FR2999007A1 - METHOD AND DEVICE FOR DETERMINING THE RELATIVE DISTANCE AND RELATIVE MOVEMENT OF SEVERAL CIRCULATION SUBJECTS - Google Patents

Abstract

Method for determining the relative distance and / or the relative movement between at least two subjects (T1, T2) in particular between at least two vehicles. Upon receipt of acoustic signals (51) from initialization transmissions in the form of acoustic signals (11) transmitted by a first subject (T1), a second subject (T2) triggers them as a reaction emission in the form of acoustic signals (71) received and operated by the first subject (T1). The second subject (T2) reaction emissions are made at the end of at least one known time delay (TD) of at least one of the subjects (T1, T2). This delay time is set so that the acoustic signals received by the first subject (T1), originating from passive reflections of the initialization transmissions of the first subject (T1) by objects of the environment, have no influence. on the operation made by the first subject (T1) of the reaction emissions (71) received by at least one receiver (30) and from the second subject (T2).

Description

FIELD OF THE INVENTION The present invention relates to a method for determining the relative distance and / or the relative movement between at least two subjects, in particular between at least two vehicles according to which, on receipt of acoustic signals originating from initialization in the form of acoustic signals emitted by a first subject, triggered by a second subject as a reaction emission in the form of acoustic signals which are received and operated by the first subject.

The invention also relates to a device for determining the relative distance and / or the relative movement between at least two subjects, in particular between at least two vehicles. Finally, the invention relates to a driving assistance system equipped with such a device.

State of the art Currently, for the acoustic capture of the environment of the vehicles, it is customary to use systems that measure in particular by pulses and operate in the ultrasound range. Thus, typically every 10 ms up to 300 ms, pulses at a frequency of the order of 50 kHz are transmitted by an electroacoustic-acoustic converter. From the travel time of the transmitter converters and those that do not emit, we determine the distance of an object in space. It has already been proposed not to limit the selection of the acoustic medium to ultrasound with a frequency of 50 kHz. This 30-year-old proposal for the ultrasound domain was at that time justified in that in this frequency range, the power of the noise decreases sufficiently strongly, in proportion to the inverse of the signal frequency and the damping. produced by the medium remains within acceptable limits and at this time, the first economically compatible electronic components correspond to this frequency range. But the technique has developed since then: motor vehicles are becoming quieter, electromagnetic compatibility (EMV compatibility) problems are being addressed and signal processing available nowadays in any MP3 player allows efficient filtering within economic limits . In particular, the introduction of electric vehicles requires that these vehicles behave acoustically by a synthetic noise to warn passersby or other subjects. In ancient patents, it has already been proposed to use the entire spectrum of frequencies of the ultrasound range of the range audible to the human ear, overall, for acoustic monitoring of the vehicle environment by the exploitation of sound transmitted by the vehicle itself, in particular by evaluating the synthetic sound emitted by the noise and / or sound necessarily generated by the operation of the vehicle to locate signal generators or sound sources and thus increase the safety of the vehicle. the circulation. DE 30 24 791 C2 describes a device for monitoring the position of a utility boat. This document describes the state of the art with a known solution consisting of equipping the underside of the hull of the vessel with four microphones spaced apart, whereas in some places, close to the drilling at the bottom of the water, there is a transponder acoustic. This acoustic transponder is controlled by the acoustic transmitter under the boat which generates acoustic signals. The acoustic signals emitted by this single point at the bottom of the water are received by three microphones according to the respective position of the boat, with a greater or lesser phase shift. The signals are processed by a computer that allows to correct the position of the boat. Documents DE 23 35 613 A1 and DE 23 35 613 B2 describe a method of measuring the distance or the distance variation and / or the speed variation of objects that move relative to each other, in particular motor vehicles of any type. The acoustic signal returned by the transmitter of a first object is received by the receiver of a second object with a phase change and then it is reflected directly actively to be received by the receiver of the first object. The use of acoustic beams is particularly suitable for measuring methods of terrestrial and aquatic vehicles and especially ultrasonics as indicated. The distance between two vehicles is determined by the exploitation of travel time and relative speed using the Doppler effect. These documents further indicate that signal information can be modulated.

In summary, according to the state of the art, it is known to determine the relative distance and / or the relative movement between at least two objects using initialization transmissions from the first of the two objects generating acoustic signals. received by the second of the two objects and recognized as such by exploitation.

