GB2358724A

GB2358724A - Counting apparatus

Info

Publication number: GB2358724A
Application number: GB0108409A
Authority: GB
Inventors: Knud Erik Jermer; Peter Sorensen
Original assignee: Honeywell Control Systems Ltd
Current assignee: Honeywell Control Systems Ltd
Priority date: 1999-03-31
Filing date: 2000-03-29
Publication date: 2001-08-01
Anticipated expiration: 2020-03-29
Also published as: GB2358725B; GB2358725A; GB2358724B; GB0108409D0; GB0108411D0

Abstract

A railway traffic control system has a mainframe computer traffic controller to which is input signals from various sources including railway line monitor 3A with respective designated railway lines 4A and sensing locations 5A. Outputs of sensors 10 pass to sensing-processor unit 11 which has two sets 12, 13 of sensing signals analysis units 14 such that, at any one time, one set is in operation while the other set is being tested, switching occurring every 10 seconds. Each unit 14 has a databank of valid sensing signals and a level controller to run sensing signal verifications, test routines and mode-switching.

Description

2358724 COUNTING METHOD The present invention relates to a method of

counting objects.

The present invention is particularly suited for the monitonng of railway carriages on railway lines whereby the number of carriage wheels entering a sensing zone is counted and compared with the count of wheels leaving the zone, but the present invention is also applicable to analogous situations with similar monitoring of different objects; it is equally suited to situations in which there is required merely the cumulative counting of objects moving past a point on a predetermined path.

A conventional system for counting railway carriages has two sensors such that, depending on the order of signals output from these sensors, the system is able to determine the direction of the movement between the two sensors.

As the direction cannot be determined by only one sensor, the counting function is inoperable if there is a fault on either sensor.

The present invention provides a method of counting objects which move along a predetermined path past a sensing location having at least three sensors, the method comprising comparing output signals from the sensing location with a databank of output patterns and/or state diagrams for the sensing location.

The present invention provides a method of counting objects passing a sensing zone with at least three sensors, the method comprising:

processing signals output from the sensing zone; and simultaneously testing a means for processing signals output from the sensing zone.

The present invention also provides a databank comprising infon-nation on patterns and/or state diagrams of signals being output at a sensing location 1 having a predetermined number of sensors being at least three, and corresponding to signals for one or more of the following conditions:

i) a plurality of characterisation value(s) for objects; ii) sequential position(s) in one, or the opposite, direction along 5 said path, optionally also the opposite direction; iii) at least one change in direction of the object along the path; iv) a fault, of one or more types, in the sensing operation and for each of the sensors in turn.

The present invention also provides a computer program product stored on a computer usable medium for counting of objects which move along a predetermined path past a sensing location having at least three sensors, comprising computer readable program means for causing a computer to compare output signals from a sensing location with a databank of output patterns and/or state diagrams for the sensing location.

In a variant, there may be provided a corresponding program for mechanical, chemical, optical, analogue or other computing.

By "software code", there can be included program code and look-up tables.

The present invention further provides apparatus for counting objects which move along a predetermined path past a sensing location having at least three sensors, the apparatus comprising means to compare output signals from the sensing location with a databank of output patterns and/or state diagrams for the sensing location.

2 The present invention is particularly suited to the monitoring of railway carriages on a railway line by the counting of wheels of the carriages as they pass individual sensors within a sensing zone defined by a group of sensors (typically 4 sensors, but also groups of 5 or 6 sensors are particularly beneficial and preferred, and in any event a group is not limited to those specific numbers). However, the present invention is also suited to a wide variety of other applications, for example:

vehicles on a road; 0 manufactured goods on a conveyor belt; 0 food cans/bottles on a bottle process line; 0 components on a manufacturingJassembly line; 0 luggage/items on a cargo-handling conveyor belt.

A wide variety of types of sensor and techniques of sensing can be used readily in the present invention, including (but not limited only to):

0 proximity sensors, 0 light sensors, 0 radar sensors, 0 magnetic sensors, 0 infra-red sensors, 0 mechanical sensors, 0 ultrasonic proximity sensors.

The present invention is not limited to binary sensing whereby a sensor merely detects the presence or absence of an object, but also encompasses tertiary or more states of sensing whereby a sensor detects three or more possible states for example:

3 i) absence of any object; ii) presence of object of type one (eg. coloured blue); iii) presence of object of type two (eg. coloured red).

