GB2266369A

GB2266369A - Vehicle manoeuvring aid

Info

Publication number: GB2266369A
Application number: GB9208419A
Authority: GB
Inventors: Laurence Everitt Sword
Original assignee: MEDITRONICS Ltd
Current assignee: MEDITRONICS Ltd
Priority date: 1992-04-16
Filing date: 1992-04-16
Publication date: 1993-10-27
Anticipated expiration: 2012-04-16
Also published as: GB9208419D0; GB2266369B

Abstract

A radiation pulse is emitted by a transmitter and a plurality of echoes are received by a receiver, the system including circuitry to discriminate from this train of echoes the first echo to be received, and the most intense echo to be received, and to provide a display indicating the distance between the transmitter and the object giving the first echo, and also the distance between the transmitter and the object giving the most intense echo.

Description

MANOEUVRING AID The present invention relates to proximity sensors1 and is particularly concerned with ultrasonic proximity detectors as aids to manoeuvring vehicles.

Ultrasonic distance measurement is a known technique, consisting of generating and transmitting an ultrasound pulse and timing the interval for an echo pulse to be received. The distance between the transmitter and the object from which the echo is received is proportional to the time interval Various attempts have been made at providing manoeuvring aids for vehicles using ultrasound techniques, relying on simple computation of the time between the transmission and the first recognised echo to determine the distance of the vehicle from the nearest detected object. In situations where a vehicle is approaching a number of distinct objects, such as a roadside kerb with a wall spaced a distance behind the kerb, the known systems of proximity detection will compute the distance to the kerb or to the wall but not both, depending on the internal processing used in the device.

The known proximity sensors also generally rely on echoes being above a certain strength in order to register as detected objects, echoes given off from 'soft' objects being largely discarded. It is therefore possible that a weak ultrasound echo from, say, a small animal or a child may well be ignored by the proximity sensor, resulting in collision particularly if the animal or child is sufficiently small as to be outside the driver's range of vision.

The present invention seeks to overcome these difficulties, by providing a proximity detection system in which an ultrasound pulse is emitted by a transmitter and a plurality of echoes are received by a receiver, the system including circuitry to discriminate from this train of echoes the first echo to be received, and the most intense echo to be received, and to provide a display indicating the distance between the transmitter and the object giving the first echo, and also the distance between the transmitter and the object giving the most intense echo.

By providing indications of the distance of the 'nearest' and of the 'strongest' echoes, the vehicle driver is better informed as to the nature and location of objects adjacent the vehicle which may well be outside the driver's range of vision. The strongest signal is defined as the strongest returned signal from an object with the system compensating for time and distance.

Numerous implementations of the system are possible.

Transmitter and receiver sub-units may be integrated individually or combined as transceivers. Display units may be represented as digital, proximity within range, or combinations thereof, and are mode programmable. Front and rear display units are slightly different in respect of usage.

An example of the present invention will now be described in detail, with reference to the accompanying drawings, in which: Figure 1 is a schematic plan view of a motor vehicle, showing an example of the positioning of transceiver units; Figure 2 is a schematic circuit diagram of the system; Figure 3 is a perspective view of an example of a transceiver unit with brackets for mounting to a vehicle; Figure 4 is a front view of a first digital display unit for use in the system; Figures 5A and 5B are front views of alternative digital display units; and Figures 6A and 6B are front views of proximity within range display units.

Referring now to the drawings, Figure 1 shows in plan view a motor vehicle 1 fitted at its front end 2 with an array of sensors 3. Each sensor 3 shown comprises a combined ultrasound transmitter and ultrasound receiver, the transmitters emitting ultrasound pulses in a forward direction relative to the vehicle parallel with the vehicle's centreline.

At the rear end 4 of the vehicle a further array of sensors is positioned. The array of sensors at the rear end of the vehicle comprises a pair of sensors 5 arranged symmetrically about the vehicle's centreline to emit ultrasound pulses in a direction extending laterally outwardly and rearwardly from the rear corners of the vehicle. The array of sensors at the rear end also included a pair of sensors 6, situated adjacent the rear corners of the vehicle and emitting their ultrasound pulses in directions extending rearwardly and inwardly relative to the vehicle's centreline. The sensors 5 and 6 are advantageously aligned orthogonally to each other, offset by about 15 from the longitudinal and transverse axes of the vehicle.

Clearly, other arrangements of sensors are possible in that the positions of the two arrays of sensors shown in the drawing may be reversed, or both arrays of sensors may adopt the configuration shown for either of the arrays illustrated in Figure 1.

