IES940711A2 - Measuring apparatus - Google Patents

Abstract

An apparatus for measuring the heights and/or determining the configuration of overhead electric cables used for supplying power to electric trains includes an elongate frame (11) locatable by feet (28) in a predetermined position across a pair of parallel rails. A pair of upwardly facing electro-acoustic transducers (21, 22) are mounted at opposite ends of the frame. A circuit (23) is adapted to energise a selected one of the transducers to transmit a burst of sound directed upwardly at overhead cables and to discriminate between multiple echoes received by a selected one of the transducers after reflection of a burst from said cables. From the measurement of a plurality of round trip delays the circuit (23) can determine the height and/or configuration of the overhead cables.

Description

An apparatus for measuring the heights and/or determining the configuration of overhead electric cables used for supplying power to electric trains includes an elongate frame 11 locatable by feet 28 in a pre-determined position across a pair of parallel rails A pair of upwardly facing electro-acoustic transducers 21, 22 are mounted at opposite ands of the frame. A circuit 23 is adapted to energise a selected one of the transducers to transmit a burst of sound directed upwardly at overhead cables and to discriminate between multiple echoes received by a selected one of the transducers after reflection of a burst from said cables. From the measurement of a plurality of round trip delays the circuit 23 can determine the height and/or configuration of the overhead cables 1 - WO711 /jpDf !(1£.Π0)4 (MO............* 90000 CS-480 MEASURING APPARATUS The present invention relates to a measuring apparatus. In particular the invention relates to a measuring apparatus for measuring the height and stagger of overhead cables for supplying power to electric trains. In this specification, as will understood by those skilled in the art, the term 'stagger' means the horizontal deviation of a cable from a vertical axis bisecting the two rails.

In order to spread wear evenly over the pick-up, or pantograph, on top of an electric train, the support structures for the overhead cables are designed to cause the cables to 'zig zag' or stagger across the rails from left to right and back again between successive support structures which are typically 60m apart.

A currently used measurement method employs a cruciform device comprising a telescopic vertical support carrying at its top a horizontal graduated scale. In use, the device is erected between the centre of the rails and offered up to the overhead cables. A linesman must then read off the measurement from the graduations on the horizontal scale. In order to use such a method a heavy unit must be manually placed for a measurement to be made. It is difficult to read all configurations of overhead cable and the method requires a team of operators .

According to the present invention there is provided a measuring apparatus comprising a support member having means for locating said member in a pre-determined position across a pair of parallel rails, first and second upwardly facing electro-acoustic transducers mounted spaced apart on the support member in a direction transverse to the rails, and circuit means for energising a selected one of said transducers to transmit a burst of sound directed upwardly at overhead cables and for discriminating between multiple echoes received by a selected one of said transducers after reflection of a burst from said cables.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a measuring apparatus according to an embodiment of the invention; Figure 2 is a plan view of the left side of the measuring apparatus of Figure 1, the right side being substantially symmetrically identical to the left side except for the circuit housing 23; Figure 3 is a front elevation of the left side of the measuring apparatus of Figure 2; Figure 4 is a detail view of the handle section of the measuring apparatus of Figure 2 in an intermediate locked state; Figure 5 is a detail view of the handle section of the measuring apparatus of Figure 2 in a storage state.

Lt-o -f 11 Figure 6 is a block diagram of the control circuitry of the measuring apparatus according to the embodiment of the invention; and Figure 7 are schematic diagrams of cable configurations to illustrate the use of the measuring apparatus, and Figure 8 is a block diagram of alternative control circuitry.

Referring now to figures 1 to 5 of the drawings wherein similar numerals have been used to indicate like parts, the measuring apparatus 10 comprises an elongate frame 11, foldable about and substantially symmetrical relative to a centre axis A-A.

The frame 11 is constructed from two parallel spaced apart elongate side members 12 and 13 fixed together with a plurality of cross members 14, 15, 16 and 17. Opposite ends 7, 8 of the frame 11 are provided with transducer-mounting surfaces 19 and 20 respectively which are fixed onto the cross-members 14. A pair of electro-acoustic transducers for the transmission and reception of acoustic signals (of which only the cones 21, 22 are shown) are fixed to the mounting surfaces 19 and 20 respectively with bolts (not shown) inserted through a pair of holes 25 passing through the cross-members 14 and the surfaces 19 and 20, Figure 2.

