave signal is generated from the frequency and the general FxLMS algorithm is applied.
CN101473371B discloses determination of active noise reduction engine speed, accepting a low latency signal representing engine speed from a vehicle data bus, transmitting a high latency signal representing engine speed from an entertainment bus; a sine wave signal is generated from the frequency and the general FxLMS algorithm is applied.
CN105164748B discloses adaptive feed-forward noise reduction for motor vehicles, sine wave generator inputs signals related to engine harmonics (including RPM, torque, accelerator pedal position, manifold absolute pressure MAP), thereby determining the frequency of the harmonics to be cancelled; a sine wave signal is generated from the frequency and the general FxLMS algorithm is applied.
CN106089361A discloses an active noise reduction system and method for an engine in a vehicle, which introduces the rotation speed of the engine as a reference signal; how the reference signal is constructed from the engine speed is not explained in detail.
CN106128449A discloses an active noise reduction method for an automobile, in which a microphone (i.e. a microphone) is disposed in an engine compartment, and a noise signal of the engine compartment is collected as a reference signal; the noise reduction effect is influenced by mixing the sound signals in the cabin with other irrelevant noises.
CN106382143B discloses an active noise reduction device and method based on engine speed, which pre-calibrate the corresponding relation between the engine speed and the engine noise, collect the noise signal near the engine, and store the reference noise signal; when the system works normally, reading an engine rotating speed signal through a bus; the calibration process is relatively complex and does not take the difference of noise of the engine under different load conditions into consideration; storing the noise signal also requires a relatively large memory space.
CN107642426A discloses an active control method and system for noise of an automobile engine, which obtains a rotation speed signal of the engine, performs frequency division integration on the rotation speed signal to construct the frequency of an engine order noise reference signal, and generates the reference signal by a cosine function; the method of constructing the reference signal is accurately described, but the calculation amount of the integration operation is large.
CN110246481A discloses an automobile active noise reduction method for predicting the engine speed, which estimates the engine speed according to a brake signal, an accelerator opening signal and an accelerator pedal signal by combining a BP neural network; calling the stored fitting noise audio frequency according to the rotating speed of the engine to play so as to realize noise reduction; the system has too high computational complexity and is difficult to implement on a vehicle-mounted embedded platform.
The active noise reduction method disclosed in the above patent document has the following disadvantages:
1. for constructing the reference signal or its frequency, part of the above-mentioned patent documents describe a method for constructing the reference signal by the engine speed, which is most simply a filtering process to obtain the fundamental frequency signal. However, in the engineering, a fundamental frequency signal with higher signal-to-noise ratio is obtained, and the design and implementation of the filter are more complicated; the existing schemes are complicated in the way of constructing the reference signal.
2. For generating the reference signal, the active noise control systems are all processed in the discrete digital domain. The existing solutions either generate sinusoidal signals or sample analog signals through an analog-to-digital converter, all based on a given sampling rate. Noise signals with different frequencies, and under the same sampling rate, the frequency resolution is different; for ultra-low frequency, too many sampling points, and for slightly higher frequency, few sampling points; but also requires a higher sampling rate to meet sufficient frequency resolution, which further increases the resource consumption of the processor.
3. For the selection of the noise reduction algorithm, the existing scheme adopts a feedforward adaptive algorithm such as FxLMS, either explicitly stated or cited in the existing literature. The key point is that the transfer function (or called response) of the secondary channel needs to be estimated, and the filter with the transfer function characteristic is used for filtering the reference signal; this requires a large amount of computation, especially in a multi-channel control system involving multiple positions in space, which increases exponentially.
Disclosure of Invention
In view of at least one of the above technical problems, an object of the present invention is to provide a vehicle active noise control apparatus and method, which have less calculation amount and significantly reduce the calculation resource consumption.
In order to achieve the purpose, the invention adopts a technical scheme that:
an on-vehicle active noise control device comprising:
the rotating speed measuring module is used for acquiring a rotating speed signal of a vehicle engine;
the shaping module is used for shaping the rotating speed signal;
the clock signal generating module is used for generating a clock signal according to the shaped rotating speed signal;
the processing unit is used for generating a reference signal according to the clock signal and filtering the reference signal to generate a control signal;
the power amplification module is used for driving a loudspeaker to sound according to the control signal; and
a microphone for acquiring an acoustic response signal of the speaker;
and the processing unit is further used for calculating the power of the residual noise in the current clock cycle according to the acoustic response signal, and comparing the power of the residual noise with the power of the residual noise in the previous clock cycle to correspondingly adjust the coefficient of the filter.