Alternatively, arrays consisting of two or three sensors, a single sensor, or a combination of combined and individual transmitter or receiver units may be used.

The sensor arrays are connected to a control unit, which feeds one or more display units placed in the driver's view. The signals emanating from the sensors in the array at the rear end of the vehicle are displayed on a rear configured display unit 24 situated in the driver's field of vision when the driver is looking rearwards during a reversing manoeuvre. The outputs from the sensors at the front end and from the rear of the vehicle may be displayed on a front configured display unit 23 on or adjacent to the vehicle's dashboard.

Suitable wiring connections are then made between the display unit or units, the control unit, and the sensors.

Figure 2 shows a schematic layout for the system. The central portion of the Figure shows a control unit 7 comprising a number of circuit elements 8, 9 and 10. Circuit element 8 is a power supply and display output arrangement, and is provided with connections to the vehicle's electrical supply. In the embodiment shown, the circuit element 8 is connected to the vehicle's battery 11 via three connections. Connection 12 is permanently made, whereas connection 13 is made only when ignition switch 14 is closed, and connection 15 is made only when the vehicle's reversing switch 16 is operated to energise reversing lamp 17. An additional connection 63 is a provision for an external input to enable and disable system operation. This would be used with an input device which provides vehicle speed information to control the operation of the system depending upon vehicle speed.Fuses 18, 19 and 20 are preferably provided to prevent overloading.

Provision may be made in a circuit element 9 for the automatic shutdown of the system after a predetermined operating time, the system being switched on initially for a short period from the ignition switch and in response to either a) the operation of reversing lamp 17 by switch 16 on selection of reverse gear, b) a switch 64 contained within the front display unit 23, using input connection 63, or c) by the operation of a switch mounted on the dashboard.

Circuit element 8 also includes plug and socket connections 21 and 22, to which display units 23 and 24 may be connected by means of conductors 25 and 26. Each display unit 23, 24 includes a visual display 27 and various controls and switches which will be described in detail later.

Within the control unit 7, and connected to the power supply circuit element 8 are two further circuit elements 9 and 10, with element 10 having a number of plug and socket connectors 28 for the connection of sensor elements 29 by means of conductors 30. As shown schematically in the Figure, the sensor elements 29 are combined transceivers, and each have a transmitter opening 29A and receiver opening 29B. As it may, in certain circumstances, be necessary to mount the transmitter units 29 on the vehicle in positions remote from the positions from which ultrasound pulses are desired to be transmitted, extension horns 31 may be attached to the openings 29A and 29B, in order to guide the ultrasound pulses to the desired transmission point, and to guide the received echoes from the reception point to the sensor 29.

Figure 3 shows a schematic arrangement of such an extension horn, wherein the sensor 29 is mounted to the vehicle body by means of a bracket 32, and at the desired transmission and reception point P a further bracket 33 supports the flared ends 34 of extension horns 31, which lead from the flared ends 34 to the openings 29A and 29B of the sensor 29. The extension horns 31 may be of flexible tubing, secured to the sensor unit by means of screw clamps 35. This arrangement allows the sensors 29 to be mounted at locations protected from impact and vandal damage while allowing the ultrasound waves to be emitted and received at the desired points in the required directions and to prevent undesired reflections from the vehicle structure.

Referring again to Figure 2, the conductors 30 are attached by means of plug and socket connectors to the connection elements 28 of the circuit elements 10a and 10b. The circuit elements 9 and 10 includes circuitry to control the transmission of ultrasound pulses by the sensors 29, and to detect the reception of echoes by the sensors 29. For each pulse transmitted, a plurality of echoes are received by the sensor 29, from objects within the cone of detection of the sensor 29. The circuit element 9 includes circuitry to process the echo signals, to determine for each pulse emitted by each sensor, the time interval between the transmission pulse and the arrival of the first echo, and further to determine the interval between the transmission pulse and the arrival of the strongest echo.

