AU633847B2 - Measuring the volume of material passing along a conveyor - Google Patents

Description

OPI DATE 23/03/90 APPLN. ID 41874 89 AOJP DATE 26/04/90 Pcr J PCT NUMBER PCT/AU89/00365 INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (51) International Patent Classification 4 (11) International Publication Number: WO 90/02318 GOF 13/00, 1/00, G01B 11/24 Al GON 21/85 1 (43) International Publication Date: 8 March 1990 (08.03.90) (21) International Application Number: PCT/AU89/00365 (81) Designated States: AT (European patent). AU, BE (European patent), BR, CH (European patent), DE, DE (Eu- (22) International Filing Date: 29 August 1989 (29.08.89) ropean patent), FR (European patent), GB, GB (European patent), IT (European patent), JP, KR, LU (European patent). NL (European patent), SE (European pa- Priority data: tent), SU, US.

PJ 0129 29 August 1988 (29.08.88) AU PJ 3474 31 March 1989 (31.03.89) AU Published With international search report.

(71) Applicant (for all designated States except US): STATE ELECTRICITY COMMISSION OF VICTORIA [AU,' AU]; 15 William Street, Melbourne, VIC 3000 (AU).

(72) Inventors: and Inventors/Applicants (for LS onlyi HOWELL. Gerald, Edward [GB 1 Wahusen Road. Heathmont. VIC 3135 GRAHAM. Roland. Tyson [AU/AU]; 11 Susanne Avenue. Nunawading. VIC 3131 (AU).

Agent: PHILLIPS ORMONDE FITZPATRICK; 36- Collins Street. Melbourne. VIC 3000 (AU).

(54)Title: MEASURING THE VOLUME OF MATERIAL PASSING ALONG A CONVEYOR

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T- 26 24 (57) Abstract An apparatus and a method for measuring the volume of material (12) on moving conveyors The apparatus comprises a light source (14) to project a beam of light (16) across a conveyor such that the leading edge (20) of the beam of light impinges on material on the conveyor at a first angle, and means (18) to receive an image of a: least the leading edge of the beam of light at a second angle, where the first angle is displaced from the second angle. The apparatus also comprises means (22) to capture and process the image at a rate necessary to provide calculation of a required volume parameter.

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RECEIVED oc 198 Q OCT 1989 -1- IMPROVED ;AP-ARATUS AND METHOD FOR MEASURING THE VOLUME (iF .ATERIAL PASSING ALONG A CONVEYOR This iiawntion relates to a method for measuring the volume aff material on moving conveyors, and the apparatus ttfhme for. Although the invention will be described with reference to the measurement of coal or overburden im an open-cut mining situation, where severe difficulties haove to be overcome (for instance, where conveyor beltts are up to 2 metres wide, where 24 hour operation is required, operation is in harsh open air conditions, ama where burden surface is extremely variable in shape), te present invention may be applied to volume-meastraement on any bulk conveyor system, and is easy to apply in other cases where operating conditions are less harst.

Mined ores and other materials such as coal and overburden are transported out of open-cut mines by conveyor systems. Although the mass transport rate may be estimated using radiation penetration measurements, accurate voluse transport rate determination has not been practicable.

The present invention is directed at providing an effective and practical means for the measurement of conveyor material volume throughput.

According to the present invention there is provided apparatus for measuring the volume of material passing along a conveyor, comprising a light sourc- to project a beam of light across said conveyor such that the leading edge of the beam of light impinges on material on the conveyor at a first angle, means to receive an image of at least the leading edge of the beam of light at a second angle, said second angle being displaced from said first angle and means to capture, and process, th; image at a rate necessary to provide calculation of a required volume parameter.

The present invention also provides a method for measuring the volume of material passing along a conveyor S 'vpomprising providing a beam of light from a light source S39 ,across a conveyor such that the leading edge of the beam PCr/AU, 3 0 0 3 6 RECEIVED G 5 OCT 1989 -2- -Eof light impinges on matcrial on the conveyor at a fre angle, receiving an image in an image receivin g ns of at least the leading edge of the beam o ght at a second angle, said second angle be' isplaced from said first angle and capturi nd processing the image at a rate necessa c culate a required volume parameter.

