GB2131172A - Transducer arrangement for ultrasonic obstacle detector - Google Patents

Abstract

A vehicle mounted ultrasonic obstacle detector e.g. for use as a reversing aid, protects an ultrasound transmitting/ receiving transducer 29 from direct contamination by providing a reflector 25 to direct sound to the transducer from a predetermined direction. The reflector may provide a broad horizontal four-shaped beam for better detection of vertical obstacles such as posts. The detector may (Figures 2-4, not shown) be withdrawn into a housing when not in use to provide greater protection. Warning means may alert the driver to the pressure of an obstacle or apply the brakes. <IMAGE>

Description

SPECIFICATION Ultrasonic detecting system The present invention relates to an ultrasonic detecting system, and in particular to such a system which is suitable for mounting on a vehicle to detectfor example obstacles in the path of a reversing vehicle.

British Patent Specification No. 2 090 410 A describes a detecting system for altering the driver of for example a heavy goods vehicle to the fact that he is reversing towards an obstacle and for providing an indication of the distance between the vehicle and the obstacle. The described system comprises an electrostatic ultrasonic transducer which is arranged to transmit signals and receive reflections of the transmitted signals from the obstacle. The ultrasonic transducer is mounted behind a movable cover which is normally closed to protect the transducer against contamination and is opened only when the system is in use. It is not possible to operate the system when the cover is closed because the cover blocks the transmission of the ultrasonic signals.

The system of British Patent Specification No. 2 090 410 A has proved acceptable in many applications but does have drawbacks. For example, the provision of the cover increases the systems cost and complexity assuming the cover is to be operable by the vehicle driver from the vehicle cab. Furthermore, the transducer can still become contaminated if it is used in very dirty conditions as is the case in some circumstances. A further problem is that the transducer output is in the form of a conical ultrasonic beam of limited cross-section. Such a beam is often not suitable for detecting obstacles that do not define a substantial generally vertical surface, for example a narrow post or the legs of a pedestrian not located within the beam.

It is an object of the present invention to provide an improved ultrasonic detecting system.

According to the present invention, there is provided an ultrasonic detecting system comprising means for transmitting an ultrasonic signal and detecting reflections of the transmitted signal from an obstacle, and means for indicating the presence of the obstacle in response to detection of the reflected ultrasonic signal, wherin the ultrasonic signal transmitting and detecting means are associated with a deflector arranged to deflect in a predetermined direction signals transmitted by the transmitting and detecting means and to deflect ultrasonic signals received from the said predetermined direction to the transmitting and detecting means being arranged such that it is protected against direct contamination by material projected from the said predetermined direction.

Although the above system prevents direct contamination of the transducer under normal circumstances, the deflector is exposed to direct contamination. This is not nearly such a serious problem however. Whereas an ultrasonic transducer may be relatively delicate and therefore cannot be easily cleaned and has an output which can be rapidly degraded by contamination, the deflector can have a rugged easily cleaned surface and can still be effective even when fairly heavily contaminated.

To reduce the risk of contamination, the transducer may be withdrawn into a protective housing except when the system is in use. This may be achieved for example by mounting the deflector on a support movable relative to the housing to a position in which both the transducer and deflector are wholly enclosed within the housing.

The deflector may be shaped to project a beam of any desired shape. For example, if the transducer delivers a conical ultrasonic beam, the deflector surface may itself be conical so as to project a fan-shaped beam. A horizontally orientated beam having such a shape is particularly suited to detecting for example a thin post which might not intersect a relatively narrow conical beam.

The ultrasonic signals may be transmitted and detected by any suitable device, for example an electrostatic transducer. The output of the transducer may be processed in any appropriate manner.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a block circuit diagram of one form of an ultrasonic obstacle detecting system according to the invention; Figure 2 is a vertical section taken on the line AA of Figure 3 of a housed transducer arrangement of the system of Figure 1; Figure 3 is a section on the line BB of Figure 2; Figure 4 is a section on the line CC of Figure 3; and Figure 5 is a perspective view of a second embodiment of the invention.

