GB2112520A

GB2112520A - Vehicle manoeuvring aid

Info

Publication number: GB2112520A
Application number: GB08134671A
Authority: GB
Inventors: Anthony David Heyes
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-11-18
Filing date: 1981-11-18
Publication date: 1983-07-20

Abstract

The vehicle manoeuvring aid is an ultra-sonic pulse echo device with an audible output display, the prime function of which is to provide information to the driver of a reversing vehicle. The distance to the nearest obstacle is displayed by means of bleeping tones the pulse repetition rate of which depends on the particular range zone in which the obstacle lies. In order to provide adequate cover for the whole width of the vehicle three pairs of ultrasonic transducers 50 are used. The serious problems of interference and diffraction caused by the overlap of the ultra-sonic beams is removed by having the receivers scanned sequentially and by alternating the phase relationship of the transmitters. Each cycle of operation comprises scanning each receiver twice, once with the central transmitter in-phase with the other two, and once with it out-of-phase. This whole cycle takes place in a time which is short compared to human reaction times. The result obtained is stored for display during the next scan cycle. <IMAGE>

Description

SPECIFICATION Vehicle manoeuvring aid This invention is concerned with a vehicle manoeuvring aid, and arose from a consideration of the problems involving in reversing a vehicle safely.

Reversing a vehicle up to an obstruction (maybe another vehicle, or a wall, when parking) presents to drivers a familiar problem. Judging the distance between the rear bumper of the vehicle (which is out of sight of the driver) and the obstruction is difficult, at least until the driver has become experienced with a particular vehicle. The problem is even more acute with a long vehicle, such as a lorry, than it is with a car. Furthermore, there is an ever present danger of a child or animal being immediately behind a vehicle and out of sight of the driver.

It is an object of this invention to provide an aid to assist a driver in manoeuvring his vehicle close to an obstruction, for example when reversing the vehicle.

The invention provides in any one of its aspects a vehicle manoeuvring aid adapted to survey a region adjacent a vehicle to detect any obstruction, within the region, towards which the vehicle is to be driven and to indicate to the driver whether the obstruction lies in the nearer or the further zone of the two surveyed zones of the region extending successively from the vehicle in the intended direction of travel, the arrangement being such that as the vehicle is moved towards the obstruction a first signal is given to the driver when the obstruction is within the further zone and a second signal is given, which is immediately distinguishable from the first signal, when the obstruction is within the nearer zone.

Any aid which could give only one signal, i.e.

when an obstruction was present in the one and only zone surveyed by the aid, would be of limited value as a manoeuvring aid since, as a practical matter, it would either give very little warning of the presence of an obstruction as the vehicle moved towards it (where the surveyed distance was very short) or it would give little useful indication of the distance to the obstruction (where the surveyed distance was reasonably long). By means of an aid in accordance with the invention, a driver whose vehicle is approaching an obstruction can be given reasonable warning of his vehicle's approach to the obstruction, by means of a reasonably long surveyed distance, but also some indication of the distance to the obstruction, since it is indicated to him in which of the two zones the obstruction lies.With advantage, the aid may be adapted to survey a train of three, or even more, zones and correspondingly to give three signals which are all immediately distinguishable from one another; it should be remembered that the driver will not necessarily hear both, or all, of the signals in sequence (as an obstruction may be introduced in the driver's absence) and by "immediately distinguishable" is meant that the driver should without hesitation be able to know which signal he is getting when one is given without very recent reference to another.

Whilst the manoeuvring aid might most usually be mounted on, or embodied in, the vehicle itself it might aiternatively be mounted on or adjacent an obstruction which vehicles will be required to approach, e.g. a loading bay for lorries, or railway buffers.

The signals given to the driver may be audible or visible signals.

