GB2131642A - Obstacle detection; vehicle parking aid - Google Patents

Abstract

In a manoeuvring aid for road vehicles, which detects obstacles in the region near behind the vehicle 13 when its reversing, transmitter units 14, 16 and receiver units 17, 18, each of which comprises several transmitter elements or receiver elements respectively, the radiating angle phi i and receiver angle eta j of which are arranged in fan shapes which overlap behind the vehicle, are at the rear corners of the vehicle 13. The transmitter elements 14/1 to 14/7, 16/1 to 16/7 are activated consecutively, whereas the receiver elements 17/1 to 17/7, 18/1 to 18/7 all receive simultaneously. The direction of transmission of the radiation is determined by the time of reception of echoes from the obstacle, and the direction of reception by the receiver element that is activated by the radiation. Simple trigonometry then gives the obstacle range. The embodiment described uses infrared radiation, although ultrasonic radiation is also stated to be usable. In place of several receiver elements, a single scanning element may be used. <IMAGE>

Description

SPECIFICATION An obstacle detection apparatus The invention relates to an obstacle detection apparatus particularly but not exclusively for use as a manoeuvring aid when parking orturning a motor vehicle, having a transmitter device provided for the intermittent repeated emission of (electromagnetic or acoustic) radiation energy into the detection space, a receiver device to detect radiation which strikes the receiver device due to reflection, diffusion or diffraction of the radiation emitted by the transmitter device from an obstacle, different transmitter elements with limited radiation angles being associated with different regions ofthe obstacle space and continuously covering the detection space at a minimum interval from the vehicle, different receiver elements with limited receiver aperture angles being likewise associated with different regions ofthe observation space detectable by means ofthe receiver device, and in turn continously covering the observation space, and an evaluation unitwhichfrom a processing ofthetime correlation of emitted and received radiation impulses delivers an indication signal characteristic ofthe location of an obstacle present in the observation space.

Known apparatus of this type operates on the radar or sonar principles, that isto say by detecting transit timeswithin impulses emitted with high repetition frequency by an optical or ultrasonic transmitter, which are reflected back or scattered bythe obstacle to be detected, are received. An apparatus ofthis type which operates on the sonar principle is described in the hournal "Asahi Evening News" of 27.01.1982.

This known apparatus comprises, in a special embodiment, three ultrasonictransmitters and three ultrasonic receivers, which are integrated into the rear bumperofa motorvehicle.Transmittersand receivers are distributed in alternating sequence equidistantly across the width ofthe motor vehicle, whilst the median axes of the radiation angles ofthetransmitters and ofthe receiver aperture angles extend parallel to the longitudinal axis of the vehicle.

This known apparatus possesses at least the following disadvantages: Duets the narrow bunching of the radiated sonic power, which is characteristic of customary ultrasonic sources, a continuously coherent detection space resulting from overlapping ofthe radiation angles is obtained only at a relatively great interval from the vehicle, with the result that obstacles present in immediate proximity of the vehicle and having reflecting surfaces of only small extent,forexample wire mesh fences or slender columns, can be detected not at all or only with difficulty.This disadvantage is further accentuated by the fact that the error of a transit time measurement increases drastically with decreasing obstacle interval, so that with the known apparatus an obstacle which is present at an interval of less then 0.2 to 0.3 m from the vehicle can no longer be located, and its interval thus detected, with sufficient accuracy. Furthermore, due to the narrow bunching ofthe radiated sonic energy, obstacles which are extremely low, orwhich are, for example, arranged pointing towards the vehicle above the transmitter plane, such as for example the load platform of a lorry, cannot be detected reliably, at least in the close region. The same applies to obstacles such as an adjacent vehicle, which cannot be detected with sufficient certainty by the known apparatus.

It is therefore the object ofthe invention to provide an apparatus ofthe type initially defined, which ensures reliable detection, even in the close region immediately adjacent to the vehicle, of those obsta cles which are to be expected with reasonable probability in road traffic.

According to the invention, there is provided an obstacle detection apparatus, comprising a transmitter device provided for the intermittent repeated emission of (electromagnetic or acoustic) radiation energy into the detection space, a receiver device due to reflection, diffusion or diffraction of the radiation emitted by the transmitter device from an obstacle, different transmitter elements with limited radiation angles being associated with different regions ofthe obstacle space and continuously covering the detection space at a minimum interval therefrom, different receiver elements with limited receiver aperture angles likewise associated with different regions of the observation space detectable by means ofthe receiver device, and in turn continuously covering the observation space, and an evaluation unit which from a processing ofthetime correlation of emitted and received radiation impulses delivers an indication signal characteristic ofthe location of an obstacle present in the observation space, wherein at least one group of transmitter elements with radiation angles arranged in fan shape and continuously covering the detection space and at-least one group of receiver elements with receiver aperture angles arranged in fan shape and continuously covering the observation space are provided the receiver elements being arranged at such an interval from the transmitter elements that they cannot receive the primary radiation of the latter, butonlythe secondary radiation emitted from obstacles the evaluation unit generating an indication signal characteristic ofthe minimum interval of the obstacle from the transmitter and receiver elements from the detection ofthe radiation angle region from which radiation emitted bythe transmitter device strikes an obstacle present in the observation space and from a detection ofthe receiver aperture angle region within which secondary radiation from the observation space strikes the receiver unit, the receiver angle region being marked by that of the receiver element reacting in each case, on the basis ofthe interval between transmitter element and receiver element and of the detected radiation angle region and receiver angle region.

According to the above the apparatus being used for example as a manoeuvring aid in a motor vehicle, transmitter elements are provided, the radiation angles ofwhich are arranged in fan shape, so that radiation energy, for example infra-red radiation, is radiated both into the space angle region directly adjoining the vehicletail, and also into the rear space region and angular regions extending to the sides of the vehicle, whilst the radiation angles ofthe indi vidualtransmitter elements adjoin mutually without gaps.An arrangement at a definite interval, or definite intervals, from thetransmitter elements is further provided for receiver elements, the receiver aperture angles ofwhich likewise continuously coverthe rear space ofthe vehicle and optionally an angular region adjoining the latter to the sides, so thatthe receiver elements can receive secondary radiation emitted by any obstacles present, which results from reflection, diffusion and/or diffraction of the primary radiation emitted by the transmitter elements and striking such obstacles, within their receiver aperture angles, but cannot receive the actual primary radiation emitted by the transmitter elements.The manoeuvring aid apparatus according to the invention produces a virtually trigonometrical evaluation of the obstacle interval on the basis ofthe interval between the respective transmitter element and receiver element which has transmitted its primary radiation at a specific angle, or which has received secondary radiation thrown back by the obstacle.