With reference to Figure 1, an ultrasonic obstacle detecting system for use as a reversing aid with a commercial vehicle comprises an ultrasonic transducer device 1 in the form of an electrostatic transducerwhich is connected to a pulse generator 2 and to a gain controlled amplifier 3, such generator and amplifier being connected to a control circuit 4.

The control circuit 4 is connected to a display system, comprising an array of light-emitting diodes 5 (LED's) with appropriate driving circuitry 6, and an output circuit 7 connected to a brake applying solenoid.

The system also includes an actuating circuit 8 operable to supply power to a solenoid used to effect retraction and extension of a deflection structure yet to be described.

The electrostatic transducer 1 may be of the type supplied by Polaroid Corporation under their part number 580112 and may be driven by conventional circuitry such as that described in British Patent Specification No. 2090410 A.

As shown in Figures 2 to 4, the transducer 1 is mounted in a housing 9 fixed to the rear of the vehicle.

The housing 9 comprises a cylindrical enclosure 10 fixed within a box structure defined by a flat top plate 11, a shaped bottom structure 12 fixed to the top plate 11 and defining a bottom wall 13 and two side walls 14, and front and back end plates 15, 16 fixed to the top plate 11 and the bottom structure 12.

The cylindrical enclosure 10 extends between and is fixed to the end plates 15, 16 and is aligned with respective holes 17, 18therein.

The transducer 1 is fixed within and seals the rear end of the enclosure 10 and the corresponding hole 17 in the end plate 15.

The housing also comprises an annular guide 19 mounted slidablywithin the enclosure 10 and pivotally connected to one end of a link bar 20 which extends through a slot in the side of the enclosure 10, the other end of the bar 20 being connected to the aforesaid linear actuator 21 which is mounted within the housing alongside the enclosure 10.

The guide 19 is connected to the aforesaid deflector structure 22 which comprises a body having a part-conical surface 23 which extends to an acute angle to the axis of the enclosure 10.

The arrangement is such that the guide 19 can be moved along the enclosure 10 by the action of the linear actuator 21 between one limit position in which the guide 19 is adjacent the opening 18 in the front plate 16 and the structure 22 projects beyond such end as shown in the drawings, and an opposite limit position in which the guide 19 is adjacent the transducer 1 and the deflector structure 22 is fully retracted into the enclosure 10 with the base of such structure level with and sealing the opening 18.

When the system is not required for use, i.e. when the vehicle is not reversing, the deflection structure 22 is in its retracted position and the transducer 1, the interior of the housing 10 and the deflection surface 23 are therefore protected against contamination by dust and dirt.

When required for use, as for example where the vehicle is being reversed, the deflection structure 22 is first moved to its extended position as shown in the drawings. This may be effected automatically (for example being initiated by a switch which is operated when reverse gear is engaged). Alternatively extension ofthe structure may require manual operation of a switch for example on the vehicle dashboard. The transducer 1 is then fed with a series of four pulse trains of different frequencies from the pulse generator 2 and a beam of ultrasonic signals is emitted from the transducer 1 along the enclosure 10 to be intercepted by the deflection surface 23. From this surface the beam is propagated in fan-shaped conformation directed downwardly at an angle.

When the beam strikes an obstacle as the vehicle is reversed, ultrasonic signals are reflected back to the transducer 1 and are amplified by the amplifier 3.

The circuit 4 produces an output dependent on the time difference between a transmitted signal and a received signal and this is displayed to the driver by illumination of appropriate ones of the LED's 5. In the event that the measured distance (as determined from the time difference) falls below a predetermined value the system may operate automatically to apply the vehicle brakes.

With this arrangement, effective and reliable ranging can be achieved even in relation to a relatively small obstacle. Also, the transducer and adjacent beam-directing surfaces are fully protected against contamination by dust and dirt when not in use, and the transducer is protected against direct contamination even when in use. The deflector can have a rugged smooth surface to enable it to be easily wiped clean if is does become contaminated.