In a preferred form the manoeuvring aid comprises a plurality, for example three, transducer heads which are intended to be mounted spaced apart across the rear of a vehicle and so positioned as to give adequate coverage of the region immediately behind the vehicle. A box of electronics of the apparatus can be mounted inside the vehicle, typically on the rear window ledge of a car. The warning signals, indicating the presence of an object behind the vehicle, are in the form of audible tones, thus leaving the driver of the vehicle free to use his vision in the normal way. In the case of a car, power may be supplied to the apparatus through the automatic reversing light switch.In the preferred arrangement the distance or 'range' of the nearest object is signalled using three different tonal displays; namely, if the object is between 2 and 5 feet away a tone of approximately 0.25 seconds duration is heard at a repetition rate of one every second; if the object is between 1 and 2 feet away the same tone is heard at an increased repetition rate of one every half a second; and if the object is less than 1 foot from the rear of the vehicle a continuous tone is heard.

If an aid according to the invention is to be used for tracked vehicles such as railway engines, the alignment of the 'object', in this case a truck or a carriage or buffers, is predetermined and only one transducer head will be required.

For example for use by deaf drivers, a visual display may be used. In this case use might be made of a single lamp, flashing according to the above sequence of repetition rates and mounted, for example, above the vehicle's rear window so as to be within the normal field of view while reversing.

Although in principle either ultra sonic or infra red energy could be used to explore the region behind a vehicle, since the range of objects is important ultra sonic is to be preferred. Using ultra sonics it is possible to produce a short transmission pulse and measure the time taken before an echo is received.

Since the speed of ultra sonics in air is a known constant this 'time' may be related to object distance. In principle the same is true for infra red radiation but since this travels with the speed of light the resultant times may be inconveniently short.

The or each transducer head comprises a transmitter and a receiver. Where more than one head is used some overlap of the coverage given by each head is inevitable. This introduces two substantial problems, namely interference and diffraction. If an object is situated in an area of overlap it is possible that the echo signal received at one receiver is equal in amplitude and opposite in phase, to the echo signal received at another receiver. If the receiver transducers formed common parallel inputs to a single receiver amplifier these two signals would interfere in such a way as to cancel out. For this reason the receivers are preferably addressed in a cyclic manner; only one receiver is actually working at any moment. A not unrelated problem arises in the space where two transmitters overlap.In this case the term diffraction is used to describe the way in which two sound waves of the same frequency may cancel each other out. In such an area of overlap there will be radial 'corridors' of insensitivity. One solution to this problem would be to switch the transmitters in step with the receivers so that during one stage in the cycle, say, only the left transmitter and the left receiver were operating. A preferred solution, involves triggering all the transmitters simultaneously but reversing the phase of the centre transmitter at the end of each complete receiver cycle. In the case of three heads, the two outer transmitter beams need not overlap, and there would be no need to reverse the phase of one with respect to the other.Thus a full cycle of operation (using three heads) would comprise six transmitter pulses, three with the centre transmitter in phase with the outer transmitters followed by three with the centre transmitter out of phase with the others.

In step with these six pulses the receivers are addressed in turn so that in essence the aid 'looks' left, centre, right, left, centre, right.

In practice, however, it may be much easier to construct a cycle of eight rather than a cycle of six and the embodiment described hereinafter incorporates a cycle of eight transmitter pulses the receiver 'looking' left, centre, right, centre - phase reversed left, centre, right, centre.

No matter which cycle is adopted, it is important that the full cycle time is short compared with human reaction times; in our embodiment 0.5 seconds.

The information collected during each cycle is stored in retriggerable memories having a hold time greater than the cycle time - typically 0.75 seconds.

Thus the user is completely unaware of the cyclical nature of the device.

There now follows a description, to be read with reference to the accompanying drawings, of a vehicle manoeuvring aid which illustrates the invention bywayofexample.

In the accompanying drawings: Figure 1 is a block diagram of electronic circuitry of the apparatus; Figure 2 illustrates three transducer heads mounted on a vehicle; and Figure 3 shows a transducer head mounted in a protective housing.