The knowledge ofthe radiation direction, and of the direction from which the secondary radiation is received, which is necessaryforthis purpose, can be obtained, when the transmitter elements are each modulated into emission duty individually for a period in the scope of repeated irradiation cycles, so that if a specific receiver element reacts within such a period, the direction from which this receiver element "sees" the obstacle is also determined.

This also applies to an embodiment ofthe invention in which the transmitter elements are each modulated individually into emission duty for a period in the scope of repeated irradiation cycles, and the receiver elements are modulated into their ready-to-receive state individually at differenttimes within such an emission period. Consequently the receiver elements are modulated into their ready-to-receive state not simultaneously, but individually and separately in a definite sequence and for correspondingly shorter periodswithin the emission period of an individual transmitter element, with the favourable result that only a single preamplifier is necessary to process their output signals.

It is advantageous in this case if, according to another embodiment of the invention, the transmitter elements are modulated into emission duty pulsatorily and in synchronism with the ready-to-receive states ofthe receiver elements within the respective emission periods.

In other embodiments of the invention a transmitter unitand a receiver unit, which can respectively transmit primary radiation into the total detection space and receive secondary radiation from the total observation space, are provided on each of the two sides of a median axis.

The transmitter elements are simultaneously mod ulatableintotheirradiation-emitting duty state in the case of simultaneous readiness of all the received elements to receive. Alternativelythetransmitter elements are modulable into their emission state in pulsatory service for consecutive emission periods which are mutually spaced bypause, enods. These embodiments of the invention are characterised by a symmetrical arrangement, relative to the longitudinal axis for example ofthe vehicle, oftransmitter elements and receiver elements, the directions of radiation and of reception which are necessary to determine the interval of an obstacle can also be determined solelyfrom the receiverelements reacting in each case.

In a further embodiment ofthe invention a receiver element, the receiver aperture angle of which,within which it can receive secondary radiation, corresponds to the radiation angle of the associated transmitter element, is associated with each transmitterelement which radiates primary radiation into the detection space with a definite radiation angle. This results in a coincidence,which is favourable to the evaluation of the secondary radiation-receiver signals ofthe manoeuvring aid apparatus according to the invention, of the detection space into which the primary radiation is radiated, with the observation space out of which the secondary radiation is received.

In another embodiment ofthe apparatus, the receiver aperture angles of mutually adjacent receiver elements of a receiver unit overlap, whilst the angular widths ofthe overlap regions are preferably equal to the angularwidth ofthat partial region of the respective receiver aperture angle which does not overlap one ofthe adjacent receiver aperture angles, in the scope ofthe evaluation apparatus a linking device is provided which detects from the alternative or combined reaction of adjacent receiver elements, whetherthe radiation received falls in an overlap region or in the unoverlapped part ofthe respective receiver angle, and a transmitter element, the radiation angle of which conforms to these receiver angle regions, is associated with each unoverlapped region ofthe receiver aperture angles and with each oftheir overlap regions.Afavourably high angular resolution power relative to the observation space can be obtained with only a few receiver elements, accompanied by a correspondingly high interval resolution power of the detectable obstacle intervals.

In combination with the above, in an embodiment of the invention as a manoeuvring aid apparatus, two receiver elements are provided on each side ofthe vehicle,whilstthe overlap region ofthe radiation angles ofthe innertransmitter elements, viewed from above, corresponds to a strip ofthevehiclewidth extending in the longitudinal direction ofthevehicle which is adjoined laterally by the radiation angles of the outertransmitter elements which widen the observation space on both sides ofthe vehicle, it is also possibleto operate with a favourably small number of transmitter elements.

The small number of receiver elements which is characteristic of this embodiment also involves con siderable cost advantages This also applies particularlyto an embodiment ofthe manoeuvring aid apparatus according to the invention in which a total of only four receiver elements is required.

Additional certainty in the detection of obstacles present to the side ofthe vehicle can be obtained by an embodimentofthe manoeuvring aid apparatus in which at leastthose receiver elements which are aligned for a reception of secondary radiation from reg ions of the observation space located outside the vehicle width are additionally constructed as threshold value detectors, which then deliver a further output signal when the intensity ofthe secondary radiation received exceeds a given threshold value.

In a preferred embodiment ofthe manoeuvring aid apparatus according to the invention, infra-red lightemitting diodes are employed as transmitter elements and infra-red-sensitive semiconductor photo-diodes are employed as receiver elements.

As an alternative to the above, an embodiment of the manoeuvring aid apparatus according to the invention can likewise be realised with current ultrasonic engineering means using ultrasonic transmitters and appropriately tuned ultrasonic receivers.

Transmitter elements and receiver elements having transmitter and receiver characteristics in which the radiation angles ofthe transmitter elements are horizontally between 5 and 30 and vertically between 30 and 70 , be realised by simple means in combina tionwith infra-red transmitter and receiver elements by lenticular configurations of their cast elements.

The combination of such a manoeuvring aid appar atuswith an ultrasonic transmitting and receiving unit arranged in the centre ofthe vehicle, which operates on the principle of transit time measurement, provided in addition to the infra-red transmitter units, ensures that obstacles permeable to infra-red radiation, our weakly reflective, which occurwith only low probability in practice, can be detected with adequate reliability, at least if they have large surfaces.

