PCT
`
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`International Bureau
`
`
`
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(51) International Patent Classification 5 :
`
`(11) International Publication Number:
`
`WO 91/07672
`
`G015 17/88
`
`(43) International Publication Date:
`
`30 May 1991 (30.05.91)
`
`(21) International Application Number:
`
`PCT/GB90/0 l 73 1
`
`(22) International Filing Date:
`
`9 November 1990 (09.11.90)
`
`Published
`Without international search report and to be republished
`upon receipt of that report.
`
`(30) Priority data:
`8925 384.3
`
`9 November 1989 (09.11.89)
`
`GB
`
`[GB/
`(71)(72) Applicant and Inventor: MONTAGUE, Lewis
`GB]; Kendal Cottage, Hemnall Street, Epping, Essex
`CM5 9LN (GB).
`
`(74) Agent: HEPWORTH LAWRENCE BRYER & BIZLEY;
`Gate House South, West Gate, Harlow, Essex CM20
`lJN (GB).
`
`(81) Designated States: AT, AT (European patent), AU, BB, BE
`(European patent), BF (OAPI patent), BG, BJ (OAPI pa-
`tent), BR, CA, CF (OAPI patent), CG (OAPI patent),
`CH, CH (European patent), CM (OAPI patent), DE, DE
`(European patent), DK, DK (European patent), ES, ES
`(European patent), FI, FR (European patent), GA (OA-
`PI patent), GB, GB (European patent), GR (European
`patent), HU, IT (European patent), JP, KP, KR, LK, LU,
`LU (European patent), MC, MG, ML (OAPI patent),
`MR (OAPI patent), MW, NL, NL (European patent),
`NO, RO, SD, SE, SE (European patent), SN (OAPI pa-
`tent), SU, TD (OAPI patent), TG (OAPI patent), US.
`
`(54) Title: REMOTE SENSING APPARATUS FOR A VEHICLE
`
`
`
`(57) Abstract
`
`Remote sensing apparatus for a vehicle (12) comprises means (13, 14, 15) for determining the separation between a vehicle
`and an object or other vehicle (11) in the region in front of the said vehicle sensitive to the speed of the vehicle for determining a
`threshold distance value which is greater at higher speeds, and means for comparing the thus determined distance of the detected
`vehicle with the said threshold value and for generating a warning signal (16) if the said determined distance is less than the said
`threshold value.
`
`UNIFIED 1013
`
`1
`
`UNIFIED 1013
`
`

`

`FOR THE PURPOSES 0F INFORMAHON ONLY
`
`Codes used to identify States party to the PCT on the front pages of pamphlets publishing international
`applications under the PCT.
`
`Madagascar
`
`Finland
`France
`Gabon
`United Kingdom
`Guinea
`Greece
`Hungary
`Italy
`Japan
`Democratic People‘s Republic
`of Korea
`Republic of Korea
`Liechtenstein
`Sri lanka
`lnxemhourg
`Monaco
`
`‘
`
`Austria
`Australia
`Barbados
`Belgium
`Burkina Faso
`Bulgaria
`Benin
`Brazil
`Canada
`Central African Republic
`Congo
`Switzerland
`can: d'lvoire
`CameI'OOn
`Germany
`Denmark
`Spain
`
`Mali
`Mongolia
`Mauritania
`Malawi
`Netherlands
`Norway
`Poland
`Romania
`Sudan
`Sweden
`Senegal
`Soviet Union
`Chad
`Togo
`United States of America
`
`2
`
`

`

`WO 91/07672
`
`PCT/GB90/0173l
`
`REMOTE SENSING APPARATUS FOR A VEHICLE
`
`The present invention relates generally to remote sensing
`
`apparatus for a vehicle, and particularly to such
`
`5
`
`apparatus for providing a proximity signal to assist safe
`
`driving.
`
`Various prior art systems for detecting the presence of
`
`remote obstacles have been described in the literature.
`
`10
`
`Such obstacle detecting systems make use of some form of
`
`electromagnetic radiation transmitted from a system on
`
`board the vehicle with a suitable receiver for detecting
`
`reflected signals coming from objects in the path of the
`
`vehicle. One such system is described in U.S. Patent
`
`15
`
`4,447,800 which relates to an obstacle detector mounted on
`
`a motor vehicle and having a light emitting element (in
`
`this case a semi—conductor infra-red laser) which
`
`transmits a light signal through an appropriate optical
`
`transmission system into the
`
`region immediately ahead of
`
`20
`
`a vehicle.
`
`The optical signal thus transmitted is of a
`
`wavelength which is outside the spectrum of solar energy
`
`wavelengths or, if within the spectrum,
`
`in a region where
`
`the solar energy at this frequency is of very low
`
`intensity at ground level.
`
`An optical receiving system
`
`25
`
`receives part of the light reflected from an obstacle in
`
`front of the vehicle and passes it to an optical filter
`
`which has a pass band width the central wavelength of
`
`3
`
`