Each sensor emits a pulse every 0.1 second with circuit elements 10a and 10b operating alternately at intervals of 0.05 seconds. The duration of each pulse is preferaby between 25pus and 800s dependent upon the nearest signal detected through circuit elements 10a and 10b and hence recorded in element 9. Reception of each return pulse causes the sensor 29 to emit a voltage pulse proportional to the strength of the echo. The voltage of the pulse is recorded within element 9, and the time interval of the echo pulse with the largest voltage is stored for transmission to the display as an indication of the distance of the 'strongest' echo. The time of reception of the first echo pulse is transmitted to the display to indicate the distance of the 'nearest' echo.Thus, each display unit is provided with information giving the distance from each respective sensor 29 of the 'nearest' object and of the 'most solid' object, i.e. the object giving the 'strongest' echo, the information being updated ten times per second The signals are transmitted via conductors linking circuit elements 9 and 10 to circuit element 8, and thence to the display or displays via conductors 30. In the example shown four sensors are arranged at each end of the vehicle. The sensors 29 at the front of the vehicle are connected to circuit element 10b, and those at the rear of the vehicle are connected to circuit element 10a.

In order to provide an easily comprehensible display of the distance information, the display units shown schematically in Figure 2 may be configured in a number of different ways.

The first digital type of display in the configuration shown in Figure 4 comprises two digital indicators, one of which indicates the distance from the vehicle to the nearest echo received by the four sensors, and the other of which indicates the distance from the vehicle to the strongest echo received. Circuitry in the display unit compares the distances from the vehicle to the 'nearest' echo sensed by each of the four sensors, and selects the shortest of these to be displayed. Likewise, the strengths of the 'strongest' echoes received by the four sensors are compared, and the distance to the strongest echo is displayed.

Associated with each digital indicator are four 'channel' indicators, one of which is illuminated to show the driver to which sensor the displayed digital information relates.

The channel indicators preferably have different illumination levels or colours, and are wil be referred to below as follows: 'Level 0' indicates no illumination (no signal); 'Level 1' indicated grey scale or green (signal present); 'Level 2' indicates 1/2 grey scale or yellow (strongest if not nearest); 'Level 3' indicates full grey scale or red (nearest) In the example shown in Figure 4, the display comprises lower and upper digital indicators 41 and 42. For added clarity, these may be of different colours. The lower indicator 41 shows the distance to the nearest echo, and associated with the indicator 41 are four channel indicators 43 to 46.When the circuitry in the display unit compares the distances to the nearest echo supplied by each of the four sensors, the shortest distance is displayed on the digital indicator and the sensor whose reading is displayed is indicated by lighting its associated channel indicator 43, 44, 45 or 46 at illumination level 3.

Similarly, when the strengths of the 'strongest' echoes from the four sensors have been compared by the display unit circuitry, the distance to the 'strongest' echo is displayed on digital indicator 42, and one of four 'channel' indicators 47 to 50 associated with the digital indicator 42 is lit at illumination level 1 to show which sensor detected the 'strongest' echo.

An alternative digital display, being either the view of the rear sensors on the rear display or the view of the forward sensors on the forward display is shown in Figure 5A. This display is intended for use with an array of four sensors with two central sensors aligned parallel to the vehicle's centreline and the other two aligned to diverge therefrom. This alternative display comprises two digital indicators 51 and 52, and associated with each indicator 51 and 52 are two channel indicators 53, 54 and 55, 56. The display unit contains circuitry to compare the 'nearest' and 'strongest' echoes as described above, but in this case the comparison is performed only in relation to signals emanating from the two sensors directed parallel to the vehicle's centreline.Thus the distance to the nearest echo is displayed on indicator 51, and the sensor producing that signal is identified by the illumination at level 3 of channel indicator 53 or 54. The strengths of the strongest echoes produced by these two sensors are compared, and the distance to the strongest echo is displayed by indicator 52, with channel indicator 55 or 56 illuminated at level 3 to show which sensor provided the signal.

The information from the two remaining sensors is indicated by two lines of lights or LED's A and B, extending obliquely outwardly at the sides of the digital indicators. Again circuitry in the display unit processes the 'nearest' signals from the sensors mounted obliquely to the vehicle and operates the lines A and B of lights thus: a) No echo detected. The indicator at the first position 57 in the line is illuminated at illumination level 1, to show that the sensor is operative but detects no echo. No other light or LED of this line is lit b) Nearest echo further than 50 cm from vehicle. All indicators in the line are at illumination level 1, indicating an echo received from an object more than 50 cm from the vehicle.

c) Nearest echo less than 50 cm but more than 25 cm from vehicle. The first two indicators 57, 58 illuminate at level 1, the third 59 is at illumination level 3.

d) Nearest echo less than 25 cm from vehicle. The first indicator is at illumination level 1, the second and third at illumination level 3.

Figure SB shows the view of the rear sensors on the forward display and operation is identical but displays in the inverse and true perspective.

Another type of display is shown in Figure 6A. All channels operate in the same way and channel 1 shall be described.