The light source ef the present invention is prerably a- otroboe light- ouree. The strobe light source may be mounted above the conveyor belt in such a way as to produce, when triggered, a pulse illuminated zone on the conveyor, preferably in the form of a rectangular beam of light. Preferably the broad beam of light extends from side to side across the conveyor to cover the width of material being conveyed although if the accuracy required is less the beam may extend over the central portion of the conveyor only. Preferably the beam extends at about right angles to the direction of the conveyor belt travel. However, in some cases it may be preferred for the beam to extend diagonally across the conveyor belt for particular resolution of irregularly placed materials on the conveyor. Also the light source and/or the image recovering means may be located directly above the conveyor belt or displaced to one or other side to suit the expected disposition and size of the materials.

The light source is preferably such as to provide a distinctly sharp leading edge across the material on the belt, and illumination of the material to one side of this leading edge. In a preferred form, the light source is a powerful strobed xenon flash discharge light source, synchronised with the rest of the system in order to capture sharp, unblurred images.

The image receiving means is preferably a solid state camera utilising a charged coupled device (CCD), or a similar target. Preferably the camera used is such as to inherently integrate the light received by its target, and provide a stable image without appreciable distortion or drift. The resulting image is captured and processed using an image-processing system. This procedure is 9, repeated prcferably several times per second so that OCT/A 3e ,65 ECEVL OCT i989 -3measurements can be made at frequent intervals on a moving belt.

By their very nature, modern television cameras of all types acquire target charge (apparent intensity) images according to the time-intensity integral of the illumination at each point over a total frame time of milliseconds. Therefore, continuous ambient illumination can build up a substantial charge image in the area of the picture which is not illuminated by the strobe light and which makes it difficult to discriminate an illuminated edge. To overcome this problem, a shutter may be used which only allows light onto the camera imaging target preferably at an optimum instance for a period equal to the duration of the strobe light pulse. Such a shutter is preferably used where the present invention requires operation in relatively high ambient light.

In a first preferred form, the shutter is a static electrically controlled window which is normally opaque, but which is rendered transparent for a period substantially equal to the duration of the strobe light pulse. Alternatively, the image receiving means itself may be electrically controlled to only receive an image for the appropriate length of time.

In a second preferred form, the shutter is a mechanical device driven by a motor which is synchronised to the image receiving means synchronising signal by using a suitable technique, such as the phase locked loop method. The shutter preferably has a single imaging aperture large enough to correctly expose the target to a significant part of the total image field.

In these alternative forms, the target elements of the image receiving means receive the flash illuminated image while the shutter aperture is open, and ambient light is blocked from reaching the camera target for the remainder of the frame. Such a shutter allows the system to be operated in strong light, and the action of the shutter reduces the effect of ambient light by a factor of about 150 without attentuating the strobe light. This Z9 enables reliable detection of the leading light edge in S. SUBSTITU-E SHUT_ S 0 J o0 3 6 RECEIVED 0 5 OCT 1989 -4daylight, providing that the working zone is protected from direct sunlight such as by a simple open ended hood.

In a preferred form, the .system is operated in a darkened area, such as in a shed, or merely under a cover. In this way, the slight problems associated with use in strong light are avoided.

It should be appreciated that the mechanical shutter may be omitted, and hooded enclosures may be used with the system.

Thus in a preferred form of the invention, the conveyor is illuminated by a continuing succession of very powerful, short duration light pulses which effectively "freeze" the belt motion, allowing for accurate measurements of section shape. To minimise distortion of the image due to a possibly subtended angle between the image receiving means and the light source, the well defined dark-to-light transition plane, which is the plane of projection of the leading edge of the light beam, is preferably substantially parallel to the image target plane of the image receiving means. Therefore, the image of anything in the transition plane is without inherent geometrical distortion, and consequently the image of the leading light edge can be extracted from the total image f'eld, and processed without geometrical matrix correction.

The above effect is preferably achieved by having the image receiving means and light source projection each at angles of 45 degrees to the level of the conveyor belt, being 90 degrees relative to the other. The light-to-dark transition plane is, in a preferred form, square across the belt, but vertically slanted 'at an angle' of 135 degrees to the direction of belt travel, and the line where this plane intersects the conveyor represents the shape of the top of the burden. The burden slant sectional shape is therefore the space between the bottom limit set by the unloaded belt, and the top limit which is the "first illuminated edge" in the direction opposite to the belt travel.