An electronic clock 1 is used to house a ten stage counter 3 which provides overall control for the remainder of the circuitry. In particular it is used to determine three zones surveyed by the device.

During count 0 transmitter pulses are released, during count 1 echos return from objects less than one foot from the vehicle, during count 2 echos return from objects between 1 and 2 feet from the vehicle, during counts 3,4 and 5 echos return from objects between 2 and 5 feet from the vehicle.

Subsequent counts 6-9 and a 30m second pause introduced by a monostable circuit 5 provide a recovery delay before the counter returns to zero and causes the release again of transmitter pulses.

The transmitter signal is derived from a free running 400 KHz oscillator 7 which after being divided by 10 by a divider 9 is gated by a 0.5m second monostable circuit 11 which is initiated on count zero of the 10 stage counter 3. The transmitter signal is split, one half being amplified 13 and used to power the two outer transmitter transducers TL and TR while the other half is fed to a phase changer 15 then amplified 17 and used to power the centre transmitter transducer TM.

The count zero pulse for the 10 stage counter 3 is also used to increment a cascade of 3 "divide-by-2" circuits 19 which in turn control (a) the phase changing for the centre transmitter (b) the receiver selection and (c) the mark to space ratio of the auditory display.

The three receiving transducers 21 are connected to their respective amplifiers 23 which are switched by the cascade of dividers 19. The outputs of the receiver amplifiers 23 are commoned and fed in turn to an amplifier 25, a commutating filter 27, another amplifier 29 and a threshold detector 31. The commutating filter 27 is controlled by ten signal lines from the "divide-by-10" circuit 9 in the transmitter chain.

The output of the threshold detector 31 is a logic head pulse similar in width to the transmitter pulse but delayed in time by an amount proportional to the distance of the object reflecting the ultra sonic pulse.

This pulse is 'anded' with outputs 1 to 5 of the ten stage counter 3 to determine in which of the three range zones the object lies. An echo pulse during count 1 is pased by an AND gate 33 and forms the input to a retriggerable monostable circuit 35. An echo pulse occurring during count 2 is passed by AND gate 37 to a retriggerable monostable circuit 39.

Counts 3,4 and 5 are combined on an OR gate 41 and form an input to an AND gate 43. An echo pulse during counts 3,4 or 5 is also fed to this AND gate 43 and subsequently to another retriggerable monostable circuit 45.

The three echo trigger monostable circuits 35,39 and 45 all have a hold period of approximately 0.75 seconds which is longerthanthefull cycle period of the receiver switching circuits. They form three separate refreshable memories. For example, let us suppose that an object lies 2.5 feet away in the beam of the right receiver. An above threshold pulse will be obtained during count 3 of the ten stage counter 3 every time the right hand receiver is used. Since this happens approximately every 0.2 seconds the third retriggerable monostable circuit 45 remains in the triggered state indicating the continued presence of an object in the far zone.

The outputs of the three retriggerable monostable circuits determine the auditory tonal display. If the retriggerable monostable circuit 35 corresponding to the near zone is in the triggered-on state the auditory display 47 is continuously energised via OR gate 49.

If the retriggerable monostable circuit 39 corresponding to the mid zone is in the triggered-on state the auditory display is arranged to be on for half of the time. This is achieved by means of AND gate 51 and the divide-by-2 signal obtained from the cascade of dividers 19. Finally, if the retriggerable monostable circuit 45 corresponding to the far zone is in the triggered-on state the auditory display is arranged to be on for one quarter of the time. This is achieved by means of two AND gates 53,55 and the divide-by-2 and the divide-by-4 signals from the cascade of dividers 19.

It must be appreciated that objects may be present in more than one of the surveyed zones. The method of enabling the tonal display is so arranged that the near zone signal over-rides either or both of the other two zone signals, and also the mid zone signal over-rides the far zone signal, The aid is thus a nearest-object-only detecting device.