Problems can arise as a result of ultrasonic signals being reflected from the interior of the housing directly to the transducer. The problems can be overcome electronically by choosing to ignore reflections from closely adjacent obstacles. Alternatively, the transducer can be mounted so as to move with the deflector, the transducer when in use being positioned so that no signals can be reflected to it from the housing.

It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiment which are described by way of example only. For example, as the deflector is easy to clean and the transducer is protected against direct contamination, it is not always necessary to provide for the deflector to be retractable or otherwise protected against contamination when not in use.

Figure 5 shows an arrangement in which the transducer/deflector assembly has no moving parts.

The assembly comprises a base 24 having a part conical upper surface 25, an upright 26 which is hollow to define a rectangular passage 27 only the top of which is visible in Figure 5, and an overhanging limb 28. The limb defines an aperture which receives a transducer 29, the lower surface (not shown) of the transducer being flush with the lower surface of the limb 28. A card (not shown) carrying appropriate electronic components is located in the passage 27 and connected to the transducer. A plastics cover 30 is then snapped onto the limb 28 to seal against damp. Connections can be made to the card via the bottom end (not shown) of the passage 27.

The operation of the device of Figure 5 is the same as that of the embodiment of Figures 2 to 4 except of course that the transducer is not retracted when not in use. Despite this, location of the transducer in a horizontal orientation means that not much contamination reaches the transducer. The deflector surface 25 can of course be easily wiped clean. It will be appreciated of course that a protective shield could be mounted around the edges of the transducer providing steps are taken to prevent unwanted reflections from the shield distrupting the operation of the system.

The shape of the beam projected from the surface 25 is of course a function of the shape of the output beam from the transducer and the shape of the surface 25. With the above-mentioned Polaroid transducer which has a diameter of approximately one inch and a conical beam which diverges at an angle of about 18 , and a core the surface of which is inclined at 450 to the horizontal, a beam results which diverges at an angle of 60 in the horizontal plane and 4" in the vertical plane. This is a very good shape for scanning the reversing path of a vehicle.

The beam could however be turned through 90" about the longitudinal axis of the vehicle. In such a configuration and with appropriate alterations to the detection electronics the system could be used to detect the edge of a tip across which a vehicle is being driven with a view to dumping material over the tip edge.

To facilitate the production of assemblies of the type shown in Figure 5 having a range of deflector shapes, the surface 25 may be defined by a separate deflector member which can be secured to the rest of the assembly by for example an interlocking engagement and/or adhesive. It is then only necessary to produce a range of deflector members any one of which can be secured to an assembly as desired.

Claims (6)

1. An ultrasonic detecting system comprising means for transmitting an ultrasonic signal and detecting reflections of the transmitted signal from an obstacle, and means for indicating the presence of the obstacle in response to detection of the reflected ultrasonic signal, wherein the ultrasonic signal transmitting and detecting means are associated with a deflector arranged to deflect in a predetermined direction signals transmitted by the transmitting and detecting means and to deflect ultrasonic signals received from the said predetermined direction to the transmitting and detecting means, the transmitting and detecting means being arranged such that it is protected against direct contamination by material projected from the said predetermined direction.

2. An ultrasonic detecting system according to claim 1,comprising means for withdrawing the transmitting and detecting means into a protective housing except when the system is in use.

3. An ultrasonic detecting system according to claim 2, wherein the deflector is mounted on a support movable from a first position in which an opening is defined in the housing through which ultrasonic signals can be deflected to and from the transmitting and detecting means and a second position in which the support seals the opening to prevent contamination of the housing interior.

4. An ultrasonic detecting system according to any preceding claim, in which the deflector is shaped so as to project a fan-shaped beam.

5. An ultrasonic detecting system according to claim 4, in which the transmitting and detecting means directs a cone-shaped beam onto the deflector, and the deflector defines a part-conical reflecting surface to provide a fan-shaped deflected beam.

6. An ultrasonic detecting system substantially as hereinbefore described with reference to the accompanying drawings.