The method may include defining sensing characterisation values for:

i) sensing resolution of a sensor; or ii) separation of sensors; or iii) sensing the nature of an object.

The nature of an object can be any one or more important aspects of an object, for example the size, colour, cross-section, profile, density, opacity, reflectivity, speed, separation.

A wide variety of electrical and electronic components and computer hardware, software and firmware can be used to implement parts of, and functional elements of, the present invention in various forms according to individual applications as appropriate, including mainframe computers, pcs, hard disks, RAMs, EPROMs.

According to another aspect of the present invention, there is provided a method of counting objects passing a sensing zone with at least three sensors, the method comprising:

processing signals output from t he sensing zone; and simultaneously testing a means for processing signals output from the sensing zone.

The method may comprise any one or more of the following features sending a synchronising signal to change the processing operation to a testing operation and to change the testing operation to a processing operation.

4 operating a first set of means to process signals output from the sensing location and simultaneously testing a second set of means for processing signals output from the sensing location.

switching the first set, thereby to effect testing thereof, and switching the second setY thereby to effect operation of it on signals output from the sensing location.

0 the switching of the two sets is done simultaneously.

0 the switching is done at predetermined time intervals.

41 the predetermined interval is of the order of 10 seconds.

the testing includes one or more of the following steps i. testing the output stages of the processing means; ii. testing that the processing means can execute logic related to data stored in the processing means; iii. testing that data stored in the processing means is intact; and iv. testing auxiliary means of the processing means (e.g.

calculator means, and/or latch means, and/or state address).

updating data held in means for processing signals output from the sensing location.

operating a first set of means to process signals output from the sensing location and simultaneously testing a second set of means for processing signals output from the sensing location and, after testing has ended, updating data held in the second set of processing means.

comparing output signals from the sensing location with a databank of output patterns and/or state diagrams for the sensing location.

the databank comprises information on patterns and/or state diagrams of signals being output at a sensing location having a predetermined number of sensors being at least three, and corresponding to signals for one or more of the following conditions:

is) a plurality of characterisation value(s) for objects; ii) sequential position(s) in one, or the opposite, direction along said path, optionally also the opposite direction; iii) at least one change in direction of the object along the path; iv) a fault, of one or more types, in the sensing operation and for each of the sensors in turn.

the fault comprises one of the following types:

i) any one of the sensors is permanently sensed; ii) any one of the sensors is permanently unsensed; iii) transition from "no fault" to "fault" for any sensor; iv) transition from "fault" to "no fault" for any sensor.

noting when the comparison step indicates that the output signals from the sensing location does not match any output pattern and/or state diagram in the databank.

noting step produces a signal advising of the lack of match between the output signals and the databank.

6 continuing the comparison of the output signals from the sensing location with the databank, thereby to monitor for subsequent matches therebetween.

producing a signal advising the existence of a match between the output signals from the sensing location and any output pattern and/or state diagram, subsequent to a time period when there has been no such match.

the sensing location comprises four sensors.

objects to be sensed comprise wheels of railway carriages on a railway track.

According to another aspect of the present invention, there is provided apparatus for counting objects passing a sensing zone with at least three sensors, the apparatus comprising two sets of means to process signals output from the sensing zones to effect a counting operation for the objects, 20 means to instruct one set to effect a counting mode and the other set to effect a test mode, and means to switch the sets from one mode to the other.

The apparatus may include one or more of the following features- the switching means comprises means to instruct the set of processing means in the counting operation to change to the testing mode and means to instruct, simultaneously with the change of the set to the testing mode, the set of processing means in the testing mode to change to the counting mode.

