JP3403209B2 - Vehicle interior noise reduction device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for reducing vehicle interior noise, and more particularly to a device for actively reducing low-frequency noise in a vehicle interior closed space. The present invention relates to a device for reducing vehicle interior noise. 2. Description of the Related Art Noise in a passenger compartment of an automobile or the like is caused by the resonance of a vehicle compartment forming a closed space under a certain condition. It is considered that the noise is caused by a rotation order component or the like caused by the explosion of the vehicle, and attempts have been made recently to adaptively reduce such vehicle interior noise, an example of which is shown in FIG. [0003] In the drawing, 1 is a vehicle such as an automobile, 10 is a cabin in the vehicle 1, 11 is an engine, and 12 is an engine 11
An engine vibration sensor or an engine speed sensor as a means for detecting a reference signal synchronized with the rotation of the vehicle, a microphone 13 for detecting a noise level in the cabin 10, a speaker 14 for generating a sound for reducing noise, and 15 is the cabin 1
It is a sheet within 0. [0004] Further, reference numeral 2 denotes a sensor 1 installed in the vehicle 1.
A controller for identifying the reverse transfer characteristic of the transfer characteristic of the vehicle interior space transfer system including the vehicle body vibration system excited by the vibration of the engine by the output of the microphone 2 and the engine 13, and converts the analog output of the sensor 12 into a digital output. / D converter 2
1 and the spatial transfer characteristic G between the speaker and the microphone measured in advance for the digital output signal of the A / D converter 21.
D, a filter 22 for inputting an output signal of the filter 22 as a reference signal, and a D / D converter for converting the output signal of the adaptive filter 23 into an analog signal.
A converter 24, switch 25 for turning on / off the analog signal, power amplifier 25 for amplifying the output signal of switch 25 and supplying it to speaker 14, and converting the analog output of microphone 13 to a digital signal for adaptation. An A / D converter 27 for providing a control signal to the filter 22; a white noise source 31; a switch 32 for turning on / off white noise from the white noise source 27; and a digital signal from the switch 32 converted to an analog signal D / A applied to the speaker 14 via the power amplifier 25
It comprises a converter 34 and a timer 35 for controlling the switches 25 and 32 based on the on / off of the key switch 16. [0005] In the operation of the configuration of FIG.
The initial identification mode shown in FIG. 4 and the normal identification mode shown in FIG. 5 can be divided. When the key switch 16 is turned on, the timer 35 turns on the switch 32 and turns off the switch 25 for a certain period of time. Enter identification mode,
After the elapse of this predetermined period, the latest tap coefficient of the adaptive filter 33 is copied to the filter 22 as the space transfer function GD, and the timer 35 turns off the switch 32 and turns on the switch 25 in FIG. Normal mode is entered. First, the initial identification mode shown in FIG. 4 will be described. The distance between the speaker and the microphone in the vehicle compartment and the atmospheric pressure, temperature, humidity, etc. of the vehicle environment differ depending on the vehicle. If not considered, the operation becomes unstable, the convergence time is delayed, and the effect of reducing the residual noise is deteriorated. Therefore, in order to obtain the space transfer characteristic (acoustic characteristic) GD between the speaker and the microphone, the system shown in FIG. Instead of using the vibration component from 11, the white noise of the digital signal generated from the white noise (random number sequence) source 31 provided in the controller 2 is converted into an analog signal by the D / A converter 34 and the amplifier 26. The converted white noise signal is picked up by the microphone 13 via the passenger compartment 10 and output from the speaker 14.