`

`WO 91/07672
`
`PCT/GB90/01731
`
`which is coincident with that of the wavelength of the
`
`light signal transmitted by the optical transmission
`
`system.
`
`The output of the filter is converted by a photo
`
`detector to a corresponding electrical signal for
`
`processing by a data processor in order to determine the
`
`distance of the vehicle from the object in front of it.
`
`Means for calculating the height of the obstacle and the
`
`relative speed between the obstacle and the vehicle
`
`carrying the detecting system are also provided. Other
`
`known systems include that described in French Patent
`
`2,576,126 which is an optical device for measuring the
`
`distance separating two moving objects travelling along
`
`the same path, again having optical transmitting means and
`
`receiving means working to detect light reflected from an
`
`object in front of the vehicle.
`
`In this case, however, it
`
`is envisaged that each vehicle would be provided with a
`
`reflective coded band at the back which reflects the
`
`incident light in a particular manner back to the vehicle
`
`behind so that it can process the received light with an
`
`electronic circuit in order to obtain information relating
`
`to the distance separating the two moving objects and the
`
`relative speed between the two vehicles. Another proposal
`
`using remote sensors is that disclosed in U.s. Patent
`
`4,694,295 which includes an ultrasonic transducer and an
`
`infra-red sensor: This system, however, is adapted to
`
`direct the beam of radiation into the quadrant immediately
`
`behind and to one side of the vehicle to cover the region
`
`10
`
`15
`
`20
`
`25
`
`4
`
`

`

`W0 91 /07672
`
`PCT/GB90/01731
`
`which is not readily visible through the rear view mirror
`
`so as to avoid the necessity for those who are not
`
`physically one hundred per cent from having to rotate the
`
`body and the head to establish the presence of an
`
`overtaking vehicle in the so~called "blind spot" of the
`
`rear View mirror.
`
`More generally, of course, many different remote sensing
`
`systems are known for various purposes,
`
`including air
`
`10
`
`borne radar used in military and civilian aircraft to
`
`detect the presence of other aircraft in the vicinity of
`
`the aircraft carrying the radar set. All of these known
`
`systems, however, fail to provide a solution to the
`
`problem which is encountered in road driving, namely that
`
`15
`
`of ensuring that drivers will maintain a safe distance
`
`behind a preceding vehicle travelling in the same
`
`direction.
`
`Especially when the driving conditions become
`
`congested there is a considerable temptation for drivers
`
`to maintain an inadequate separation between their vehicle
`
`20
`
`and the one in front, especially if this may lead to the
`
`interposition of an overtaking vehicle. Strict guidelines
`
`are laid down by the Ministry of Transport based on the
`
`average time taken by a vehicle to come to rest from any
`
`given speed, and the distance travelled by the vehicle
`
`25
`
`while the driver reacts to an emergency situation, which
`
`have been promulgated as recommended minimum vehicle
`
`separation distances at certain speeds in order to allow
`
`5
`
`