Furthermore, it is known according to the state of the art to generate acoustic signal reaction transmissions of the second object as a direct response to the acoustic signals received corresponding to the initialization transmissions. The acoustic signals of the second object's reaction emissions are received by the first object and are used to determine the relative distance and / or relative motion between the two objects. The disadvantage of the realization of conventional transponder methods in the sound or ultrasonic field is the short range of sound or ultrasound compared to the transmission of electromagnetic waves. Thus, conventional acoustic transponders already begin to radiate reaction emissions while initialization emissions are not completely complete. In addition to this collision in the time that one has in such a transponder method, there are moreover time collisions with the echo coming from passive reflective objects. The disadvantage lies in the importance of the means of realization to be used for the exploitation of the received acoustic signals, corresponding to the reaction emissions if at the same time or in an almost simultaneous manner, one receives the echo signals which come from passive reflections of acoustic signals of initialization emissions on objects of the environment. In normal road traffic, several subjects use one and the same environment. The necessary means increase if several subjects generate reaction emissions and initialization emissions in the same medium. Another disadvantage is that each electroacoustic converter equipping a subject responds in the same way to the arrival of each initialization broadcast. The disadvantage of conventional transponder methods is that they are suitable only for some forms of initialization signals. Often it is not possible to have interoperability between different acoustic transponder methods and the use of new techniques such as the more complex modulation method which is not compatible with existing transponders. But on a public road network, we have multiple subjects whose equipment is often very different. DESCRIPTION AND ADVANTAGES OF THE INVENTION The subject of the present invention is a method for determining the relative distance and / or the relative movement between at least two subjects of the type defined above, characterized in that the reaction second subject are made at the end of at least one known delay time of at least one of the subjects, this delay time being adjusted so that the acoustic signals received by the first subject, from passive reflections of the transmissions of initialization of the first subject by objects of the environment, have no influence on the operation that the first subject does with the reaction transmissions received by at least one receiver and from the second subject. The invention also relates to a device for determining the relative distance and / or the relative movement between at least two subjects, in particular between at least two vehicles which receive the initialization transmissions of acoustic signals by at least one receiver for these emissions coming from at least one of the two subjects and recognize them as such by an operation and in response to the acoustic signals received from the initialization transmissions of at least one subject, they generate signal reaction transmissions acoustic. The reaction emissions of the acoustic signals are generated with at least one predefined signal duration at the end of at least one predefined delay time known to the subjects. In the method of the invention, in particular the acoustic signals received from the first subject trigger the second subject's reaction to the acoustic signals of the first subject at the end of a known delay time of at least one of the first subject. one of the subjects. This delay time is set sufficiently long that the acoustic signals received from the second subject and resulting from the passive reflections of the acoustic signals of the first subject's reaction emissions on objects of the environment do not influence the operation by the second subject for determining the relative distance and / or the relative movement between the two subjects, this operation being performed by the second subject using the acoustic signals of the reaction emissions of the acoustic signals received by a receiver of the second subject. In other words, each time at the end of a period of time agreed firmly and known to the corresponding subjects there are such reaction transmissions generated upon receipt of an initialization and optional transmission, emissions generated in response to the reception of the reaction emissions by other reaction emissions from at least one subject receiving and recognizing the acoustically generated emission signals (initialization emissions and / or reaction emissions) at least one other subject and, optionally, an existing sound source in the acoustic environment. The use of a time-out period agreed in a firm or fixed manner and known to at least the subjects concerned can not give rise to collisions between reaction or other reaction transmissions of such subjects who are at the same location. distance from the subject generating the acoustic signal emissions. If there are several subjects in circulation, the reaction emissions or the other acoustic signal response emissions in response to the emissions can be generated actively by the generating subject or the sound source at the end of a delay period. - tion agreed firmly or fixed and known at least of the subjects concerned and in particular with time delays each time different. The use of a fixed duration of time, known at least to the subjects concerned, makes it possible to avoid in a simple manner collision of reaction transmissions of such subjects equidistant from the subject emitting acoustically generated signals. In other words, the pseudo-random use of each time another delay time of a set of timing durations, different from a known set of all the subjects and which differs significantly, makes that the collision probability of the reaction emissions, even of subjects that equidistant for the travel time, decreases statically very strongly. The use of a fixed and known duration of the delay of at least the subjects, allows the subject who has made the emission of acoustic signals generated in an active manner, to conclude the time of travel between the moment at which he made its actively generated emissions and the time of reception of the acoustic signals which are the response to the acoustic signals received, the reaction emissions generated actively by the other subject, and thus to conclude the distance between the two subjects at the time of signal exchange. The invention uses fixed time delay times that are sufficiently long so that all potentially passive reflection object echoes, far removed from the environment, are closer to the receiving subject. Thus, in a simple manner, the collisions of the active signals of the corresponding reaction emissions with the echoes of the objects of the passive reflection environment are minimized. As during the operation according to the invention acoustic signals received from the reaction emissions, there are no other exploitation of echoes of objects of the passive reflection environment which would be received simultaneously or from a almost simultaneously, this considerably reduces the means of realization necessary for the exploitation according to the invention of the acoustic signals of the reaction emissions of the corresponding operating unit. The use of the delay times according to the invention also avoids the problems of loud sounds and weak sounds, that is to say, strong reaction emissions compared to the echoes of passive reflections. Appropriate operating units of subjects receiving acoustic signals from initialization or reaction transmissions from other subjects will first be tuned to the reception of weak echoes from passive reflections of the acoustic signals of the transmitters. initialization or reaction emissions. These operating units can then additionally, when no more echo arrives, that is to say at the end of the delay times according to the invention, to adjust to the reception of strong acoustic signals of the reaction emissions generated as reactions to the acoustic signals received from the initialization emissions or on the reception of strong acoustic signals from the other reaction emissions which result from the reaction to the acoustic signals received by the reaction transmissions. Thus, the probability of detection of both light echoes and also strong reaction emissions increases, which significantly avoids the problem of loud and weak sounds mentioned above.

