WO2019007700A1

WO2019007700A1 - Noise cancellation system

Info

Publication number: WO2019007700A1
Application number: PCT/EP2018/066654
Authority: WO
Inventors: Nicolas DRIOT; Dirk Wiemeler; Roland Moschel
Original assignee: Tenneco Gmbh
Priority date: 2017-07-07
Filing date: 2018-06-21
Publication date: 2019-01-10

Abstract

The invention relates to a method for operating a motor vehicle noise cancellation system (1) comprising a Helmholtz resonator (2) with a Helmholtz chamber (13), a neck (3), and a connection opening (4); a speaker (5) within the Helmholtz resonator; a complex variable resistance (6) which is electrically connected to the speaker; a control unit (7) for changing the complex variable resistance (6); and an ECU unit (8) as part of the motor controller for supplying at least the rotational speed RPM as a motor parameter, wherein the Helmholtz resonator can be connected to an exhaust gas line or inlet line (9) of an internal combustion engine via the neck, and the speaker (5) partly delimits the volume of the Helmholtz resonator (2). In order to achieve a value for the acoustic impedance at the connection opening, a value Z2 for the acoustic impedance directly upstream of the speaker (5) is first ascertained according to (formula I), a target value Z 20 is ascertained for Z 2 according to (formula II) when Z 1=0, and subsequently the complex resistance (6) is set to an artificial electric impedance ZL, which is ascertained according to (formula III), such that the noise at the connection opening can be at least partly canceled.

Description

"

Noise Reduction System

The invention relates to a method for operating a motor vehicle noise suppression system comprising a Helmholtz resonator with a Helmholtz chamber, a neck and a connection opening, a loudspeaker within the Helmho! Tzresonators, a variable variable resistance, which is connected to the speaker, a control unit for varying the variable complex resistance and comprising an ECU unit as part of the engine control for obtaining at least the rotational speed RPM as engine parameter, wherein the Helmholtz resonator is connectable via the neck to an exhaust or intake pipe of an internal combustion engine, wherein the speaker is the volume of the Helmholtz resonator limited.

It is already known from DE 10 2013 112 409 A1 a system having a Helmholtz resonator, in the end a speaker is placed. The active system generates and / or influences vehicle noise, in particular engine noise, intake noise and exhaust noise. The system further includes a controller that may process data from at least one downstream error microphone and a motor controller to calculate control signals for the speaker therefrom. Further, a control signal may be generated for a single tone with a constant fundamental frequency.

Furthermore, an intake noise damping system with an actively tuned Helmholtz resonator is known from EP 1 085 201 B1. Inside the Helmholtz resonator, a loudspeaker is installed that shares the volume of the Helmholtz resonator. The loudspeaker can be used to change the absorption frequency of the Helmholtz resonator. The control signal of the loudspeaker is only dependent on the motor frequency. This is detected by a frequency sensor.

Another active silencer is known from WO 98/22700 A2. The muffler has a Helmholtz resonator, on the rear wall of a speaker is provided. The loudspeaker is controlled by a control unit. regulates which measurements are taken into account by a sound pressure transducer. The speaker is controlled so that its vibrations affect the reflection properties on the back wall of the Helmholtz resonator. In this procedure, the acoustic resistance of the loudspeaker diaphragm is adjusted to control the resonant frequency of the Helmholtz resonator. An active generation of a sound wave is not provided.

From EP 2 384 023 A1 a communication system is known. To suppress noise, a speaker is used as a sound sensor in this communication system. From WO 2006/048557 A1 a passive Helmholtz resonator for an exhaust system is known, whose impedance frequency is set by means of a loudspeaker placed on the back wall of the resonator. For this purpose, discrete, sometimes complex resistors are provided, which are switched depending on the motor speed in order to ensure the highest possible sound attenuation. A control unit controls the circuit of the resistors based on the speed.

