GB2493278A

GB2493278A - Anti-collision system based on passive acoustic sensor

Info

Publication number: GB2493278A
Application number: GB1213104.1A
Authority: GB
Inventors: Karl Matthias
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2011-07-25
Filing date: 2012-07-23
Publication date: 2013-01-30
Anticipated expiration: 2032-07-23
Also published as: FR2978584B1; CN102901969A; DE102011079707A1; GB201213104D0; FR2978584A1; GB2493278B

Abstract

Detecting objects in the environment surrounding a vehicle by detecting an acoustic signal impinging thereon from a predetermined direction using a sensor 20, analyzing a sensor output signal (e.g. by auto-correlation or cross-correlation) relative to comparable features and, in the event of a potential collision between the vehicle and object, providing a warning to the vehicle driver, actively acting on the vehicle dynamics or activating anti-collision functions. The detected signal comprises either intrinsic noise generated by the own-vehicle or external noise from the environment. The system may use control data from the vehicle such as vehicle speed or engine speed. The sensor may comprise an electro-acoustic transducer 10 wherein a diaphragm 11 is surrounded by a heavier core housing 15 which is in turn embedded in a sound damping medium 15 within housing 16. Its directional characteristic may be adjustable by varying the core housing shape.

Description

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Description Title

Method and device for detecting objects from the vehicle environment of a vehicle

Field of the invention

The present invention relates to a method and a device for detecting objects from the vehicle environment of a * vehicle. The inventionalso relates to a vehicle assistance system comprising a device according to the invention.

Prior art

Currently, ultrasound systems which carry out. measurements in a pulsed manner are conventionally used for the acoustic environment detection of vehicles, in which short signal pulses of 0.3 ms are transmitted and in which the distance from the objects is determined using the propagation time of reflections of said pulses from objects in the environment and the soutd velocity.

The ultrasound frequency range is used for acoustic environment monitoring, as conventionally the intensity of interference noise from the environment reduces as the frequency increases. As the spatial damping increases with an increased signal frequency, however, generally the lower range of the ultrasonic band is used, typically at 48 kHz.

This choice pf frequency, therefore, represents a compromise As a result of this compromise, situations frequently arise in which only an inadequate measurement * range is achieved, due to a level of interference and/or spatial damping which is too great.

It is known from the prior art that, in spite of finite transmission power, by increasing the pulse width both the energy transmitted per echo cycle and, with efficient reception, the range may be slightly increased. The measurement signal power used hitherto in acoustic environment monitoring is entirely negligible, however, in comparison with the acoustic power present in some situations in road traffic.

Methods for localised vehicle-vehicle communication are

also known from the prior art.

A method for determining a direction of incidence of a signal from an acoustic signal source and a device for carrying out the method are disclosed in the document DE 103 13 331 B4. Different methods are disclosed in the same document, in which a distance from the signal source is also determined. It is also disclosed that, for the signal analysis, a correlation analysis takes place between delayed microphone signals of different length. The auditory scene analysis set forth therein relates, jr-i particular, to hearing aids i.e. determining the environment of a head.

A method for passively determining at least the distance from a target emitting sound and a sonor installation are disclosed in the document DE 10 2007 034 054 Al. It is disclosed therein that an estimated value of the distance and a horizontal bearing angle relative to a arget emitting sound may be determined in the reception range of the antennae. In this case, the signals obtained from the different antenna systems are in each. case subjected to a spectral analysis and then compared with one another in the frequency range. Provided the spectral features coincide, an indicator of a target with a horizontal bearing angle and an estimated value of the distance is displayed on a corresponding display device and/or on a screen.

The document DE 699 03 171 T2 discloses a device and a method for the automatic control of video cameras by means of microphones, a video camera being able to be oriented towards a localised Sound source. In this case the delay time of the arrival of a sound wave front at selected pairs of microphoneis determined and the spatial and temporal coordinates of a sound source calculated therefrom, and one or more cameras directed towards the source. The cross-correlation bf the signals from two microphones is provided as the signal processing method.