Figure 2 shows the three transducer heads 50 mounted on the rear bumper of a car. Each head is arranged to transmit ultra sonic waves which diverge from the head to provide a conical surveyed region, the apical angle of the zone being approximately 54". The three regions surveyed by the heads are arranged with their transmission axes inturned towards the transmission axis of the middle head, in orderto maximisethe proportion surveyed of the region behind the car and to avoid unnecessarily detecting objects well beyond the width of the car.

Figure 3 illustrates the mounting of the transducer heads. The mounting provides a bracket, for securemenu to the vehicle bumper, which allows adjust mentofthe direction of the transmission axis in both horizontal and vertical planes, to enable best use to be made of the conical emissions. A transducer unit 52 is housed within a tubular housing 54 to protect it from the environment.

CLAIMS (filed on 13/12/82) 1. An ultra-sonic ranging device for a vehicle, the device comprising means for sensing the distance of an obstacle to a part of the vehicle and an auditory display which is a function of the said distance.

2. A device according to claim 1 comprising three sensing heads spaced out along the front or the rear of a vehicle each head comprising a means of transmitting and a means of receiving ultra-sonic energy.

3. A device according to the previous claims in which the three receivers are sequentially scanned, the result, corresponding to the distance to the nearest obstacle detected, being stored in memory for subsequent display.

4. A device according to claims 1 and 2 in which the outer two ultra-sonic transmitters are in a constant phase relationship and in which the relative phase of the central transmitter is switched through 180 degrees partway through the receiver scan cycle.

5. A device according to claims 1 and 2 which incorporates both functions described in claims 3 and 4.

6. A device according to any of the previous claims in which a complete scan cycle involved comprises at least two activations of each receiver, one for each of the two transmitter phase conditions.

7. A device according to claims 3 and 4 in which the time for a complete scan cycle is short compared to human reaction times, typically 0.5 seconds.

8. A device according to any of the previous claims wherein the auditory display comprises a bleeping tone the pulse repetition rate of which increases by clearly recognizable steps as the vehicle approaches the obstacle and the measured distance falls within successive predetermined zones.

9. A device according to any of the preceding claims comprising sensor heads mounted external to the vehicle and an electronic control unit and auditory display unit mounted within the vehicle.

10. A device according to any of the preceding claims wherein the transducer head comprises transducers mounted vertically within the protection of the head, the ultra-sonic energy being reflected in the required direction.

11. A device to aid vehicle manoeuvring substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. triggered-on state the auditory display is arranged to be on for one quarter of the time. This is achieved by means of two AND gates 53,55 and the divide-by-2 and the divide-by-4 signals from the cascade of dividers 19. It must be appreciated that objects may be present in more than one of the surveyed zones. The method of enabling the tonal display is so arranged that the near zone signal over-rides either or both of the other two zone signals, and also the mid zone signal over-rides the far zone signal, The aid is thus a nearest-object-only detecting device. Figure 2 shows the three transducer heads 50 mounted on the rear bumper of a car. Each head is arranged to transmit ultra sonic waves which diverge from the head to provide a conical surveyed region, the apical angle of the zone being approximately 54". The three regions surveyed by the heads are arranged with their transmission axes inturned towards the transmission axis of the middle head, in orderto maximisethe proportion surveyed of the region behind the car and to avoid unnecessarily detecting objects well beyond the width of the car. Figure 3 illustrates the mounting of the transducer heads. The mounting provides a bracket, for securemenu to the vehicle bumper, which allows adjust mentofthe direction of the transmission axis in both horizontal and vertical planes, to enable best use to be made of the conical emissions. A transducer unit 52 is housed within a tubular housing 54 to protect it from the environment. CLAIMS (filed on 13/12/82)

1. An ultra-sonic ranging device for a vehicle, the device comprising means for sensing the distance of an obstacle to a part of the vehicle and an auditory display which is a function of the said distance.