The / D converter 25 converts the digital signal into a digital signal and controls the adaptive filter 33 receiving white noise. FIG. 6 shows an example of the configuration of the adaptive filter 33. Examples of the adaptive algorithm in this case include a well-known steepest descent method, a learning identification method, and an LMS method. The method is as follows. That is, Z ^-1 denotes a delay element for delaying the input signal X (n) for each sample, and h (0) to h (n-
1) is a filter (tap) coefficient for multiplying the output signal of each delay element Z ^-1 , and each filter coefficient is L
It is updated on a sample-by-sample basis according to the MS algorithm: h (n + 1) = h (n) +2 μe (n) X (n). Where n = 0... I,
μ is the above-mentioned step size. By selecting the step size μ in this case, the convolution operation of multiplying and adding the filter coefficient to the input signal X (n) of each sample and performing an output to the speaker 14 is performed. Signal y
(n) is required. Then, the speaker output y (n) is transmitted to the microphone 13 via the cabin 10 so that an error component e reduced by the component Y (n) attenuated by the cabin 10 is output from the microphone 13. (n) = Y (n) −y (n) is generated,
If the filter coefficient is updated for each sample so that the microphone output e (n) converges to the minimum value using the LMS algorithm, the characteristic GD of the vehicle interior space transmission system can be identified. Thus, the characteristic G of the vehicle interior space transmission system is obtained.
D is actually measured and obtained, so in the adaptive control in the normal identification mode shown in FIG. 5, the spatial transfer characteristic GD from the speaker 14 to the microphone 13 and the
The transfer characteristic GP from the engine mount including the transfer characteristic GC of the transfer system up to the microphone 13 to the microphone 13 is GP = GD + G
C, therefore, after the elapse of the predetermined time set by the timer 35, only the remaining transfer characteristics GC are identified by the adaptive filter 23 in FIG. In the case of the adaptive control shown in FIG. 5, the input signal is the engine vibration component X (n) from the vibration sensor 12, and the component Y (n) corresponds to the occupant's ear noise in the seat. Become. In this way, the speaker measured in advance
The filter 22 of the space transfer characteristic GD between the microphones is provided with the filter coefficients h1... Hn obtained by the adaptive filter 33 to have a fixed filter configuration as shown in FIG. As a result, adaptive control can be performed from the beginning in consideration of the transmission delay between the loudspeaker and the microphone, and changes in the characteristics of the vibration transmission system, which follows the frequency change accompanying the engine speed change and changes from engine vibration to vehicle interior noise. , And further follows transmission characteristics that vary depending on the number of occupants, thereby improving the degree of convergence and improving the effect of reducing residual noise. The transmission characteristics of the space determined as described above are as follows. The transmission speed v of the sound wave in the atmosphere is as follows: v = 331.5 + (1 + t / 273) ^1/2 ≒ 331.5 + 0. It has been theoretically and experimentally confirmed that the temperature is greatly dependent on the temperature t. Particularly, in a vehicle cabin, a large temperature change may occur even in a daily driving condition. For example, under a hot summer sun, the vehicle cabin temperature may be around 60 to 70 ° C., while the air in the vehicle cabin is effectively cooled. And the temperature inside the vehicle becomes 20 to 30 ° C., and the difference (absolute value) becomes 30 to 50 ° C. In cold regions, the temperature inside the cabin is minus tens of degrees.
When the temperature becomes C and the heater is activated, the temperature becomes about 20 ° C. In this case, the difference (absolute value) becomes 30 to 40 ° C. On the other hand, the above-described measurement of the transfer characteristics in the vehicle compartment is performed within a fixed time after the engine is started. However, the transfer characteristics differ greatly immediately after the start of the engine and when the temperature in the vehicle compartment becomes constant. (See FIGS. 8 (a) and 8 (b)), and it is necessary to cope with the change in the transfer characteristic. If no countermeasure is taken, the adaptive filter 23 of the main control system which operates in the normal identification mode is used. The change in the transfer characteristics must be absorbed. That is, assuming that the spatial transfer characteristic between the speaker and the microphone at the temperature t1 ° C. immediately after the start of the engine is A and the spatial transfer characteristic at the temperature state t2 ° C. in the steady state is B, When the room temperature and the corresponding engine temperature are controlled by the transfer characteristic B of the space when the engine temperature is in a steady state, the characteristic of BA is adaptively controlled by the main control system using the adaptive filter 23. Will occur. If the transfer characteristics of the space cannot be accurately identified, control accuracy will deteriorate. There is a limit in the adaptation area in the main control system, and beyond this, abnormal phenomena such as oscillation occur. This identification work takes a certain amount of time and is executed every time the key switch is turned on. When the frequency increases, the user feels troublesome. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to realize a device for reducing vehicle interior noise in which control is not oscillated without troublesome identification every time. In order to solve the above-mentioned problems, a vehicle interior noise reduction device according to the present invention includes a means for detecting a reference signal synchronized with the rotation of an engine, and a device provided in the vehicle interior. Speaker, a microphone for detecting vehicle interior noise, and a spatial signal transfer characteristic between the speaker and the microphone by the first adaptive filter in the initial identification mode by white noise based on the ON signal of the key switch, and the reference in the normal identification mode. The signal gives an inverse transfer characteristic to the transfer characteristic of the vehicle interior space transmission system including the vehicle body vibration system .