US 2015/0303884 A1 shows a drive device for driving a loudspeaker, which comprises an amplifier, a voltmeter and a device for activating the diaphragm. DE 42 26 885 A1 shows a sound absorption method for motor vehicles in which sound pressure values are generated by means of a loudspeaker and in which sound pressure is absorbed by means of a Helmholtz resonator, wherein cavity body volumes are simulated by the generated sound pressure values. From WO 2014/053994 A1 a system for broadband noise suppression is known. The noise reduction takes place in two steps. First, electrical, mechanical and acoustic parameters of the loudspeaker in the noise environment are determined. Finally, these parameters are used to calculate the impedance to be connected to the speaker to control the speaker's acoustic response for noise suppression pretend. For further adaptation, the current voltage is measured on the loudspeaker, which is converted into a current via a transfer function. This current is applied to the loudspeaker. The object of the invention is to design and arrange a motor vehicle noise suppression system in such a way that an improved effect is achieved.

In particular, engine noises, intake noises and exhaust noises are referred to as motor vehicle noises.

The object is achieved according to the invention by the fact that in order to obtain a value Zi for the acoustic impedance at the connection opening, first a value Z ₂ for the acoustic impedance directly in front of the loudspeaker is obtained.

, "

averages to Z ₂ =

as angular frequency of the firing order, with N as engine order, l _a [kg / m ⁴ ] as mass inertia of the fluid at the port, R _a [kg / m ⁴ s] as loss of damping at the port and C _a [m ⁴ s ² / kg ] as the conformity constant for the fluid in the Helmholtz resonator and for

a target value Z ₂ o for Z _{2 is} determined by

and then adjusting the complex resistance to an artificial electrical impedance Z _L which is detected

Z _L = -Z _e + [Ohm] with Z _e [Ohm] as the electrical impedance of the loudspeaker, Z _m [kg / s] as the mechanical impedance of the loudspeaker, Bl [Tm] as the loudspeaker coil power factor, S [m ² ] as Speaker surface, so that the noise at the connection opening are at least partially or largely extinguished. This ensures that the speaker can be supplied with any artificial impedance and thus a comprehensive noise cancellation at the end of Helmholtz resonator is possible. The noise cancellation takes place in particular in the exhaust or inlet pipe in the region of the connection opening of the Helmholtz resonator. The complex resistor is connected in parallel with the loudspeaker. In addition, the complex resistance can be infinitely adjusted to any value of the artificial impedance Z _L.

Furthermore, it may be advantageous if at least one temperature sensor is provided, wherein the temperature value T is taken into account in the calculation of Z _L and for this purpose an adaptation of the fluid characteristics l _a , R _a and / or C _a takes place. The propagation velocity of sound depends on the temperature of the medium in which the sound propagates. By taking into account the temperature value of this medium in the calculation of Z _L , noise cancellation is further optimized.

It may also be advantageous if at least one first temperature sensor is provided for measuring the temperature value T _c in the Helmholtz chamber, wherein the fluid characteristic value C _{a is} determined according to

with (p _c = 1.292 x 273 / T _c [kg / m ³ ], c = 20.06 x JT _C [m / s] and the volume V _c [m ³ ] of the Helmholtz chamber.

The sound should be extinguished at one end of the Helmholtz resonator. The extinction is mainly caused by the loudspeaker located at the opposite, other end of the Helmholtz resonator. Accordingly, the sound must pass through the Helmholtz chamber, which is why the consideration of this temperature is advantageous.

It may be advantageously provided that a second temperature sensor for measuring the temperature value T _{N is provided} in the neck, the fluid characteristic l _{a is} determined according to

with φ _Ν = 1,292 x 273 / T _N [kg / m ³ ], l _eq = l _n + 1,7 r [m], where l _n [m] describes the length and r [m] the radius of the neck, and with s _N = π r ² . The consideration of a second temperature value T _N in the neck is advantageous on the one hand the sound propagated through the neck. On the other hand, it is advantageous if, in addition to the temperature value T _N , the temperature value T _{c is also} measured at the same time, since this optimizes the noise cancellation on the temperature gradient between the Helmholtz chamber and the neck. Such a temperature gradient is particularly great when the neck opens into an exhaust pipe through which hot exhaust gas flows.

Of particular importance may be for the present invention, when the determination of R _{a of} the temperature value T _N , T _{c is} not considered. Just when the corresponding temperature values T _N , T _{c are} taken into account in the fluid characteristics C _a and l _a , an additional adaptation of R _{a is} not necessary.