If the channel is on and there is no received signal detected then indicator 111 shall be at illumination level 1, with indicators 112, 113, 114 and 115 off at illumination level 0.

Once a received signal is detected, then all indicators 111 to 115 shall be at illumination level 1.

If the nearest detected object becomes less than 8 ft (2.4 m), but greater than 4 ft (1.2 m) from the preselected reference position then indicators 111 to 114 shall be at illumination level 1 and indicator 115 shall be at illumination level 3.

If the nearest detected object becomes less than 4 ft (1.2 m), but greater than 2 ft (60 cm) from the preselected reference position then indicators 111 to 113 shall be at illumination level 1 and indictors 114 and 115 shall be at illumination level 3.

If the nearest detected object becomes less than 2 ft (60 cm), but greater than 1 ft (30 cm) from the preselected reference position then indicators 111 and 112 shall be at illumination level 1 and indicators 113 to 115 shall be at illumination level 3. If, however, a strongest signal becomes less than 8 ft (2.4 m), but greater than 4 ft (1.2 m) from the preselected reference position then indicator 115 will illuminate at level 2 rather than level 3.

If the nearest detected object becomes less than 1 ft (30 cm), but greater than 6 ins (15 cm) from the preselected reference position than indicator 111 shall be at illumination level 1 and indicators 112 to 115 shall be at illumination level 3. If, however, a strongest signal becomes less than 4 ft (1.2 m), but greater than 2 ft (60 cm) from the preselected reference position then indicator 114 will illuminate at level 2 rather than level 3.

If the nearest detected object becomes less than 6 ins (15 cm) from the preselected reference position then indicators 111 to 115 shall be at illumination 3. If, however, a strongest signal is less than 4 ft (1.2 m), but greater than 2 ft (60 cm) from the preselected reference position then indicator 114 will illuminate at level 2 rather than level 3.

In the display of Figure 6B, the central channels operate in the same way as the channel described above, and the angular channels operate in the same way as the angular channels of Figure 5A.

An audible warning is provided to the driver under certain circumstances.

By comparing the successive signals from each sensor, knowing the time interval between transmitted sensing pulses, the speed at which the vehicle is approaching a detected object may be calculated. In an advantageous embodiment of the invention, element 9 processes the signals from the sensors 29 to calculate the speed of approach of each detected object, compares the speed of approach with the distance to the object, and emits an alarm signal if the approach speed is such that the distance travelled between successive echo pulse transmissions is greater than a preset fraction, conveniently 1/16th, of the distance remaining between the vehicle and the object.

This alarm signal is included within the information sent to the display units which generates an audio output to warn the driver of the vehicle or any impending collision.

This alarm signal may also be given if any nearest object is within a minimum distance from any preselected relative reference position. At this condition, if any display is not indicating the sensor which is within the minimum distance, it will flash the perspective view of that sensor reading for a short period of time.

The control unit 7 may also contain an audio output module 60 which comprises circuitry to give an audible indication of the distance to the nearest object detected, by element 9 comparing the distances to the 'nearest' echoes from all sensors, and then controlling element 60 to emit a sound whose audible characteristics change as the distance to the nearest object decreases. Preferably, the audio output is a series of pulses of 'bleeps' interspersed with intervals of silence, the lengths of the intervals decreasing to zero as the distance of the nearest echo decreases to a predetermined lower limit of, say 12.5 cm, whereupon the frequency may change to ensure the driver's attention.

The audio referenced distance information and the alarm signal may be emitted via a loudspeaker element 61 and/or to a buzzer/LED configuration 62. The output lines to element 62 may well be used on expanded systems for 'deceleration' and 'brake' controls.

To ensure continuing accuracy in differing environmental conditions, the control unit 7 may also include sensors which detect the ambient temperature, humidity and atmospheric pressure since these parameters affect the speed of sound and thus the time for ultrasound pulses to return as echoes. Preferably, sensors 71 for atmospheric pressure, temperature and relative humidity are provided at suitable points on the vehicle and are linked to an environmental control circuit 72 in the control unit 7. The environmental control circuit 72 will provide an adjustment voltage to circuit element 9 which will then modify the distance information. It is expected that this feature will enhance system accuracy by compensating for changes in the speed of sound due to altitude or airborne contaminants.

