GB2264782A - A vehicle parking aid - Google Patents

Abstract

The parking aid (2) is for indicating the distance of a vehicle from an obstacle and comprises a single transmitter (4), two receivers (6, 8) for the transmitter (4), computer means (10) for producing an indication of the distance of the vehicle from the obstacle consequent upon information being received from both of the receivers (6, 8), and audible means (for example a piezo-electric device) for giving an audible indication of the distance of the vehicle from the obstacle as determined by the computer means (10). In use the receivers (6, 8) are positioned one on either side of the transmitter (4), thereby to enable the receivers (6, 8) to receive at different times ultrasonic signals which emanate from the transmitter (4) and which are reflected by the obstacle when the vehicle is at an angle with respect to the obstacle, thereby to enable the computer means (10) to give a substantially accurate indication of the distance of the vehicle from the obstacle irrespective of the angle at which the vehicle is to the obstacle. <IMAGE>

Description

A VEHICLE PARKING AID This invention relates to a vehicle parking aid and, more especially, this invention relates to a vehicle parking aid for indicating the distance of a vehicle from an obstacle likely to be encountered when the vehicle is being parked.

The parking of vehicles is often difficult, especially when parking in confined spaces. Damage often occurs due to the vehicle being parked hitting an obstacle such for example as another vehicle or a wall.

Vehicle parking aids are known. Simple vehicle parking aids involve touch sensors which extend from the vehicle and which are adapted to cause an audible warning when they touch an obstacle. Such simple touch sensors are unsatisfactory in that they do not give a progressive indication of the distance of the vehicle from the obstacle and they only operate when the vehicle is extremely close to the obstacle, which may be too late for some drivers not having good control of their vehicle.

More sophisticated electronic vehicle parking aids are known. These known vehicle parking aids overcome the disadvantages of the above mentioned simple touch sensors but they in turn suffer from other disadvantages.

More specifically, the known sophisticated vehicle parking aids use ultrasound to measure the distance between the vehicle and the obstacle but they only measure the straight line between a transmitter/receiver unit and the obstacle. This is no problem if the obstacle is at 900 to (ie straight behind) the transmitter. However, if the obstacle is at an angle to the transmitter (ie off to one side), then vehicle reversing aids measuring only the straight line distance between the transmitter/receiver unit and the obstacle give an incorrect indication and they indicate that the obstacle is farther away from the vehicle than it actually is. This tends to cause the driver of the vehicle to misjudge the distance between the vehicle and the obstacle, with the possible risk of a collision.

One known attempt to overcome the above mentioned problem in the electronic vehicle parking aids has been to use a plurality of transmitter/receiver pairs based along the vehicle, for example the rear bumper of the vehicle, in order to make sure that the obstacle is always at 900 from one of the transmitters/receiver pairs on the obstacle.

The need to use a plurality of transmitters and receivers increases the overall cost of the vehicle parking aid and thus tends to make the vehicle parking aid too costly to produce.

Another known attempt to meet the above mentioned problem with the electronic parking aids has been to use a transmitter/receiver unit which scans.

Such a unit needs a drive motor in order to enable it to scan and the cost of the drive unit again tends to make the vehicle parking aid prohibitively expensive to manufacture.

It is an aim of the present invention to provide a vehicle parking aid which is able to give a substantially accurate indication of the distance of a vehicle from an obstacle irrespective of the angle at which the vehicle is to the obstacle, and which can also be produced more cheaply than the above mentioned known electronic vehicle parking aids.

Accordingly, in one non-limiting embodiment of the present invention there is provided a vehicle parking aid for indicating the distance of a vehicle from an obstacle likely to be encountered when the vehicle is being parked, which vehicle parking aid comprises a single transmitter, two receivers for the transmitter, computer means for producing an indication of the distance of the vehicle from the obstacle consequent upon information received from both of the receivers, and audible means for giving an audible indication of the distance of the vehicle from the obstacle as determined by the computer means, and the vehicle parking aid being such that in use it is fitted to the vehicle such that the receivers are positioned one on either side of the transmitter thereby to enable the receivers to receive at different times ultrasonic signals which emanate from the transmitter and which are reflected by the obstacle when the vehicle is at an angle with respect to the obstacle, thereby to enable the computer means to give a substantially accurate indication of the distance of the vehicle from the obstacle irrespective of the angle at which the vehicle is to the obstacle.