`

`\NT)91/07672
`
`PCI'/GB90/01731
`
`for stopping in an emergency.
`
`Even such regulations are
`
`only a blunt instrument attacking the problem of excess
`
`proximity because by averaging the characteristics of a
`
`wide range of vehicles it leaves each driver in possession
`
`of the facts still with the impression that his own
`
`vehicle may behave differently from (and in this case
`
`better than) the average.
`
`The present invention seeks,
`
`therefore,
`
`to provide means
`
`by which drivers can be encouraged to maintain a suitable
`
`safe distance between themselves and the preceding
`
`vehicles at all speeds, notwithstanding the fact that the
`
`safe distance required at a higher speed is greater than
`
`that required at a lower speed.
`
`It is, of course, unwise
`
`for any such system to be more than an advisory one since
`
`the whole import of the driving conditions can only be
`
`determined by the driver in charge of the vehicle at any
`
`particular time, and there may arise circumstances during
`
`a journey when it is actually safer to be close to the
`
`vehicle in front than otherwise and any system which took
`
`10
`
`15
`
`20
`
`over control to prevent a driver from using his own
`
`judgment based on the prevailing road conditions may in
`
`fact lead to a loss of safety rather than an increase in
`
`it.
`
`25
`
`According to one aspect of the present invention remote
`
`sensing apparatus for a vehicle comprises means for
`
`6
`
`

`

`W0 91/07672
`
`PCT/GB90/01731
`
`determining the separation between a vehicle and an object
`
`or other vehicle in the region in front of the said
`
`vehicle sensitive to the speed of the vehicle for
`
`determining a threshold distance value which is greater at
`
`5 higher speeds, and means for comparing the thus determined
`
`distance of the detected vehicle with the said threshold
`
`value and for generating a warning signal if the said
`
`determined distance is less than the said threshold value.
`
`10 According to another aspect of the present invention,
`
`there is provided remote sensing apparatus for a vehicle,
`
`particularly a motor vehicle, comprising means for
`
`generating and radiating an electromagnetic signal
`
`directed forwardly of the vehicle, and means for detecting
`
`15
`
`radiation reflected from an object in the path of the
`
`vehicle in which there are provided means for determining
`
`from the reflected radiation the distance of the
`
`reflecting object from the vehicle, means sensitive to the
`
`vehicle speed for determining a threshold distance value
`
`20 which is greater at higher speeds, and means for comparing
`
`the thus determined distance of the detected object from
`
`which the radiation is reflected with the said threshold
`
`value and for generating a warning signal if it does not
`
`exceed the said threshold value.
`
`25
`
`This threshold value will,
`
`in accordance with the
`
`invention,
`
`therefore accordingly increase as the speed of
`
`7
`
`

`

`W0 9] /07672
`
`PCT/GB90/01731
`
`the vehicle increases and decrease as the speed of the
`
`vehicle decreases.
`
`The precise relationship between the
`
`threshold value and the vehicle speed will vary from
`
`vehicle to vehicle in dependence on its characteristics.
`
`u
`
`A heavy lorry with relatively high mass and relatively low
`
`contact area with the ground may therefore require an
`
`exponential curve between the safe distance at a low speed
`
`and the safe distance at a high speed.
`
`10
`
`15
`
`20
`
`25
`
`Preferably the said warning signal is an audible signal
`
`although a visual warning which may be in addition to the
`
`audible warning may also be provided. Usually, when
`
`driving,
`
`the vehicle driver will maintain his visual
`
`attention on the road and although periodic observation of
`
`the vehicle instruments is made the time lapse between
`
`successive observations of the instruments and the
`
`necessity to remove the driver's attention from the road
`
`ahead make it preferable that the signal should be an
`
`audible one rather than a Visual one.
`
`There may, of course, further be provided means for
`
`displaying a visual indication of the said determined
`
`distance of the detected object ahead of the vehicle and
`
`this may be of particular value in training the driver to
`
`appreciate the relationship between the observed phenomena
`
`and the numerical values of the distances concerned.
`
`There may also be provided means for generating a visual
`
`8
`
`

`

`W0 91/07672
`
`PCT/GB90/01731
`
`display of the said threshold distance value, and such
`
`display may conveniently be in the form of an analogue
`
`graphic display, for example in the form of a bar graph or
`
`chart, or may be (or may additionally be)
`
`in the form of a
`
`numerical representation of the distance.
`
`The audible warning signal generated by the system when
`
`the distance detected between the vehicle and the vehicle
`
`ahead is less than the safe threshold distance may be a
`
`10
`
`single tone the frequency of which may vary in dependence
`
`on the magnitude of the discrepancy between the threshold
`
`value and the detected value, for example rising in pitch
`
`as the distance reduces, or may be a synthesised speech
`
`signal,
`
`in which case the said means for generating a
`
`15
`
`warning signal includes means for generating a synthesised
`
`speech signal or speech signals.
`
`The means by which the threshold speed is calculated or
`
`otherwise determined may, alternatively,
`
`incorporate some
`
`20
`
`means for varying the radiated electromagnetic signal,
`
`in
`
`which case the said means for generating and radiating an
`
`electromagnetic signal may include means for varying the
`
`transmitted beam characteristics in dependence on the
`
`speed of the vehicle.
`
`In this way the beam sensor may
`
`25
`
`simply detect radiations reflected from a "safe" area
`
`beyond the threshold and a “dangerous” area closer than
`
`the threshold.
`
`9
`
`