In summary, the implementation of environment detection via separately generated adoustic signals is known from the documents set forth above relating to the prior art. Other signal processing methods are also known, such as auto-correlation and cross-correlation of the signals.

basic requirement for carrying out environment detection via separately generated acoustic signals is the continuous presence of external noise in the environment to be detected. The use of such environment detection which is only based on external noise would be very unreliable in road traffic, as the driving situation, and thus also the presene of external noise in the environment to be driven through, are not predictable.

Disclosure of the invention

According to the invention, a method is provided for detecting objects from the vehicle environment of a vehicle, in which a plurality of signals, in particular electrical signals, suitable for signal processing, and which are generated from acoustic signals, are analysed relative to comparable features and, in the event of a potential collision of the vehicle with a detected object, a warning is emitted to the driver and/or the vehicle dynamics are actively acted upon and/or functions for reducing or avoiding a severe accident are activated; In the method according to the invention, for detecting at least one first object from the vehicle environment, acoustic signals are used from the vehicle environment, * said signals impinging on the vehicle from at least one first predefined direction and comprising intrinsic noise generated by the vehicle, depending on the function, and/or external noise from the rehicle environment.

According to the invention, a device is further provided for detecting objects from the vehicle environment of a vehicle, which is configured for carrying out the method according to the invention and comprises at least one sensor for vehicle environment monitoring, which is configured to generate signals which are suitable for signal processing, in particular electrical signals, from acoustic signals. The device according to the invention comprises a signal processing device which is configured to analyse a plurality of signals generated from the acoustic signals from the vehicle environment for detecting at least one object from the vehicle environment, relative to comparable features and, in the event of a potential collision of the vehicle with a detected object, to generate a warning and/or control signal. The device according to the invention also comprises a warning unit which is configured in the presence of a warning signal generated by the signal processing device to emit a warning to the driver and/or a control device which is configured in the presence of a control signal generated by the signal processing device to act on the vehicle dynamics and/or to activate functions for reducing or avoiding a severe accident.

The sub-claims set forth preferred developments of the invention.

According to the invention, a method and a device are provided by which acoustic environment monitoring may also be implemented in a noisy environment, in which the otherwise present external noise and/or the intrinsic noise of the vehicle, depending on. the function, are used as measurement signals. As a result, the cost of generating and transmitting measurement signals is reduced, .at least in a noisy environment.

According to the invention, in particular a device is provided for acoustic detection of objects in the environment of a vehicle, at least one sensor being present on the vehicle for converting acoustic signals from the vehicle environment into a form suitable for signal processing, such as for example into electrical signals. In this case, at least partially, preferably in situations in which the vehicle environment is already filled with external noise or, depending on the function, the intrinsic noise of the vehicle, no acoustic signals which are specifically generated by the vehicle for the environment measurement, suchas for example ultrasound pulses which are usual nowadays, are transmitted. Using the acoustic signals from the vehicle environment received by the sensors, information and/or warnings are generated, for example for the operator of the vehicle, about situations in the vehicle environment. Using the acoustic signals from the vehicle environment received by the sensors, the vehicle may also be influenced in its driving movement, for example by steering, accelerating and/or braking and/or devices for avoiding damage and/or reducing a severe accident, such as belt tensioners, window lifters, * adjustable headrests, airbags, etc. may be parameterised and/or activated.

The decision to use ultrasound measurement pulses originates from a time when it was possible to receive electrical signals of higher frequency, i.e. ultrasound, using a few electronic components which were available at the time, in a narrow frequency range, and to carry out analogue, processing at reasonable cost.

In the following 30 years the technology was developed further and nowadays it is possible to convert acoustic signals with a substantially greater dynamic of 14-bit to 16-bit and above into digital formats by means of inexpensive analogue-digital transducers, such as sigma-delta transducers, in particular in the signal frequency range of up to 20 kH.z, i.e. in particular below the ultrasonic band and by means of signal processing technology which in the meantime has been able to be produced cost-effectively, it is possible to filter and to process said signals in a different manner.