In an advantageous embodiment of the manoeuvring aid apparatus according to the invention in its structure and arrangement, which communicate an obvious and impressive representation of the detectable obstacle intervals, an indicator device communicating the indication of the obstacle interval comprises an electronic matrix memory with line indexing determined by the numbering ofthetransmitter elements and with column indexing determined by the numbering ofthe receiver elements, whilstthe memory content, characteristic of an irradiation cycle ofthe manoeuvring aid apparatus, of an element of the matrix memory, which is associated with each of the overlap regions ofthe transmitter radiation angles and ofthe receiver aperture angles covering the observation space, is a logic ONE when the receiver element corresponding to the column indexing has received, during the irradiation cycle to be evaluated, secondary radiation which was emitted by the trans mitter element corresponding to the line indexing and is otherwise ZERO.

In another embodiment ofthe invention, an indicator device comprises a display panel which exhibits, in an arrangement which is geometrically similar to that ofthe overlap regions ofthe radiation angles ofthe transmitter elements with the aperture angle regions ofthe receiver elements, indicator elements which light up or assume a coloration contrasting with the surroundings when the memory contentoftheir associated memory elements of the memory matrix is respectively a logic ONE.

In a further embodiment of the invention a decoding device is provided which produces from a decoding of the memory content of the memory matrix a digital or analog indication characteristic of the minimum interval from the vehicle of an obstacle present in the observation space. In these embodiments the indicatorfield provided for an analog indication ofthe interval of an obstacle can be arranged in the rear space ofthe vehicle alternatively, an acoustic indicator device is provided which generates sound impulses which varyintheir pitch and/or repetition frequency with the interval of an obstaclefrom the vehicle.

The automatic switching-on of the manoeuvring aid apparatus according to the invention can be provided for example by selecting reverse gear and/or commencing to drive a vehicle in reverse. This ensures thatthe margin of safety provided by the apparatus is availabletothedriverin case of need.

Instead of receiver units which each comprise a group of receiver elements with mutually adjacent receiver aperture angles, it is also possible, to provide a single receiver element, the effective receiver aperture angle ofwhich is rotatable, so that this receiver element can be operated with consecutive detection of mutually consecutive regions of the detection space.

In somefurther embodiments ofthe single receiver element, relating to its fundamental construction the receiverelement has a receiver aperture angle narrowly limited in the horizontal direction and is arranged rotatably about a vertical axis. Alternatively, the receiver element is arranged so as to be stationary and has a receiver aperture angle covering the total detection space, and a rotatable light guide device, for example a shutter device, is provided, through which lightfrom different angular regions ofthe detection space is feedable to the receiver element at different times.

Embodiments ofthe invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 shows the principle of construction of a manoeuvring aid apparatus according to the invention integrated into the rear lamps of a motor vehicle, in a diagrammaticpartlyfragmentedviewfrom above, Fig. 2 shows the apparatus of Fig. 1 viewed from the rear of the vehicle, Fig. 3a and 3b show details of the arrangement of transmitter elements and receiver elements ofthe manoeuvring aid apparatus, Fig. 4 shows a memory matrix provided in the scope of an evaluation unit of the manoeuvring aid apparatus according to Figs. 1 to 3b, Fig. 5 shows details ofthe modulation of the memory matrix according to Fig. 4, Fig. 6 shows a further memory matrix of its evaluation device suitable forthe evaluation of receiver signals of a manoeuvring aid apparatus constructed symmetrically relative to the longitudinal axis of the vehicle, Figs. 7a and 7b show an illustration, corresponding to Fig. 1, of the manoeuvring aid apparatus according to the invention and of a memory matrix to explain a specific mode of operation of the manoeuvring aid apparatus, and Fig. 8 shows a special arrangement of receiver elements of a receiver unit which may be employed in the scope ofthe manoeuvring aid apparatus accord ingtoFig.1 or7b.

The purpose of the manoeuvring aid apparatus 10 illustrated in Fig 1 is the reliable detection of obstacles 11 or 12 in a part of the rear space of a motorvehicle 13, which is difficultforthe driverto see whilst reversing the vehicle. Obstacles of the type illustrated in Fig. 1 may be, for example, telephone distribution boxes, work site barriers and the like.

The essential functional constituents ofthe manoeuvring aid apparatus 10 are two infra-red transmitter units 14 and 16 and two infra-red receiver units 17 and 18, which in the arrangement which can best be seen from Fig. 2 are integrated into the rear lamps 19 and 21 of the vehicle 13, whilstthe horizontal intervals b ofthetransmitter units 14 and 16, and ofthe receiver units 17 and 18 arranged beneath the latter, is chosen as great as possible and correspondsvirtuallyto the width ofthevehicle.

Forthe purpose of explanation, and without restricting generalities, itwill be assumed thatthe transmitter units 14 and 16 each have seven transmitter elements 1411 to 1417 and 16/1 to 1617 (Fig. 3a), andthatthe individual transmitter elements of the transmitter units 14 and 16 are arranged in each case so that the angular regions #i(i=1,2... 7) of 15 each covered by their radiation fields ("transmission cones") adjoin each othercontinuously,sothatwith simultaneous energisation of all the transmitter elements 14/1 to 1417 or 16/1 to 16S ofthe relevant transmitter unit 14 or 16, a total radiation field is obtained which corresponds to that of a single punctiform radiation source with a horizontal aperture angle =(pi +(p2+ ...

+ #7 or in the specific example selected, a total aperture angle m of 105".

Correspondingly, it will be assumed for the receiver units 17 and 18 that they each comprise seven receiver elements 17/1 to 1717 (Fig. 3b) or 18/1 to 18/7 with receiver aperture angles rli to rI7 of at least 150 in each case, whilstthe receiver elements 17/1 to 1717 or 18/1 to 18/7 are in turn arranged so that their receiver aperture angles fli to n7 are mutually continuously adjacent and complement each other to form a total apertu re angle E, the amount of which corresponds to the total radiation angle PI of the associated transmit terunit 14or 16.As may be seen bestfrom Fig. 1,the transmitter units 14 and 16 are arranged so that no vehicle parts whatever project into the radiation fields or radiation angles (Pi to cp7 emissable by the transmitter elements 14/1 to 1417 or 16/1 to 1617, but the inner edges 22 and 23 of the radiation fields (p of the innertransmitter elements 14/1 and 16/1 of the transmitter units 14or 16 are oriented as steeply as possible, that is to sayvertually at right angles to the vertical longitudinal median plane 24 ofthe vehicle 13, so that the radiation fields (Pi ofthe innertransmitter elements also coverthe rear space region immediately adjacent to the vehicle tail as completely as possible.