The invention provides a method for determining the position and / or movement of acoustically and / or optionally acoustically transmitting subjects of passive reflection objects in the environment of the moving means. The auxiliary means of travel can be wheelchairs for patients, personal carriers, cyclists, electric vehicles or other vehicles such as for example cars, coaches and trucks. Users of travel aids and / or other subjects are informed in particular by acoustic and / or optical signals of the traffic situation. The method according to the invention makes it possible to influence, automatically by the reduction of the acceleration and the guidance in the direction of the assistance, the planned movement such as, for example, the evolution of the speed with respect to a system coordinates. Facilities can also be activated to reduce the consequences of inappropriate movements in the traffic, including accidents such as belt tensioners, windows, air bags and / or other hood positioning systems. In particular, at least one acoustically active subject recognizes at least one characteristic of the acoustic signals generated in information technology and / or functionally necessary for the initialization transmissions of at least one other acoustically active subject and / or at least one other sound source which is in the environment of the acoustically active subjects and then sends, after a delay time and for a limited period of time, an acoustic reaction emission which preferably has an unambiguous relationship with the acoustic environment. initialization issue. Thus, at least one characteristic such as, for example, the intensity of the signal and / or the evolution of the signal intensity (for example in the form of a pulse pattern) and / or the evolution of the frequency is used. signal or frequency mix of the signal. Optionally, the subject responsible for the initialization broadcast responds to the reception of a feedback program, in the same manner by transmitting another reaction program. Both active acoustic transmitters and subjects who only receive and exploit acoustic signals produced in the environment can be used to determine the position and / or movement of active acoustic transmitters and / or objects passive reflectors of the environment both the initialization emissions made for the reaction emissions sent and optionally also the other reaction emissions emitted and generated as a reaction to the reception of reaction emissions, and also the echoes thus generated by the passive reflective objects. Preferably, for determining the relative distance and / or the relative movement between at least two subjects, by exploiting the acoustic signals of the initiating transmissions of an initiating subject and / or the reaction emissions of at least 1 one of the subjects uses at least one characteristic of the acoustic signals of these initialization emissions and / or of these reaction emissions, such as, for example, the signal intensity and / or the chronological evolution of the intensity of the signal. signal, for example in the form of a pulse pattern and / or the frequency of the signal and / or the time course of the signal frequency or the frequency mixing of the signal of the corresponding acoustic signals. In the method of the invention, the subject who generates the initialization transmissions furthermore knows what time delay between the instant at which at least one characteristic of the acoustic signals of these initialization transmissions is fulfilled and the beginning of the reaction, the subject receiving the acoustic signals of the initialization transmissions. This allows the initiating subject to obtain the distance between the two subjects from the total travel time of the acoustic signals of the initialization emissions and the corresponding reaction emissions. In order to reduce the probability of collision between the reaction emissions of several subjects reacting in particular to the same emissions of a subject, it is preferable to use a few delay times different from the set of agreed delay times for the reaction emissions. To reduce the collision probability of the acoustic signals of the reaction emissions of several subjects, according to a particularly advantageous development of the method of the invention, the duration of the acoustic signals of the reaction emissions of at least one subject is less than a predefined fraction. the duration of the acoustic signals of the initialization transmissions of the initiating subject (first subject). In particular, the subjects receiving the acoustic signals of the reaction emissions experience at least one signal duration and / or at least one frequency or at least one change in frequency of the acoustic signals of the reaction emissions of at least one subject . In other words, in particular even if at least one characteristic of the acoustic signals of the initialization transmissions of a subject is continuously fulfilled, the receiving subjects generate time-limited reaction emissions for the acoustic signals. In particular, the emission duration of such reaction emissions will be less than 1%. If, for example, a characteristic to be fulfilled by the acoustic signals of an initialization transmission produces a signal intensity, then a permanent sound source which generates an initialization emission, can produce a reaction emission which includes a reproduction if appropriate. brief of the permanent sound source. To further reduce the risk of collision between the reaction emissions of several subjects reacting in particular to the same emissions of a subject, it is used for these reaction emissions preferably a few different reaction emission times, taken in all agreed reaction emission times. According to another preferred development of the method of the invention, the reaction signals of at least one subject are modulated in the acoustic signals, information relating to these reaction transmissions, including in particular information for the delay time used for the reaction emissions and / or the signal duration and / or the signal frequency and / or the evolution of the signal frequency for the corresponding acoustic signals.

According to another preferred development of the method of the invention, the acoustic signals of the reaction transmissions of at least one subject have a unique relationship with the initialization transmissions of the initiating subject. Preferably, the intensity of the signal and / or the evolution of the acoustic signals of the reaction emissions of at least one subject have an unequivocal relationship with the signal intensity and / or the evolution of the acoustic signals of the transmissions. initialization of the initializing subject and which have in particular a variable frequency in time. The acoustic signals of the feedback programs preferably comprise a predefined signal extract of the acoustic signals of the initialization transmissions and predefined signal extracts are transmitted in the reverse order (in usual language, in reverse reading) or in a chronological order unchanged at the same reproduction speed and / or at another reproduction speed (playback speed) and thus with another signal frequency than the acoustic signals of the initiating transmissions of the initiating subject. The modified reading speed is realized in information technology, in particular by the use of a modified sampling rate compared to the reception. The use of another reading speed for the acoustic signals of the reaction emissions has the advantage that the acoustic signals of the reaction emissions can easily separate from the acoustic signals of the initialization emissions by filtering. In particular, for the signal form of the acoustic signals of the reaction emissions, a coded signal form is used which is for example made by an association table or by an algebra. In order to facilitate the separation of the acoustic signals from the reaction emissions of several subjects reacting in particular to the same transmissions of a subject, acoustic signals of these reaction emissions are used for the reading speed, a few different reading speeds taken in the set of agreed reading speeds. To further reduce the risk of collision between the reaction emissions of several subjects reacting in particular to the same emissions of a subject, the delay time, the transmission duration concerned, the reaction transmission duration are preferably varied. , the signal strength, the reading order and / or the reading speed, preferably depending on the degree of use of the acoustic medium by other subjects and / or by other sound sources and / or by the actual velocity of the transmitting subject and / or the relative position and / or relative motion of other objects and / or subjects. In the method of the invention, at least one receiving subject receives the acoustic signals of the active transmissions of at least one other subject, preferably by at least two reception systems, and exploits the differences of the acoustic signals received from the active transmissions as to the relative position and / or relative movement, in particular using differences in travel time, Doppler shift and / or signal strength. In addition, upon the arrival of an echo, this subject can also exploit the acoustic signals generated after the acoustic emissions by the passive reflections on reflective objects by exploiting them also. From the signal variations during the transmission path, at least the spatial relationship between the transmitting subject and the receiving subject and / or the passive reflective objects of the sound is determined and / or information relating to the relative motion is collected. between the subjects and / or the objects of passive reflection of the sound and / or the conditions of circulation between the subjects, in particular as regards the position and / or the form of the other subjects which are between them or even fixed objects such as trees and / or characteristics of the roadway.

In particular, each subject may make acoustic signal initialization transmissions and also react by reaction transmissions to acoustic signals from other acoustic emission signals activated by other subjects.