In this form, the primary processed image is 39 effectively a 45 degree slant section through conveyor and PC-T/A'U. 9 0 03 6 RECEIVED 0 5 OC T'1989 burden, whereas a true vertical section is needed to calculate throughput volume. This is compensated for in subsequent processing by allocating appropriately different horizontal and vertical scaling factors.

However, the image receiving means may be at a greater angle to the level of the conveyor belt, such as normal to that level, and at some acute angle relative to the light source although in this event additional processing may be required.

Although a thin stripe of light may be employed, the present invention preferably utilises a broad beam of light, thereby to minimize the effect of masking of the light source by the -uneven level of the material being conveyed. By utilizing a broad beam of light, the illumination extends some distance along the belt to provide an area of the target image which is well illuminated on the "lit" side of the dark/light transition plane. This provides reliable detection of the first illuminated edge.

The extended up-stream illumination also means that a sharp edge will be formed in the image plane even if the actual image of the dark/light transition plane is obscured by a lump of burden on the dark side, between the camera and the dark/light plane. This part of the first illuminitted edge will then be the shadow of the lump against: the upstream illuminated burden and not the true edge. However,, it has been found in practice, the size of the lumps are such that usually only a small part of any image will be affected in this way, and the number of such occurrences is small. Overall calibration provides a means of determining what corrections (if any) are needed to compensate for this and other possible sources of error.

The means to capture, process, and display said primary pzocessed image may be any suitable means. In one form of the invention the imaging syL-tem consists of a .~~MicroVAX-II mini computer, imaging cards which interface a MicroVAX-II 0-bus, and appropriate high resolution m, mnitors and monochrome cameras. Other facilities which 39 .Sfryy allow for greater flexibility include a digitizing SSURSTMTITC cucE,- PCT/AU 3 0 3 6 RECEIVED 3 5 OCT 1989 -6tablet, video recorder, and a time-base corrector.

Separate instrumentation measures the instantaneous belt speed, and this may also be fed into the computer.

The signal from the image receiving means, preferably a standard interlaced video signal, is fed to the computer system, which may be fitted with commercially available image processing hardware, allowing images to be digitised, processed, and displayed. The system described above provides a resolution of approximately 512 x 512 pixels, which provides ample resolution for any conceived conveyor measurement system.

Images are preferably captured and processed at a rate necessary to provide accurate calculation of the volume rate and total running volume, and will depend on the speed of the belt and the expected variation in the material volume.

As each image is captured it is processed and the cross-sectional area of the material is calculated by measuring the area between the unloaded belt reference profile and the new edge profile on the current image.

These calculations take into account lens distortion, the vertical scaling required due to the camera's angle of view, and the pixel/real world measurements' ratio which is calculated initially when the unloaded belt reference -is taken.

The image is processed by searching across the image from the dark area until the light edge threshold is found, and recording the co-ordinates of that point. This is done for a number of lines across the belt image (approximately 100 has been found satisfactory) in order to build up a profile of the burden. This profile is compared with the unloaded belt reference profile to calculate the area of the burden for that image sample, taking into account known distortions. In some applications where the image signals are not sufficiently clear, due to signal noise for example, initial image enhancement of the image is required by using enhancement -techniques such as noise filtering or edge enhancement.

39 ,.These can be carried out in the hardware on the image PtL-/ A U. 7 /0 03 6 RECEIVED 1 5 O CT 1989 -7process ing boa rds o r may be done in sof twa re.

Knowing the belt speed, and the time elapsed since the last image sample, the distance the belt has travelled and the volume of burden transported are then calculated.

The calculation assumes that the cross sectional area is constant between samples; any error introduced by this assumption depends on the belt speed, and the sampling rate.

A dynamic visual computer generated display of the conveyor material preferably is then displayed on the high resolution monitor, together with a graphical presentation of the instantaneous volume rate and total burden volume transported.

In situations where no graphical output display and.minimal output information is required, an alternative method of processing the video image from the camera may be employed. For example, where the only output required is the instantaneous or averaged cross section of the burden, then the video signal may be processed directly by analogue/digital circuitry and the output fed directly to a digital display unit. Such a system does not require the use of an imaging computer, and avoids one of the major costs of the measurement system. In a preferred form this alternative method can be operated as follows. The video signal from the camera may be fed directly to specially designed analogue/digital circuitry which effectively measures the time from start of the line to the occurrence of the light edge on each of the video image lines. The circuitry sums these measurements, and subtracts from the result, a previously measured reference measurement made on an empty belt.