The receiver elements 17/1 to 17/7 and 18/1 to 18/7 of the receiver units 17 or 18, the receiver aperture angles fli to 177 of which are assumed to be identical in width and orientation to the radiation aperture angles (Pi to cp7 ofthetransmitter elements 14/1 to 1417 or 16/1 to 16n in the exemplary embodiment a ording to Fig. 1, are arranged and constructed so that they cannot receive the direct radiation or primary radiation emitted into the radiation angles ep, to #7, but can receive radiation energy resulting from a reflection, scattering and/or diffraction of the primary radiation, summarily designated secondary radiation, which strikes the receiver surfaces of the receiver elements 17/1 to 1717 or 18/1 to 18/7 within theiraperture angles rli to 117. Functional characteristics ofthe manoeuvring aid apparatus 10 according to the invention will now be discussed belowwith additional reference to Figs. 4 and 5, whilst alternative service possibilites ofthe same will also be dealt with.

For a first explanatory example, it will be assumed that the apparatus 10 exhibits only one transmitter unit, forexamplethe transmitter unit 16 arranged on the right reartail lamp 21, and onlythe receiver unit 17 arranged on the left-hand side ofthe vehicle. By means of a control unit, notshown, the transmitter elements 16/1 to 16S areenergised consecutively, for example in the sequence indicated bytheir indexing 1 to 7,forshort periods Atj of equal duration.These irradiation cycles, comprising the successive activation of the individual transmitter elements 16/1 to 1617, within which the regions ofthe obstacle space marked bythe radiation angles cpl to cp, of the transmitter elements 16/1 to 16S are illuminated consecutively, are continually repeated. All the receiver elements 17/1 to 17/7 of the receiver unit 17 are maintained permanently ready-to-receive.

The manoeuvring aid apparatus 10so far explained then operates as follows: During the energisation period At2 ofthe second transmitter element 16/2, in which the latter emits infra-red radiation into the radiation angle region 92, the receiver element 17/6 ofthe receiver unit 14-and this receiver element 17/6 alone-- receives secondary radiation which results from a reflection or scattering of the primary light striking the obstacle 12, for example in the direction ofthe arrows 26 and 27, into the receiver aperture angle 6, as illustrated diagrammatically bythefurther arrows 28 and 29.Secondary radiation which is reflected by the obstacle 12 in directions otherthan towards the receiver element 17/6 indicated for example by the arrows 28 and 29, for example in the direction ofthe arrow31 cannot be received by any of the other receiver elements.

Because the direction of spread or radiation angle 92 ofthe transmitter element 16/2 isfixedforthe period At2 during which it emits infra-red radiation, and the receiver aperture angle region 5from which the secondary radiation is received is also determined bythe reaction of the receiver element 17/6, and the lateral interval b between the activated transmitter element 16/2 and the reacting receiver element 17 is also known, it is possible from these data, for example by means of a simpletrigonometncal calculation which can be performed by means of an electronic computer of an evaluation unit not shown in detail, to locate the obstacle 12 at least approximately and to determine its interval from the vehicle tail in the sense of a minimum estimate.

Similar considerations apply if infra-red primary radiation emitted from the transmitter elements 16/5 and 16/6 during the activation periods At5 and At6 strikes the obstacle 11 and the receiver element 17/ of the receiver unit 17 receives the resulting secondary radiation.

In the scope of an evaluation unit, which generates output signals characteristic of the interval of an obstacle 11 or 12 from the vehicle 13 and its arrangement relativeto the vehicle 13, at least one electronic memory matrix 32 (fig. 4) is provided the line indexing i of which corresponds to that ofthe indexing 1 to 7 of the transmitter elements 16/1 to 1617, and the column indexing of which corresponds to that ofthe indexing "/j" of the receiver elements 17/1 to 17/7.Within the scope of this memory matrix 43 the memory places sjj provided with the corresponding indexing ij is associated with each ofthe rhomboidal overlap regions 33, in Fig. 1, of the radiation angles cpi and of the receiver angles rlj. The modulation of the memory places sjj of the memory matrix 32 may be effected for example, as indicated diagrammatically in Fig. 5, from an AND-conjunction ofthe modulation signals generated in time sequenceforthetransmitter elements 16/1 to 16S and of the receiver reply signals thereupon generated by the reacting receiver elements 17/1 to 1717.The memory content of the memory matrix 32 resulting after expiry of the described irradiation cycle is reproduced in Fig. 4, where the memory content "1 " of the memory place S2.6 contains the information as to the location ofthe obstacle 12 (Fig. 1), whilst the memory contents "1" of the memory places Sag.3 and 55,3 contain the information relating to the location of the obstacle 11. These data can be indicated in analog or digital format by current data processing techniques.

For this purpose, for example, an indicator field substantially corresponding to Fig. 1 may be provided, in which an indicator element, for example a lightemitting diode 34, is associated with each ofthe overlap regions 33 and lights up when the content of the memory places sjj associated with the relevant overlap region is a logic 1.An indication is also possible such that a crossbeam oriented at right angles to the longitudinal axis 24 of the vehicle 13, the interval of which from the vehicle tail correspondsto the minimum detected obstacle interval, lights up in an indicator field.

It may also be advantageous if, alternatively or additionally, a numerical indication of the obstacle intervals compiled from the memory contents is provided, which can be brought into the desired numerical indication format by means of current decoding devices.

It may further be advantageous if, alternatively or additionally, an acoustic analog indication is provided, for exampie such thatthe pitch and/orthe repetition frequency of acoustic impulse signals increases with decreasing obstacle interval from the vehicle.

If optical indicator devices are provided, whereby obstacles 11 and 12 present behind the vehicle 13 are intended to be indicated, then it is expedient for safety reasons if such indicator devices are accommodated in the rear space of the vehicle, so that the driverwhen driving backwards is virtually compelled to face in that direction. In the case of a combined realisation of an analog-optical indication field with a numerical indication, this may also be accommodated on the dashboard ofthevehicle.