The invention also relates to a driving assistance system comprising a device as described above for determining the relative distance and / or the relative movement between at least two subjects, in particular between at least two vehicles. Drawings The present invention will be described in more detail below with the aid of exemplary embodiments of a method for determining the relative distance and / or the possible relative movement between at least two traffic subjects represented in FIGS. The accompanying drawings, in which: FIG. 1 is a schematic representation of a state of the traffic in which a first initiating traffic subject generates acoustic signal initialization transmissions that are received by a second subject at the receiving the acoustic signals of the initialization transmissions for triggering acoustic signal reaction emissions, FIG. 2 is a schematic representation of the position of the Doppler band of the acoustic signals of a reaction emission of a subject at the by reacting, in comparison with the position of the Doppler band, the acoustic signals of origin of the initiating emission the initialization subject for a run rate equal to 1.5 times the reception speed. DESCRIPTION OF EMBODIMENTS OF THE INVENTION FIG. 1 explains the method according to the invention (autoreplay protocol) by way of example for a traffic situation in which only two subjects with circulation Ti and T2 are represented many topics, acoustically active, possible. To simplify the description, the term "subject to circulation" will be called "subject". The first subject Ti comprises a signal generator 10 for generating acoustic signals 11, a transmission system 20 for emitting acoustic signals, a reception system 30 for receiving acoustic signals 31 and at least one operating installation 40 to exploit the acoustic signals received 31. The second subject T2 comprises the device 100 according to the invention with at least one reception facility 50 for receiving acoustic signals 51, a transmission facility 60 for emitting acoustic signals as well as at least one control device 70 for detecting the incoming acoustic signals 51 by means of the characteristic elements of the acoustic signals 51 and for triggering the emission of acoustic signals 71 in response to the incoming signals 51 after a delay time or TD delay. The control installation 70 is in particular made for the acoustic signals 71 generated by the second subject T2 in response to the acoustic signals 51 received and which are generated by the first subject Ti or by sources of acoustic signals in the environment, and which have been emitted and which differ significantly from the conventional echo on reflective, passive objects, for the first subject Ti and which have been carried out as a reaction emission 71 of the second subject T2 responding to the active emissions of acoustic signals 11 by the first subject Ti.

Optionally and in addition, the first subject Ti which generated the initialization transmission 11, of origin, comprises a control installation (not shown) which generates according to the invention, other reaction transmissions (not shown). ) according to the signals 31 received by the reception facility 30; these other reaction emissions are also received and exploited by subjects in the environment, such as, for example, subject T2. The other generated reaction emissions are preferably related to other received acoustic signals and / or other signals exchanged by other media which characterize the presence and the mobile behavior of other subjects and / or or objects with passive reflection, by merging the sensor data. Further, not only the first subject Ti, but also the second subject T2, may include an operating installation (not shown) for exploiting the acoustic signals 51 received by the reception facility 50. The sound medium 80a has been represented by hatching; this medium connects the subjects Ti, T2 communicating acoustically. FIG. 1 shows, under the reference TP1, the duration of the pulse of the acoustic signal 11 emitted by the first subject Ti by the transmission installation 20. The reference T12 represents the time necessary to transmit the acoustic signal 11 of the first subject Ti until the beginning of the recognition by the control facility 70 of the second subject T2. The reference TP1 designates the pulse duration of the acoustic signals 51 emitted by the first subject Ti or an equivalent signal source (not shown) by the transmission facility 20 and received by the reception facility 50 of the second subject T2. The reference TP2 designates the pulse duration of the acoustic signals 51 received by the control unit 70 of the second subject T2 as a reaction to the emissions of the first acoustic signals 71 generated by the first subject Ti. The reference TD denotes the delay time between the beginning of the recognition of the acoustic signals 51 emitted by the first subject Ti by the transmission installation 20 and received by the second subject T2 by the reception installation 50 and also the triggering reaction emissions of the acoustic signals 71 of the second subject T2. The reference T21 characterizes the time elapsed between the beginning of the emission of the acoustic signals generated by the second subject T2 until the beginning of the reception by the reception facility 30 of the first subject Ti. The pulse duration of the acoustic signals 31 emitted by the second subject T2 and received by the reception facility 30 of the first subject Ti is referred to as TP21. According to a preferred development, using the received signals 51, the control installation manages the reaction transmissions 71 using the characteristics of the reception signals 51 of the initialization transmission applications such as, for example, the signal strength, the chronological evolution of the signal strength (for example in the form of a pulse pattern) and / or the duration of the signal frequency or the signal frequency mix. According to a particularly preferred development, the control installation (not shown) which is optional has the function of generating other reaction transmissions (not shown) of the subject Ti which initially generated the initialization transmissions 11 as a reaction to receiving acoustic signals 31 from the reaction transmissions 71; these acoustic signals are exploited from the point of view of their characteristics in reception. Thanks to the equivalence between the above preferred development with respect to the control unit 70, the development mentioned will no longer be detailed with regard to the additional control installation (not shown). Optionally, the initialization signals 11 may originate not from the subject Ti but from another sound source in the acoustic environment. The initialization signals 11 comprise acoustic signals such as functionally linked sound, for example engine noises or transverse crushing of the brakes or other acoustic signals, such as, for example, the chirping noise emitted by the red lights. , walking and traffic noises, building ventilation noise, building alarms. According to a preferred development, the control installations 70 and / or the existing control installations and in addition optionally, are preferably designed to limit the duration TP1 or TP2 transmitted acoustic signals 11, 71 and / or their frequency with that of acoustic signals emitted 11, 71, for example even if the characteristic of the acoustic signals received 31, 51 is fulfilled over a prolonged period, or even permanently. It is also advantageous for the sound medium 80 to be used only partially so as to reduce the probability of collision with the acoustic signals coming from the transmissions of other subjects, emitting actively and / or with echoes generated by the reflections of acoustic signals on passive reflection objects. So far, the behavior of the issue time with 1% issue breaks has been interesting. If many subjects Ti, T2 use a single sound medium 80, the numerous acoustic signals 31, 51 exchanged between the subjects Ti, T2 and the associated echoes manage at least redundant information so that the sound monitoring of the environment is possible for a ratio between the emission times and the emission rest for each electro-acoustic converter, significantly below 1% and up to below 0.1 °) / 0. Even for scenes that vary only slowly, such as traffic or a slow motion to come into a parking space, usually a low transmission frequency is sufficient. In the case of high circulation velocities, especially if only few acoustically active subjects T 1, T2, use acoustically medium 80, it is advantageous to have a high frequency of acoustic emissions and in particular of electronic converters. acoustic (not shown separately) and whose alignment is oriented mainly along the path upstream. This is particularly true if it is possible to divide the sound medium 80 for example by frequency multiplexing, coding and / or signal strength. In these circumstances, it is advantageous to have an emission frequency by the electro-acoustic converter that is greater than 10%. According to a very preferential development, the time delay TD between the beginning of the arrival of the initialization signal 51 and the beginning of the emission of a reaction signal 71 is independent of the signal intensity and also independent of the variation. of the signal by the Doppler shift. In addition, the delay time TD of all subjects Ti, T2 that have been acoustically emitted according to this method of the invention or "autoreplay" protocol for determining the position and / or movement of other subjects T2, T21 is a known solution. In this way, each subject Ti, T2 which receives the acoustic signals exchanged in the damping medium 80 can use the signal runtimes, in particular between an initialization transmission 11 and a transmission in response 71 if only two acoustically active subjects Ti, T2 are in the sound medium 80 or also from the signal travel times between the reaction transmissions 71, if there are in the sound medium 80 more than two subjects with acoustic activity Ti, T2 according to the space relationships between the subjects reacting actively and acoustically Ti, T2 and / or between reflective objects (not shown). According to another preferred development, the signal intensity of the initialization emission has a fixed value in the main acoustic emission direction of the electro-acoustic converter or several signal intensities, known, clearly distinct from each other and known to all subjects Ti, T2. As a directional characteristic, the spatial distribution of the signal intensities vis-à-vis the electro-acoustic converter is used. According to another preferred development, at least one T2 receptor subject, T1 knows the directional characteristic of the transmitting subject Ti, T2. This results, for example, from the fact that all the electro-acoustic converters (not shown separately) use the same directional characteristic or that, in the messages exchanged, in particular the acoustic messages exchanged, the information relating to the directional characteristic used by the transmitter electro-acoustic converter (not shown separately) and / or the intensity of the emitted signal.