7 switching means to effect switching at predetermined time intervals.

the predetermined interval is of the order of 10 seconds.

means to effect any one or more of the following tests i. testing the output stages of the processing means; ii. testing that the processing means can execute logic related to data stored in the processing means; iii. testing that data stored in the processing means is intact; and iv. testing auxiliary means of the processing means (e.g.

calculator means, and/or latch means, and/or state address).

means to update data held in the set of processing means which is in the test mode.

means to compare output signals from the sensing location with a databank of output patterns and/or state diagrams for the sensing location.

i) a plurality of charactefisation value(s) for objects; ii) sequential position(s) in one direction along said path, optionally also in the opposite direction; iii) at least one change in direction of the object along the path; 8 iv) a fault, of one or more types, in the sensing operation and for each of the sensors in turn.

the fault comprises one of the following types:

i) any one of the sensors is permanently sensed; ii) any one of the sensors is permanently unsensed; iii) transition from "no faulf' to "fault" for any sensor; iv) transition from "fault" to "no fault" for any sensor.

means to notice when the comparison step indicates that the output signals from the sensing location does not match any output pattern and/or state diagram in the databank.

the noting means produces a signal advising of the lack of match between the output signals and the databank.

means to continue the comparison of the output signals from the sensing location with the databank, thereby to monitor for subsequent matches therebetween.

means to produce a signal advising of the existence of a match between the output signals from the sensing location and any output pattern and/or state diagram subsequent to a time period when there has been no such match.

the sensing location comprises four sensors.

objects to be sensed comprise wheels of railway carriages on a railway track.

9 Any of the aspects of the invention may include a computer program product directly loadable into the internal memory of the digital computer, comprising software code portions for performing the invention.

Any of the aspects of the invention may include electronic distribution of such a software program.

In order that the present invention may more readily be understood, a description is now given, by way of example only, reference being made to the accompanying drawings, in which:

Figure 1 is a schematic diagram of a rail traffic control system; Figure 2 is a block diagram of the train sensing system of the present invention being part of the system of Figure 1; Figure 3 is a more detailed diagram of part of the system of Figure 2; Figure 4 is a block diagram of the circuitry of a unit in Figure 2; Figures 5(a) to (f) show sensing signals for movement of various wheel types; Figure 6 shows part of a databank for signals sensed in accordance with Figure 5; Figure 7 shows an example of a state diagram for the signal sequences as shown in Figure 6; and Figure 8(a) to (c) show the construction of a state diagram.

Figure 1 shows a railway traffic control system, generally denoted by reference numeral 1, having a mainframe computer traffic controller 2 to which is input signals from a plurality (only three being shown) of railway line monitor units 3A, 3B, 3C, and various other sources of relevant data (for example data on historic operation/incidents of system 1, on timetables/schedules for passenger and/or freight movements, on historic weather conditions, on weather forecasts).

Each line monitor unit 3A, 3B, 3C has its respective designated railway line 4A, 4BY 4C and a number of sensing locations SA, 5B, 5C positioned along each line typically at a separation of 1000 metres in addition to one near the end of each line; in circumstances involving very great traffic, the separation between adjacent sensing locations may be reduced significantly, for example of the order of 200 metres. A line unit 3A, 3B, 3C has a respective train detector unit 6A, 6B, 6C corresponding to each sensing location SA, 5B, 5C.

Figure 2 shows in greater detail the major elements of one sensing zone SA and train detector unit 6A for one line 4A, namely four identical proximity sensors 10 positioned on the side of one metal rail of the railway line 4A at a separation of 0.125 metres between sensors. Outputs of sensors 10 pass to sensing-processor unit 11 which has two sets 12, 13 of sensing signals analysis units 14 such that, at any one time, one set (for example 12 as shown in Figure 3) is in operation monitoring the signals from sensing zone SA while the other set (13 as shown in Figure 3) is being tested by traffic control system 2 to ensure that it is able to operate correctly. After 10 seconds, system 2 sends unit 11 an instruction effecting a change in mode whereby set 12 is switched to the test mode and set 13 is switched to the operational mode in which it monitors the signals from sensing zone 5A. After a further 10 seconds, system 2 sends unit 11 a further instruction to change set 12 to the operational mode and set 13 to the test mode. This mode-switching of sets 12, 13 occurs every 10 seconds continuously throughout operation of train detector unit 6A. If an error in a set is detected during testing, then the system enters the "fail-safe" state.

11 The mode-switching operation operates to ensure that, at all times, there is continuous processing of sensing signals being output from sensing zone 5A, regardless of the type or intensity of train movements on line 4A. It is essential that, in order to maintain the exceptionally high standards of safety and reliability required of a train detecting system of the present invention, effective testing of the counting equipment must be achieved, and this arrangement of two sets 12, 13 ensures that this can be done without any interruption of the counting operation.

