GB2178875A

GB2178875A - Plant maintenance training

Info

Publication number: GB2178875A
Application number: GB08520124A
Authority: GB
Inventors: Trevor John Hunter
Original assignee: Ferranti PLC
Current assignee: Ferranti International PLC
Priority date: 1985-08-10
Filing date: 1985-08-10
Publication date: 1987-02-18
Also published as: GB2178875B; GB8520124D0

Abstract

For electronically controlled plant 10 including e.g. an interface means 16 by which data from a controller 13 such as computer 14 is converted to signals to operate plant 10, maintenance is taught by simulating hardware faults on sub-assemblies (circuit cards) in the interface unit by setting the output levels via the control computer. Simulated hardware 23 e.g. for interface means 16 carries dummy replaceable sub-assemblies and circuit test points. The simulated hardware has test points linked to those on the real hardware and a monitor of dummy sub-assemblies detects removal which prompts the control computer to set the corresponding real sub-assembly outputs accordingly. A trainee can trace and correct faults with signals from, and having effect on, the real interface hardware without risking physical damage to the expensive circuitry. A simulated computer cabinet 46 and duplicate (real) computer operating console 45 create the illusion of working directly on the real apparatus and the computer may additionally generate specific simulated outputs to those to simulate faults and working on the computer hardware. <IMAGE>

Description

SPECIFICATION Plant maintenance training This invention relates to plant maintenance training and in particularto training in the maintenance of electronically controlled plant.

Such electronically controlled plant may be considered as configured by an electronic controller, such as a computer, the plant itself and interface means for converting between plant control data generated and/or utilised by the controller and electrical signals utilisedand/orgenerated by the plant.

By way of example, such plant may be a directly functioning plant e.g. performing an industrial process or a routing control, or may itself be a simulator for a different type of plant, e.g. a flight control simu latorforan aircraft orthe like.

The plant itself is of course usually extremely com plex in function and the control electronics corres pondinglyso. To maintain operation ofthe plant maintenance personnel require special training not only in respect of dealing with routine maintenance and fault correction in the plant per se but also in the electronic control thereof. As stated above plant may take many forms and the maintenance ofthe plant per se depends on the nature ofthe plant and is not, other than incidentaally, pa rt of the present i nventio n which concerns the electronic control arrangement.

Hitherto such maintenance has often been carried out in functional plant with faults being simulated by an instructor imposing specific signal levels within the electronic control and causing a 'fault' situation to arise in the plant.

The trainee, by reference to the effect of such 'fault' on plantoperation, measurements taken atappropriate accessible test points, the running of diagnostic programs (wherethe controller is a computer) and the effects of removing control circuit subassemblies, determines the nature and location ofthe fault. If the simulated fault is attributable to such a removable sub-assembly then the procedure involves replacement of the sub-assembly and re-start ofthe plant. By the nature of generally adopted construction technique most faults in the electronic hardware will be in respect of such replaceable subassemblies.

Thetraining of maintenance personnel in this manner does however have several disadvantages which may not readily be apparent.

The principle of training relates as much to the following of set procedures and normally this in volves for each exercise the shutting down and sub- sequent starting up of the control electronics and possibly parts ofthe plant as well. Such operation often accelerates wear on the system and shortens its operating life, particularly where the controller is a computerto which software must be loaded on each occasion.

Furthermore, where the controller is a computer which functions as plant controller by virtue ofsoft- ware programmed into it, such computer is usually called upon to set up and monitorthe simulated faults, making it difficult, if not impossible, to simulate faults in the hardware ofthe computerwhilst retaining control.

Finally, and in practice, most troublesome, is that the continual removal and replacementofcircuitsub- assemblies causes damage both to the subassemblies and their connection points resulting in real faults which mask, or are masked by,thesimulated faults interrupting training and shortening the working life of the expensive electronic equipment involved.

It is an object ofthe present invention to provide for electronically controlled plant a control maintenance training arrangement which mitigates at least some ofthe above outlined problems.