According to another preferred development, the ratio of the intensities of the received signals 51 of the initialization transmissions and the acoustic signals received 31 are known from the corresponding reception emission 71 and / or from a reaction emission generated as a reaction to a transmission. received reaction 71 (not shown) according to the rule that at least some subjects Ti, T2 are known. In addition, the ratio preferably varies independently of the signal variation by the Doppler phase shift. In addition, in the reaction transmissions 71, there is preferably information relating to the intensity of the received signal 51 by the initialization transmissions. According to a preferred development, the ratio between the signal intensity for the initialization emission and the corresponding reaction emission 71 is fixed with respect to the other unrepresented reaction emissions generated as a reaction to reaction 71 received (not shown). In this alternative embodiment, the collision probability of the reaction emissions 71 decreases with decreasing intensity of the acoustic signals received by the initialization transmissions and in the reception signal of the subject Ti which has radiated. the initialization emission 11, the influence of the damping of the transmission between the two subjects Ti, T2 is contained in its expression squared.

According to an alternative embodiment, the emission of reaction 71 is always made with the greatest signal intensity possible. The collision probability of the reaction emissions 71 is not influenced by the intensity of the acoustic signals received 51 from the initialization transmission, the transmission range is much higher compared to the known embodiment variant because the influence of the damping of the transmission between the two subjects Ti, T2 is not simple and is not squared. Knowing the transmission properties of the transmission medium 80, in a variant embodiment above, it is possible to draw the conclusions of the intensity of the signal because of the geometric relationship between the subjects, in particular because the electroacoustic converters used in the Sensors are usually distinguished by a directional feature. Among these conditions, only from the intensity of the signal received, linked to a signal 11, 71 emitted by an electro-acoustic converter of a subject Ti, T2, the total damping of the electronic converter is already determined. -acoustic transmitter and receiver. If the receiver 30, 50 comprises at least two electro-acoustic converters respectful (not shown) and if the two electro-acoustic converters are separated by the time of travel, from the different intensities of the reception signals, in connection with the times Different paths can determine the alignment of the electro-acoustic converter of the transmitting subject Ti, T2 to the electro-acoustic converter of the receiver subject Ti, T2, whose directional characteristics are known. If the position of the transmitting electro-acoustic converter is known to the transmitting subject Ti, T2, this makes it possible to define in this way, solely with the aid of a single piece of information, the spatial relation, including the direction of the electro-acoustic converter, and thus that of the subjects Ti, T2, with respect to each other. Insofar as the scenario does not change or changes only slowly, negligibly, the acoustic information subsequently exchanged contains the spatial relations of the subjects T1, T2 being in the sound medium 80, in an equivalent manner as redundant information; if not, this information appears as new information on the varying spatial conditions. According to another preferred development, the signals received via the sound medium 80 of an initialization transmission 11 and / or the signals 51 of a reaction transmission 71 received by the transmission in the sound medium 80 are exploited at using features such as signal strength. If, for example, the intensity of acoustic signals 51 received by the subject T2 and corresponding to the initialization emission of the subject Ti or of a sound source which is in the acoustic environment, exceeds a predefined threshold , adjusted for example according to the signal intensity of the noise, then the subject T2 applies to this acoustic signal 51 a particularly preferential impression by detection as non-discrete signal in time. After a fixed duration TD which can correspond to different lengths TD1, TD2, the second subject T2 emits at least during a fixed segment in the agreed time, for example at least the beginning of a signal of initialization 51, acoustic, previously received by the subject T2. In particular, the signal segment 71 to be transmitted is preferentially amplified in the inverse chronological order, which means that the last received signal segment will be transmitted first. This is preferably done at another reading speed, that is to say that the signal extract 71 to be transmitted will be transmitted at another frequency, which again makes it possible to separate by filtering this signal extract relative to acoustic signals 11 emissions of the first subject Ti and that with reduced means. According to a very preferential development, the reaction emissions 71 by the subject T2 and / or those of at least one other subject (not shown) is a one-to-one relationship with the initialization transmissions of the first subject Tl. signal of the emissions of the first subject Ti in the reaction emissions 71 can develop in the reverse chronological order (according to the current language "back in time") or in the chronological order unchanged and selectively at the same speed of reproduction or at another reproduction speed and thus at a frequency other than that of the transmission frequency of the first subject T1. The recording of the signal extracts can preferably be done by sampling. In addition, the reproduction at a modified frequency will preferably be at a modified read speed of the detection values. As a variant, the form of the signal used in the reaction transmissions 71 is defined by coding, which is done for example by means of a correspondence table or by an algebra. According to the invention, by varying the transmission detection frequency with respect to the reception detection frequency, the frequency and the pulse duration of the reaction emissions 71 of the subjects reacting to at least one initialization signal received (initialization information) 51 such as the subject T2. For example, by emitting the acoustic signals 71 of the second subject T2's double-speed response emissions, a sound medium 80 of a length half of that required for the same signals 71 emitted at the speed at which they are present is sufficient. have been registered. If, in addition to the subjects Ti, T2, the medium 80 also contains other subjects (not shown) which, according to the invention, using an exploitation of the characteristics of the received signals 51, 31 initialize the transmission respectively. reaction 71 or other reaction emissions (not shown), because of the halving, the use of the medium 80 decreases the probability of collision of the reaction emissions in the medium 80. The use of a double signal frequency leads to a smaller range of this feedback signal 71 because of the frequency-dependent space damping or else of another feedback signal (not shown) so that this also reduces the collision probability in the space between the reaction emissions. Moreover, by doubling the frequency of the acoustic signals 71 of the reaction emissions with respect to the acoustic signals 11 of the initialization transmissions, the signals can be easily separated by means of frequency filters. The same remark applies to the reaction emissions (not shown) by the subject Ti for the initialization transmissions (not shown) of the subject T2. Thanks to the fixed delay time TD, there can not be between such subjects, reaction emission collisions which are at the same distance from the subject Ti having initialized the acoustic exchange. If subjects at the same distance move at a different relative speed, the Doppler effect reduces the collision effect.