After conversion the result is a measurement of the burden cross sectional area, which is then directly displayed on a simple digital display unit.

Where multiple or complex outputs are required, ~~-.which are d f f icult to produce f rom discrete circuitry, a minimal low cost specially designed microprocessor board mayr be used to do some of the processing.

39 In order to assist in arriving at an understanding i'cr//U 0 0 3 6 RECEIVED 0 OCT 18 o f the present invention, several preferred embodiments are illustrated in the attached drawings. However, it should be understood that the following description is illustrative only and should not be taken in any way as a restriction on the generality of the invention as described above.

In the drawings: Figure 1 is a schematic diagram of the present invention; Figure 2 is a schematic diagram of a preferred Image Processing sys~tem for use with the present invention; Figure 3 illustrates possible images as processed by the apparatus of the present invention, and utilised.for-calculations; and Figure 4 illustrates the masking effect created by non-uniform material when using the apparatus of the present invention.

Figure 1 shows the general arrangement of the principal parts of the apparatus of a'preferred embodiment of the present invention. Illustrated is a conveyor belt having thereon material or burden, 12. A strobe light source 14 provides a broad beam of light 16 on the surf ga of the material 12. A camera 18 is arranged to receive the image of at least the leading edge 20 of the broad beam of light 16, to transfer the image to the processing means 22.

The strobe light source 14 is preferably based on a Xenon flash tube with a fused quartz envelope, which is about 300 mm long by about 10 mm diameter. It is rated for an average discharge power of about 500 watts with forced air cooling, and has an expected life of at least million flashes at about 40- joules per flash.

Satisfactory images are obtained at about 16 -joules per flash and therefore a life of at least six months per tube in continuous operation at 24 hours per day and 5 flashes per second is expected.

The energy for the f lash is stored in high grade, 39 h'igh peak current rated capacitors which are RECEIVED 25OCT 1989 -9non-dissipatively charged f rom 240 volt mains. The flash is triggered by a lower power short duration firing pulse derived from the shutter and strobe synchroniser, under control from the processing meatis 22.

The shapedI illumination pattern is formed by a full length slit, approximately 8mm wide located in front of the tube, and a one metre wide single sided gate at a distance of about 600 mm from the slit.

Preferably, a high resolution camera 18 is used which includes a power supply/electronics unit providing AGC, Garmna and Aperture Correction. This unit has the advantage of providing a number of synchronising waveforms which are useful in connection with the general circuits designed to synchronise the. camera, shutter, and lightsource functions. The camera preferably has a standard CCD target of 2/3 inches diagonal with a matrix of 550(H) by 582(V). The supply/electronics unit may be modified to provide wide range manual gain control.

The processing means 22 captures and processes the image using specialist operating software, and provides a display 24 on a display monitor 26. Connected to the processing means 22 is a terminal 28 to input, data and information, together with a belt speed sensor 30, and-e-a strobe trigger 32. Belt speed sensor 30 provides the processing means 22 with the speed of the conveyor belt in order to assist in calculat~ons. The strobe trigger 32 is coordinated with a phase locked loop control 34 attached to the camera 18, so that the processing means can coordinate the triggering of the strobe light to emit the beam of light at the ,same time as a mechanical shutter provided in the camera is open.

The operating software preferably consists of two programs. The first program calculates certain parameters and stores them on disc. The main operating program retrieves this information when first run and uses this data to search for the light edge and to calculate the necesaryareas and volumes.

"'ii~ain The first program is run prior to the start of the 39)'ai operating program and need only be run again if some PC1r/AU J 0 0 3 b RECEIVED OCT 1989 change has ocMcrred to the relative positions of the camera, light source and conveyor belt. This program calculates, fron a number of empty belt images, the following parameters: the empty belt reference position as a string of co-ordinates; S the vertical and horizontal pixel calibrations (mm/pixel); the position of the belt images, and hence the co-ordinates of a search frame.

Figure 3 illustrates a typical empty belt image 62, with the search frame shown as the rectangular border.

The sides of the search frame running across the belt are set to a position which ensures that the belt illuminated.light edge always occurs within these lines. The other limits are calculated after searching across the full width of the frame to determine the edges of the belt.