In particular in loud situations i.e. in an environment filled with a high acoustic power, increasing the range, for example by transmitting higher acoustic powers or by using acoustic-electro transducers with an even greater directional characteristic, is restricted, even in the ultrasound range, in spite of the potential which is still not completely utilised.

In particular, the signals generated from acoustic signals from the vehicle environment are analysed in a form suitable for signal processing by means of auto-correlation and/or cross-correlation relative to comparable features.

The mode of operation is based on the fact that instead of emitting individual acoustic signals in the absence of quiet in at least one first measuring direction, the signals coming from onedirection towards at least one sensor, such as for example preferably a combination of an acoustic-electro transducer and the housing surrounding said transducer, are analysed relative to comparable features. This takes place, for example, by means of auto-correlation and cross-correlation of the signals. In each acoustic signal which impinges on the vehicle from a propagation direction, the information about its sound path is stored. For example, the information may be obtained * from the determined sound path extensions as a result of reflections from objects with a specific reflection intensity. Thus, the result of the auto-correlation function in the sound path extensions already contains S information about the spatial relationship of a plurality of objects between the sound source and the receiving sensor, about the reflectability thereof in the signal strengths, about the extension thereof in the signal deformation and about the relative movements thereof in the Doppler shift of the signals.

By evaluating the information from further sensors in the cross-correlation, equivalent results for the sensor pairs are obtained in the knowi manner.

Different ways for implementing an auto-correlation and/or cross-correlation calculation and signal evaluation are known to the person skilled in the art, such as for example by appropriate multiplication of the measurement signals transformed in the frequency range. Details are, therefore, not explicitly provided here.

It is known that a localisation is carried out by using a plurality of sensors using sound path differences.

According to the invention, such sources are preferably used as measurement signals which, depending on the function, produce sound in any case. The advantage of sound which is present in any case, depending on the function, is its considerably higher power and its dontinuous availability in comparison with ultrasound signals emitted in a pulsed manner.

Such sound sources of the individual vehicle, depending on the function, are, for example, engine and 4ear noise, rolling noise of the wheels and/or chains, rattling/natural resonance of parts of the vehicle, acoustic sound from listening to music from the sound system etc. emitted from the vehicle and intrinsic noise and/or noise dependent on the wind speed of the media flowing around the vehicle (generally air, but also rain, snow etc.) . Other sound * 10 sources are present, for example, from other vehicles in the vehicle environment and/cr from fixed energy converting devices or even in the form of noise from footsteps, the squeaking of bicycle chains, railed vehicles, etc. For the automatic evaluation of noise from the individual vehicle and/or other vehicles, depending on the function, in particular, such signals which nowadays are only used for providing acoustic warnings from road users, such as for example horns, sirens, bells and/or warning signals, are suitable and which are emitted as an alternative to customary engine noise, for example from electric vehicles, in order to make passers-by aware of the vehicles.

The sound thus generated is propagated and is superimposed with sound due to reflections from objects surrounding the vehicle, before it arrives at the sensors. The more sensors installed at different locations on the vehicle, the more accurately the vehicle environment may be analysed acoustically.

One possible application is the detection of a side impact on a vehicle. Due to the many gaps at the side in the bodywork, many measuring points may be produced with a large base distance. The rolling noise of the individual vehicle is proportionally reflected from an object approaching from the side, before it returns to the sensor and/or sensors attached to the side of the individual vehicle. The propagation time ratios, signal alterations due to Doppler shift, signal strength ratios and/or signal deformations due to different surface conditions are generally contained in the signals. Preferably, the measurement is carried out in a manner which is continuous and not pulsed, in order to obtain in each case a continuously updated information stream. If the individual vehicle is in total quiet, the object approaching from the side generally generates at least rolling noise, which without further reflection, or superimposed with reflections from objects corresponding to their sound paths, reaches the sensor or sensors attached to the side of the vehicle.