Thanks to the fixed delay or delay time TD, the subject T1 who initiated the initialization transmission can conclude at the distance between the two subjects Ti, T2 at the time of the exchange of the signals to from the time of travel between the time at which the initialization emissions were created and the moment of reception of the corresponding reaction emission. Thanks to the exploitation of the acoustic signals with the simple characteristic, that of the "signal intensity", the Doppler information contained in the signal remains preserved in the relative movement of the subjects (for example vehicles) Ti, T2.

By using the signal strength as a simple feature in the operation of the received signals 51, 31, interoperability is easy. The process is easy to implement. The subjects Ti, T2 reactants and / or the other reactants (not shown) do not require, to carry out the process of the invention, any knowledge of the internal structure of the initialization transmission 11, sent, in particular concerning the chronological evolution of signal frequencies or chronological evolution of signal amplitudes. Only a threshold switch, easy to perform, determines after the first exceeding of a first threshold by the signal strength, the instant from which an incoming signal 51, 31 will be recorded. With the aid of the easy-to-use time measuring system, the recording time and the delay time TD are determined. At the end of the fixed delay or delay time TD, the recorded signal will be transmitted again.

The interoperability of the different processes applied for example by different manufacturers is possible. The method according to the invention operates for example independently of the type of modulation of the initialization signals 11. For example a system can use an amplitude modulation, economic, or even an amplitude sampling while other systems use a frequency conversion or alternatively a frequency modulation of order (m) or frequency-modulated signals with a continuous change of the frequency or else noise-like signals or a phase modification such as amplitude modulation in quadrature. A subject, such as, for example, the subject T2 which generates a feedback transmission 71 (replay) to any modulated initialization program thus, does not require any knowledge of the type of modulation used. This even allows compatibility in the upward direction between different systems. For example, a system which itself only uses amplitude sampling as a type of modulation using an initialization transmission 11 can also generate a feedback transmission (readback) to the modulated signal reception, analogous to noise. In a preferred embodiment, the frequency of the signal changes at least in the time segment of the initialization transmission and this continuously with time, i.e. the initialization transmission is modulated in chirp in the evoked time segment. By using the signal strength as a simple feature for the operation of the received signals 31, 51, in the described method, a response emission 71 is preferably generated in response to the arrival of such signals. which are not explicitly generated as measurement signals for environmental monitoring and include, but are not limited to, engine noises, footsteps, squeal, for example, of vehicle wheels or acoustic signals of vehicles. traffic lights. This effect makes it possible for other subjects, such as the subject T2, not to orient themselves only with the aid of such initialization programs 11 explicitly issued as measurement signals for monitoring the environment and using echoes generated by the reflective objects passively for orientation but also also during the reaction transmissions of other subjects to the circulation such as for example Ti and the echoes generated by the passive reflection of the objects. Thus, the medium 80 used in which the sound develops, will already measure for low emissions 11, 71, with a multiplicity of signals that, thanks to the redundant information they generally contain, quickly and reliably determine the position and movement of subjects with circulation Ti, T2 which are in the middle 80 and of objects, even if only few subjects to the circulation such as for example the subject T2, cooperate by the active emission of emissions 71. These traffic subjects who do not actively emit but simply use the incoming acoustic signals, as for example for the subject T2, make it possible to determine the position and the movement of the other subjects who are in the medium. 80 such as the subject Ti and the objects normally found in the medium 80. The use of a combination of several characteristics (signal properties) such as the intensity of u signal and / or the chronological evolution of the signal intensity (for example in the form of the frequency of the occupation of the medium 80 and / or the chronogram of the frequency of the signal or of the frequency It is possible, for example, for the reaction signals 71 to be generated frequently in response to such initialization transmissions 11. frequently can be reproduced, in particular with another read speed and / or be generated with another delay time TD and / or have another transmission duration TP2 and / or have a different reproduction order if they have preference adjacent to, for example, a minimum signal amplitude, other special signal characteristics such as, for example, a special change in the frequency of the signal. The characteristics of the reaction emissions 71 made in this way thus have properties that are easy to verify. This is the total travel time between the sending of the initialization transmission 11 and the reception of the reaction emission 71 taking into account all the known time delays TD of all the subjects Ti, T2 as measurements. of the distance between the subjects Ti, T2. The frequency variations, taking into account the known rules of all the subjects Ti, T2 of the modified reading speeds, are a measure of the relative movement of the subjects T 1, T2 between them and the variation of the intensity of the signal, taking into account account of the instantaneous deployment damping in the medium 80, is a measure of the orientation of the subjects (communication partners) Ti, T2, with respect to each other. To avoid collisions in the reaction emissions with reflexes of non-active objects, ie reflective objects, either a longer delay time TD must be used so that all object echoes potentially far apart are already closer to the receiver 30 and in particular use at least one form of signal acoustic signals 71 actively transmitted by the reaction emissions and which differ significantly from the signal form of the echo of passive reflection objects . The acoustic signals 71 of the reaction emissions can be generated for example by means of the signal frequency timing diagram for frequency modulated signal forms and / or by means of the frequency of the signal which is generated in particular at using a modified read speed to distinguish echo from passive reflection objects. For a good signal separation between the acoustic signals 11 of the initialization emissions and the acoustic signals 71 of the reaction emissions by frequency filters, it suffices for some applications to use a slight frequency offset or variation of the reading speed. If one has in a region of the sound medium 80, for example two vehicles Ti, T2 with absolute speeds of 60 km / h that is to say 17 m / s, then the maximum relative speed of the two vehicles Ti, T 34 m / s, which corresponds to a Doppler shift of about 10% of the frequency of the acoustic signals 11 of the initialization transmissions to the reaction receiver T1. FIG. Doppler DR band of a reaction emission for a reactive subject (reactor) T2 can be compared with the position of the double band D1 of the corresponding initialization emission for the initializing subject Ti of origin, for a reading speed of 1.5 times. The ratio between the reading speed and the rate of reception for the reactor T2 is referred to in this context as the relative reading speed RA.