It will thus be apparent that the vehicle parking aid of the present invention only needs to use one single transmitter and two receivers as compared to the above mentioned known vehicle parking aids which either use a plurality of transmitter/receiver pairs or a drive motor for permitting scanning.

The vehicle parking aid of the present invention is especially useful as a vehicle reversing aid. In this case, the vehicle parking aid will usually be mounted on a rear bumper of the vehicle but the vehicle parking aid may be mounted at other positions on the rear of the vehicle if desired. Where the vehicle parking aid is to be used when reversing during parking, then the vehicle parking aid can be arranged automatically to come into operation on engagement of the reversing gear of the vehicle. If desired however, the vehicle parking aid can be arranged to be operated manually.

The vehicle parking aid can also be used for forward parking. Many persons find difficulty in judging the distance of the front of their vehicle from an obstacle, for example a garage wall or a wall in a multistorey car park. Where the vehicle parking aid is to indicate the distance of the front of the vehicle from an obstacle, then the vehicle parking aid would usually be manually operated.

If desired, a vehicle may be provided with two vehicle parking aids, one for indicating the position of the rear of the vehicle relative to an obstacle, and the other being for indicating the position of the front of the vehicle relative to an obstacle. Where front and rear vehicle parking aids are employed on a vehicle, then one or more automatic or manual switch means may be employed and, if desired, different audible warning tones may be employed so that there is a different tone for reverse movement and for forward movement of the vehicle0 Preferably, the computer means comprises an analog to digital converter means, timer means and a calibrated look-up table relating to the overall distance of the vehicle from the obstacle to received signal times from the receivers.

The vehicle parking aid may be one in which the analog to digital converter means comprises four analog to digital converters, and in which the timer means comprises two timer units, one for each receiver.

The vehicle parking aid may include converter means for converting electrical signals from the receivers to a lower frequency representation, thereby to permit the use ofslower analog to digital converter means than would otherwise be possible. Generally, slower analog to digital converter means are cheaper than faster analog to digital converter means, so that the use of the converter means for providing the lower frequency representation is advantageously employed to reduce manufacturing costs of the vehicle parking aid still further.

The converter means may be a diode and a filter to produce a signal which is at the lower frequency and which represents the amplitude or size of the receiving ultrasonic signals.

The vehicle parking aid may include amplifier means for amplifying signals from the receivers. The amplifier means may comprise a pair of amplifiers for each receiver.

The audible means may be a piezo-electric device.

The vehicle parking aid may include protection means for protecting the analog to digital converter means.

The protection means may comprise a pair of Zener diodes, one for the signals from each receiver.

The vehicle parking aid may be sold as an accessory for fitting to existing vehicles. Alternatively, the vehicle parking aid may be included in vehicles at the time of their manufacture.

The present invention also extends to a vehicle when provided with the vehicle parking aid.

An embodiment of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows the various components of a vehicle parking aid; Figures 2 - 5 illustrate the operation of the vehicle parking aid shown in Figure 1; and Figure 6 illustrates the signal processing which occurs with the vehicle parking aid shown in Figure lo Referring to Figure 1, there is shown a vehicle parking aid 2 for indicating the distance of a vehicle from an obstacle likely to be encountered when the vehicle is being parked. The parking aid 2 comprises a single transmitter 4 and two receivers 6, 8 for the transmitter 4.The parking aid 2 also comprises computer means in the form of a microprocessor 10 for producing an indication of the distance of the vehicle from the obstacle consequent upon information received from both of the receivers 6, 8.