In an equivalent manner, an acqustic environment sensor system which does not use measurement signals may preferably be implemented to the rear and to the front of the vehicle, the signals of passing and following vehicles also being used as measurement signals in addition to the reflections of the individual noises.

A very typical case for an acoustic enyironment sensor system which does not use measurement signals is the Side View assist function, in which the presence of vehicles and other objects in the environment of the vehicle is inferred from received acoustic signals-Nowadays, due to the limited link budget the function is restricted to specific application positions and maximum speeds, especially as in every case each sensor only hears the measurement signals emitted thereby and is thus interrupted by flow noise, intrinsic rolling noise and rolling noise from external objects. According to the invention, in principle this noise is not regarded as disruptive but is converted into a useful signal.

In a particularly advantageous embodiment of the invention, acoustic signals from the vehicle environment are used for detecting the first object and/or at least one second object front the vehicle environment, which impinge on the vehicle from at least one second predefined direction and comprise the measured noise generated by at least one acoustic sensor located on the vehicle, which differs from the intrinsic noise of the vehicle, depending on the function.

According to the invention, therefore, in situations where external noise and intrinsic noise, depending on the function, are absent, i.e. in a quiet vehicle environment, measured noise from the vehicle is emitted in at least one measurement direction, from which no sound impinges ott the vehicle.

In an exceptional case where the entire surrounding area is quiet and, in addition, no further sound sources are in the vicinity, an acoustic measurement signal is preferably emitted from the individual vehicle, in particular in the direction of the vehicle side.

According to the invention, an operation in the ultrasound range and/or a coexistence with systems emitting

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measurement signals is also conceivable, preferably in quiet locations.

In particular, for detecting the at least one first and/or the at least one second object from the vehicle environment, acoustic signals from the vehicle environment or acoustic signals emitted from the individual vehicle are used, which are in the frequency range of no mare than kHz.

Due to the reduced spatial damping, the frequently available "natural" sound sources in the form of otherwise present external noise or intrinsic noise, depending en the function, and due to the wide availability of acoustic-electro couplers and further conponents which are preferably designed for a frequency range of up to 20 kHz, the frequency range below the ultrasound band should preferably be used, especially as common objects in the vehicle environment have a larger dimension than 0.85 cm, which corresponds to half the wavelength of 20 kHz.

Preferably, such a measurement signal should be in th frequency range of 3 kHz to 20 kHz, as in this range the half wavelengths of the signals are in the range of the object dimensions of 5.7 cm to 0.65 cm, in particular in the device according to the invention, as the human ability to hear and thus potential interference are already reduced, and because generally the interference power density is already reduced and small microphones are available. thus the adjacent acoustic frequency ranges, such as the ultrasound range which is common nowadays or the standard human acoustic range below 3 kHz are not explicitly excluded.

According to the invention, it is particularly preferred to accommodate sensors in concealed mountins, such as for example in or behind the radiator grille or in gaps and openings otherwise present in the vehicle.

Due to its small construction and its very wide avaIlability on the market, electret microphone capsules are particularly suitable as electra-acoustic transducers in the acoustic sensors, in particular for concealed mounting in the vehicle. Such electret microphone capsules are nowadays preferably designed for a frequency range of up to 20 kHz.

In a particularly advantageous embodiment of the invention, at least one sensor for vehicle environment monitoring is designed to determine at least one sound signal emitted by the vehicle, using control data from the vehicle, which in particular comprises information about the vehicle speed and/or the engine speed, and in particular is suitable for exchange by at least one data bus, and to provide the signal processing device in suitable form.

In particular, the determination of at least one emitted sound signal by means of control information, as exchanged for example as data on a data bus, is also used as the sensor for acoustic environment monitoring.

A simple form of correlation is to determine the type of sound emitted by the individual vehicle using control signals and/or measurement signals, such as for example using information on a data bus. For example, conclusions may be drawn from a speed signal about the speed of the media flowing around the vehicle or from the rotational speed, information about the repetition frequency of the engine. Thus due to said control signals, conclusions may be drawn at low cost about the emitted sound signals, depending on the function and, without specific measurement of said emitted signals, a cross-correlation inexpensively carried out.