`

`WO 91/07672
`
`PCT/GB90/01731
`
`The said variation of the beam characteristics may
`
`comprise any of the following, namely a variation in the
`
`direction of the transmitted beam, a variation in the
`
`transmitted beam divergence angle, a variation in the
`
`a):
`
`source intensity of the transmitted beam, a variation in
`
`the source frequency of the transmitted beam or a
`
`modulation or pulse coded signal the modulation frequency
`
`or pulse code of which is varied in accordance with the
`
`detected vehicle's speed.
`
`10
`
`15
`
`20
`
`25
`
`In the case of a beam direction variation this may be seen
`
`to set up a suitable threshold if the transmitter is
`
`located at one front corner of the vehicle and the
`
`receiver at the opposite front corner of the vehicle
`
`since, with a suitable directional sensitivity, only light
`
`reflected from an object within a certain range will reach
`
`the detector since. Because the beam is inclined to the
`
`longitudinal axis of the vehicle in such a system, any
`
`reflected radiation from a vehicle further than the
`
`threshold determined by the inclination of the beam will
`
`pass the detector without being incident thereon. As far
`
`as a variation in the transmitted beam divergence angle is
`
`concerned, because of the reduction in intensity as the
`
`beam is transmitted,
`
`in accordance with the well known
`
`inverse square law of radiation,
`
`the corresponding
`
`reduction in intensity in the reflected radiation received
`
`from a vehicle ahead of the vehicle carrying the sensing
`
`10
`
`10
`
`

`

`W0 91/07672
`
`PCTIGB90/0173]
`
`equipment will enable the system to use the received
`
`signal intensity as the characteristic by which the system
`
`determines whether the reflector is further or closer than
`
`the selected threshold.
`
`The same fundamental physical
`
`principles apply to a variation in source intensity.
`
`On the other hand, by varying the source frequency with
`
`speed it is possible to make use of a suitable stored
`
`signal or range of signals for comparison purposes with
`
`10
`
`the reflected signal, for example by comparing the phase
`
`of the received signal or otherwise determining the
`
`ranging information, for example by pulse shaping and
`
`counting to determine transit times.
`
`Such techniques can
`
`also be used if the variation in transmitted beam
`
`15
`
`characteristics comprise modulation or pulse code signal
`
`in which the modulation frequency or the pulse code is
`
`varied in accordance with the detected vehicle's speed,
`
`and again the value of the threshold is then varied in
`
`accordance with the frequency or pulse code encountered in
`
`20
`
`the received signal.
`
`Such a system may easily be put into
`
`practice, for example, by using a range of band pass
`
`filters which will allow only signals of the appropriate
`
`frequency to pass for comparison.
`
`25
`
`By using more sophisticated electronic computing
`
`technology the apparatus of the present invention may also
`
`be provided with means for computing automatically,
`
`from
`
`M
`
`11
`
`

`

`WO 91/07672
`
`PCTlGB90/0173]
`
`.. 10 _.
`
`parameters including the vehicle parameters,
`
`the said
`
`threshold value for comparison with the determined
`
`distance from a reflecting object.
`
`In such a case,
`
`therefore,
`
`the computer may be able automatically to work
`
`out the appropriate threshold at a different value when a
`
`commercial vehicle is laden from that which it would
`
`calculate if the vehicle is unladen so that no external
`
`controls need to be modified in order for the system
`
`properly to generate a warning signal at the appropriate
`
`10
`
`point without giving a spurious signal which, because the
`
`driver would himself be aware of the different conditions,
`
`may tend towards encouraging the driver to neglect the
`
`warning signal or to take some counter measures to prevent
`
`it from being generated such as disconnection of the alarm
`
`15
`
`indicator or plugging his ears.
`
`The nature of the electromagnetic radiation must, of
`
`course, be chosen to be appropriate for the conditions
`
`encountered and although radio frequency radiation may be
`
`20
`
`employed the risk of interference with other radio
`
`frequency equipment leads to a belief that the preferred
`
`range of frequencies for the radiated electromagnetic
`
`signal would lie in the infra—red region.
`
`If an infra-red
`
`light beam is used there must, of course, be provided
`
`25
`
`means for discriminating between reflected signals from a
`
`reflecting object ahead of the vehicle and background
`
`radiation such a solar radiation:
`
`Such discrimination
`
`12
`
`12
`
`