The pixel calibrations are calculated from the known distances between the edges of the belt and from the bottom of the belt to the mean height of the two edges.

In a preferred form, the main operating program works as follows. After completing the processing of each image a trigger pulse is sent to the strobe light at tlenext eppropriate point in the repetitive television camera signal reaudut sequence and the illuminated image is recorded on the camera target. The image is then read out from the camera over approximately the next I milliseconds in broadcast television format, and recorded into a digital image storage buffer for subsequent analysis.

The computer then commences searching the stored image for the "first illuminated edge", scanning from below the empty belt position towards the maximum expected burden height in the previously defined search area.

Figure 3 also depicts the image obtained with a loaded belt 64.

The search is done at a large number of positions across the belt width (approximately 100) and the software 39 calculates the height of the burden above the ,CT/MI 2 0 0 3 6 RECEIVED OCT 1989 -11corresponding empty belt position at each lateral step.

It then calculates the corrected area for each of these incremental sections making use of lateral and vertical calibration factors which were obtained during the initial calibration program. On completion of the search steps these areas are summed to produce a total cross sectional area for that measurement point.

The burden volume between the current and the previous measurement point is then calculated by multiplying the burden cross sectional area just computed by the distance of the belt travel between the two measurement points. In this preferred form a constant belt speed was assumed and the distance computed from the belt speed and the elapsed time between the two." measurements.

Since burden section of adjacent measurement points is often variable, an integrated running average of the volume throughput rate is derived from the last ten processed images for display purposes.

The total throughput volume for the conveyor is recorded by summing the burden volumes which have been calculated between each measurement point.

On completion of the analytical scan of the full- '1It width image, the computer displays the averaged volumetric rate and the total throughput vol-ume. It then plots the same information on a graph and generates a graphical display of the burden shape on the belt (see Figure 1, numerals 24 and 26).

f The strobe trigger 32, phase .ocked loop control 3A, and the shutter on the camera 18 are optional features wh.ch may be utilised when operating in extremely bright conditions, or with fast moving belts. They may also be used in other conditions if desired. The strobe light source may also be enclosed in a rapidly detachable sub-assembly which will ensure precise location and easy field replacement. Such an assembly is preferably totally ealed, and will passively dissipate waste heat from the otside of the unit.

39 The shutter preferably consists of a disc rotating b4' PCTr/AU. 0 /03 6 TECEIVED- OCT 1989 12in the space between the lens and the came ra imaging target, driven by a d.c. motor at a speed of about 1500 R. P.M. i. e. about 25 revolutions per second, corresponding to the television camera frame rate.

The camera/shutter unit is also preferably fully sealed, and made tough enough to tolerate frequent bursts of high pressure wash down water. Tt may also be provided with an automatic window cleaning system, to be operated on *a regular time schedule.

The strobe light source 14 is here illustrated projecting a beam of light at an angle of about 45 0 to the level of the conveyor belt, and the camera receives the image also at an angle of about 45 0 to the level of the conveyor belt.

A preferred processing means 22 is further illustrated in Figure 2. Figure 2 illustrates a micro VAX2 based image processing system having image processing boards 40 to 50, from the IP512 family of Imaging Technology Inc., which include: an AP512 image digitiser an ALU512 arithmnetic and logic unit (42) incorporating pipelined multiplication, logical operations such as addition, subtraction, etc., and barrel shifter; three FB512 frame buffers (44,46,48); and an HF5.1.2 histogram and feature extraction unit where "feature extraction" consists of generating a list of the indices of pixels of specified intensities. The IP512 boards process 512 x 512 x 8 bit black and white images from composite video sources at full frame rate.

Auxilliary equipment illustrated in Fig. 2 includes 31cm and 48cm color monitors 52, two black and white cameras 54, a video cassette recorder 56 with a good single frame advance, a. time base corrector 58, and a digitising tablet Figure 4 illustrates a section 70 of the material 12 illuminated by the broad beam of light 16. In this section the leading edge of the illuminated material is ,obscured from the view of the camera 18. This has the effect of making the detected pseudo edge 72 different to 39 'the actual leading edge 20. If the light source projected ?CT/AU 0 0 3 6 RECEIVE OCT 1989 -13a thin stripe of light at the leading edge, instead of a broad beam of light as illustrated, no measurement could be made. The use of a broad beanr of light overcomes this problem.