In prticular, at least one sensor for vehicle environment monitoring comprises an electro-acoustic tranducer which is surrounded by a heavier core housing relative to the transducer diaphragm, which is embedded in a sound damping medium and, in particular, is surrounded by a housing.

Preferably, the sensor is designed to adjust its directional characteristic by varying the core housing shape. This is achieved, in particular, by means which are configured to carry out a suitable variation of the core housing shape.

Preferably, the housing of the sensor is protected on the side where the sound enters by at least one rigid grille and/or by a movable protection device and/or an alignment device which may be altered, in particular, depending on the driving situation.

The acoustic environment sensor system has to be robust in everyday use. This is achieved nowadays by a diaphragm which is very rigid mechanically and which is able to

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withstand flying stones, dirt and the jet of a high pressure cleaner. The usual forms df electra-acoustic transducers nowadays, such as for example electret microphones and other electra-acoustic transducers, are very sensitive relative to such influences. Thus the microphone is intended to be protected by at least one additional grille. Alternatively, adjustable devices are also conceivable, for example by a screen being arranged between the diaphragm and the grille, which is opened only during travel, for example by applying a current.

Alternatively such a screen may replace the grille or even be arranged in front of the grille.

According to the invention, a vehicle assistance system is also provided with a device according to the invention.

Drawings Exemplary embodiments of the invention are described in detail hereinafter with reference to the accompanying drawings, in which: Figure 1 is a sectional view of a sensor for acoustic vehicle environment monitoring in a device according to the invention with an integrated electro-acoustic transducer, and Figure 2 is a perspective view of a common design of an electro-acoustic transducer, for example implemented as an electret microphone capsule.

Embodiments of the invention Figure 1 is a sectional view of a sensor 20 for acoustic vehicle environment monitoring for use in a device (not shown) according to the invention.

Such a sensor 20 according to the invention is designed to be robust, in particular against direct input of the intrinsic noise of the vehicle (not shown), depending on the function.

The sensor 20 contains the electro.-acoustic transducer 10.

The electro-acoustic transducer 10 from Figure 1 comprises the diaphragm 11 which represents the actual transducer surface, as well as the cable 12 connected thereto.

Optionally, the electro-acoustic transducer may also be designed as a purely passive component or contain amplifiers as active components.

The electra-acoustic transducer 10 is surrounded in the sensor 20 by a high-mass core housing 14. Preferably, the electro-acoustic transducer 10 is held therein by means of the support 13, which is characterised by a low acoustic conductivity. At least one further layer 15 poorly conducting the structure-borne noise separates said core housing 14from the outer housing 16 which, amongst other things, serves for fastening the sensor 20 to the vehicle.

Preferably, the entire construction or parts thereof -comprises sound-conducting components aligned in the measurement direction, such as for example a funnel-shaped portion 17 on the core housing 14. Preferably, the diaphragm 1]. is protected against external bodies by means of a protective device 18 arranged in front, such as for example a grille, the protective device being preferably arranged such that external bodies are able to fall out.

According to Figure 1, this occurs by means of a chamfer.

Also it is conceivable to dispense with the separate support 13, preferably by combining the core housing 14 and the housing 16 of the transducer 10.

In Figure 2, a perspective view of an elctret microphone capsule 30 is shown which, for example, may be used as an electro-acoustic transducer in the sensor 20 for vehicle environment monitoring. In Figure 2, amongst other things, the sound entry side 40 and the connecting elements 50 may also be identified, which serve for the electrical connection of the electret microphone capsule 30 to the device according to the invention.

In addition to the written disclosure of the invention, reference is hereby explicitly made to the drawings thereof in Figs. 1 and 2.