`

`W0 91/07672
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`renown/01731
`
`-
`
`_
`
`means may include electronic or optical filters.
`
`In a further refinement of the present invention there may
`
`also be provided means for detecting a change in the
`
`relative speed between the vehicle and a vehicle ahead in
`
`order to provide early warning that the vehicle ahead may
`
`be braking.
`
`For this purpose there are further provided
`
`means sensitive to the frequency of the radiated
`
`electromagnetic signal reflected from an object ahead of
`
`10
`
`the vehicle, and operable to produce a second warning
`
`signal in the event of a shift in the spectrum indicating
`
`a deceleration of the reflecting vehicle.
`
`Embodiments of the present invention will now be more
`
`15
`
`particularly described, by way of example, with reference
`
`to the accompanying drawings in which:
`
`Figure l is a schematic plan View from above
`
`illustrating the positioning of various components of a
`
`20
`
`sensing system on a vehicle for one embodiment of the
`
`invention;
`
`Figure 2 is a block schematic diagram of an exemplary
`
`system;
`
`Figure 3 is a block schematic diagram of a
`
`25
`
`transmitter forming part of a second embodiment; and
`
`Figure 4 is a block schematic diagram of a receiver
`
`suitable for use with the transmitter of Figure 3.
`
`13
`
`13
`
`

`

`\V()9l/07672
`
`PCT/GB90/01731
`
`_ l 2 -
`
`Referring now to the drawings the system broadly
`
`illustrated in Figure 1 acts to indicate to the driver of
`
`If
`
`a vehicle to which the system is fitted that the distance
`
`between the vehicle and a preceding vehicle identified
`
`with the reference numeral 11 is not too short to allow
`
`safe stopping.
`
`The vehicle carrying the warning system is generally
`
`indicated with the reference numeral 12 and the system
`
`10
`
`itself with the reference numeral 13.
`
`The system 13
`
`generates an electrical signal which is applied to an
`
`infra—red transmitter 14 to generate a train of pulses
`
`transmitted forwardly in a direction inclined slightly to
`
`the longitudinal axis of the vehicle 12 so as to impinge
`
`15
`
`on the rear of a vehicle such as the vehicle 11 in front
`
`of the vehicle 12 and be reflected therefrom towards a
`
`suitable positioned infra-red sensor 15 which is also
`
`connected to the monitoring system 13. As will be
`
`described in more detail in relation to Figure 2,
`
`the
`
`20
`
`system 13 acts to determine the separation between the
`
`vehicles 11 and 12 on the basis of the propagated and
`
`received signals, and to compare these with a threshold
`
`value determined by the speed of the vehicle 12.
`
`If the
`
`distance determined by the system 13 separating the
`
`25
`
`vehicles 11 and 12 is less than the threshold determined
`
`u
`
`by the speed of the vehicle 12 then an output alarm signal
`
`is sent to an alarm indicator 16.
`
`The details of the
`
`14
`
`14
`
`