It is clear that the succession frequency of the modulation impulses by which the transmitterelements 16/1 to 16S are energised to emit infra-red radiation, and the repetition frequencies of the irradiation cycles, must be chosen sufficiently high to enable the variations in obstacle intervals which occur during the manoeuvring of the vehicle to be detected sufficiently rapidly. However, this presents no problem if commercially available infra-red light-emitting diodes are employed as transmitter elements, and semiconductor photo-diodes as receiver elements, which have reaction times in the ns ranges, and if customary semiconductor memories are employed in the scope ofthe evaluation device.

An account is given below of a further mode of operation which appears particularly suitable forthe practical service ofthe manoeuvring aid apparatus 10, wherein the transmitteru nits 14 and 16 and receiver units 17 and 18 provided on both sides ofthevehicle are now used for their purpose.In this case the transmitter elements 16/1 to 16S ofthe transmitter unit 16 arranged on the right-hand side ofthe vehicle are first of all modulated to emit infra-red radiation in consecutive periods At, to At7, then the transmitter elements 14/1 to 1417 in the following periods At1 to At7 (Fig. 6) in the sequence indicated by the indexing, whilstthe receiver elements 18/1 to 18/7 and 17/1 to 1717 of both receiver units 18 and 17 are permanently readyto receive. An irradiation cycle then naturally comprises the successive modulation of all the said transmitter elements 16/1 to 16S and 14/1 to 1417 in the stated sequence.In this mode of operation ofthe manoeuvring aid apparatus 10 according to the invention, if for example the transmitter element 16/2 is activated in the period At2 and radiates infra-red radiation into its radiation angle (P2r secondary radiation which is cast bythe obstacle 12 into the corresponding aperture angles 112 and 11s ofthe receiver elements 16/2 or 17/6 is then received both by the receiver element 18/2 of the right-hand receiver unit 18 and by the receiver element 17/6 ofthe receiver unit 17 arranged on the left-hand side ofthe vehicle.

In this case a memory matrix 35 comparable to the memory matrix 32 and designed as an appropriate variantforthis mode of operation has the configura- tion reproduced in Fig. 6, and the memory content reproduced in Fig. 6 after the conclusion of an irradiation cycle.

In this memory matrix35,the response behaviour of the receiver elements 18/1 to 1817 of the receiver unit 18 arranged on the right-hand side of the vehicle is stored in its left upper quadrant, and the response behaviour of the receiver elements 17/1 and 1717 of the receiver unit arranged on the left-hand side ofthe vehicle in its right upper quadrant, resulting from the modulation ofthe transmitter elements 16/1 to 1617 of the transmitter unit 16 arranged on the right-hand side ofthevehicle.

The response behaviour of the receiver elements 18/1 to 1817 of the receiver unit 18 arranged on the right-hand side of the vehicle is stored in the left lower quadrant of this memory matrix 35, and the response behaviour of the receiver elements 17/1 to 1717 of the receiver unit 17 arranged on the left-hand side of the vehicle is stored in the right lower quadrant of the matrix 35, resulting from the activation ofthe trans mitter elements 14/1 to 1417 ofthetransmitter unit 14 arranged on the left-hand side, which are energised consecutively in the periods At1 to At7.

It is clearthatthe memory content of the memory matrix 35 may be processed, in a similar mannerto that previously described, into analog or digital indication signalsforthe relevant obstacle intervals.

The emissive energisation of the transmitter elements 14/1 to 1417 and 16/1 to 1617 is of course not restricted to the sequence indicated by the indexing of the periods Atj; on the contrary, the transmitter elements may be modulated to emit radiation in any desired sequence within an irradiation cycle, because only the "physical" conjunction of the memory places sij with the transmitter elements (index "i") and with the receiver elements (index "j") is significant for the decoding ofthe memory content of the memory matrix 35; the emissive energisation of the radiation elements 14/1 to 1417 and 16/1 to 16/7 may therefore also occur alternately or alternately by groups.

In the embodiment explained with reference to Figs.

1 and 6 the manoeuvring aid apparatus loins characterised by particularly high reliability in the detection of obstacles. This is due on the one hand to the fact that the obstacles 11 and 12 are irradiated twice in the scope of the irradiation cycle, and generally with different irradiation geometry, where- by the probability of a favourable radiation geometry existing for the detection ofthe secondary radiation during at least one irradiation process is considerably increased; on the other hand, virtually double certainty exists in the detection ofthe direction in which radiation emitted by the transmitter elements strikes an obstacle, sincethis emission direction can be determined firstly from the modulation ofthe trans mifterelements 14/1 to 1417 or 16/1 to 16/7 and secondly from the response behaviour ofthose receiver elements 17/1 to 1717 or 18/1 to 18/7, into the receiver apertu re angles , to 117 which the respective secondary radiation resulting from the scattering ofthe primary radiation by the obstacle is cast.

By sacrificing this redundancy inthe determination ofthe radiation angles (pj within which primary infra-red radiation strikes an obstacle 11 and/or 12, the manoeuvring aid apparatus 10 may also be designed so that all the transmitter elements 14/1 to 1417 and 16/1 to 16S are energised to emit radiation simultaneously in consecutive emission periods At, possibly mutually spaced off-periods 3t, and the determination ofthe directions or radiation angles (pj is made solely from the detection of the response behaviourofthe receiverelements 17/1 to 1717 and 18/1 to 1817. In orderto explains this mode of operation of the manoeuvring aid apparatus 10, reference will now be made to Fig. 7a, which shows, in an illustration similarto Fig. 1, a situation in which a relatively large obstacle36,for example a trunk, which cannot be seen by the driver is present in the arrangementto be seen from Fig. 7a in the detection space which can be monitored by the manoeuvring aid apparatus 10.In this situation in tlqe case of a simultaneous energisation of all the transmitter elements 14/1 to 1417 and 16/1 to 1617', the response event detectable by means ofthe receiver units 17 and 18 is that, of the receiver unit 17 arranged onthe left-hand side ofthe vehicle, only its receiver elements 17/4,17/5 and 17/6 respond, and ofthe receiver unit 18 arranged on right-hand the right-handsideofthevehicle,only its receiver elements 18/2,18/3 and 18/4 respond.This response event is illustrated in the two-line matric 37 reproduced in Fig. 7b, the matrix elements sj,, to S1,7 and 52',1 to s2,7 of which again represent memory elementsof a memory provided in the scope of an electronic evaluation unit, the memory content ofwhich can bew indicated, by appropriate decoding, in units of the interval ofthe obstacle 36 from the vehicle 13.In this memory a memory place identified by a matrix elementsb (j=1 to 7) ofthe u-per line ofthe matrix 37 is associated with each receiver element of the left-hand receiver unit 17, and a memory place identified by a matrix element s;6 of the lower line of the matrix 37 is associated with each receiver element of the right-hand receiver unit 18. Forthose receiver elements which have reactedthat is to say, received secondary radiation -- in the scope of an irradiation cycle-just occurred or also previous-to be evaluated, a logic 1 is stored in the associated memory element, and for those receiver elements which have "seen" no secondary radiation, a 0 is stored.

