FR2692709A1 - Active control device for noise inside cabin of motor vehicle - uses target signal related to engine or road conditions and minimises received noise against target signal - Google Patents

Abstract

The active noise control device has a controller (6) that receives signals (ej) captured by receivers (4) together with a reference signal (Smr) derived from rotation of the motor (2). The controller processes these signals and delivers noise control signals into the cabin through an actuator. A generator (7) establishes a target signal (Sc) that is transmitted to the controller. The generator responds to engine speed or road speed. The controller implements a control algorithm that takes as set input the difference between the target signal (Sc) and the received signal (ej), and seeks to minimise this difference. USE/ADVANTAGE - Active noise reduction that reduces rather than suppresses engine and vehicle noise, retaining some sound as feedback to driver.

Description

ACTIVE NOISE CONTROL DEVICE IN
THE INTERIOR OF A MOTOR VEHICLE
The present invention relates to the technical field of active sound reinforcement. It aims to increase the sound comfort of the interior of a motorized vehicle such as a motor vehicle, while minimizing the inconvenience due to unwanted noise and vibrations perceived by the driver and passengers.

Active noise control devices known to date endeavor to reduce, as much as possible, the noise and vibrations perceptible by the occupants of a vehicle. According to a first type of existing device, illustrated in particular by publication WO / 8 802 912, this result is obtained by collecting a reference signal of the rotation of the source to be combated. This signal is sampled at a fixed frequency, then filtered in various ways, before being amplified and emitted by actuators producing a control signal. The characteristics of these adaptive filterings are calculated by the controller, so as to minimize the energies of the signals picked up by the receivers.

Another type of control device, illustrated by the publication GB 2 230 920, relies on the digitization of the signals picked up by control receivers at a sampling frequency multiple of the frequency of rotation of the source. After calculating the averages of the digitized signals, these are expressed in the time domain by a Fourier transform. The algorithm implemented by the device consists in minimizing one or more frequency lines of this spectrum. The suitable spectral forms, to be emitted by the actuators, are then described in the time domain by an inverse Fourier transform. The signals thus obtained are amplified and then sent to the actuators.

Active control systems are very effective in reducing the noise created by periodic sources. Above all, they seek to minimize this type of inconvenience. This very appreciable result does not however fully meet the expectations of users. Indeed, to the outright reduction, or even the elimination of the noises generated by the operation of the engine and the movement of the vehicle, users will generally prefer an "acoustic atmosphere" consistent with their driving style, and allowing them for example to hear the engine when accelerating.

The present invention provides an active sound device based on the modulation of noise and vibrations transmitted inside the passenger compartment of a vehicle.

It relates to an active noise control device inside the passenger compartment of a vehicle, comprising a controller which receives signals picked up by at least one receiver as well as a reference signal of the rotation of the engine, and sends in the passenger compartment active control signals via at least one actuator. This device is characterized in that it comprises a generator establishing a target signal transmitted to the controller, the control algorithm of which is instructed to minimize the difference between the signals picked up by the receivers and the target signal transmitted by the generator.

According to one embodiment of the invention, the generator collects a set of signals including at least one signal describing the speed of rotation of the engine, and / or a signal representative of the speed of the vehicle, and / or a signal relating to the vehicle acceleration and / or a signal indicating the gear ratio.

According to one embodiment of the invention, the engine speed reference signal is collected in the ignition system thereof.

According to one embodiment of the invention, the controller delivers signals with a period multiple of that of the motor, and / or the target signal is expressed in the form of a series of samples of sound pressure value, of the same period as that of the controller.

According to one embodiment of the invention, the controller digitizes the reference signals of the motor and expresses them according to a Fourier transform, the target signal also being expressed in frequency form in a Fourier transform, so that the differences between the error signals and the target signal can be minimized on several frequency lines, by the controller control algorithm.

According to one embodiment of the invention, the actuators are constituted by the loudspeakers of the vehicle.

The invention will be better understood on reading the following description of a particular embodiment thereof, in conjunction with the appended drawings in which - FIG. 1 is an overall diagram of the device of the invention, and - the curves of FIG. 2 represent the evolution of the level of the
humming in a vehicle, depending on engine speed.

In FIG. 1, the body 1 of a motor vehicle, its engine 2 and two seats 3 is represented schematically. The active control device of the invention comprises receivers 4, constituted by several microphones ml to mj, distributed in the passenger compartment, as well as actuators 5, constituted by the speakers HPi of the sound installation. A controller 6, conforming for example to the devices described in the publications WO 0 88 02 912 or GB 2 230 920 receives all the signals ej picked up by the receivers 4, as well as a reference signal Smr of the rotation of the motor 2. The reference signal Smr can in particular be collected in the ignition system of the engine 2. Conventionally, the controller 6 transmits control signals Ck in the direction of the actuators 5.