Each set 12, 13 of sensing signal analysis units has two units 14, both working with the signals from the sensing zone 5A. One is passing output to the true part of the comparator system 15 and the other passing output to the inverse part of the comparator system 15 to check for consistency. The comparator system 15 is included in the line unit 3A.

Each unit 14 has a databank 16 (typically an EPROM) of valid sensing signals, a level controller 17 (typically a Field Programmable Gate Array) to run sensing signal verifications and test routines and mode- switching, latches 18 and counters 19.

When one of the sets 12, 13 is switched into the test mode by the appropriate instruction signal from controller 3A, and units 14 of that set begin a test routine performed by its internal processor, the results of the tests being output to controller 3A for verification of the test and confirmation that the units 14 are operating correctly; once these issues have been validated, controller 3A can then effect mode-switching of the units 12, 13 at the end the appropriate time interval (10 seconds).

12 Consider a situation whereby unit 12 is in the operational mode and is processing the signals being output from sensing zone 5A, while unit 13 is under test.

There are five different test modes which together demonstrate and ensure correct functioning of the entire hardware and software of units 14. Each test operation is directed to a specific area of the sensing signal analysis unit 14, with a degree of overlap between the test operations. The tests done include the following:

1. A test of all the output stages from unit 14 and a test that the unit can execute the databank logic; 2. A test of the content of databank 16 including that the contents are intact and that unit 14 can take decisions in relation to the counting operation based on signals received from the sensing location and on the contents of databank 16; 3. A test of the calculator within unit 14; 4. A test of the latch 18 which is the key function of the Test Ring mode. This test of latch 18 sources a sequence of "one high" bit pattems through the 16-bit wide latch to demonstrate that it is functioning correctly; 5. A test of the state address of the set 13 of units under test, achieved by copying the state address of set 12 units in the operational mode into the set 13 in the test mode, executing it immediately and latching both the original and the copied state address into the state address latch. In this way, this procedure confirms that the state address was copied and executed correctly. As a result, it is known that the two sets 12, 13 are running exactly in parallel, so that the set 12 is now ready to be switched to the test mode and set 13 switched into the operational mode.

13 As part of the last test above, set 13 goes into a Preset mode which prepares it for switching into operational mode synchronised with the state of set 12 before switching set 12 into the test mode. A synchronisation signal from operational set 12 to set 13 under test triggers the Preset mode ensuring synchronisation of the two sets 12, 13 in a few nanoseconds; the synchronisation, transfer of state address and the latching of actual and copied state address are completed within a few microseconds, and in considerably less time than it takes for a unit 14 to execute one processing operation of the signals from a sensing location 5A. so. a switch sequence of units 14 does not influence, and cannot be affected by, monitoring of trains.

Figure 4 shows in greater detail the level controller unit 17, which controls all functional modes of unit 14, which again is controlled and monitored by the controller 3A. The functional modes are:

- Operational mode. Unit 17 monitors normal operation of unit 14. Components used are: 17F, J, L, M and N.

- Test Simulation mode. Unit 17 tests that unit 14 can execute the databank logic unit 16, can operate latch unit 18 and can output to unit 19.

Components used are: 17F, J, L, M and N.

- Test Binary mode. Unit 17 tests that databank logic unit 16 is valid. Components used are: 17A, C, G, H, I, F, J, M and N.

- Test Calculation mode. Unit 18 tests that the calculator unit 20 is valid. Components used are: 17A, C, G, H, 1, F, J, M and N.

- Test Ring mode. Unit 17 tests that latch unit 18 is functioning correctly. Components used are: 17A, B, D, E, F, J, M and N.

- Test Preset mode. Unit 17 tests that ie. set 12 unit 14 can take over state address from set 13 unit 14. Components used are: 17F, J, K, L, M and N.

14 The features of the specific example described with reference to the Figures can be implemented in a variety of ways in practice, and may make use of technically equivalent procedures and techniques as appropriate including EPROMs, RAMs, computer hardware, software, fin-nware; Table 1 provides exemplary but not limitative implementations.

In the first part of the process for producing the data on sensing signals, the four sensors 10A in a sensing zone are named A, B, C, and D. Each sensor can be in two states: "sensed" (namely it detects a wheel above the sensor) and "unsensed" (it detects no wheel present).