It can also be advantageous for this purpose if the loudspeaker can be used, for example, to generate anti-sound, for which purpose the current voltage U (t) on the loudspeaker is determined by means of the control unit and as part of a signal analysis by a fast Fourier transformation U (oo). is obtained, the current Ι (ω) is calculated using the transfer function 1 / Z _L and ultimately this current is applied as a converted time signal l (t) on the speaker. The application of anti-sound eliminates residual noise despite the complex resistance control. This further improves the noise cancellation. The regulation for the generation of the anti-noise is independent of the regulation of the complex resistance. The rules can therefore be parallel, but also sequential. However, a transfer of the artificial electrical impedance Z _L to the control loop to generate the anti-noise must take place. The current I (t) is provided via an electrical connection. For this purpose, it may be advantageous if, as part of an iteration loop, the voltage Uwi + i (t) or 1 ⁾ _Μ (ω) is determined after application of the current I (t) and then a difference value ε is calculated as the difference of U _M + i and U _M (t) and UM + _I (CÜ) and U _M (W), respectively, where the iteration loop is repeated until the difference value e is less than 1 or less than 0.1 or less than Is 0.001. All time values or t values can be transformed into ω values by Fast Fourier Transformation FFT. This signal analysis can be be tegraler part of the respective control block of the control unit or be integrated as a separate control block.

In connection with the design and arrangement according to the invention, it can be advantageous if the recalculation of the angular frequency ω is implemented in a main control loop and if the recalculation of the impedance Z _{L is implemented} in a Z-control loop and if the Z-control loop in the Main control loop is integrated. The recalculation of the impedance Z _L then takes place on the basis of the current angular frequency ω.

For this purpose, it is advantageous if the determination of the voltage Uivi (t) at the loudspeaker, the calculation of the current Ι (ω) and the application of the current I (t) to the loudspeaker is implemented in an I-control loop and if the I- Control loop is integrated into the main control loop, with the Z-control loop is placed before the I-control loop. Thus, based on the most recent impedance Z _L, the current I (t) is optimized. In addition, it may be advantageous if the I-control loop has a repetition frequency which is higher by a factor of 3 - 100 or 10 - 500 than the repetition frequency of the main control loop and / or the Z-control loop. Thus, the iteration loop can be executed several times for a value Z _L and the current I (t) can be optimized on the basis of Z _L. Further advantages and details of the invention are explained in the patent claims and in the description and illustrated in the figures. It shows:

Figure 1 Schematic representation of the noise reduction system;

FIG. 2a main control loop for setting the complex resistance;

Figure 2b Z-control loop for controlling the complex resistance; Figure 2c I-control loop for optimizing the current l (t).

1, a noise suppression system 1 comprises a Helmholtz resonator 2. The Helmholtz resonator 2 has a Helmholtz chamber 13 and a NEN neck 3, which is formed as a tube with a radius r and a length l _n . The neck 3 discharges via a connection opening 4 in an exhaust gas or intake pipe 9 of an internal combustion engine and couples these, in particular with respect to the sound with the Helmholtz chamber 13. Opposite the neck 3, a loudspeaker 5 is provided which forms the rear wall of the Helmholtz resonator 2.

In addition, a control unit 7 is provided which controls the noise cancellation. The control unit 7 regulates on the one hand a complex resistor 6, which rests on the loudspeaker 5, and on the other hand a current I (t), which is applied to the loudspeaker rather 5 via an electrical connection 12. The individual steps of the arrangements are described in more detail later in FIGS. 2a to 2b.

The control unit 7 is supplied via an ECU unit 8 with vehicle data, such as in particular the engine speed RPM. Furthermore, the control unit 7 is supplied with a temperature value T _c , which is measured by a first temperature sensor 10, and a temperature value T _N , which is measured by a second temperature sensor 11. The first temperature sensor 10 is mounted in the region of the Helmholtz chamber 13 in order to measure the exhaust gas temperature in the Helmholtz chamber 13. The second temperature sensor 11 is mounted in the region of the neck 3 in order to measure the exhaust gas temperature in the neck 3.