The surfaces 19 and 20 are inclined inwardly so that the longitudinal axes 26 of their respective transducer cones 21 and 22 are inclined towards the centre axis A-A. The cones 21 and 22 transmit and receive signals through a 30o cone and are spaced approximately 1.5 metres apart on the frame 11. The angle of inclination 27 of the cones 21 and 22 is such that their axes X6 *7 o~T 11 intersect at a height of about 5 metres above the frame 11, which is approximately the height around which overhead cables (not shown) are located.

The transducers preferably operate at ultrasonic frequency, that is to say greater than 35kHz, to avoid interference from ambient noise at acoustic frequencies. Preferably, the frequency is 100kHz.

In order to facilitate folding the frame 11 in half from the in-use extended position shown in Figures 1 to 3 to a storage position, the side members 12 and 13 are formed in two parts 12', 12 and 13', 13 respectively which are hinged at their adjoining ends through bolts 32. Because the underside of the frame 11 is not flat it is desirable for the half-frame sections to be spaced apart when the frame 11 is folded in half. Thus, each sub-section 12', 12, 13' and 13 is bent downwardly at 90 degrees at its hinged end to form a leg 34, and the free end 35 of each leg 34 is further curved at 90 degrees so that each free end 35 extends to the centre axis A-A of the frame 11 where it is drilled to receive a respective bolt 32. Thus, as seen in Figure 5, when the frame 11 is folded in half the two half-frame sections comprising 12',13' and 12,13 respectively are located parallel to one another but spaced apart by a small distance.

In order to ensure that the two half-frame sections are co-planar when extended, a pair of bolts 36 and 37 are threaded into juxtaposed cross-members 17. The bolts 36 and 37 may be rotated as desired such that their abutting heads define a stop position for the frame 11 in which the two halves of the frame 11 are co-planar, Figure 3. Alternatively, and preferably, the two halves of the frames may be slightly over-centre in the οΤ 1 1 extended position, and this position can be defined by screwing the bolts 36 and 37 slightly further into the cross-members 17.

The underside of the frame 11 is provided with a pair of resilient feet 28 which are fixed to the cross-members 15. In a first embodiment of the invention, each foot 28 comprises a downwardly projecting plate 29 which runs across substantially the width of the frame 11. Each plate 29 projects downwardly to approximately the depth of the legs 34. Each plate 29 is bent towards the respective outer end 7 or 8 of the frame 11 to form a seating into which a rubber tube 30 is placed. In an alternative embodiment, each foot 28 comprises a spring loaded sliding nylon block (not shown). In any event, each foot 28, or at least the part touching the rail 5, is made of an electrically insulating material to ensure that signal messages which use the rails are not corrupted.

When the frame 11 is unfolded, the feet 28 are located adjacent the inside surfaces 31 of the parallel rails 5. The frame 11 is then pushed downwards against the resilient bias of the feet 28 until it locks into its extended position wherein the two half-frames are co-planar or, more preferably, slightly over-centre. Assuming that the spring force of each foot 28 is equal, the frame 11 will be centered laterally between the rails 5. In such a position the frame is normal to the rails and the transducers 21 and 22 are located symmetrically on opposite sides of a vertical plane P-P intersecting the axis A-A and bisecting the two rails 5.

A handle 38 is provided to enable the frame 11 to be lifted easily. The handle 38 comprises two parallel spaced apart straddle members 39, connected by a cross-piece 40, which are disposed inside and parallel to the side members 12 and 13. The straddle members 39 bridge the cross-members 17 on the top side of the frame 11 when the frame 11 is extended. The straddle members 39 are pivotally fixed at one end to respective sub-sections 12 and 13 by respective bolts 41.