The method is described with reference to Figures 5 to 7. The width of a wheel can differ so, for the purpose of the production of this data, the wheels are divided into the following types, based on the number of sensors which can be sensed at the same time by a given wheel:

Type 1. Only one sensor can be sensed at the same time; Type 2. Two sensors can be sensed at the same time; Type 3. Three sensors can be sensed at the same time; Type 4. Four sensors can be sensed at the same time.

In addition there are types intermediate the above-mentioned types, these limiting types are named "1.5"; "2.5"; and "3.5".

Figure 5 shows the movement pattern for the individual wheel-types in the direction from sensors A to D, and also shows the resulting pulse sequences, caused when that wheel-type passes the sensors.

In Figure 5a, the four sensors are illustrated by four boxes, named A, B, C and D. and the pair of horizontal lines under the boxes illustrates the possible positions of the wheel during the movement, a sensor being sensed when the line is under the sensor.

The horizontal lines also represent the possible movements of a wheel. So 5 the first line represents a wheel, which comes from the left, stops as soon sensor A is sensed, and then reverses and returns to the left; the second line represents a wheel which stops just before sensor B is sensed; the third line represents a wheel which stops as soon as sensor B is sensed, etc. The last line in each Figure represents a wheel which passes all the sensors, i.e. does not reverse.

Under the horizontal lines, the resulting sensor output sequences are shown. In these sequences, "0" means that no sensors are sensed; 'W' means that sensor A is sensed; "AW that both sensor A and B are sensed, etc.

Figures 5b to 5f show the equivalent movement patterns for the other wheel-types and the corresponding resultant signal sequences.

Table 1 below illustrates the possible sequences for all significant positions 20 for the individual wheel-types, when the wheel is passing from sensor A to sensor D (no reversing). The pulses are represented by a block of four digits, each having the value "V' if the corresponding sensor is sensed, and "0" if the corresponding sensor is unsensed.

TABLE 1: Signal sequences for wheel-types TYPE 1.5 2 2.5 3 3.5 4 SEQUENCE 0000 0000 0000 0000 0000 0000 1000 1000 1000 1000 1000 1000 16 1100 1100 1100 1100 1100 0100 0110 1110 1110 1110 0001 0110 0011 0110 0111 1111 0000 0010 0001 0111 0011 0111 0011 0000 0011 0001 0011 0001 0001 0000 0001 0000 0000 0000 This process of producing the possible sequences for individual wheel- types is repeated, but this time for movement of the wheel when passing through sensing zone 5A in the direction from sensor D to sensor A.

The process is repeated again, but this time for a shunting movement whereby the wheel passes into sensing zone 5A in one direction, halts while in sensing zone 5A, changes direction of movement and then exists zone 5A ftom the same side that it entered. The signal sequence for each variant of this motion in respect of the previous permutations is determined, including movement from each side, halting at each position, for each wheel-type.

The process is repeated again, but this time it is assumed that, for each of the above variants, there is a faulty sensor, and so the signal sequence is determined for when each of four forms of fault occurs at each of the sensors A, B, C, D in turn. The four forms of fault are:

i) any one of the sensors is permanently "sensed"; ii) any one of the sensors is permanently "unsensed"; iii) transition from "no fault" to "fault" for any sensor; iv) transition from "fault" to "no faulf' for any sensor.

The process is repeated, but this time assuming that a noise pulse occurs, in turn, in each sensor output.

17 All the sensor output patterns are compiled in a data-table with identification as to the respective circumstances, Figure 6 showing a section of the data-table. In the shown section of the data-table which concerns sequences relating to faults for wheel-type 3 and involving movement from sensor A to sensor C and back to sensor A for mode 1, the possible faults on the sensors are listed in the column "Sensor Faults" (not complete in the shown section), the sensor output sequences in the columns 1 - 17 and the incidents attributable to a given sequence in the column "OutpuC. By "mode 1 ", there is specified which of a number of possible movements from A to C to A is involved; thus, for example, "mode 1 " may be represented by line 5 in Figure 5d, while "mode 2" may be represented by line 6 in Figure 5d. In the lines 2 - 25 in the "Sensor Faults" column, the "permanentlysense& sensors are represented by capital letters, e.g. "C" for sensor C being "permanently-sensed", while "permanently-unsensed" sensors are represented by small letters, e.g. b for sensor B being "permanentlyunsensed". In the "OutpuC column, the incidents are described by a capital letter, followed by a small letter. The capital letter describes the type of the incident ("C" for count; "F" for a transition to a fault and 'W' (for "working") for a transition from a fault to a normal-working condition. The small letter indicates to which sensor the incident is related (a - d).