The vehicle parking aid still further comprises audible means in the form of a piezo-electric device (not shown) for giving an audible indication of the distance of the vehicle from the obstacle as determined by the microprocessor 10.

As can be seen from Figure 1, the vehicle parking aid 2 includes for each receiver 6, 8 a first stage amplifier 12, a second stage amplifier 14, a diode 16, a filter 18 and a Zener diode 20.

Figures 2 - 5 show the vehicle parking aid 2 fitted to a rear bumper 22 of a vehicle 24. An obstacle 26 is shown positioned at an angle to the vehicle 24. As shown schematically in Figures 2 - 5, the microprocessor 10 includes left and right timers L,R associated one with each of the left and right receivers 6, 8 as shown in Figures 2 to 5. The receivers 6, 8 are positioned one on either side of the transmitter 4 as shown and this enables the receivers 6, 8 to receive at different times ultrasonic signals which emanate from the transmitter 4 and which are reflected by the obstacle 26.

Generally, the vehicle parking aid 2 operates by transmitting a short pulse of ultrasound by the transmitter 4 and receiving the. echos back at the two receivers 6, 8 which are ultrasonic receivers. As shown in Figures 2 - 5, one receiver 6 is placed slightly to the left of the transmitter 4 whilst the other receiver 8 is placed slightly to the right of the transmitter 4. The echos received contain certain information about the obstacle 26 in the field of the transmitter beam 28.

For example, the overall time taken for the pulse of ultrasound to leave the transmitter 4 and return to the receivers 6, 8 is directly proportional to the distance between the transmitter 4 and the obstacle 26. The difference in time between the pulse arriving at the left receiver 6 and at the right receiver 8 is related to the angle of the obstacle 26 to the rear bumper 22.

The transmitter 4 and the receivers 6, 8 are each an ultrasonic transducer. One ultrasonic transducer is used as the transmitter 4 and the other two transducers are used as the receivers 6, 8. The microprocessor 10, the amplifiers 12, 14, the diode 16, the filter 18 and the Zener diode 20 may be provided on a single chip.

The microprocessor 10 contains a microprocessor core, analog to digital converter means in the form of four analog to digital converters, and timer means in the form of two timer units L and R. The four analog to digital converters are used to convert a voltage level into a number that the microprocessor 10 can use. The microprocessor 10 has 24 digital inputs and outputs.

The transmitter 4 is connected to two of the digital outputs of the microprocessor 10. A small program routine drives the outputs to cause the transmitter 4 to send out a burst of ultrasound at a frequency of 40Kh, lasting for approximately 200 microseconds. When this happens during operation of the vehicle parking aid 2, the two timers L,R are started.

The receivers 6, 8 convert the ultrasound waves into a varying voltage, but due to inefficiency of the transducers, the loss of energy as the waves spread out through the air, and absorption of energy from the waves as they are reflected by the obstacle 26, the voltages produced by the receivers 6, 8 are very small. Thus each receiver 6, 8 is connected to the amplifiers 12, 14 to boost the signal above the background noise, and to a level that the microprocessor 10 can use. At this stage, the signal changes too quickly for the microprocessor to use the signal, so the signal is passed through the diode 16 and the filter 18 to produce a signal at a much lower frequency that represents the amplitude or size of the ultrasound waves received.Thus the diode 16 and the filter 18 act as converter means for converting electrical signals from the receivers of 6, 8 to a lower frequency representation. This permits the use of slower analog to digital converters than would otherwise be possible.

The converted signal is then passed to the analog to digital converters to provide a digital representation of the received ultrasound signal. The microprocessor 10 monitors both the left and the right receivers 6, 8, and when the level rises above a preset threshold, the microprocessor 10 deduces that a pulse has arrived back at the associated receiver 6, 8 and stops the timer associated with that receiver.

The processor 10 has a calibrated look-up table relating the overall distance of the obstacle 26 from the rear bumper 22 to the observed left and right receiver time. The microprocessor 10 uses the values measured by the two timers L, to look up the distance.