To the second adaptive filter placed in series with the
Spatial transfer characteristic pixels in accordance with a more identified tap coefficients of the second <br/> adaptive filter used in the normal identification mode with the input of the microphone for controlling the speaker so as to minimize
Correct from the maximum value so as to be positioned in the middle of the minimum value, or more
The tap coefficient is also located between the maximum value and the minimum value.
And a controller to make it possible. According to the present invention, when the driver first turns on the key switch, the controller measures the spatial transfer characteristic between the loudspeaker and the microphone by the first adaptive filter in the initial identification mode by white noise, and then measures the characteristic. In the normal identification mode using the space transfer characteristics, the reverse transfer characteristics to the transfer characteristics of the vehicle interior space transfer system including the vehicle body vibration system are identified by a reference signal synchronized with the rotation of the engine so that the microphone input is minimized. To control the speaker. [0020] In this case, the controller typically monitors the tap coefficient <br/> number of second adaptive filter used in the identification mode, the tap coefficients (transfer characteristic) to a value within the desired range The spatial transfer characteristic obtained in the initial identification mode is corrected so as to be as follows. Thus, the second mode used in the normal identification mode can be used .
In this adaptive filter, since it is not necessary to compensate for the change in the spatial transfer characteristic used in the initial identification mode, adaptive control can be realized in a normal manner, and control accuracy is improved. FIG. 1 shows an embodiment of a vehicle interior noise reduction apparatus according to the present invention. In this embodiment, a judgment unit 36 is provided, as compared with the conventional example of FIG. The tap coefficient of the adaptive filter 23 in the main control system is constantly monitored, and the spatial transfer characteristic GD of the filter 22 provided as the tap coefficient of the adaptive filter 33 in the initial identification system is corrected accordingly. FIG. 2 conceptually shows the interior noise reduction device shown in FIG. 1. As shown in FIG. 2A, the driver first turns on the key switch 16 shown in FIG. When
The controller 2 measures the spatial transfer characteristic GD between the speaker 14 and the microphone 13 by the initial identification system C (see FIG. 4) based on the white noise from the white noise source 31,
Using the space transfer characteristic GD, the main control system M determines a reverse transfer characteristic with respect to the transfer characteristic of the vehicle interior space transfer system including the vehicle body vibration system by a reference signal synchronized with the rotation of the engine 11.
The speaker 14 is controlled so that the input of the microphone 13 is identified and minimized (see FIG. 5). In the control system of the controller 2, the space transfer characteristic (tap coefficient of the adaptive filter 33 of the initial identification system) GD obtained by the initial identification ideally as shown in FIG. It is located at an intermediate position between the maximum value and the minimum value (which can be experimentally obtained as an optimum value of the impulse response), and the space transfer characteristic GD
That is, the tap coefficient of the adaptive filter 23 of the main control system M for performing the normal identification using the filter 22 (see FIG. 7) also exists in the intermediate predetermined range from the maximum value to the minimum value. However, when the space transfer characteristic GD of the adaptive filter 33 of the initial identification system C greatly changes from the initial identification value to the maximum value side as shown in FIG. Unless the transfer characteristic GD is re-identified and given to the filter 22, the main control system M performs adaptive control with the initial identification value as it is and attempts to absorb the change.