Preferably, the processing unit includes:
the signal generation module is used for updating an addressing address according to the triggering of the clock signal so as to read a signal amplitude value from a prestored sine signal lookup table and generate a sine signal and a cosine signal as the reference signal;
an adaptive filtering module, configured to perform filtering processing on the reference signal;
and the noise power monitoring module is used for calculating the power of the residual noise of the current clock cycle, comparing the power with the power of the residual noise of the previous clock cycle and correspondingly adjusting the coefficient of the adaptive filtering module.
Further, the processing unit further includes:
a multiplication module for coefficient update iterations of the adaptive filtering module.
Furthermore, the input end of the multiplication module is electrically connected with the noise power monitoring module, the input end of the multiplication module is also electrically connected with the microphone through the analog-to-digital conversion module, and the output end of the multiplication module is electrically connected with the adaptive filtering module.
Further, the adaptive filtering module includes an adaptive filter that can vary with a trend of a power variation of the residual noise.
Further, the clock signal generation module is a phase-locked loop frequency divider.
The invention also adopts the following technical scheme:
a vehicle-mounted active noise control method comprises the following steps:
s1, acquiring a rotating speed signal of the vehicle engine;
s2, shaping the rotating speed signal;
s3, generating a clock signal according to the shaped rotating speed signal;
s4, generating a reference signal according to the clock signal and filtering the reference signal to generate a control signal; collecting the acoustic response signal of a loudspeaker, calculating the power of the residual noise in the current clock period according to the collected acoustic response signal, and comparing the power with the power of the residual noise in the previous clock period to correspondingly adjust the coefficient of the filter.
Further, the step S4 specifically includes:
s41, generating a reference signal which comprises a sine signal and a cosine signal, counting from the 1 st clock period, starting by a counter cnt, and generating a sine signal x1(k) Sig (k), cosine signal
The second clock cycle, counter cnt +1, k + 1; when counter
Zero clearing counter, k is also zero clearing, sine signal
Cosine signal x2(k) -sig (k); with the counter again accumulating and
zero clearing counter, k is also zero clearing, sine signal x1(k) Cosine signal ═ sig (k)
With the counter again accumulating and
zero clearing counter, k is also zero clearing, sine signal
Cosine signal x2(k) Sig (k); at this time, a complete cycle is finished and is recorded as T; the cycle is repeated, and sine wave signals and cosine signals with fixed frequency resolution are generated along with the clock; wherein k represents a table index in the sine signal table, sig represents a numerical value corresponding to the table index in the sine signal table, and Δ f represents the frequency resolution;
s42, generating control signal y (k) w1*x1(k)+w2*x2(k) Wherein w is1、w2Respectively representing filter coefficients;
s43, picking up the acoustic response signal of the loudspeaker, and recording the acoustic response signal as a residual noise signal e (k);
s44, updating the coefficient of the filter to be w1＝w1+sign*μ*e(k)*x1(k)；w2＝w2+sign*μ*e(k)*x2(k) Wherein sign is a constant representing a positive or negative number, such as sign +1 or sign-1, and μ is a constant for adjusting the convergence step of the algorithm, which affects the convergence effect and stability of the algorithm;
s45, monitoring the noise variation trend,accumulating residual noise power E1＝E1+[e(k)]2Until a complete period T is over; in the next cycle, the residual noise power E is accumulated2＝E2+[e(k)]2(ii) a Comparison E1And E2If E is2＞E1The sign number sign is changed to-sign; otherwise, the number of symbols remains unchanged; two periods T are over and zero clearing E1And E2The monitoring is re-accumulated in the next period T.
Further, the step S4 further includes a step S45 of introducing a leakage factor λ into the filter coefficient update, w1＝(1-λ)*w1+sign*μ*λ*e(k)*x1(k)；w2＝(1-λ)*w2+sign*μ*λ*e(k)*x2(k)。
Further, in step S3, the clock signal is generated by a phase-locked loop divider.