`

`W0 91/07672
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`PCT/GB90/01731
`
`_ l3 ._
`
`system 13 are illustrated in the block schematic diagram
`
`of Figure 2.
`
`From this it will be seen that the infra—red
`
`transmitter 14 is driven by a transmitter driver 19 which
`
`receives a signal from a signal generator comprising a
`
`sweep generator 17 and pulse generator 18.
`
`The signal
`
`applied to the transmitter driver 19 is also fed to a
`
`comparator 21.
`
`The infra-red transmitter 14 is also provided with means
`
`10
`
`for controlling the focus and the dispersion (namely the
`
`beam angle) by appropriate physical means.
`
`The infra—red pulses reflected from the vehicle 11 are
`
`received at the receiver 15 which,
`
`likewise,
`
`is provided
`
`15
`
`with appropriate focusing means 24, and the electrical
`
`signal generated by the receiver 15 is passed to an
`
`amplifier 23 the output from which is fed via a filter 22
`
`to the comparator 21. This latter acts to determine from
`
`the phase of pulses supplied from the pulse generator 18
`
`20
`
`and the received reflected signal applied via the filter
`
`22 the time lag between transmission and reception, and
`
`this signal is converted in the time distance counter 25
`
`to a signal representing the distance separating the
`
`vehicles 11 and 12.
`
`The output from the counter 25 is fed
`
`25
`
`to a display device 26 operating to provide a visual
`
`display of the separation distance between the vehicle 12
`
`and the vehicle 11 ahead, and the distance signal is also
`
`15
`
`15
`
`