As a result of deviating out of the adaptive control range, an abnormal phenomenon in which the control system oscillates or a situation in which the adaptive control does not converge occurs. Therefore, in the embodiment of the present invention, as shown in FIG. 3D, the judging section 36 monitors the tap coefficient of the adaptive filter 23 of the main control system M, for example, in a control range or a state like that shown in FIG. If so, the determination unit 36 detects this and corrects the tap coefficient of the filter 22 from the initial value so that the tap coefficient of the adaptive filter 23 of the main control system M finally falls within the range by the tap coefficient. Perform control. The determining operation of the determining unit 36 is not limited to every sample and may be performed every several tens or several hundred cycles. As described above, the main control system M does not need to compensate for the change in the space transfer characteristic GD.
Adaptive control can be realized in a normal manner, and control accuracy is improved. As described above, in the vehicle interior noise reduction apparatus according to the present invention, when the key switch is turned on, the space transfer characteristic between the speaker and the microphone is initially identified by white noise, and the normal operation is performed. In the identification mode, a reference signal is used to identify an inverse transfer characteristic with respect to a transfer characteristic of a vehicle interior space transfer system including a vehicle body vibration system, and the space transfer characteristic is desired according to a tap coefficient of an adaptive filter used in the normal identification mode.
Equivalent since also the tap coefficients modified Te than the range of the configuration so that such a desired range, even without each time the initial identification operation it even in the event of a change of the spatial transfer characteristic due to change in environmental temperature of the vehicle The same effect as when the initial identification is performed every time can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of an embodiment of a vehicle interior noise reduction device according to the present invention. FIG. 2 is a diagram for explaining the operation of the vehicle interior noise reduction device according to the present invention. FIG. 3 is a block diagram showing a configuration example of a conventional vehicle interior noise reduction device. FIG. 4 is a block diagram showing a configuration for measuring a spatial transfer characteristic between a speaker and a microphone in an initial identification mode. FIG. 5 is a block diagram showing a configuration for measuring a reverse transmission characteristic with respect to a transmission characteristic of a vehicle interior space transmission system including a vehicle body vibration system in a normal identification mode. FIG. 6 is a block diagram showing a configuration of an adaptive filter used in a vehicle interior noise reduction device according to the present invention and a conventional example. FIG. 7 is a block diagram showing a configuration of a filter having a filter coefficient obtained by initial identification. FIG. 8 is a graph showing a change in transfer characteristics with temperature. [Description of References] 1 Vehicle 2 Controller 10 Cabin 11 Engine 12 Engine vibration sensor (engine speed sensor) 13 Microphone 14 Speaker 16 Key switch 22 Filters 23 and 33 Adaptive filter 31 White noise source 36 Judgment unit Indicates the same or corresponding parts.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazumi Yamaguchi 8 Tsuchiya, Fujisawa-shi, Kanagawa Transtron Co., Ltd. Fujisawa Plant (58) Field surveyed (Int.Cl. ⁷ , DB name) G10K 11 / 178 B60R 11/02

Claims (1)

(57) [Claim 1] Means for detecting a reference signal synchronized with rotation of an engine, a speaker provided in a vehicle interior, a microphone for detecting vehicle interior noise, and an ON signal of a key switch First adaptive filter in initial identification mode due to white noise
Identifying the spatial transfer characteristics between the microphone, - a speaker by motor
In the normal identification mode, the reference signal indicates the reverse transfer characteristic with respect to the transfer characteristic of the vehicle interior space transfer system including the vehicle body vibration system ,
The spatial transfer characteristic is arranged in series with a given filter.
Spatial transfer characteristics up to its depending on tap coefficients of the adaptive filter of the second used in the normal identification mode with the input of the identified said microphone by the second adaptive filter for controlling the speaker so as to minimize the Intermediate value to minimum
So that the tap coefficient is also at its maximum value.
And a controller that is located at an intermediate position between the minimum value and the minimum value .