When the memory content specifically reproduced in Fig. 7b exists, this means that the obstacle 36 is present in the detection region 38 shown hatched in Fig. 7a and is located both within three receiver angles 2, n3, 114 ofthe receiver unit 18 on the right-hand side of the vehicle and also within three receiver angles 114, 5, and 116 of the receiver unit arranged on the left-hand side ofthe vehicle.An evaluation ofthis memory content in units of the obstacle interval is expediently made in this embodiment ofthe manoeuvring aid apparatus 10 by reading out -- in analog or digital form the minimum interval of the detection region 38 from a base line 39 oriented at right angles to the vehicle longitudinal axis 24, and shown by dash lines, that is to saythe interval dl of the base line 39 from the corner 41 ofthe detection region 38 closest to it.In the specific example according to Fig. 7a, if the observation space had been scanned by the mode of operation of the manoeuvring aid apparatus 10 described with reference to Figs. 1 and 6, then for an otherwise comparable evaluation a greater interval ofthe obstacle 36 from the base line 39would result, namelytheinterval d1' ofthe base line39from the corner 42, nearest thereto, of the overlap region of the receiver angle 112 ofthe receiver element 18/2 of the receiver unit 18 arranged on the right-hand side of the vehicle with the receiver angle #6 of the receiver element 17/6 of the receiver unit 17 arranged on the left-hand side of the vehicle.

Comparison of the two modes of operation shows that in the case of simultaneous irradiation ofthetotal observation space, and if extensive obstacles 36 are present which extend across a plurality of overlap regions 33 ofthe observation space, the interval resolution power is somewhat lowerthan in the case of successive illumination ofthe radiation angles e but that the interval indication always lies on the safe side, inasmuch as, if anything, a shorter obstacle interval than the true one is indicated.However, a substantial advantage ofthe mode of operation of the manoeuvring aid apparatus 10 described with reference to Figs. 7a and 7b is that the period At, in which an obstacle 36 can be detected is very much shorterthan in the case of successive illumination ofthe radiation angles (pj.The mode of operation of the manoeuvring aid apparatus 10 described with reference to Figs. 7a and 7b is therefore advantageous particularly at the beginning of a manoeuvring process, when it is importantto get an idea of existing obstacles as quickly as possible, and it is still possible to assume relatively long obstacle intervals, for example in the 2 metre range.Itisthen expedient ifthe manoeuvring aid apparatus 10 can be switched over, or switches over automatically, from one mode of operation to the other when an obstacle interval smallerthan for example 80 cm occurs and the manoeuvring aid apparatus 10 thereafter operates in the mode with successive illumination of the radiation angles (p;.

To enable the available space to be utilised as fully as possible, for example when turning a vehicle on a narrow road or when parking into a restricted parking gap, it is desirable for obstacle intervals to be detectable in fine graduation, particularly in the region close to the vehicle, that is to say the interval resolution power ofthe manoeuvring aid apparatus 10 should be as high as possible in the region instantaneously nearthevehicle.

Forthis purpose, smaller aperture angles 11i to 113 may be provided for the inner receiver elements, for examplethe receiver elements 17/1 to 17/3 and 18/1 to 18/3 ofthe left-hand and right-hand receiver units 17 and 18, than for the respective outer receiver elements; similarly, correspondingly narrower radiation angles (P1 to (P &commat;3 maybe provided forthe associated inner transmitter elements 14/1 to 14/3 or 16/1 to 16/3.

In this case, however, it may be that a largertotal number of transmitter and receiver elements will be required to enable the total observation space to be scanned with a sufficiently close raster.

An advantageous opportunity to achieve a favou rably high angle resolution power in respect ofthe secondary radiation reception directions, and hence also a correspondingly high radiation resolution power, even with relatively few receiver elements per receiver unit 17 and 18, is, as illustrated in Fig. 8 only for the receiver unit 18 on the right-hand side of the vehicle, to employ receiver elements with enlarged receiver aperture angles 11i to 11sthan those shown in Fig. 1 or7a, and to makethefan-shaped arrangement of these receiver elements such thatthe receiver angles of adjacent receiver elements overlap in the regions 1,2, 112,3,113,4' 4,5 and 5,6 shown by dash lines, whilst it is again expedientto choose the angle widths ofthe overlapping and unoverlapped regions of approximately equal magnitude.In this way it is then possible, with for example only six receiver elements, to achieve a division of the observation space into eleven receiver angle regions of prescribable angle width, which can be identified by the fact that either one receiver element alone, which is associated with one of the receiver aperture angles q1 to also reacts, or two receiver elements react at a time, if the radiation strikes both receiver surfaces of receiver elements arranged mutually adjacent from the overlap regionsrll,2to 11s,s However, it is then necessary for the mode of operation of the manoeuvring aid apparatus 10 described with referenceto Figs. 1,4and6to provide an increased number of transmitter elements which can emit radiation selectively into the different angular regions detectable by alternative or conjoint reaction of receiver elements.