By adopting the scheme, compared with the prior art, the invention has at least one of the following advantages:
according to the vehicle-mounted active noise control device and method, the active noise control system with the time-varying sampling rate is provided, and the clock of the system can change along with the rotating speed of the engine, so that the tracking performance of the system is guaranteed;
the sampling rate changes along with the change of the rotating speed of the engine, and the sampling precision of each noise frequency needing to be controlled is ensured to be consistent, so that less noise reduction is realized;
sine signals generated by sin or cos functions are not needed to be used as reference signals, and the consumption of computing resources is reduced;
the transfer function of a secondary channel does not need to be measured, so that the complexity of training is reduced;
and the reference signal does not need to be filtered, so that the calculation amount is reduced.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a block diagram of a vehicle-mounted active noise control apparatus according to an embodiment of the present invention;
FIG. 2 is a flow chart of the adaptive processing operation within one clock cycle according to an embodiment of the present invention;
fig. 3 is a flowchart of the adaptive processing operation within one cycle period T according to the embodiment of the present invention.
Detailed Description
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the advantages and features of the invention may be more readily understood by those skilled in the art. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention aims to pay attention to engine noise and intake and exhaust noise, the noise frequency is distributed in a low frequency range, an active noise reduction scheme is suitable, the noise frequency component is relatively simple, mainly linear spectrum noise, and the noise frequency is strictly related to the engine speed. Based on this, the present embodiment provides an in-vehicle active noise control device. The vehicle-mounted active noise control device of the embodiment comprises: the device comprises a rotating speed measuring module, a shaping module, a clock signal generating module, a processing unit, a power amplification module, a loudspeaker and a microphone. The apparatus is described in detail below with reference to fig. 1.
And the rotating speed measuring module is used for acquiring a rotating speed signal of the vehicle engine. In this embodiment, the speed measurement module is a sensor of the vehicle, such as a crank signal sensor and/or an ignition pulse signal sensor.
The shaping module is specifically a square wave shaping module, and the input end of the shaping module is electrically connected with the output end of the rotating speed measuring module. The rotating speed signal of the engine is a square wave signal, but due to background noise of a sensor, transmission loss of a transmission line and the like, the waveform may have some noise waves and is not regular enough. In this embodiment, the signal is shaped by the shaping module to filter out clutter, interference waves and the like. A general voltage comparator is specifically selected, and the general voltage comparator is further a Schmitt trigger.
And the clock signal generating module is used for generating a clock signal according to the shaped rotating speed signal, and the input end of the clock signal generating module is electrically connected with the output end of the shaping module. In this embodiment, the clock signal generating module is specifically a pll divider. The square wave signal is passed through a phase-locked loop frequency divider to generate a clock signal. The clock signal is determined by the periodic characteristics of the square wave signal, and the variation of the engine speed can cause the periodic variation of the square wave signal, and the frequency of the clock signal is changed. The period of the clock signal does not completely correspond to the period of the square wave signal, and the present embodiment adjusts the period of the square wave signal by using the parameter of the frequency division number of the phase-locked loop frequency divider.
The processing unit is used for generating a reference signal according to the clock signal and filtering the reference signal to generate a control signal; and meanwhile, the device is also used for calculating the power of the residual noise in the current clock period according to the acoustic response signal, comparing the power with the power of the residual noise in the previous clock period and correspondingly adjusting the coefficient of the filter.
And the power amplifier module is used for driving a loudspeaker to sound according to the control signal output by the processing unit. The input end of the power amplifier module is electrically connected to the output end of the processing unit through the digital-to-analog conversion module. The control signal output by the processing unit is a sweep frequency signal in a digital format, and the digital-to-analog conversion module is used for converting the control signal into an analog signal. The loudspeaker in the embodiment is specifically a door panel loudspeaker installed on an automobile door panel, converts an electric signal into an acoustic signal, and replays in an in-automobile sound field space.
And the microphone is used for synchronously acquiring the acoustic response signals of the loudspeaker in real time. The microphone is electrically connected to the input end of the processing unit through the analog-to-digital conversion module and used for converting the acoustic response signals which are analog signals and collected by the microphone into digital signals.