It can be seen that certain of the lines are repeated within the table 1, e.g. line #1 and line 0, and therefore the table can be rationalised somewhat.

Consolidation of the signal sequences results in a data-table having more than 12000 patterns and 200 state diagrams.

The contents of the data-table is represented in a set of state diagrams. Figure 7 shows an example of these diagrams. The implementation of the data-table in the state diagrams further reduces the table by deleting any 18 recurring duplications of the patterns. The circles represent the individual states in the sensor output patterns, and the connecting arrows the possible connections between the states. The letter code on some of these arrows shows the resulting output (the codes are described hereinabove). Each type 5 of sensor fault ( 10 in total):

i) no faulty sensors; ii) one of the sensors is permanently "sensed"; iii) one of the sensors is permanently "unsensed"; and each direction (A - D and D - A) is represented by a separate diagram.

The patterns may be generated manually, and/or by computer; generation of the patterns by one such method may be checked by comparison of the results produced by another such method.

Line by line, the contents of the data-table is converted to the representations in the state diagrams. The reduction is carried out by using as much of the existing state diagram as possible, every time a new datatable line is implemented.

Typically, when all state diagrams have been produced, the contents ofthese is transformed into binary form and burned into the databank EPROM 16.

In the second part of the process for producing the data on sensing signals, there is an analysis of how the sensing pattem of the four sensors I OA in a sensing zone can evolve. If, for example, sensor B is sensed by a wheel, this pattern can evolve in the following ways. The pattern is represented by a block of four digits, as described previously.

19 => 1100 1000 0110 0010 In other words, analysis is made to determine which transitions are possible from a given state to other states. When all possible patterns and their evolutions are analysed, these are gathered in a transitions list. This transitions list is implemented in a special software tool, which is able to generate the databank EPROM 16.

Conversion of the patterns to state diagrams is as follows, using as an example the pattern for line #2 in Figure 6.

1. Start with the first state in the pattern which will always be equal to the idle state (in this case "1000"). As that state already exists in the diagram, nothing is added.

2. For the second state, as in this case it is identical to the first, so nothing is added to the state diagram.

3. For the third state, one checks whether the transition from the previous state is represented in the state diagram. In this case it exists and so nothing is added.

4. For the fourth state (i.e. "1110"), one checks whether the transition from the previous state is represented in the state diagram. In this case it is not already existing, and so the state diagram is extended as shown in Figure 8(b) by the addition of state 6.

5. For the fifth and sixth states, they are identical to the fourth, so nothing is done.

6. For the seventh state (i.e. "1100"), one checks whether the transition from the previous state is represented in the state diagram. In this case it is not represented, and so the state diagram is extended as shown in Figure 8(c).

7. For the eighth state (i.e. "1000"), one checks whether the transition from the previous state is represented in the state diagram. In this case it is, and so nothing is to be added.

The pattern is now implemented, as a result of which one new state (state 6) and two new transitions have been added.

The basic rule is, that if a given state or transition in a given pattern already exists, nothing is added to the state diagram; if a given state or transition does not already exist, it is added to the state diagram. As a result, when the very first pattern is implemented, all states and transitions in the sequence are added to the then empty state diagram.

is Table 2: Examples of preferred implementations of elements of traffic control system 1.

Implementation 1 Implementation 2 Traffic control 2 channel fail-safe 2 of 3 channel fail-safe System 1 computer computer Railway and monitor 2 channel fail-safe 2 of 3 channel fail-safe Unit 3A, 3B, 3C computer computer Train detector unit State-machine Computer technology 6A5,613, 6C technology Sensing signal Programmable logic, Central Processing Unit Analysis unit 14 Storage device and discrete logic Databank 16 Look up table Pattern recognition 21 The individual elements of railway traffic control system 1 can be implemented in practice in a variety of forms according to particular circumstances of use, application and ancilliary equipment, and can incorporate various technologies, including mainframe computers, pc's, hard disks, RAN4's, EPROM's, hardware, software firmware. Table 2 indicates two particularly advantageous (but not the sole) practical implementations of principal elements of system 1.