Two knurled bolts 42 screw through the side members 12',13' respectively and, when the handle 38 is rotated so that the ends 44 of the straddle members 39 are adjacent the bolts 42, the bolts 42 are screwed through holes {not shown) in the ends 44 of the straddle members 39 to lock the frame 11 into an intermediate state, Figure 4. In the intermediate state the frame 11 is free to rotate by approximately 10 degrees. This enables the frame 11 to be positioned over the rails 5 and then pushed into the final extended position, Figure 3.

When measurement of the overhead cables (not shown) is complete the knurled bolts 42 are unscrewed and the frame 11 is folded over into a storage position, Figure 5. The handle 38 is further rotated in the direction shown until it lies substantially within the two halves of the frame 11. A handle latch 43 is provided on the sub-section 13, which holds the handle 38 within the frame 11 while in the storage position.

A housing 23 is provided between the centre axis A-A and the left end 7 of the frame 11 for housing control circuitry, Figure 6 for the transducers associated with the cones 21 and 22.

Referring to Figure 6, in use of the apparatus a microprocessor (not shown) emits a start signal which $£ 94o7 ι1 - 7 triggers a monostable 60 defining the duration of a burst provided by a 100kHz pulse generator (oscillator) 61. In the present case it is assumed that the pulse generator 61 gives a burst of 4 x 100kHz cycles. This length of burst gives approximately 1cm resolution. The start signal also triggers a circuit 62 which resets a counter 63 and holds it reset for a given time period which corresponds to the minimum valid distance an overhead cable can be away from either transducer, thus holding the counter outputs Q0 to Q3 low for that period of time after the beginning of a burst. This ensures that the apparatus 10 does not respond to spurious echoes from nearby artifacts.

The burst from the pulse generator 61 is supplied to driver circuits Tx for each of the two transducers 21 and 22, further identified in Figure 6 as left L and right R transducers. However, the particular transducer which is actually to transmit an ultrasonic burst at any given time is defined by a transmit select line 64, which is set by the microprocessor. Thus when the transmit select line 64 is high a driver circuit Tx associated with the left transducer 21 is enabled by the signal on the line 64, whereas the driver circuit Tx associated with the right transducer 22 is disabled by the low signal produced by the same signal at the output of an inverter 66. Conversely, when the transmit select line 64 is low the driver circuit Tx associated with the left transducer 21 is disabled, whereas the driver circuit Tx associated with the right transducer 22 is enabled by the high signal at the output of the inverter 66 .

The burst transmitted by the selected transducer 21 or 22 will be reflected from one or more overhead cables and the reflection(s) will be received by both 94e>7 11 transducers. However, the particular transducer which is to be used in the detection of the reflections from a particular burst is defined by a receiver select line 65, which is also set by the microprocessor. Thus, when the receive select line 65 is high an amplifier 67 at the output of receiver circuit Rx associated with the left transducer 21 is enabled by the signal on the line 65, whereas the amplifier 67 associated with the right transducer 22 is disabled by the low signal produced by the same signal 65 at the output of an inverter 68. Conversely, when the receive select line 65 is low the amplifier 67 at the output of the receiver circuit Rx associated with the left transducer 21 is disabled, whereas the amplifier 67 associated with the right transducer 22 is enabled by the high signal at the output of the inverter 68.

Thus, the microprocessor can select which of the two transducers 21 or 22 transmits a burst, and which of the two is used in its detection. In other words the microprocessor can define a L-L round trip (transmission and detection by the left transducer 21), a R-R round trip (transmission and detection by the right transducer 22) or a L-R or R-L round trip (transmission by one transducer and detection by the other).

Since there will in general be several overhead cables there will be several echoes from a single transmitted burst. The circuit shown in Figure 6 therefore has means to select a particular echo (first, second, third, etc.) from those received.

The number of the echo to be selected is presented by the microprocessor to the input of a two bit decoder 69 which selects one of four NAND gates 70 connected to the respective outputs QO to Q3 of the counter 63 (it is ΊΜΐι assumed that no echo later than the fourth is to be detected in this embodiment). Received burst envelopes are detected, shaped and digitised by a conditioning circuit 71, the leading edge of whose output pulses clocks the input of the counter 63 so that counter outputs Q0 to Q3 go high in sequence as successive echoes are detected. When a counter output connected to the selected NAND gate goes high, the output of the respective NAND gate goes low pulling a pulse signal low through a wired-or diode arrangement 75. The negative going edge of the pulse signal disables the counter 63 through the feedback path 72, thus holding the pulse signal low until the counter is reset at the beginning of the next measurement cycle. A maximum distance delay circuit 73 is also included to disable the counter 63 after all echoes should have been received, to ensure that a measurement finishes.