According to the present invention for electronically controlled plant having a controller and interface means for converting between plant control data generated and/or utilised by the controller and electrical signals utilised and/orgenerated by the plant and wherein said controller and/or interface means has a plurality of replaceable circuit sub-assemblies a control maintenance training arrangement comprises a simulated control hardware arrangement including a plurality of replaceable dummy sub-assemblies corresponding to at least some of said replaceable circuit sub-assemblies, monitor means operable to provide monitor signals indicative of the presence of absense of each of said replaceable dummy sub-assemblies, and signal processing means responsivetothe moni- tor signals to cause said controllerto produce outputs consistent with said real sub-assemblies having the same presence status as the dummy sub-assemblies.

An embodiment ofthe invention will now be described by way of example with reference to the accompanying drawings, in which Figure lisa schematic plan showing the component parts and the interconnections therebetween of electronically controlled plant in which thecontroller is a computer and including a control maintenance training arrangement according to the present invention, Figures 2(a) and 2(b) are cut away perspective illustrations ofthe real and dummy interface means respectively ofthe arrangement of Figure 1 illustrating the sub-assembly structures and differences between them, and Figure3is a schematic plan viewsimilarto Figure 1 but in which the control maintenancetraining arrangement is extended to include a dummy control computer.

Referring to Figure 1 electronicallycontrolled plant 10 has plant operator output devices, such as instruments orV.D.U.'s 11 and plant operator input devices, such as potentiometer controls 12 by which normal operation ofthe plant is monitored and controlled.

The function ofthe plant does notform partofthe invention and further discussion is omitted here for clarity.

The plant functions, that is, performs a sequence of operations or maintains an operating state, underthe control of an electronic controller 13. The controller may be a specifically constructed or dedicated elec troniccircuitbutconveniently,and more usually, comprises a general purpose computer 14(which may be a microprocessor) having stored in the mem orythereofthe sequence of instructions for causing and controlling plant operation.The computer 14 also typically has an input/output (li0) means 15 such as a console containing an output V.D.U. an input keyboard and storage disc reader by which the programme sequence may be entered and/or modified and the computeroperated, as distinctfrom plant operation, in such functions as computer start up, shut down orthe running of diagnostic programmes.

Depending on the nature ofthe plant, the I/O means 15may in effect be duplicated atthe plant as partof the plant control means although in general plant control instructions will be fed, together with plant parameters being monitored, to the computer by way of interface means which converts the signals representing control instructions and measured values into suitable data forthe computer and converts data output bythe computer into suitable signals for operatingthe plant and driving the plant operator output devices.

Whilstthe computerl4 may be a general purpose machine running software specific to the plant being control led the interface means will be implemented in hardware, again specific to the plant.

Referring also to Figure2(a)the hardware unit forming the interface means 16 comprises a typical equipment rack 17 having a back board 18 carrying a pluralityofsockets 19 connected by wiring loom 20to each other and via loom 21 to the plant and via inputs output busses 22 to the computer 14. The rack 17 is arranged to carrya plurality of replaceable circuit sub-assemblies 23 in the form of standard sized printed circuit cards carrying components 24 and conductive tracks 25 which are inserted with the edge ofthe card into appropriate connector 19.

The rack 17 and possibly at least some ofthe circuit sub-assemblies have test points 26,27 respectively at which voltages levels of power rails, interface managementsignals (e.g. clock signals) and plant control signals can be measured.

The computer controlled plantthusfardescribed is conventional and in teaching maintenancethereof, particularly of the interface unit, the computer 14 is caused to run an additional program whereby at preprogrammed times or points of plantfunction or in response to instructions input by an instructor the computer generates outputs to mask one ofthe interface outputs. The plant reacts as if a fault exists in the interface unit. Such afault is simulated by driving all accessible test points also to the levei they would assume if the simulated fault were genuine.

The trainee proceeds, as outlined above to observe the effects on plant operation, make appropriate test fault measurements, shut down the computer and interface means (and possibly the plant) replace the appropriate sub-assembly or assemblies at fault and thenstartupthesystem.

Sub-assembly replacement mat in fact consist only of removing and replacing the sub-assembly after identifying itto the instructorwho, if satisfied, in structs the computer to remove the masking signals characteristic ofthe simulated fault.

It will be appreciated that [some] faults are in fact diagnosed whilstthe computer control is in operation runningthe plantoperating, ora special diagnostic, program and the consequences of removal of one or more sub-assemblies are reflected by changes in computer output monitored at said test points and the plant operation output means.

Referring to Figures 1 and 2(b), in accordance with the present invention simulated control hardware is provided in the form of dummy interface means 30.