For the purpose of controlling the current to be applied to the loudspeaker, the main control loop 7a shown in FIG. 2a is used. Based on the rotational speed RPM is determined according to the illustrated equation ω as the angular frequency of the ignition order. There flows the engine order N, which is significantly dependent on the number of cylinders and the engine timing, but also of Kurbelwellenkröpfung and the architecture of the manifold. In a 4-stroke engine, for example, for a 4-cylinder engine, the most important engine orders are N = 2, 4, 6, 8, 10, and 12. For a 6-cylinder engine, the most important engine orders are N = 3, 6 , 9 and 12. For a 5-cylinder engine, the most important engine orders are N = 2.5, 5, 7.5 and 10. Combinations, in particular, can be used for cylinder deactivation. In this main control loop, two further control loops are used, the Z-control loop 7b and the I-control loop 7c.

According to Figure 2b, the temperature values T _c, T _N and the angular frequency of the firing order to be detected ω in the Z control loop 7b. From these values, the artificial electrical impedance Z _{L is} subsequently calculated. In the second step, the complex resistor 6 is set to the calculated value Z _L. The control is carried out continuously with a frequency of 10 Hz to 00 Hz.

According to FIG. 2c, the I-control loop 7c comprises the following steps to optimize the desired anti-noise. First, the voltage generated by the residual noise by the movement of the membrane current voltage U _M (t) is measured on the speaker 5.

From this time signal, the voltage Uivi (t), a voltage υ _Μ (ω) is determined as part of a signal analysis by means of a fast Fourier transformation FFT. The FFT supplies a voltage spectrum of, for example, 1024 values U (u>). From this voltage spectrum, the voltage values U (u>) are selected for the relevant angular frequencies of the ignition order. The signal analysis can be done in a separate control module 7.1. The signal analysis can also be part of the control module 7.2 for l (t).

Subsequently, a current Ι (ω) is calculated from U (u>) using the artificial electrical impedance Z _L according to equation / (ω) = υ (ω) / Z _L , which is transformed into a time-dependent current I (t) of the equation / (t) = Re (/ (a>)) cos (it) + Im (/ (cL>)) sin (it) and is applied to the loudspeaker 5. Within the scope of an iteration loop, the resulting actual voltage U _M + i (t) is repeatedly determined, and thereafter a difference value ε of the amounts of the two voltages, hence the amount of the difference between U _M + i (t) and U _M (t ). If the difference value ε is less than 1 or less than 0, 1 or less than 0.001, the iteration loop is not repeated. Otherwise, this iteration loop is repeated.

The I-control loop 7c operates at a repetition frequency of 100 Hz to 1000 Hz. If the difference value e is greater than the defined threshold value, 201

- 9 -

the iteration loop is repeated. However, the defined threshold value is preferably reached for the difference value ε and the iteration loop is ended before a recalculation of the angular frequency ω of the ignition order and the impedance Z _L takes place in the context of the main control loop 7a.

LIST OF REFERENCE NUMBERS

1 noise reduction system

2 Helmholtz resonator

3 neck

4 connection opening

5 speakers

6 complex resistance

7 control unit

7.1 Control Module

7.2 Control Module

7a main control loop

7b Z-control loop

7c I control loop

8 ECU unit

9 exhaust or inlet pipe

10 first temperature sensor

11 second temperature sensor

12 electrical connection

13 Helmholtz chamber

In length of the neck

r radius of the neck

V _c volume of the Helmholtz chamber

Claims

claims

A method of operating a motor vehicle noise suppression system (1) comprising a Helmholtz resonator

(2) with a

Helmholtz chamber (13), a neck

(3) and a connection opening (4), a loudspeaker (5) within the Helmholtz resonator, a variable variable resistor (6) electrically connected to the loudspeaker, a control unit (7) for varying the variable complex resistance (6) and comprising an ECU unit (8) as part of engine control for supplying at least RPM RPM as engine parameter, said Helmholtz resonator being connectable via neck to an exhaust or intake duct (9) of an internal combustion engine, said loudspeaker (5) controlling the volume of said Helmholtz resonator (2) partially limited,

characterized ,

that in order to obtain a value Zi for the acoustic impedance at the connection opening, first a value Z ₂ for the acoustic impedance immediately before the loudspeaker (5) is determined according to 2 = IT 2 ff

a ^{/ a} 'a ^1a ' a ^1L a ^{[kg / m4s] with}

ω - ^NR ™ ⁿ _a | _s angular frequency of the firing order, with N as engine order, l _a [kg / m ⁴ ] as mass inertia of the fluid at the port, R _a [kg / m ⁴ s] as loss of damping at the port and C _a [m ⁴ s ² / kg ] as the conformity constant for the fluid in the

Helmholtz resonator (2),

and for Z ^ = 0 a target value Z ₂ o for Z _{2 is} determined after

₁ -; ω- ~.