The processing unit comprises a signal generating module, a self-adaptive filtering module, a noise power monitoring module and a multiplying module. And the input end of the signal generation module is electrically connected with the output end of the phase-locked loop frequency division area, the signal generation module updates an addressing address according to the triggering of each clock signal, reads a signal amplitude value from a sine signal lookup table prestored in the storage unit, and generates a sine signal and a cosine signal which are used as reference signals. The input end of the adaptive filtering module is electrically connected with the output end of the signal generating module and is used for filtering the reference signal, and the coefficient of the filter is updated along with the residual noise signal and the reference signal; in particular, in the present embodiment, the coefficients of the filter also change due to the tendency of the remaining noise power to change. In this embodiment, a general adaptive filter, such as LMS, RLS, or the like, is selected; or adaptive notch filter, which is particularly useful for engine noise reduction. And the input end of the noise power detection module is electrically connected with the output end of the analog-to-digital conversion module, and is used for calculating the power of the residual noise in a fixed period, comparing the power of the residual noise with the power of the noise in the previous period, judging the noise reduction performance of the active noise reduction system, and correspondingly adjusting the updating parameters of the adaptive filter, so that the noise reduction system is ensured to work stably and normally without generating divergence or howling. The multiplication module is used for finishing the function of signal multiplication and updating and iterating the coefficient of the self-adaptive filtering module, one input end of the multiplication module is electrically connected with the output end of the noise power monitoring module, the other input end of the multiplication module is also electrically connected with the microphone through the analog-to-digital conversion module, and the output end of the multiplication module is electrically connected with one input end of the self-adaptive filtering module.
The embodiment also correspondingly provides a vehicle-mounted active noise control method, which comprises the following steps:
s1, acquiring a rotating speed signal of the vehicle engine;
s2, shaping the rotating speed signal;
s3, generating a clock signal according to the shaped rotating speed signal;
s4, generating a reference signal according to the clock signal and filtering the reference signal to generate a control signal; collecting the acoustic response signal of a loudspeaker, calculating the power of the residual noise in the current clock period according to the collected acoustic response signal, comparing the power of the residual noise with the power of the residual noise in the previous clock period, and correspondingly adjusting the coefficient of a filter.
The step S4 specifically includes:
s41, generating a reference signal which comprises a sine signal and a cosine signal, counting from the 1 st clock period, starting by a counter cnt, and generating a sine signal x1(k) Sig (k), cosine signal
The second clock cycle, counter cnt +1, k + 1; when counter
Zero clearing counter, k is also zero clearing, sine signal
Cosine signal x2(k) -sig (k); with the counter again accumulating and
zero clearing counter, k is also zero clearing, sine signal x1(k) Cosine signal ═ sig (k)
With the counter again accumulating and
zero clearing counter, k is also zero clearing, sine signal
Cosine signal x2(k) Sig (k); at this time, a complete cycle is finished and is recorded as T; the cycle is repeated, and sine wave signals and cosine signals with fixed frequency resolution are generated along with the clock; wherein k represents a table index in the sine signal table, sig represents a numerical value corresponding to the table index in the sine signal table, and Δ f represents the frequency resolution;
s42, generating control signal y (k) w1*x1(k)+w2*x2(k) Wherein w is1、w2Respectively representing filter coefficients;
s43, picking up the acoustic response signal of the loudspeaker, and recording the acoustic response signal as a residual noise signal e (k);
s44, updating the coefficient of the filter to be w1＝w1+sign*μ*e(k)*x1(k)；w2＝w2+sign*μ*e(k)*x2(k) Wherein sign is a constant representing a positive or negative number, and μ is a constant for adjusting the convergence step of the algorithm;
s45, monitoring the noise variation trend, and accumulating the residual noise power E1＝E1+[e(k)]2Until a complete period T is over; in the next cycle, the residual noise power E is accumulated2＝E2+[e(k)]2(ii) a Comparison E1And E2If E is2＞E1The sign number sign is changed to-sign; otherwise, the number of symbols remains unchanged; two periods T are over and zero clearing E1And E2The monitoring is re-accumulated in the next period T.
The step S4 further includes a step S45 of introducing a leakage factor λ into the filter coefficient update, w1＝(1-λ)*w1+sign*μ*λ*ek*x1k；w2＝1-λ*w2+sign*μ*λ*ek*x2k。
The active noise control process of the embodiment is as follows:
(1) and generating a sine signal lookup table. Generating a sinusoidal signal sequence off-line from
Frequency resolution Δ f (e.g. frequency resolution selection)
When the frequency resolution is as high as possible, a set of sequences is generated and recorded as
The sequence has 2 pi/deltaf values, and considering the characteristics of the sine wave, the amplitude values in 1/4 periods only need to be generated, and the amplitude of all sampling points can be calculated. Also by using the symmetry property, the amplitudes of all the sampling points of the cosine signal can be calculated. It should be noted that the sampling points are frequency points obtained by normalizing the sampling rate. The smaller the frequency resolution, the higher the number of sequence points, which requires more memory space on the processor, but the finer and smoother the signal generated, which requires trade-offs in the specific engineering. In addition, the sine signal sequence is generated at the PC end, and the calculation resource of the active noise control system is not consumed; the sine signal sequence is stored in a storage unit of the processor, namely a sine signal lookup table.