`

`\V()91/07672
`
`PCT/GB90/01731
`
`_14..
`
`fed to a distance speed comparator 29.
`
`A signal
`
`representing the vehicle speed is generated by a speed
`
`signal detector 27, for example a phonic wheel the output
`
`signal from which, typically frequency dependent,
`
`is fed
`
`‘11
`
`I!
`
`via a signal processor 28 which conditions it to
`
`appropriate form for supply to the distance speed
`
`comparator 29 for comparison with the distance signal from
`
`the counter 25.
`
`The output signal from the processor 28
`
`thus effectively constitutes the threshold the value of
`
`10
`
`which varies in dependence on the speed of the vehicle 12,
`
`and the comparator 29 operates to provide and output
`
`signal if the threshold signal from the processor 28 is
`
`greater than the distance signal from the counter 25,
`
`which is applied to the display device 16 which, as in
`
`15
`
`Figure 1, may be an audible warning device or,
`
`alternatively, as referred to above may be a visual
`
`display indicating whether or not the vehicle is too close
`
`to the vehicle in front.
`
`20
`
`The operation of the time—distance counter may be modified
`
`to take account of road conditions.
`
`For this there is
`
`provided a moisture sensor 30 which in practice is
`
`suitably located on the vehicle to be able to detect
`
`moisture thrown up front he road wheels and therefore
`
`25
`
`generate an output signal representing whether the road is
`
`Al
`
`dry or wet.
`
`The output signal from the sensor 30 is fed
`
`to a signal processor 31 which in turn controls the time—
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`W0 91/07672
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`PCT/GB90/Dl731
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`_ 15 -
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`distance counter 25 in a sense such as to increase the
`
`threshold safe stopping distance in wet weather by a
`
`predetermined value related to the known braking
`
`performance of vehicles on a wet road.
`
`Although the specific embodiment described here makes use
`
`of infra-red electromagnetic radiation it is possible that
`
`radiation of other frequencies may be used for the remote
`
`sensing provided always that a frequency is chosen that
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`10
`
`will not present problems of interference with the
`
`operation of other equipment.
`
`Referring now to Figure 3,
`
`the transmitter illustrated is
`
`adapted to be supplied from the normal 12 volt DC supply
`
`15
`
`carried on a vehicle.
`
`The transmitter comprises a voltage
`
`regulator 31 supplied from the 12 volt DC supply, and
`
`feeds a voltage generator 32 operating to generate a
`
`negative supply for the AC component of the transmitter.
`
`The supply is fed via a constant current diode which
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`20
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`monitors and regulates the current,
`
`to the first stage
`
`amplifier 35. This ensures that the broadcast signals
`
`remains at an exactly predetermined strength, which is of
`
`course necessary in order to be able to establish the
`
`distance from the transmitter by the receiving vehicle.
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`25
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`The first stage amplifier 35 also receives a coded pulse
`
`signal from a code pulse generator 34 fed from the voltage
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`W0 91/07672
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`PCT/GB90/01731
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`regulator 31.
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`The code pulse generator can be configured
`
`to produce a variety of input waveforms for the
`
`transmitter, possibly allowing vehicle type identification
`
`to be incorporated into the signal. Other information may
`
`‘0
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`also be incorporated if desired.
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`The output from the
`
`first stage amplifier 35 is fed to a second stage 36 which
`
`feeds an antenna 37 to radiate the transmitted signal.
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`The transmitter can be tuned to operate at any frequency
`
`from, for example, about 88 MHz to 150 MHz and above
`
`allowing it to be configured to meet local broadcasting
`
`waveband regulations.
`
`It is considered that a frequency
`
`in the region between 144 and 148 MHz, which is allocated
`
`to amateur radio transmissions may be appropriate.
`
`A transmitted range of approximately 200 metres can be
`
`achieved using an air wound coil antenna comprising four
`
`turns of SWG 20 at a 5 mm diameter. Energising such a
`
`coil with a 12 mA supply current will generate a signal
`
`having an appropriate strength to cover a range of 200
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`10
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`15
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`20
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`metres .
`
`Turning now to Figure 4,
`
`the signals transmitted from
`
`antenna 37 in a preceding vehicle may be picked up on an
`
`antenna 41 in a receiver fitted on a vehicle in a position
`
`25
`
`to detect radiation in the region forwardly of the
`
`vehicle. Conveniently a position close to the front of
`
`the vehicle, or close to the front of the roof line may be
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`t’
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`at
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`18
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`W0 9] /07672
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`PCT/GB90/Ol731
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`-17-
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`suitable.
`
`The signal picked up by the antenna 41 is
`
`supplied to a radio frequency amplifier 42 the output from
`
`which passes to an input signal conditioning unit 43 which
`
`separates out the coded pulse element to supply this to a
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`Schmidt trigger 45 the output from which is supplied to a
`
`microprocessor 48.
`
`The analogue signal from the input
`
`signal conditioning unit 43 is also fed to an analogue-to—
`
`digital converter 44 which, via a latch 46, also supplies
`
`the microprocessor 48.
`
`The entire input signal is summed
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`10
`
`to produce the input for the analogue-to—digital
`
`converter .
`
`The microprocessor 48 analyses the pulse element of the
`
`received signal until a predetermined code is recognised.
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`15
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`The output from the converter is then latched and read,
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`this reading indicating the overall strength of the
`
`received signal.
`
`The strength of the received signal is
`
`used by the microprocessor to determine the separation of
`
`the receiving vehicle from the source transmitter.
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`20
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`The microprocessor also receives input signals from a
`
`speed sensor 49, and the comparison between the vehicle
`
`speed and the distance from the source transmitter is
`
`effected within the microprocessor using appropriate look
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`25
`
`up tables.
`
`The look up table contains a series of
`
`associated threshold values.
`
`If the comparison between
`
`the instantaneous vehicle speed and the determined
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`\V()91/07672
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`PCT/GB90/0173I
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`distance between the source transmitter and the vehicle
`
`indicates that the instantaneous distance is less than the
`
`threshold required for that speed a visual and/or audible
`
`warning is given via a display device 50.
`
`The supply to the microprocessor 48 is derived from the
`
`electrical system on board the vehicle via suitable
`
`regulation to ensure reliable operation. Operation of the
`
`microprocessor is controlled by software resident in a
`
`separate ROM or EPROM indicated 47 in Figure 4.
`
`An
`
`internal ROM or EPROM housing the software may, of course,
`
`be employed if a microcontroller is used.
`
`The means by which the instantaneous speed of the vehicle
`
`may be determined using the speed sensor 49 may be
`
`acquired in a number of ways.
`
`For example,
`
`the speed
`
`information may be derived from the vehicle's own
`
`electronic management system if it has such.
`
`Alternatively an optical or electromagnetic sensor may be
`
`used to measure drive shaft rotation, especially in the
`
`case of front wheel drive vehicles.
`
`In the case of rear
`
`wheel drive vehicles an optical or electromagnetic sensor
`
`may be used to measure the speed of rotation of the
`
`propeller shaft. As a further alternative the means for
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`10
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`15
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`20
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`25
`
`providing a speed indication in the vehicle (the
`
`speedometer) which may be an electronic or a mechanical
`
`device, may be used to tap off the signal for operation of
`
`m}
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`‘(l
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`(3‘
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`m?
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`20
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`WO 91/07672
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`PCTIGBQO/01731
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`_
`
`_
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`the vehicle safety system described hereinabove.
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`W0 91/07672
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`PCT/GB90/01731
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`._
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`_
`
`CLAIMS
`
`1.
`
`Remote sensing apparatus for a vehicle comprises
`
`means for determining the separation between a vehicle and
`
`“I
`
`an object or other vehicle in the region in front of the
`
`said vehicle sensitive to the speed of the vehicle for
`
`determining a threshold distance value which is greater at
`
`higher Speeds, and means for comparing the thus determined
`
`distance of the detected vehicle with the said threshold
`
`value and for generating a warning signal if the said
`
`determined distance is less than the said threshold value.
`
`2.
`
`Remote sensing apparatus for a vehicle as claimed in
`
`Claim 1,
`
`in which the means for determining the separation
`
`comprise means for generating and radiating an
`
`electromagnetic signal directed forwardly of the vehicle,
`
`and means for detecting reflected radiation from an object
`
`in the path of the vehicle.
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`10
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`15
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`20
`
`3.
`
`Remote sensing apparatus as claimed in Claim 1,
`
`in
`
`which there are provided means for generating a visual
`
`display of the said threshold distance value.
`
`4.
`
`Remote sensing apparatus for a vehicle, as claimed in
`
`25
`
`Claim 1,
`
`in which the said means for generating a warning
`
`0'
`
`at
`
`signal includes means for generating synthesised speech
`
`signals.
`
`SUBSTITUTE SHEET
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`22
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`W0 91/07672
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`PCT/GB90/01731
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`_. 2 1 ._
`
`5.
`
`Remote sensing apparatus for a vehicle, as claimed in
`
`Claim 1,
`
`in which the said means for generating and
`
`radiating an electromagnetic signal includes means for
`
`varying the transmitted beam characteristics in dependence
`
`on the speed of the vehicle.
`
`6.
`
`Remote sensing apparatus for a vehicle, as claimed in
`
`Claim 5,
`
`in which the said variation of the beam
`
`characteristics comprises a variation in the direction of
`
`10
`
`the transmitted beam.
`
`7.
`
`Remote sensing apparatus for a vehicle, as claimed in
`
`Claim 5,
`
`in which the variation in the transmitted beam
`
`characteristics comprises variation in the transmitted
`
`15
`
`beam divergence angle.
`
`8.
`
`Remote sensing apparatus for a vehicle, as claimed in
`
`Claim 5,
`
`in which the said variation in transmitted beam
`
`characteristics comprises a variation in the source
`
`20
`
`intensity of the transmitted beam.
`
`9.
`
`Remote sensing apparatus for a vehicle, as claimed in
`
`Claim 5,
`
`in which the said variation in transmitted beam
`
`characteristics comprises a variation in the source
`
`25
`
`frequency.
`
`10. Remote sensing apparatus for a vehicle, as claimed in
`
`23
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`23
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`