Therefore, the apparatus and method of the present invention employs an active lighting technique coupled with non-contact image capture, processing, and display output equipment, in order to measure the volume of coal and overburden, for example, on moving conveyors (both fixeJ and on dredger conveyors) with more accuracy and reliability than existing methods.

5

Claims (19)

1. Apparatus for measuring the volume of material passing along a conveyor, said apparatus comprising a light source located above said conveyor to project a beam of light having a leading edge across said conveyor such that the leading edge of the beam of light impinges on material on the conveyor at a first angle, means to receive an image of at least the leading edge of the beam of light at a second angle, said second angle being displaced from said first angle, and means to capture, and process, the image at a rate necessary to provide calculation of a required volume parameter; wherein the light source is a strobe light source producing a strobe light pulse.

2. Apparatus according to claim 1 wherein the light source projects a substantially broad beam of light.

3. Apparatus according to claim 1 or 2, wherein the image receiving means is electrically controlled to receive an image only for a period substantially equal to the duration of the strobe light pulse. S

4. Apparatus according to claim 1 or 2, wherein the image receiving means includes a shutter adapted to only allow light to be received at an optimum instance for a period substantially equal to the duration of the strobe light pulse.

Apparatus according to claim 4, wherein said shutter is a mechanical device driven by a motor which is synchronised to a synchronising signal of the image receiving means.

6. Apparatus according to claim 4, wherein said shutter is a static electrically controlled window which is normally opaque, but which is rendered transparent for a period substantially equal to the duration of the strobe light pulse.

7. Apparatus according to any one of claims 1 to 6, wherein the image receiving means is a camera capable of inherently integrating light received thereby, and capable of roviding a stable image without appreciable distortion or W) ^T O\/ 15 drift.

8. Apparatus according to any one of claims 1 to 7, including an open ended hood located to project said apparatus from direct sunlight or other light.

9. Apparatus according to any one of claims 1 to 8, wherein the receiving means and the light source are each at about 45 degrees to the level of the conveyor, being about 90 degrees relative to each other.

Apparatus according to claim 9, wherein the leading edge of the beam of light is perpendicular to the direction of conveyor travel, across the conveyor, and impinges on the material on the conveyor at about 135 degrees to the direction S of conveyor travel.

11. A method for measuring the volume of material passing along a conveyor comprising providing a beam of light having a leading edge from a light source located above said conveyor across said conveyor such that the leading edge of the beam of light impinges on material on the conveyor at a first angle, S receiving an image in an image receiving means of at least the leading edge of the beam of light at a second angle, said second angle being displaced from said first angle, and capturing and processing the image at a rate necessary to i calculate a required volume parameter; wherein the light source is a strobe light source producing a strobe light pulse.

12. A method according to claim 11, wherein the light source projects a substantially broad beam of light.

13. A method according to claim 11 or 12, wherein the light source and the image receiving means are each at about 45 degrees to the level of the conveyor, being about degrees relative to each other.

14. A method according to any one of claims 11 to 13, n' c- erein the image is processed by: i42f, searching across the image to locate a point ~C" 16 representative of the leading edge of the beam of light, being the boundary between illuminated and non-illuminated regions; recording the co-ordinates of that point; repeating steps and for a number of lines across the image to build a profile of the burden; comparing the profile of the burden with a profile of the conveyor when unloaded to calculate the area of the burden for that image; and calculating the volume of burden transported.

A method according to any one of claims 11 to 14, wherein the image receiving means includes a shutter adapted to only allow light to be received at an optimum instance for a period substantially equal to the duration of the strobe light pulse.

16. A method according to claim 14, wherein the image processing includes the further step: repeating steps to for an immediately succeeding image to also calculate an average volume of burden transported. S

17. A method according to claim 14 or claim 16, wherein the volume of burden transported is displayed on a high resolution monitor.

18. Apparatus according to claim 1, substantially as herein described with reference to the accompanying drawings.

19. A method according to claim 11, substantially as herein described with reference to the accompanying drawings. DATED: 3 December 1992 PHILLIPS ORMONDE FITZPATRICK f~c 9 k4~J Patent Attorneys For: STATE ELECTRICITY COMMISSION OF VICTORIA (4286h)