(2) And initializing parameters. Setting a counter cnt and resetting the counter; setting a filter coefficient w1,w2Zero clearing filter coefficients; the sign number sign is set to 1.
(3) The following are the processing steps of the active noise control system:
1) and obtaining a rotating speed signal of the engine. Attempts have been made to obtain a signal of the engine speed from a source, for example from a sensor of the vehicle itself, such as a crank sensor, an ignition pulse signal, etc. The rotating speed signal of the engine is a square wave signal, the period of the square wave signal changes along with the change of the rotating speed of the engine, the rotating speed signal of the engine is obtained from the source, the delay (more than 10ms at least) of the rotating speed signal obtained from a vehicle communication bus such as a CAN line and the working condition of processing the rapid acceleration are avoided, and therefore the tracking performance of the noise reduction system is prevented from being weakened and the noise reduction performance is prevented from being influenced.
2) And shaping the engine speed signal. The rotating speed signal of the engine is a square wave signal, but due to background noise of a sensor, transmission loss of a transmission line and the like, the waveform may have some noise waves which are not regular enough.
3) And generating a clock signal. The square wave signal passes through a phase-locked loop frequency divider to generate a clock signal; the clock signal is determined by the periodic characteristics of the square wave signal, and the change of the rotating speed of the engine can cause the periodic change of the square wave signal, so that the frequency of the clock signal is changed; the period of the clock signal does not exactly correspond to the period of the square wave signal, and can be adjusted by the parameter of the frequency division number of the phase-locked loop frequency divider.
4) And the clock signal drives the processing unit. The clock signal is fed to a processing unit, and the processing unit is an embedded processing platform in various forms such as an MCU, a DSP or an FPGA; alternatively, the processing unit is a module integrated in the car audio system, or may be a separate component. The processing unit starts to operate according to the period of the clock signal, and mainly operates the self-adaptive filtering algorithm. With reference to fig. 2 and 3, the specific steps are as follows:
i. reference signal generation, mainly generating a sine signal and a cosine signal. From the time of the 1 st clock cycle, the counter cnt starts counting; sinusoidal signal x1(k) Sig (k); cosine signal
The second clock cycle, counter cnt +1, k + 1; when counter
Zero clearing counter, k is also zero clearing, sine signal
Cosine signal x2(k) -sig (k); with the counter again accumulating and
zero clearing counter, k is also zero clearing, sine signal x1(k) -sig (k); cosine signal
With the counter again accumulating and
zero clearing counter, k is also zero clearing, sine signal
Cosine signal x2(k) Sig (k); at this time, a complete cycle is finished and is recorded as T; the above steps are repeated in a circulating way; generating a sine wave signal and a cosine signal with fixed frequency resolution along with a clock; the frequency of the signal corresponds exactly to the clock frequency; as the clock frequency changes; the frequency of the reference signal is changed without delay;
ii. Generating control signal, calculating output signal of main noise control system to obtain y (k) w1*x1(k)+w2*x2(k)；
iii, synchronously picking up microphone signals, and recording as residual noise signals e (k);
iv updating the coefficient of the filter to w1＝w1+sign*μ*e(k)*x1(k)；w2＝w2+sign*μ*e(k)*x2(k)；
v, monitoring the noise variation trend and accumulating the residual noise power E1＝E1+[e(k)]2Until a complete period T is over; in the next cycle, the residual noise power E is accumulated2＝E2+[e(k)]2(ii) a Comparison E1And E2If E is2＞E1The sign number sign is changed to-sign; otherwise, the number of symbols remains unchanged; two periods T are over and zero clearing E1And E2In aMonitoring by accumulating again in the next period T;
vi, introducing a leakage factor into the filter coefficient update, such as:
w1＝(1-λ)*w1+sign*μ*λ*e(k)*x1(k)；
w2＝(1-λ)*w2+sign*μ*λ*e(k)*x2(k)；
to maintain stability of the active noise reduction system.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and are preferred embodiments, which are intended to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (10)
1. An on-vehicle active noise control device, characterized by comprising:
the rotating speed measuring module is used for acquiring a rotating speed signal of a vehicle engine;
the shaping module is used for shaping the rotating speed signal;
the clock signal generating module is used for generating a clock signal according to the shaped rotating speed signal;
the processing unit is used for generating a reference signal according to the clock signal and filtering the reference signal to generate a control signal;
the power amplification module is used for driving a loudspeaker to sound according to the control signal; and
a microphone for acquiring an acoustic response signal of the speaker;
and the processing unit is further used for calculating the power of the residual noise in the current clock cycle according to the acoustic response signal, and comparing the power of the residual noise with the power of the residual noise in the previous clock cycle to correspondingly adjust the coefficient of the filter.