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Claims

1. A method of counting objects passing a sensing zone with at least three sensors, the method comprising:

2. A method according to Claim 1 comprising sending a synchronising signal to change the processing operation to a testing operation and to change the testing operation to a processing operation.

3. A method according to Claim 1 or 2 comprising operating a first set of means to process signals output from the sensing location and simultaneously testing a second set of means for processing signals output is from the sensing location.

4. A method according to any preceding claim comprising switching the first set, thereby to effect testing thereof, and switching the second set, thereby to effect operation of it on signals output from the sensing location.

5. A method according to any preceding claim comprising the switching of the two sets is done simultaneously.

6. A method according to any preceding claim comprising the switching is done at predetermined time intervals.

7. A method according to any preceding claim comprising the predetermined interval is of the order of 10 seconds.

23

8. A method according to any preceding claim wherein the testing includes one or more of the following steps:- i. testing the output stages of the processing means; ii. testing that the processing means can execute logic related to data stored in the processing means; iii. testing that data stored in the processing means is intact; and iv. testing auxiliary means of the processing means (e.g.

calculator means, and/or latch means, and/or state address).

9. A method according to any preceding claim comprising updating data held in means for processing signals output from the sensing location,

10. A method according to any preceding claim'comprising operating a first set of means to process signals output from the sensing location and simultaneously testing a second set of means for processing signals output from the sensing location and, after testing has ended, updating data held in the second set of processing means.

11. A method according to any preceding claim comprising comparing output signals from the sensing location with a databank of output patterns and/or state diagrams for the sensing location.

12. A method according to any preceding claim wherein the databank comprises information on patterns and/or state diagrams of signals being output at a sensing location having a predetermined number of sensors being at least three, and corresponding to signals for one or more of the following conditions:

i) a plurality of characterisation value(s) for objects; ii) sequential position(s) in one, or the opposite, direction along said path, optionally also the opposite direction; 24 iii) at least one change in direction of the object along the path; iv) a fault, of one or more types, in the sensing operation and for each of the sensors in turn.

13. A method according to any preceding claim wherein the fault comprises one of the following types:

i) any one of the sensors is permanently sensed; ii) any one of the sensors is permanently unsensed; iii) transition from "no fault" to "fault" for any sensor; iv) transition from "faulf 'to "no fault" for any sensor.

14. A method according to any preceding claim comprising noting when the comparison step indicates that the output signals from the sensing location does not match any output pattern and/or state diagram in the 15 databank.

15. A method according to any preceding claim comprising noting step produces a signal advising of the lack of match between the output signals and the databank.

16. A method according to any preceding claim wherein comprising continuing the comparison of the output signals from the sensing location with the databank, thereby to monitor for subsequent matches therebetween.

17. A method according to any preceding claim comprising producing a signal advising the existence of a match between the output signals from the sensing location and any output pattern and/or state diagram, subsequent to a time period when there has been no such match.

18. A method according to any preceding claim wherein the sensing location comprises four sensors.

19. A method according to any preceding claim wherein objects to be 5 sensed comprise wheels of railway carriages on a railway track.

20. A method substantially as hereinbefore described with reference to, and/or as illustrated in, any one or more of the Figures of the accompanying drawings.

21. A computer program product directly loadable into the internal memory of the digital computer, comprising software code portions for performing a method according to any one or the preceding claims.

22. A computer program for performing a method according to any one of Claims I to 20.

23. Electronic distribution of a product according to Claim 21 or a program according to Claim 22.

24. A method of counting objects which move along a predetermined path past a sensing location having at least three sensors, the method comprising comparing output signal from the sensing location with a databank of output patterns and/or state diagrams for the sensing location.

25. Apparatus for counting objects which move along a predetermined path past a sensing location having at least three sensors, the apparatus comprising means to compare output signal from the sensing location with a databank of output patterns and/or state diagrams for the sensing location.

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26. A databank comprising information on patterns and/or state diagrams of signals being output at a sensing location having a predetermined number of sensors being at least three, and corresponding to signals for one or more of the following conditions:

i) a plurality of characterisation value(s) for objects; ii) sequential position(s) in one, or the opposite, direction along said path, optionally also the opposite direction; iii) at least one change in direction of the object along the path; iv) a fault, of one or more types, in the sensing operation and for 10 each of the sensors in turn.

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