It is clear that the two bands D1 and DR do not overlap, even in an extreme case. For the relationship between an initialization emission and a corresponding reaction emission, the situation is even better because the two bands vary in the same direction. In traffic situations in which only a few acoustically active subjects Ti, T2 share a region of the sound medium 80, it is however recommended to emit acoustic signals of the reaction emissions with a lower reading speed, which results in a shift to the low frequencies of the signal. Due to the small number of subjects Ti, T2, the collision probability of the reaction emissions is low despite the lengthening of the pulse duration compared to the initialization emissions. The choice of the lower frequency of the signal is advantageous for having larger ranges because the spatial damping increases with the frequency of the signal. Alternatively, it is interesting to change the frequency of the signal to escape disturbances. This is true for both initiating transmissions by the initialization subject Ti and for reaction emissions by the reacting subject T2. Preferably, the method is applied so that the choice of the signal frequencies for the initialization transmissions and also for the relative playback speed RA at reproduction is adapted to the situation but so that the respective subject (partner of communication) Ti, T52 can recognize by means of the rules of change acoustic signals previously agreed. For example, for this purpose significantly different levels are selected in the relations contained in the feedback transmission 71 for each initialization transmission 11, notably the relative read speed and / or the different delay time TD and / or the chosen length of the signals. Taking into account that a subject Ti, T2 for acoustic environmental detection first records the active emissions of at least one other subject T2, Ti with at least two reaction systems which are all distributed in space in subjects Ti, T2, then using the spatial differences of the received transmissions, in particular with the help of the differences in travel time and / or signal intensity and / or signal variation during the transmission path, at least the spatial relationship between the transmitting subject and the receiving subject T1, T2 is determined and information is provided concerning the relative movement between the transmitting subject and the receiving subject Ti, T2 in a function of the traffic conditions between the transmitting subject and the receiving subject Ti, T2, in particular as a function of the position and / or the shape of the other subjects to the circulation which are in the interval and / or of fixed objects such as that trees and / or carac - characteristics of the roadway. For a preferential development, at least one subject T2, of which several electro-acoustic converters (not shown separately) are oriented on a region of the medium, emits a reaction emission 71 but not by all the electro-acoustic converters. For example, after the reception of an initialization transmission 11, a corresponding reaction emission 71 is made by the electro-acoustic converter which has received the acoustic signals 51 of the initialization transmission with the greatest signal intensity. and at the same time or time shifted, i.e. from another time delay TD, at least one other reaction emission 71 is made by the electro-acoustic converter which has received the acoustic signals 51 of the initialization transmission with the lowest signal amplitude. Other combinations are possible.

For another preferential development, at least one of the subjects Ti, T2 which are in the medium 80, provides alternately various functions mentioned above, that is to say that this subject plays for example on the one hand the role of the initiator subject Ti of the acoustic exchange and, on the other hand, the role of a reactive subject such as, for example, the subject T2 which, by the reaction emissions 71, reacts to the reception of the acoustic signals 51 from a initialization broadcast. According to another preferred development, an initiator subject T1 confirms the reception of the acoustic signals 31 of a subject T2 which reacts to a previously transmitted emission emission 71, also by the emission of another reaction emission (not shown). In this way, both the initiating subject T1 receives a confirmation that the reactive subject T2 has received the acoustic signals 51 from its initialization transmission and that also the reactive subject T2 receives the confirmation of the reception of the acoustic signals. 31 of its reaction emission by the initiator subject T1. Such confirmed transmissions facilitate compliance with the requirements of increasing reliability for environmental monitoring. Both the reaction transmissions 71 and the initialization transmissions 11 may contain, in addition to the process information of the invention (replay read protocol), also other information such as, for example, the state of the process. the driving dynamics of the vehicle and / or the identification of the vehicle. 15 NOMENCLATURE OF THE MAIN ELEMENTS 10 Signal Generator 11 Acoustic Signal 20 Transmission Installation 30 Reception Facility 31 Acoustic Signals 40 Operating Installation 50 Reception Facility 51 Signals Acoustic 60 Transmission installation 70 Control system 71 Acoustic signals 80 Sound medium 100 Device according to the invention RA Reading speed T1, T2 Subject TD Delay time TP1 Pulse duration TP2 Pulse duration25