Clearly, the time between the leading edge of the start signal provided to the monostable 60 and the leading edge of a pulse appearing at the output of the diode arrangement 75 can be measured by the microprocessor, which can then calculate the distance travelled by the burst using the known speed of sound in air.

In use the microprocessor will cause the make a set of measurements, typically as following table: apparatus to shown in the Tx Rx Echo d# L L 1 dl L L 2 d2 R R 1 d3 R R 2 d4 L R 1 d5 L R 2 d6 L L 3 d7 Table 1 R R 3 d8 L L 4 d9 R R 4dio -10In the table the first two columns specify the transducers used for transmission and reception respectively, and the third column shows the number of the echo selected. The fourth column shows the distance measured by the microprocessor. It is to be noted that where the same transducers is used for both transmission and detection (all except the fifth and sixth entries) the distance d is the one way distance to the cable providing the echo, obtained by halving the round trip distance. However, for the fifth and sixth entries the round trip distance is shown. Figure 7 shows the distances dl to dlO in arbitrary units thus obtained for four different configurations of overhead cables.

Having made a set of measurements a number of tests by the microprocessor then follow to ascertain and confirm the configuration of the over-head cables. For example: 1. If no echo (n/a) is received for second (or further) echo measurements d2 , d4 or d6 then there is only one cable corresponding to configuration #1. Accordingly, if there are no more than second and third echo measurements then there are only two or three cables respectively. Thus, configurations 1..4 can be ascertained. 2. If d5=dl+d3 or d6=d2+d4 then si and s2 are disposed vertically above one another and configuration #2 is confirmed. In this case the first echo measurements dl and d3 are both reflected from the cable si. Thus, dl,d3 must be used to calculate the co-ordinates of si; and d2,d4 used to calculate the co-ordinates of s2. Otherwise dl,d4 are used to calculate the position of wl and d2,d3 are used to calculate the position of w2 of configuration #4. 3. In the case of configuration #4, it is known that there are two catenary cables cl and c2 supporting wl and w2, and their position is calculated using measurements d7,d9 and d8,dl0. 4. In configuration #3 d2,d8 and d7,d4 are used to measure the co-ordinates of cl and c2.

Once the configuration of a number of cables is known the distances from a given cable to both transducers can be ascertained. Simple trigonometry may then be performed to calculate the height and stagger of any overhead cable.

Sets of height and stagger results taken along the line can be stored and dumped into a computer which can graph or record the data as required.

It will be realised that the embodiments may be varied to measure configurations comprising more than four cables. By employing a 3-to-8 bit decoder, the first to eighth echoes can be selected from counter outputs Q0 to Q7. The microprocessor may, however, need more information about the extra configurations to know which measurements to combine and what to do if echoes coincide before the location of each cable can be calculated.

The display of the cable measurements can be indicated as height and stagger measurements for each wire or they can be included in a graphic display of the particular configuration being measured.

In the control circuit of figure 6, all the processing circuitry is concentrated in the common housing 23, and the transducers 21, 22 simply receive signals from and send signals to the processor. These signals may be affected by noise, so in an alternative embodiment of the control circuit much of the signal processing is performed locally at the transducers which communicate with the main processor through a digital link.

In this alternative embodiment a PCB is fitted under each transducer 21 and 22, the circuitry on each such PCB being shown in figure 8. The circuitry comprises a local microprocessor 80 which communicates through conventional digital signal lines with a main microprocessor which is located, as before, in the housing 23. For ease of understanding the diagram shows the tasks which are carried out by the software in the processor 80 in equivalent hardware terms, and indeed hardware could be used for these tasks if desired. The other components shown in figure 8 correspond to the similarly referenced components in figure 6.

