WO1991007672A2

WO1991007672A2 - Remote sensing apparatus for a vehicle

Info

Publication number: WO1991007672A2
Application number: PCT/GB1990/001731
Authority: WO
Inventors: Lewis Montague
Original assignee: Lewis Montague
Priority date: 1989-11-09
Filing date: 1990-11-09
Publication date: 1991-05-30
Also published as: AU6644790A; GB8925384D0; WO1991007672A3

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.

Description

REMOTE SENSING APPARATUS FOR A VEHICLE

The present invention relates generally to remote sensing apparatus for a vehicle, and particularly to such 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. 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 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 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 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 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 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 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 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 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 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 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 over control to prevent a driver from using his own judgment based on t e prevailing road conditions may in fact lead to a loss of safety rather than an increase in it.

According to one aspect of the present invention remote sensing apparatus for a vehicle comprises means for determining the separation between a vehicle and an objec 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.

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 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 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.

This threshold value will, in accordance with the invention, therefore accordingly increase as the speed of 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. 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.

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 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 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 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 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 simply detect radiations reflected from a "safe" area beyond the threshold and a "dangerous" area closer than the threshold. 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 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.

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 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 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 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 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.

By using more sophisticated electronic computing technology the apparatus of the present invention may also be provided with means for computing automatically, from 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 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 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 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 means for discriminating between reflected signals from a reflecting object ahead of the vehicle and background radiation such a solar radiation: Such discrimination 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 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 particularly described, by way of example, with reference to the accompanying drawings in which:

Figure 1 is a schematic plan view from above illustrating the positioning of various components of a 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 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. Referring now to the drawings the system broadly illustrated in Figure 1 acts to indicate to the driver of 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 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 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 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 vehicles 11 and 12 is less than the threshold determined by the speed of the vehicle 12 then an output alarm signal is sent to an alarm indicator 16. The details of the 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 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 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 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 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 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 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 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 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.

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 generate an output signal representing whether the road i dry or wet. The output signal from the sensor 30 is fed to a signal processor 31 which in turn controls the time- 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 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 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 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.

The first stage amplifier 35 also receives a coded pulse signal from a code pulse generator 34 fed from the voltage regulator 31. 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 also be incorporated if desired. 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. 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 S G 20 at a 5 mm diameter. Energising such a coil with a 12 πiA supply current will generate a signal having an appropriate strength to cover a range of 200 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 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 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 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 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. The output from the converter is then latched and read, 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.

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 up tables. The look up table contains a series of associated threshold values. If the comparison between the instantaneous vehicle speed and the determined 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 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 the vehicle safety system described hereinabove.

Claims

1. Remote sensing apparatus for a vehicle comprises means for 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 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.

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 Claim 1, in which the said means for generating a warning signal includes means for generating synthesised speech signals.

SUBSTITUTESHEET

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 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 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 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 frequency.

10. Remote sensing apparatus for a vehicle, as claimed in 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.

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 Clai 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 the reflecting vehicle.

15. Remote sensing apparatus as claimed in Claim 1, in which the said means for determining the separation comprises a transmitter positioned to transmit signals rearwardly of a vehicle and a receiver carried to receive signals from a region forwardly of the vehicle.

16. Remote sensing apparatus as claimed in Claim 15, in which the transmitter is operable to transmit coded pulse signals.