Claims (2)

CLAIMS 1 °) Method for determining the relative distance and / or the relative movement between at least two subjects (Ti, T2), in particular between at least two vehicles according to which upon receipt of acoustic signals (51) originating from initialization transmissions in the form of acoustic signals (11) emitted by a first subject (Ti), a second subject (T2) triggers them as a reaction emission in the form of acoustic signals (71) received and operated by the first subject (T1), characterized in that the second subject (T2) reaction emissions are made at the end of at least one known time delay (TD) of at least one of the subjects (Ti, T2), said duration time delay so that the acoustic signals received by the first subject (Ti), originating from passive reflections of the initialization transmissions of the first subject (Ti) on objects of the environment, have no influence on the exploitation made by the first suje t (Ti) reaction emissions (71) received by at least one receiver (30) and from the second subject (T2). Method according to Claim 1, characterized in that the acoustic signals (31) of the second subject (T2) reaction emissions received by the first subject (Ti) are reaction transmissions triggered by the acoustic signals of the first subject. (1) at the end of at least one delay time, of known duration of at least one of the subjects (Ti, T2) so that the acoustic signals received by the second subject (T2) and which come from the passive reflections of the acoustic signals of the first subject's (T1) reaction emissions on objects of the environment have no influence on the exploitation made of the acoustic signals received by the second subject (T2) with the aid of at least one receiver (50) and corresponding to the first subject's (Ti) reaction emissions by the second subject (T2) to determine the relative distance and / or relative movement between the two subjects (Ti, T2) .353 Method according to claim 1, characterized in that the signal duration (TP2) of the acoustic signals (71) of the reaction emissions of at least one subject (T2) is less than a predetermined fraction of the signal duration (TP1) of the acoustic signals of the transmissions initialization of the first subject (Ti) and / or at least one signal duration (TP2) and / or at least one frequency or at least one frequency change of the acoustic signals (71) of the reaction emissions are known from at least one subject (T2) among the two subjects (Ti, T2). Process according to Claim 1, characterized in that the acoustic signals (71) of the reaction emissions of at least one subject (T2) contain information relating to these reaction emissions, in particular information comprising at least one duration of time delay (TD) used for these reaction transmissions and / or the signal duration (TP2) and / or the signal frequency or the signal frequency evolution for the corresponding acoustic signals, this information being combined by modulation. Method according to Claim 1, characterized in that for at least one evaluation of the acoustic signals (11), initialization transmissions of the first subject and / or acoustic signals (71) of the reaction transmissions of at least one subject (T2) for determining the relative distance and / or the relative movement between the subjects (Ti, T2), at least one characteristic of the acoustic signal (11) of the initialization transmissions and / or the acoustic signals (71) is used reaction emissions, in particular the signal strength and / or the timing of the signal strength and / or the signal frequency and / or the change over time of the signal frequency and / or the mixing signal frequencies of the corresponding acoustic signals. Method according to Claim 1, characterized in that the signal strength and / or the signal evolution of the acoustic signals (71) of the reaction emissions of at least one subject (Ti) have an unambiguous relationship with the signal intensity and / or the signal evolution of the acoustic signals (11) of the initialization transmissions of the first subject (Ti) which in particular have a variable frequency evolution over time. 7 °) Device (100) for determining the relative distance and / or the relative movement between at least two subjects (Ti, T2), in particular between at least two vehicles which receive initialization emissions of acoustic signals by at least a receiver (50) for these transmissions of at least one of the two subjects (Ti) and recognize them as such by operation and generate in response to the acoustic signals received (51) initialization transmissions from least one subject (T1), acoustic signal reaction emissions (71), device (100) characterized in that the feedback transmissions of the acoustic signals (71) are generated with at least one predefined signal duration (TP2) at the end of at least one predefined time delay (TD) known to the subjects. 8 °) Device (100) according to claim 7, characterized in that it generates acoustic signal initialization transmissions having at least one predefined signal duration, recognizable as such by at least the other subject (Ti ) by the operation and which are generated by the other subject (T1) as a response to the initialization emissions generated by the device (100) at the end of at least one predefined timeout period (TD) known to the subjects as acoustic signal reaction transmissions using at least one receiver (50) for reception and to recognize them as such by operation. Apparatus (100) according to claim 7, characterized in that in response to the acoustic signal reaction emissions generated by at least one subject, it generates further acoustic signal reaction emissions of at least one a predefined duration of signal at the end of at least one predefined time delay (TD) known to the subjects (Ti, T2). Device (100) according to claim 7, characterized in that it generates acoustic signal reaction emissions (71) of known signal duration (TP2) of at least one of the subjects (Ti , T2) and / or a known frequency of at least one of the subjects (Ti, T2) or a known frequency change of at least one of the subjects (Ti, T2). Apparatus (100) according to claim 7, characterized in that it generates acoustic signal reaction emissions (71) on which information about said reaction emissions is modulated. Device (100) according to Claim 7, characterized in that the acoustic signals received (51) from the signaling transmissions and / or the acoustic signals received from at least one other subject (Ti) are operated using at least one characteristic of these acoustic signals received. Device (100) according to claim 7, characterized in that it generates acoustic signal reaction transmissions (71) having a signal intensity and / or a signal evolution which are in unambiguous relation with the intensity. signal and / or signal evolution of the received acoustic signals (71) and in particular acoustic signals generated with a time-dependent frequency evolution (11) of the initialization transmissions of at least the other subject (Ti). 14 °) driving assistance system comprising a device (100) according to one of claims 7 to 13.