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`W0 91/07672
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`PCT/GB90/01731
`
`Claim 5,
`
`in which the said variation in transmitted beam
`
`characteristics comprises a modulation or pulse coded
`
`signal and the modulation frequency or the said pulse code
`
`is varied in accordance with the detected vehicle speed.
`
`441
`
`11. Remote sensing apparatus for a vehicle, as claimed in
`
`Claim 1,
`
`in which the said radiated electromagnetic signal
`
`is an infra—red light beam.
`
`12. Remote sensing apparatus for a vehicle, as claimed in
`
`Claim 1, further provided with means for discriminating
`
`between reflected signals from a reflecting object ahead
`
`of the vehicle and background radiation such as solar
`
`radiation.
`
`13. Remote sensing apparatus for a vehicle, as claimed in
`
`Claim 12,
`
`in which the said discrimination means include
`
`electronic or optical filters.
`
`14. Remote sensing apparatus for a vehicle, as claimed in
`
`Claim 1,
`
`in which there are further provided means
`
`sensitive to the frequency of the radiated electromagnetic
`
`signal reflected from an object ahead of the vehicle, and
`
`operable to produce a second warning signal in the event
`
`of a shift in the spectrum indicating a deceleration of
`
`U”
`
`'8)
`
`the reflecting vehicle.
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`24
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`WO 91/07672
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`PCT/GB90/0173l
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`_ 23 _
`
`15. Remote sensing apparatus as claimed in Claim 1,
`
`in
`
`which the said means for determining the separation
`
`comprises a transmit