A further digital output of the microprocessor 10 is used to drive audible warning means in the form of a piezo-electric sounder. After each distance measurement is made, the microprocessor 10 produces an audible tone and then waits. The length of this wait is determined by the measured distance. The further away the obstacle 26 is, the longer the wait. In this way, the frequency of repetition of the bleeps tells the vehicle driver how far the obstacle 26 is away from the rear bumper 22. At very close distances of a few inches or so, the tone becomes continuous and acts as a danger warning.

The vehicle parking aid 2 has the ability accurately to indicate the distance of obstacles such as the obstacle 26 anywhere along the rear bumper 24, whilst keeping the component cost of the vehicle parking aid 2 to a minimum. This is effected in the illustrated embodiment by the use of the single transmitter 4, the two receivers 6, 8, and the use of a low cost single chip microprocessor 10 which relates the observed readings back to accurate distances. Production costs are further modified by the use of the filters 18 and Zener diodes 20 which allow the conversion of the signal to a lower frequency representation, which in turn allows the use of slower analog to digital converters which are commonly found on low cost single chip microprocessors.

Figure 6 illustrates the processing of the signals and the information given on Figure 6 makes Figure 6 self-explanatory.

It is to be appreciated that the embodiment of the invention ddscribed above with reference to the accompanying drawings has been given by way of example only and that modifications may be effected. Thus, for example, the vehicle parking aid 2 may be produced as a car accessory or it may be fitted as an extra by car manufacturers.

Claims (12)

1. A vehicle parking aid for indicating the distance of a vehicle from an obstacle likely to be encountered when the vehicle is being parked, which vehicle parking aid comprises a single transmitter, two receivers for the transmitter, computer means for producing an indication of the distance of the vehicle from the obstacle consequent upon information received from both of the receivers, and audible means for giving an audible indication of the distance of the vehicle from the obstacle as determined by the computer means, and the vehicle parking aid being such that in use it is fitted to the vehicle such that the receivers are positioned one on either side of the transmitter thereby to enable the receivers to receive at different times ultrasonic signals which emanate from the transmitter and which are reflected by the obstacle when the vehicle is at an angle with respect to the obstacle, thereby to enable the computer means to give a substantially accurate indication of the distance of the vehicle from the obstacle irrespective of the angle at which the vehicle is to the obstacle.

2. A vehicle parking aid according to claim 1 in which the computer means comprising an analog to digital converter means, timer means and a calibrated look-up table relating to the overall distance of the vehicle from the obstacle to received signal times from the receivers.

A A vehicle parking aid according to claim 2 in which the analog to digital converter means comprises four analog to digital converters, and in which the timer means comprises two timer units, one for each receiver.

4. A vehicle parking aid according to claim 2 or claim 3 and including converter means for converting electrical signals from the receivers to a lower frequency representation, thereby to permit the use of slower analog to digital converter means than~would otherwise be possible0

5. A vehicle parking aid according to claim 4 in which the converter means is a diode and a filter to produce a signal which is at a lower frequency and which represents the amplitude or size of the receiving ultrasonic signals.

6. A vehicle parking aid according to any one of the preceding claims and including amplifier means for amplifying signals from the receivers.

7. A vehicle parking aid according to claim 6 in which the amplifier means comprises a pair of amplifiers for each receiver.

8. A vehicle parking aid according to any one of the preceding claims in which the audible means is a piezo-electric device.

9. A vehicle parking aid according to any one of claims 2 to 5 and including protection means for protecting the analog to digital converter means.

10. A vehicle parking aid according to claim 9 in which the protection means comprises a pair of Zener diodes, one for the signals from each receiver.

11. A vehicle parking aid for indicating the distance of a vehicle from an obstacle likely to be encountered when the vehicle is being parked, substantially as herein described with reference to the accompanying drawings.

12. A vehicle when provided with a vehicle parking aid as claimed in any one of the preceding claims.