GB2047405A - Proximity warning devices for vehicles - Google Patents

Abstract

As an aid to manoeuvring a vehicle in tight spaces, the vehicle is fitted with three sensor heads (1), a control module (2) and a dash indicator unit (3). Each sensor head (1) incorporates a transmitter transducer for emitting bursts of ultrasonic radiation and a receiver transducer for receiving radiation reflected from an obstruction in the intervals between emitted bursts. When the back of the vehicle approaches to within a predetermined distance of an obstruction, the radiation reflected from the obstruction will cause actuation of visual and/ or audible warning means of the indicator unit (3). <IMAGE>

Description

SPECIFICATION Proximity warning devices for vehicles The invention relates to proximity warning devices for vehicles and sets out to provide a device for sensing the distance between a part of the vehicle, such as the front or rear thereof, and an obstruction, such as a wall or other stationary vehicle, when manoeuvring in tight spaces.

According to the invention there is provided a proximity warning device for a vehicle, the device comprising means for sensing the proximity of an obstruction to a part of the vehicle, and visual and/or audible warning means the actuation of which is effected by the sensing means when it senses an obstruction less than a predetermined distance from said part of the vehicle.

The sensing means may comprise a transmitter for emitting a beam to be reflected from an obstruction, a receiver for receiving the beam when reflected from the obstruction, means for monitoring, from a characteristic of the reflected beam, the proximity of the obstruction with respect to a datum position on the vehicle, and means for actuating said visual and/or audible warning means when a predetermined proximity is detected.

The beam may consist of light waves, sound waves, X-rays or radio waves.

The sensing means is preferably adapted to emit bursts of ultrasonic radiation at predetermined intervals and to detect radiation reflected from the obstruction in the intervals between emitted bursts. The interval between successive emitted bursts is generally chosen to be such as to enable the reflected burst corresponding to the first of these emitted bursts to be received before emission of the next burst, when the obstruction is at the maximum of the intended range of the device.

The invention also provides a vehicle fitted with at least one such proximity warning device.

The following is a more detailed description of one embodiment of the invention, reference being made to the accompanying drawings in which: Figure 1 is a view from above of a car fitted with a proximity warning device in accordance with the invention; and Figure 2 is a circuit diagram of the device.

Referring to Fig. 1, the device comprises three sensor heads 1 spaced along the rear bumper of the car, a control module 2 disposed in the boot of the car, and an indicator unit 3 mounted on the dashboard in the passenger compartment. Each sensor head 1 comprises a transmitter transducer in the form of a ceramic resonator for emitting an ultrasonic beam to be reflected from an obstruction, and a receiver transducer for receiving the ultrasonic beam when reflected from the obstruction. When the reflected beam received by at least one of the receiver transducers indicates that the obstruction is less than a predetermined distance from the rear bumper of the car, the control module 2 activates a warning tone and/or light of the dashboard indicator unit 3.

In operation, each transmitter transducer generates a series of pulses, each pulse comprising a burst of ultrasonic radiation having a frequency of about 40KHz. Each pulse has a width of about 0.8 mS and the pulses are repeated at about 50mS intervals. As sound travels at a rate of approximately one foot per millisecond, the leading portion of the ultrasonic burst will be about 10 inches from the transmitter transducer before the trailing portion of the ultrasonic burst is emitted by the transmitter transducer. Immediately the transmitter transducer ceases emitting a burst, the corresponding receiver transducer is switched on to receive any radiation reflected from an obstruction. The obstruction can be any solid object capable of introducing a discontinuity in the characteristic impedance of air to sound waves. Hard objects will give the best reflections.

Since the ultrasonic bursts are only repeated at 50mS intervals, it should theoretically be possible for the receiver transducer to receive an echo of a burst reflected from an object at a distance of up to above 30 feet before the next burst is emitted by the transmitter transducer. However, in practice, the maximum permissible range of the device is limited by the sensitivity of the receiver transducer to backscatter (reflection from the ground). This generally limits the maximum permissible range to about 10 feet. The minimum range also depends on the transducers used and is typically about 3 inches.

The control module is preferably adapted to trigger a repeated pipping tone when reflected signals are received by one or more of the transmitter transducers which indicate the presence of an obstruction at a distance within a particular distance range having an upper limit which may be adjusted by a control between about 10 feet and 3 feet. The repetition frequency of the pipping tone increases as the distance of the obstruction decreases until, at a particular distance, between about 2 feet and 3 inches depending on the adjustment control, the pipping tone is replaced by a continuous tone.Thus the device may be set such that, on reversing of the car during parking for example, the driver is warned that the car is within 3 feet of an obstruction by the onset of the pipping tone so that, as he continues to reverse the car, the driver may judge the distance of the obstruction from the repetition frequency of the tone.

Then, at a distance of about 6 inches, the emitted tone will suddenly become continuous and the driver is warned to immediately stop the car.

Alternatively, it would be possible for the control module to actuate a visual display of the distance between the obstruction and the back of the car. The dashboard indicator unit is preferably provided with a failsafe warning indicator, such as a lamp, for indicating malfunction of the device due to a circuit break or clogging of one of the sensor heads with mud, for example. In order to provide such failsafe warning a certain amount of cross pick-up, that is pick-up by the receiver transducer of radiation emitted directly by the transmitter transducer, is allowed to take place for each sensor head. If this cross pickup ceases for any reason, the failsafe warning indicator is triggered. The transducers are rendered waterproof by being provided with an epoxy resin covering.So that the radiation transmitted and received by the transducers is substantially unattenuated by this covering, the covering has a thickness of about half a wavelength in the path of the radiation.