Claims

<claim-text>Claims 1. Method for detecting objects from the vehicle environment of a vehicle, in which a plurality of signals, in particular electrical signals, suitable for signal processing, and which are generated from acoustic signals by means of at least one sensor (20) for vehicle environment monitoring, are analysed relative to comparable features and, in the event of a potential collision of the vehicle with a detected object, a warning is emitted to the driver and/or the vehicle dynamics are actively acted upon and/or functions for reducing or avoiding a severe accident are activated, characterised in that for detecting at least one first object from the vehicle environment, acoustic signals are used from the vehicle environment, said signals impinging on the vehicle from at least one first predefined direction and * comprising intrinsic noise generated by the vehicle, depending on the function, and/cr external noise from the vehicle environment.</claim-text> <claim-text>2. Method according to Claim 1, characterised in that the signals generated from acoustic signals from the vehicle environment are analysed in a form suitable for signal processing by means of auto-correlation and/or cross-correlation relative to comparable features.</claim-text> <claim-text>3. Method according to one of Claims 1 or 2, characterised in that for detecting the first object and/or at least one second object from the vehicle environment, acoustic signals are used from the vehicle environment which impinge on the vehicle from at least one second predefined direction and comprise the measured noise generated by at least one acoustic sensor located on the vehicle, which differs from the intrinsic noise of the vehicle, depending on the function.</claim-text> <claim-text>4. Method according to one of the preceding claims, characterised in that acoustic signals from the vehicle environment cr acoustic signals emitted from the individual vehicle are used for detecting at least one first and/or the second object from the vehicle environment, said signals being located in the frequency range of no more than 20 kl-Iz from the vehicle.</claim-text> <claim-text>5. Device for detecting objects from the vehicle environment of a vehicle for carrying out a method according to one of the preceding claims, characterised by at least one sensor (20) for vehicle environment monitoring which is configured to generate signals which are suitable for signal processing, in particular electrical signals, front acoustic signals from the vehicle environment, a signal processing device which is configured to analyse a plurality of signals generated from the acoustic signals from the vehicle environment for detecting at least one object from the vehicle environment, relative to comparable features and, in the event of a potential collision of the vehicle with a detected object, to generate a warning and/or control signal, a warning unit which is configured, in the presence of a warning signal generated by the signal processing device, to emit a warning to the driver and/or a control device which is configured in the presence of a control signal generated by the signal processing device to act on the vehicle dynamics and/or to activate functions for reducing or avoiding a severe accident.</claim-text> <claim-text>6. Device according to Claim 5, characterised by an acoustic sensor for generating measured sound.</claim-text> <claim-text>7. Device according to Claim 5 or 6, characterised in that at least one sensor for vehicle environment monitoring is configured to determine at least one sound signal emitted by the vehicle, using control data from the vehicle, which in particular comprises information about the vehicle speed and/or the engine speed and, in particular, is suitable for exchange by means of a data bus, and to provide the signal processing device in suitable form.</claim-text> <claim-text>8. Device according to one of Claims S to 7, characterised in that at least one sensor (20) for vehicle environment monitoring comprises an electro-acoustic transducer (10) which is surrounded by a heavier core housing (14) relative to the transducer diaphragm (11) which is embedded in sound damping medium (15) and, in particular, is surrounded by a housing (16).</claim-text> <claim-text>9. Device according to Claim 8, characterised in that the electro-acoustic transducer (10) is configured to adjust its directional characteristic by varying the core housing shape.</claim-text> <claim-text>10. Device according to Claim 8 or 9, characterjsed in that the electro-acoustic transducer (10) comprises at least onc rigid grille (18) and/or a movable protection device and/or an alignment device which may be altered, in particular, depending on the driving situation, said compohents being arranged on the side of the housing (16) where the sound enters, for protecting the housing (16) 11. Vehicle assistance system comprising a device according to one of Claims 5 to 10.12. A method for detecting objects from the vehicle environment of a vehicle substantially as herein described.13. A device for detecting objects from the vehicle environment of a vehicle substantially as herein described with reference to the accbmpanying drawings.</claim-text>