When it is desired to make a measurement, a START signal is provided by the main processor which is received on line 81 of each local processor 80. The particular transducer 21 or 22 which is to transmit is determined by a signal on the corresponding Tx select line 82, so that the START signal is passed through an AND gate 83 only in respect of the selected transducer. The START pulse triggers a monostable 60 which defines the duration of a burst provided by, in this case, a 50kHz pulse generator 61, and the burst from 61 drives the respective transducer 21 or 22 via the driver circuit Tx. The START signal also starts a timer or counter 84 in each processor 80 which is clocked by the processor clock.

Both transducers 21 and 22 will detect the burst echoes, and these are processed through an amplifier 67 and conditioning circuitry 71 as before to produce a train of square signals whose leading edges correspond with the received echoes. The leading edge of each square signal is supplied to the timer 84 which in response thereto outputs the then current count value to a buffer 85. Clearly, since the counter 84 was started by the START signal the value of the count corresponding to each received echo will be a measure of the round trip delay of the burst.

Each count in the buffer 85 is passed to the main processor via the output line 86 provided the gate 87 is enabled by a signal on the receive select line 88. Thus, just as the signal on the line 82 determines which of the two transducers is to transmit, so the signal on the line 88 determines which of the transducers is to act as receiver for the particular transmitted burst. Thus by appropriate signals on the lines 82 and 88 of the two processors 80, the main processor can define a L-L round trip, a R-R round trip, a L-R round trip or a R-L round trip. As before, the processor 80 includes means 62 and 73 for defining minimum and maximum distance delays operating substantially as described with reference to figure 6.

The main processor converts each of the digital count values received on the output line 88 to the corresponding round trip delay, which given the speed of sound in air can be translated to the corresponding round trip distances. In this connection it should be mentioned that the main processor has associated temperature circuitry to enable it to adjust its calculations to take into account variations in the speed of sound with temperature. This is true also of the first embodiment of the control circuitry. le hfoi-i t In use, the main processor makes a set of measurements and then makes a number of tests to ascertain the configuration of the overhead cables, as previously described in relation to figure 6. However, whereas in the figure 6 embodiment the processor selected, through the NAND gates 70, only a single echo from the multiple echoes received in respect of a single transmitted burst, so that in order to determine the round trip delay of different order echoes a number of bursts had to be transmitted, in the figure 8 embodiment the round trip delay of all the echoes can be determined from a single transmitted burst since each count value in the buffer 85 is passed to the main processor. In both the case of figure 6 and figure 8 it is preferred that the main processor make successive sets of measurements and the results thereof compared until two consecutive results match. This will enable transient errors, due for example to disturbance of the cables by wind or birds, to be rejected.

In both embodiments of the control circuitry the housing 23 containing the main processor, and in the case of the second embodiment the housings containing the processors 80 and associated circuitry, shields the circuitry from the EMF present around the railway lines.

The invention is not limited to the embodiments described herein which may be modified or varied without departing from the scope of the invention.

(I - 15 CLAIMS :

Claims (5)

1. A measuring apparatus comprising a support member having means for locating said member in a pre-determined position across a pair of parallel rails, first and second upwardly facing electro-acoustic transducers mounted spaced apart on the support member in a direction transverse to the rails, and circuit means for energising a selected one of said transducers to transmit a burst of sound directed upwardly at overhead cables and for discriminating between multiple echoes received by a selected one of said transducers after reflection of a burst from said cables.

2. An apparatus as claimed in claim 1, wherein the locating means comprises a pair of feet on the underside of the support member each adapted to resiliently engage a respective rail, at least the part of each foot contacting the rail being of electrically insulating material.

3. An apparatus as claimed in claim 1 or 2, wherein the circuit means comprises means for measuring the round trip delay of at least a selected one of multiple echoes received by said selected transducer in response to a transmitted burst.

4. An apparatus as claimed in claim 3, wherein the circuit means includes means for determining the configuration of overhead cables from a plurality of round trip delay measurements in respect of different round trip paths.

5. An apparatus as claimed in claim 4, wherein said different round trip paths include at least one path - Ιό returning to the same transducer as that emitting a burst and at least one path returning to the other transducer to that emitting a burst.