Obviously, ultrasonic transmitter and receiver elements may also be used in the scope of a manoeuvring aid apparatus 10 instead of transmitter elements and receiver elements which are designed for the emission or the detection of electromagnetic radiation, particularly infra-red radiation, and may be employed in the functions described with reference to Figs. land 4to 7a, 7b. It is then possible in a simpler mannerthan with the use of electromagnetic radiation sources and receivers, although not impossible even with the latter, thanks to the extremely short reaction times of light-emitting diodes and semiconductor radiation receivers, to execute additional transittime measurements by a rapid pulsatory operation of such ultrasonic transmitter elements and therebyto achieve a high interval resolution power in particular even in the case of major obstacle intervals between 1 and 3 m.

An advantageous variant of a manoeuvring aid apparatus 10 may also consist in that individual receiver elements, particularly the outer ones which receive radiation from the outer receiver angle regions 7, deliver an additional signal if the secondary radiation received exceeds a minimum intensity, that is to say the obstacle detected is relatively close. Such a receiver elementthen acts additionally as an approach switch,which can trigger an indication signal or an alarm signal if the interval of an obstacle from the vehicle falls below a minimum value.

It is further advantageous if the transmitter and receiver elements provided in the scope of the above-explained manoeuvring aid apparatus 10, viewed inthevertical direction, havethelargest possible aperture angles, so that even obstacles located at a relatively short distance from the vehicle atground level or approximately atthe height ofthe boot lid can be reliably detected. Such radiation and reception characteristics oftransmitter and receiver elements are considerably easier to realise by appropriately constructed lenses where infra-red light-emit- ting diodes and infra-red receiver elements are used than with conventional ultrasonic sources and ultrasonic receiver elements.

Further variants ofthe manoeuvring aid apparatus 10,which may be used with advantage for the above-described purpose, will not be dealt with below: The manoeuvring aid apparatus 10 may be modified sothatthe receiver elements 18/1 to 18n or 17/1 to 1717 are modulated into their ready-to-receive state, not all simultaneously, butsinglyandconsecutivelyin a definite sequence, within a period At in which a7 single one of the transmi4 ter elements 14/1 to 1417 or 16/1 to 16S is modulated into its radiation-emitting state.Here again the direction from which the secondary radiation of an emitting transmitter element coming from the radiation space is received is detectable from the indexing ofthe respective receiver element which is ready to receive. Although in this mode of operation thetime during which an individual receiver element is ready to receive is shortened, namely to an order of magnitude of a period At1n, where Atj is the period during which the transmitter element is energised and n is the number of the receiver elements which have to be modulated into the ready-to-receive state consecutively within this period, nevertheless the advantage of such an embodimentofthemanoeuvring aid apparatus 10 is that only a single preamplifier is required to amplify the output signals generated bythe individual receiver elements. However, it may be expedient from consid erationsofwiringsimplicity, if one preamplifier is also provided for each receiver unit comprising a group of receiver elements.

It is also advantageous ifthe respective transmitter element is itself modulated into emission duty in a pulsatory operation synchronous with the modulation ofthe receiver elements within the period At; within which the associated receiver elements are successively modulated into their ready-to-receive state. By this means the transmitter elements may be operated with shorter emission times and therefore, as a general rule,withsubstantiallyhigheroutputpower or radiation power.

Avariantofthemanoeuvringaidapparatus 10 which is embraced bythe idea ofthe invention may also consist in that, instead of a group of receiver elements with mutually adjacent receiver aperture angles, only a single receiver element is provided, the effective aperture angle 11 of which is rotatable, so that when this receiver element reacts the direction from which the secondary radiation has been received can be deduced from the simultaneous detection of the orientation of its receiver aperture angle.

Such a rotatability of the receiver apertu re ang le may be realised in thatthe receiver element itself is arranged rotatably, orthat a receiver element with the receiver aperture angle covering the total detection region is arranged stationary and a rotatable shutter device is provided which permits different sections to be shuttered out ofthe overall receiver aperture angle range at differenttimes. Such a device may also be realised by means of a light conductor, mirror or prism arranged rotatably or pivotably in front of the receiver element, with the various pivotal or rotary positions of which, assumed in the course of an emission period of the transmitter element, defined different detection angle regions are associated.

Claims (25)

1. An obstacle detection apparatus, comprising a transmitter device provided forthe intermittent repeated emission of (electromagnetic or acoustic) radiation energy into the detection space, a receiver device to detect radiation which strikes the receiver device due to reflection, diffusion or diffraction ofthe radiation emitted by the transmitter device from an obstacle, different transmitter elements with limited radiation angles being associated with different regions ofthe obstacle space and continuously covering the detection space at a minimum inte val therefrom different receiver elements with limited receiver aperture angles likewise associated with different regions ofthe observation space detectable by means ofthe receiver device, and in turn continuously covering the observation space, and an evaluation unitwhichfrom a processing ofthetimecorrelation of emitted and received radiation impulses delivers an indication signal characteristicofthe location of an obstacle present in the observation space, wherein at least one group oftransmitterelements with radiation angles arranged in fan shape and continuously covering the detection space is provided and at least one group of receiver elements with receiver aperture angles arranged in fan shape and continuously covering the observation space is provided,the receiver elements being arranged at such an interval from the transmitter elements that they cannot receive the primary radiation ofthe latter, but only the secondary radiation emitted from obstacles, the evaluation unit generating an indication signal characteristic ofthe minimum interval of the obstaclethe transmitter and receiver elements from a detection of the radiation angle region from which radiation emitted by the transmitter device strikes an obstacle present in the observation space and from a detection ofthe receiver aperture angle region within which secondary radiationfromthe observation space strikes the receiver unit, the receiver angle region being marked by that ofthe receiver element reacting in each case, on the basis of the interval between transmitter element and receiver element and ofthe detected radiation angle region and receiver angle region.

2. An apparatus according to Claim 1, wherein the transmitter elements are each modulated individually into emission dutyforthe period in the scope of repeated irradiation cycles, whilst all the receiver elements are modulated simultaneously into their ready-to-receive state.

3. An apparatus according to Claim 1, wherein the transmitter elements are each modulated individually into emission dutyfor a period in the scope of repeated irradiation cycles, and the receiver elements are modulated into their ready-to-receive state indf vidually at differenttimes within such an emissiarr period.