Z ₂ o = r ₂ . _Ra ^a if ^k 9 ^{/ m} s]

'α' a ^L a

and then adjusting the complex resistor (6) to an artificial electrical impedance Z _L which is detected

Z _L = -Z _e + - ^ - [ohm] with Z _e [ohm] as the electrical impedance of the loudspeaker, Z _m [kg / s] as mechanical impedance of the loudspeaker, Bl [Tm] as the strength factor of the loudspeaker coil, S [m ² ] as loudspeaker surface, so that the noise at the connection opening can be at least partially extinguished.

Method (1) according to claim 1,

characterized,

in that at least one temperature sensor (10, 11) is provided, wherein the temperature value T is taken into account in the calculation of ZL and for this purpose an adaptation of the fluid characteristics l _a , R _a and / or C _a takes place.

Method (1) according to claim 2,

characterized,

in that at least one first temperature sensor (10) is provided for measuring the temperature value Tc in the Helmholtz chamber (13), wherein the fluid characteristic value C _{a is} determined according to

with φ = 1.292 x 273 / T _c [kg / m ³ ], c = 20.06 x JT _C [m / s] and the volume V _c [m ³ ] of the Helmholtz chamber (13).

4. Method (1) according to claim 2 or 3,

characterized,

a second temperature sensor (11) is provided for measuring the temperature value TN in the neck (3), wherein the fluid characteristic value I _{A is} determined according to

with φ _Ν = 1,292 x 273 / T _N [kg / m ³ ], l _eq = l _n + 1,7 r [m], where l _n [m] describes the length and r [m] the radius of the neck, and with s _N = π r ² .

5. Method (1) according to one of claims 2 to 4,

characterized,

that the temperature value T is not taken into account when determining R _a .

6. Method (1) according to one of the preceding claims,

characterized,

in that the current voltage U _M (t) is determined at the loudspeaker (5) by means of the control unit (7) and is obtained by fast Fourier transformation υ _Μ (ω), using the transfer function 1 / Z _L the current Ι (ω) is calculated and ultimately this current is applied as a converted time signal l (t) on the speaker (5).

7. Method (1) according to claim 6,

characterized,

in the context of an iteration loop, after application of the current I (t), the voltage UM ₊ i (t) is determined again and a difference value ε is calculated as the amount of the difference of U _M + i (t) and UW, the iteration loop being repeated so often until the difference value ε is less than 1 or less than 0.1 or less than 0.001.

8. Method (1) according to one of the preceding claims,

characterized,

the recalculation of the angular frequency ω is implemented in a main control loop (7a).

9. Method (1) according to one of the preceding claims,

characterized,

the recalculation of the impedance Z _{L is implemented} in a Z-control loop (7b).

10. The method (1) according to claim 9,

characterized,

the Z-control loop (7b) is integrated in the main control loop (7a).

11. Method (1) according to one of claims 6 to 10,

characterized,

in that the determination of the voltage UW at the loudspeaker, the calculation of the current Ι (ω) and the application of the current l (t) to the loudspeaker (5) are implemented in an I-control loop (7c).

12. The method () according to claim 1,

characterized,

in that the I-control loop (7c) is integrated in the main control loop (7a), the Z-control loop (7b) being placed before the I-control loop (7c).

13. Method (1) according to one of claims 8 to 12,

characterized,

in that the main control loop (7a) and / or the Z-control loop (7b) has a repetition frequency of 10 Hz - 100 Hz or 50 Hz - 500 Hz.

14. Method (1) according to one of claims 8 to 13,

characterized,

in that the I-control loop (7c) has a repetition frequency which is higher by a factor of 3-100 or 10-500 than the repetition frequency of the main control loop (7a) and / or the Z-control loop (7b).