To obtain the desired modulation effect, the invention proposes to introduce, upstream of the controller 6, a generator 7 intended to develop the "target" sound signal Sc which one wishes to see picked up by the receivers 4. According to the invention , the instruction of the controller 6 is not to eliminate the noise transmitted inside the passenger compartment, but to make it as close as possible to the target signal Sc, which can be non-zero. The control algorithm developed inside the controller 6 therefore has the instruction, not to minimize the signals ej picked up by the receivers 4, but to minimize the difference existing between them, and the target signal Sc.

The operation of the generator 7 is as follows: from the reference signal Smr (transmitted to the generator 7 and to the controller 6), and from a set of signals Sml representative of the operation of the vehicle, such as the speed of rotation of the engine Sml and / or the speed of the vehicle Sm1 and / or its acceleration Sm2, and / or the transmission ratio Sm3, the generator 7 establishes the target signal Sc. The latter is calculated according to a set of rules taking account of the conditions of use of the vehicle and of users' aspirations, as they may have been codified, in particular following appropriate psycho-acoustic studies.

As indicated above, the target signal Sc is transmitted to the controller 6 which seeks to minimize the differences between the error signals ej and the target signal Sc. The latter must therefore be consistent with the algorithm developed in the controller 6. In if the controller is such as that of publication WO 88 02912, the target signal may be expressed in the form of a series of samples of sound pressure values, the sampling period of which will be that used in the controller 6 , in order to allow the latter to deliver sinusoids with a period multiple of those of the motor 2. On the other hand, if the controller 6 corresponds to that of the publication GB 2 230 920, the target signal Sc will be expressed in frequency form, according to a Fourier transform so that one or more frequency lines can be minimized by the algorithm of controller 6, and so that the differences ei - Sc can be minimized by this same algorithm, on one or more frequency lines.

While the known active noise control devices seek to minimize the noise level of the passenger compartment of the vehicles, the device of the invention therefore makes it possible to modulate this noise according to the expectations of the users.

The invention makes it possible in particular to take into account the phenomena of "buzzing" (occurring during the appearance of the double frequency noise of the engine if the latter has four cylinders).

Curve 8 in FIG. 2 shows by way of example the sound pressure level Pa of a passenger compartment as a function of the engine speed, in the absence of the active control device (curve 8). Resonance takes place around 4000Hz. A conventional active control system will erase the peak of curve 8, but the engine noise will then go from an excessive level to a level below normal (curve 9). The active control device proposed by the invention makes it possible to target the desired sound pressure level Pa, in order to obtain an intermediate level (curve 10), without excessive reduction in noise.

Claims (1)

 CI1 Active noise control device inside the passenger compartment  of a vehicle, comprising a controller (6) which receives  signals ej received by at least one receiver (4) as well as a  Smr reference signal of the motor rotation (2), and sends  in the passenger compartment of the active control signals Ck by  via at least one actuator (5), characterized in  that it includes a generator (7) establishing a target signal Sc  transmitted to the controller (6), whose control algorithm has  for instructions to minimize the difference Sc-ej between the  signals picked up by the receivers ej and the target signal Sc  transmitted by the generator (7).  [2J Control device according to claim 1, characterized in  that the generator (7) collects a set of Smr signals  including at least one signal describing the speed of rotation of the  Smr motor, and / or a signal representative of the speed of the  Sml vehicle, and / or a signal relating to the acceleration of the  vehicle Sm2 and / or a signal, Sm3 indicating the ratio of the  transmission.  L3J Control device according to claims 1 or 2,  characterized in that the engine speed reference signal  Smr is collected in its ignition system.  [4J Control device according to claim 3, characterized in  what the controller (6) delivers signals ej of period  multiple of that of the motor (2), and / or in that the target signal  Sc is expressed as a series of value samples  sound pressure, same period as that of  controller (6). [5] Control device according to claim 3, characterized in  that the controller (6) digitizes the reference signals of the  Smr engine and expresses them according to a Fourier transform,  the target signal Sc also being expressed in the form  frequency in a Fourier transform, so that  the differences ej - Sc can be minimized on several  frequency lines by the controller control algorithm (6). [6] Control device according to any one of  previous claims, characterized in that the  actuators (5) consist of the HPi speakers of  vehicle sound system.