4. An apparatus according to Claim 3, whereinthe transmitter elements are modulated into emission duty pulsatorily and in synchronism with the receiver elements within the respective emission periods.

5. An apparatus according to anyone ofthe preceding claims, wherein a transmitter unit and a receiver unit, which can respectively transmit primary radiation into the total detection space and receive secondary radiation from the total observation space, and provided on each side a median axis.

6. An apparatus according to Claim S, wherein all the transmitter elements are simultaneously modul able into their radiation-emitting duty state in the case of simultaneous readiness of all the receiver elements to receive.

7. An apparatus according to Claim 6, wherein the transmitter elements are moduable into their emission state in pulsatory service for consecutive emission periods which are mutually spaced by pause periods.

8. An apparatus according to anyone of Claims 5 to 7, wherein a receiver element, the receiver aperture angle ofwhich, within which it can receive secondary radiation, corresponds to the radiation angle of the associated transmitter element, is associated with each transmitter element which radiates primary radiation into the detection space with a definite radiation angle.

9. Apparatus according to anyone of Claims 1 to 7, wherein the receiver aperture angles of mutually adjacent receiver elements of a receiver unit overlap, whilstthe angularwidths ofthe overlap regions are preferably equal to the angularwidth ofthat partial region of the respective aperture angle which does not overlap one ofthe adjacent receiver aperture angles, in the scope of the evaluation apparatus a linking device is provided which detects from the alternative or combined reaction of adjacent receiver elements, whetherthe radiation received falls in an overlap region or in the unoverlapped part of the respective receiver angle, and a transmitter element, the radiation angle of which conforms to these receiver angle regions, is associated with each unoverlapped region of the receiver aperture angles and with each of their overlap regions.

10. An apparatus according to Claim 3, wherein, for a motor vehicle, two receiver elements are provided on each side of a median axis of the vehicle, whilstthe overlap region ofthe radiation angles ofthe innertransmitter elements, viewed from above, corresponds to a strip ofthe vehicle width extending in the longitudinal direction of the axis, which is adjoined laterally by the radiation angles ofthe outertransmitter elements which widen the observation space on both sides ofthe vehicle.

11. An apparatus according to anyone of Claims 2 to 8, wherein, for a motorvehicleat least those receiver elements which are aligned for a reception of secondary radiation from regions of the observation space located outside the vehicle width are additionallyconstructed as threshold value detectors, which then deliver a furtheroutputsignal when the intensity of the secondary radiation received exceeds a given threshold value.

12. An apparatus according to anyone ofthe preceding claims, wherein the transmitter elements are constructed as infra-red radiation sources, and the receiver elements as infra-red-sensitive semiconductor photo-detectors.

13. An apparatus according to anyone of Claims 1 to 11, wherein ultrasonic sources are provided as transmitter elements and ultrasonic detectors, tuned to the radiation frequency ofthe transmitter elements are provided, as receiver elements.

14. An apparatus according to Claim 12, wherein the radiation angles of the transmitter elements, measured horizontally, are between 50 and 30 , and measured vertically, between 30 and 700.

15. An apparatus according to anyone of Claims 2 to 12 orclaim 14,wherein,fora motorvehicle, an ultrasonic transmitter and receiver unit arranged in the centre of the vehicle, which operates on the principle of transit time measurement, is provided in addition to the transmitter units.

16. An apparatus according to anyone of the preceding claims, wherein an indicator device communicating the indication of the obstacle interval comprises an electronic matrix memory with line indexing determined by the numbering ofthetransmitter elements and with column indexing determined by the numbering ofthe receiver elements, whilst the memory content, characteristic of an irradiation cycle ofthe manoeuvring aid apparatus, of an element of the matrix memory, which is associated with each ofthe overlap regions ofthe transmitter radiation angles and of the receiver aperture angles covering the observation space, is a logic ONE when the receiver element corresponding to the column indexing has received, during the irradiation cycle to be evaluated, secondary radiation which was emitted by the transmitter element corresponding to the line indexing, and is otherwise ZERO.

17. An apparatus according to Claim 16, wherein the indicator device comprises a display panel which exhibits, in an arrangement which is geometrically similartothat of the overlap regions of the radiation angles ofthe transmitter elements with the aperture angle regions of the receiver elements, indicator elements which light up or assume a coloration contrasting with the surroundings when the memory content oftheir associated memory elements of the memory'matrix is respectively a logic ONE.

18. An apparatus according to Claim 16, wherein a decoding device is provided which produces from a decoding ofthe memory content ofthe memory' matrix a digital or analog indication characteristic of the minimum interval of an obstacle present in the observation space.

19. An apparatus according to Claim 17 or Claim 18, wherein for a vehicle the indicator field provided for an analog indication of the interval of an obstacle is arranged in the rear space of the vehicle.

20. An apparatus according to anyone of the preceding claims, wherein an acoustic indicatordevice is provided which generates sound impulses which vary in their pitch and/or repetition frequency with changes in the distance of an obstacle.

21. An apparatus according to anyone ofthe preceding claims, wherein, for a vehicle, the apparatus can be switched on automatically by engaging the reverse gear of the vehicle, optionally in combination with releasing the parking brake and/or releasing the clutch pedal or commencing a reverse movement ofthe vehicle.

22. An apparatus according to anyone of the preceding claims, wherein instead of a group of receiver elements with mutually adjacent receiver aperture angle regions, only a single receiver element, the effective receiver aperture angle of which is rotatable, is provided.

23. An apparatus according to Claim 22, wherein the receiver element has a receiver aperture angle narrowly limited in the horizontal direction and is arranged rotatably about a vertical axis.

24. An apparatus according to Claim 22,wherein the receiver element is arranges so as to be stationary and has a receiver aperture angle covering the total detection space, and a rotatable light guide device is provided,through which light from different angular regions ofthe detection space is feedable to the receiver element at differenttimes.

25. An obstacle detection apparatus, substantially as hereinbefore described and with reference to Figures 1 to 5, or Figures 1 to 5 modified as shown in Figure 6, Figures 7a and 7b or Figure 8 of the accompanying drawings.