The diagram of a possible circuit for the above described device is illustrated in Fig. 2.

Although only one transmitter transducer X, and only one receiver transducer X2 are shown in this figure so as to make the diagram easier to read, it will be appreciated that, in practice, three transmitter transducers X, and three receiver transducers X2 each associated with a respective transmitter transducer will be provided.

The circuit is provided with a stabilized power supply 10. An oscillator 11 generates a carrier signal of 80 KHz frequency which is pulsed by a modulator 1 2. In order to suppress false echoes so that only echoes emanating from the obstruction serve to trigger the device, a guard oscillator 1 3 is provided for emitting a guard signal to disable the receiving section of the circuit for a short period after transmission of each pulse. A divider 14 serves to divide the carrier signal by two in order to ensure equal mark/space ratio. Four transistors 15, 16, 1 7 and 1 8 serve to amplify the signal before it is transmitted by the transmitter transducer X,.

The signal received by the receiver transducer X2 is amplified by a single transistor 19, false echoes being suppressed by a suppression stage 20 under control of the guard signal from the transmitting section. The resultant signal is supplied to a threshold detector 21, the output of which is supplied to a monostable 22 having a time constant of 28 ys which provides a further degree of frequency selection. The output of the monostable 22 is amplified by a transistor 23 and then subjected to a persistence check by a stage 24 in order to reject unwanted noise.

When the transmitting section is not actually transmitting a pulse the output of the receiving section is supplied to a triggering section by means of a latch comprising four NAND gates 25, 26, 27 and 28. A marker stage 29 determines the maximum range of the circuit in dependance on the setting of an adjustment control 30. The output of the latch is supplied to a voltage controlled oscillator comprising the circuit elements 31, 32, 33, 34 and 35 which serves to provide a pulsed output having a repetition frequency dependant on the interval between the transmitted pulses and the received pulses, except when the oscillator is triggered by a minimum range detector comprising an inverter 36 and a NAND gate 37 in which case the output becomes continuous. The output is supplied to an Audio circuit comprising three transistors 38, 39 and 40 and a loudspeaker 41.

Although not shown in the drawings, it would also be possible to attach sensor heads to the front of the car so as to also provide a means of sensing the distance of the car from an obstruction when the car is being driven forwards in a confined space.

The device is preferably so wired as to be operable whenever the vehicle's ignition system is switched on. In addition the device may be interconnected with the vehicle's automatic reversing light switch, as an added safety factor against being accidentally set off.

Although the invention has been described in relation to motor vehicles, it will be appreciated that it is applicable to all types of vehicles, including, for example, railway vehicles and aircraft. In the latter case an aeroplane may have one or more sensor heads attached to its undercarriage so that the height of the aeroplane above the runway can be accurately monitored during landing. Furthermore it is envisaged that the device of the invention would be particularly useful on a lorry as an aid to backing of the lorry into an unloading bay.

Claims (11)

1. A proximity warning device for a vehicle, the device comprising means for sensing the proximity of an obstruction to a part of the vehicle, and visual and/or audible warning means the actuation of which is effected by the sensing means when it senses an obstruction less than a predetermined distance from said part of the vehicle.

2. A device according to claim 1, wherein the sensing means comprises a transmitter for emitting a beam to be reflected from an obstruction, means for monitoring, from a characteristic of the reflected beam, the proximity of the obstruction with respect to a datum point on the vehicle, and means for actuating said visual and/or audible warning means when a predetermined proximity is detected.

3. A device according to claim 2, wherein the sensing means is adapted to transmit and receive ultrasonic radiation.

4. A device according to claim 3, wherein the sensing means is adapted to emit bursts of ultrasonic radiation at predetermined intervals and to detect radiation reflected from the obstruction in the intervals between emitted bursts.

5. A device according to claim 4, wherein each burst of radiation has a width of the order of one millisecond and the bursts are spaced apart at intervals of the order of 50 milliseconds.

6. A device according to any preceding claim, wherein the visual and/or audible warning means is adapted to provide an indication of the distance of the obstruction over a range of distance.

7. A device according to claim 6, wherein audible warning means are provided for emitting pipping tones when actuated by the sensing means at a repetition frequency which increases as the proximity of the obstruction decreases, and for emitting a continuous tone when the proximity of the obstruction reaches a predetermined minimum value.

8. A device according to any preceding claim, comprising a sensor head, incorporating an ultrasonic transmitter transducer and an ultrasonic receiver transducer, for fitting to the back or front of a vehicle, a control console for fitting within the vehicle, and an indicator unit for fitting to the dashboard of the vehicle.

9. A proximity warning device substantially as hereinbefore described with reference to the accompanying drawings.

1 0. A vehicle fitted with at least one proximity warning device according to any preceding claim.

11. A vehicle according to claim 10, when appended to claim 8, being a car, wherein a plurality of sensor heads are spaced out along the rear bumper of the car, the control console is fitted within the boot of the car and the indicator unit is fitted to the dashboard of the car.