It will be readily appreciated that, once installed in a vehicle, the system will require calibration to ensure that distances displayed are accurate, in that the distance displayed is the distance between the detected object and the closest part of the vehicle from a predetermined referenced position. To provide for such calibration, the system circuitry will include adjustment means either incorporated into the circuit elements 9 and 10, or incorporated into circuit element 9 and the circuitry of a display unit. To perform the calibration, a solid object is placed In the detection area of a sensor at a known distance from the vehicle. The system is energised, and the adjustment means operated until the distance displayed corresponds to the known distance. All sensors will have to be calibrated after installation to ensure the accuracy of the display information.

Alternatively, all calibration settings may be set by using switch element 65, within any display unit, in conjunction with circuit element 9.

Claims

1. A manoeuvring aid for a vehicle, comprising at least one sensor unit including a transmitter for sending a beam of radiation and a receiver for receiving radiation echo signals reflected from objects in the beam, processing circuitry to determine the distance from the sensor of the nearest object giving rise to an echo and to determine the distance from the sensor of the object giving rise to the strongest echo signal, and display means to indicate the said distances to the vehicle's driver.

2. A manoeuvring aid according to Claim 1, wherein a plurality of sensors are mounted on the vehicle, each sensor being associated with a display indicating the azimuth direction of the sensor's beam relative to the vehicle, and indicating the respective distances of the objects giving rise to the nearest and strongest echo signals.

3. A manoeuvring aid according to Claim 1 or Claim 2, wherein the radiation emitted by the sensors is sound radiation.

4. A manoeuvring aid according to Claim 3, wherein the sound is of an inaudible high frequency.

5. A manoeuvring aid according to any preceding Claim, wherein the display means comprises a row of lights whose illumination is selectively modified to represent the distance of the objects detected from the sensor.

6. A manoeuvring aid according to claim 5, wherein all the lights in a row are illuminated in a first mode when an object is first detected in the beam of the associated sensor.

7. A manoeuvring aid according to claim 5 or claim 6, wherein the row of lights is arranged to provide an indication of the direction of the beam of its associated sensor relative to the vehicle, and is positioned in such a way that the line of sight from the driver to an obstacle detected by the beam is indicated by the row of lights.

8. A manoeuvring aid according to claim 5, claim 6 or claim 7, wherein four sensors are arranged in a transverse row at one end of the vehicle, the beams of the two central sensors being directed substantially parallel to the vehicle's longitudinal axis and the beams of the other two sensors diverging obliquely away from the vehicle's longitudinal axis, and wherein a display associated with the four sensors comprises four rows of lights in side-by-side relation, two central rows of lights being arranged vertically and two outer rows of lights being upwardly divergent.

9. A manoeuvring aid according to any of Claims 1 to 4, wherein each display means comprises two digital indicators, one displaying the distance of the nearest echo and the other that of the strongest echo.

10. A manoeuvring aid according to claim 9, wherein the display means comprises a combination of digital and graphic display elements.

11. A manoeuvring aid according to any preceding Claim, including: a) means to cause the sensors to emit discrete pulses of radiation; b) timing means to measure the elapsed time between emission of a pulse and detection of echoes; c) comparator means to compare the relative strengths of the echoes; d) processing means to compute the distance between the object giving rise to an echo and the sensor, based on the elapsed time measurement; and e) display means to indicate the distance from the respective sensor of the objects giving rise to the first echo from each pulse, and the strongest echo from each pulse.

12. A manoeuvring aid according to Claim 11, wherein pulses are emitted at intervals of less than 1 second.

13. A manoeuvring aid according to Claim 12, wherein pulses are emitted at intervals of 0.1 second, the duration of each pulse being from 25 to 800 milliseconds.

14. A manoeuvring aid according to any preceding Claim, wherein an array of sensors is mounted to the front and/or to the rear of a vehicle, the array including sensors whose beams are directed obliquely with respect to the vehicle's longitudinal axis so as to diverge therefrom.

15. A manoeuvring aid according to any preceding Claim and including at least one sensor whose beam is directed rearwardly of the vehicle, wherein a display means associated with that sensor is arranged in the rear of the driver's compartment of the vehicle so as to be visible to the driver either in the rear view mirror or by the driver turning round to face the rear of the vehicle.

16. A manoeuvring aid according to any preceding Claim which further includes audible warning means actuated to alert the driver when the distance of the nearest object detected by a sensor falls below a predetermined distance.

17. A manoeuvring aid according to any preceding Claim which further includes means to initiate operation of the system for a predetermined time interval whenever the vehicle's electrical system is switched on.

18. A manoeuvring aid substantially as described herein with reference to Figures 1, 2, 3, 4, 5 or 6 of the accompanying drawings.