2. The on-vehicle active noise control device according to claim 1, wherein the processing unit includes:
the signal generation module is used for updating an addressing address according to the triggering of the clock signal so as to read a signal amplitude value from a prestored sine signal lookup table and generate a sine signal and a cosine signal as the reference signal;
an adaptive filtering module, configured to perform filtering processing on the reference signal;
and the noise power monitoring module is used for calculating the power of the residual noise of the current clock cycle, comparing the power with the power of the residual noise of the previous clock cycle and correspondingly adjusting the coefficient of the adaptive filtering module.
3. The on-vehicle active noise control device according to claim 2, wherein the processing unit further includes:
a multiplication module for coefficient update iterations of the adaptive filtering module.
4. The vehicle-mounted active noise control device according to claim 3, wherein an input end of the multiplication module is electrically connected with the noise power monitoring module, an input end of the multiplication module is further electrically connected with the microphone through an analog-to-digital conversion module, and an output end of the multiplication module is electrically connected with the adaptive filtering module.
5. The active noise control device according to claim 2, wherein the adaptive filtering module includes an adaptive filter that is variable according to a trend of power variation of the remaining noise.
6. The active noise control device of claim 1, wherein the clock signal generation module is a phase-locked loop divider.
7. A vehicle-mounted active noise control method is characterized by comprising the following steps:
s1, acquiring a rotating speed signal of the vehicle engine;
s2, shaping the rotating speed signal;
s3, generating a clock signal according to the shaped rotating speed signal;
s4, generating a reference signal according to the clock signal and filtering the reference signal to generate a control signal; collecting the acoustic response signal of a loudspeaker, calculating the power of the residual noise in the current clock period according to the collected acoustic response signal, and comparing the power with the power of the residual noise in the previous clock period to correspondingly adjust the coefficient of the filter.
8. The vehicle-mounted active noise control system according to claim 7, wherein the step S4 specifically includes:
s41, generating a reference signal which comprises a sine signal and a cosine signal, counting from the 1 st clock period, starting by a counter cnt, and generating a sine signal x1(k) Sig (k), cosine signal
The second clock cycle, counter cnt +1, k + 1; when counter
Zero clearing counter, k is also zero clearing, sine signal
Cosine signal x2(k) -sig (k); with the counter again accumulating and
zero clearing counter, k is also zero clearing, sine signal x1(k) Cosine signal ═ sig (k)
With the counter again accumulating and
zero clearing counter, k is also zero clearing, sine signal
Cosine signal x2(l) Sig (k); at this time, a complete cycle is finished and is recorded as T; the cycle is repeated, and sine wave signals and cosine signals with fixed frequency resolution are generated along with the clock; wherein k represents a table index in the sine signal table, sig represents a numerical value corresponding to the table index in the sine signal table, and Δ f represents the frequency resolution;
s42, generating control signal y (k) w1*x1(k)+w2*x2(k) Wherein w is1、w2Respectively representing filter coefficients;
s43, picking up the acoustic response signal of the loudspeaker, and recording the acoustic response signal as a residual noise signal e (k);
s44, updating the coefficient of the filter to be w1＝w1+sign*μ*e(k)*x1(k)；w2＝w2+sign*μ*e(k)*x2(k) Wherein sign is a constant representing a positive or negative number, and μ is a constant for adjusting the convergence step of the algorithm;
s45, monitoring the noise variation trend, and accumulating the residual noise power E1＝E1+[e(k)]2Until a complete period T is over; in the next cycle, the residual noise power E is accumulated2＝E2+[e(k)]2(ii) a Comparison E1And E2If E is2＞E1The sign number sign is changed to-sign; otherwise, the number of symbols remains unchanged; two periods T are over and zero clearing E1And E2The monitoring is re-accumulated in the next period T.
9. The active noise control system of claim 8, wherein the step S4 further comprises the step S45 of introducing a leakage factor λ into the filter coefficient update, w1＝(1-λ)*w1+sign*μ*λ*e(k)*x1(k)；w2＝(1-λ)*w2+sign*μ*λ*e(k)*x2(k)。
10. The active noise control system according to claim 7, wherein in step S3, the clock signal is generated by a phase-locked loop divider.
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