This comprises a rack system 31 similar in appearanceto that 17 and containing replaceable dummy sub-assemblies 32 in the form of circuit cards each carrying an appropriate layout of dummy components 33 to add realism and plugged into a connector 34. The rack 31 and, where appropriate, subassemblies 32 carry test points 35,36 and these test points are connected to corresponding test points on the real interface hardware. Test points 36 on the sub-assemblies are connected by way of the connec tor34.

Thus asfarasthetrainee is concerned the dummy interface means looks the same asthe real interface means, has replaceable sub-assemblies which look the same and accessible test points which provide the same signal levels.

Additionally, monitor means 37 is provided comprising switching means 38, such as a micro-switch, located adjacent an edge ofthe dummy sub- assembly circuit board to detect the physical presence or absence ofthe sub-assembly.

The switching means of each sub-assembly is connected by wires formed into a separate hidden loom 39 to a monitorcircuit, shown by circuit housing 40.

The monitorcircuit is notshown in detail and conveniently, but not necessarily, comprises a microprocessor. The precise nature of the circuit is immaterial provided it operates to scan the status of each switching meanstodeterminewhetheranysub- assembly has been removed and to transmit a signal indicative of the sub-assembly location in the rackto signal processing means indicated by block41.

In an arrangement in which the controller 13 is a dedicated control circuit the signal processing means would also be provided by a separate circuit arrange ment, possibly a microprocessor, but when,as de- scribed, the controller is formed buy a programmed computer 14 the signal processing means41 is also conveniently formed by the computer 14which contains program instructions run with the plant control instructions and responsivetosignalsfromthemonitor means indicative of a particular sub-assembly removal to modify its output signals such that the outputs of the corresponding real sub-assembly are masked by no-output signal levels.

Clearly this simulates removal ofthe real subassemblywhich is reflected in plant operation and at the plant operators output means and at the circuit test points on the (real and) dummy interface means.

The computer is arranged to monitorwhetherthe sub-assembly is removed from a location at which a simulated fault is impressed so that subsequent monitoring of its replacement not only restores the outputs to the corresponding real sub-assembly but also 'clears' the 'fault'. By this technique the same dummy sub-assembly may be employed and the effect of replacement seen immediately and automa tical ly without waiting forthe instructorto remove the faultcondition by way of a manual inputto the com- puter.

It will be appreciated that in general there will be several different groups of identical sub-assemblies said groups having different functions and containing different components.

It will also be appreciated that more than one dummy sub-assembly may be removed orthatforadded realism it may be preferred that a dummy subassembly removed be exchanged before replacement, but bringing the risk of inserting a dummy sub-assembly ofthe correct dimensions but incorrect forthat location whilst apparently effecting correct procedure.

To obviate this risk each dummy sub-assembly has associated therewith encoding means identifying the functional nature ofthe sub-assembly and monitored by the monitor means such that when removal of a sub-assembly is monitored, the functional nature or type of sub-assembly is encoded on the signal provided to the processing means. Similarly, when a sub-assembly is replaced that sub-assembly type as well as its presence is encoded in the monitorsignal so that the processing means (computer 14) effects a check that the sub-assembly is ofthe correct type before clearing the simulated fault.

If the monitor means is of a suitable nature, such as a microprocessor, then correlation between subassembly encoded signals may be made in the monitor means and a sub-assembly presence status signal only forwarded to the processing means if the replacement sub-assembly is of the correct type.

The encoding means may take numerous forms, for example by providing a plurality of switches simi lartothoseofswitching means of mechanical, optoelectronic inductive or magneticform 38 cooperating with apertures or markers disposed in a coded pattern on the sub-assembly card. Alternatively the subassembly may carry a plurality of switches 42 such as miniature toggle switches interconnected to define a code on printed tracks 43 which connect by way of unused contacts of the connector 34to the monitor means 40.It will be appreciated that instead ofsepa- rate presence status switching means 38 and encoding means, the signal provided by the encoding means when a sub-assembly is present may also be used to providethe monitormeanswith an indication ofthe presence ofthe sub-assembly, that is, the encoding means also forms the switching means.

Afurtherfunction may be provided by the monitor means, particularly if the monitor meanstakesthe form of a microprocessor. Some ofthe signals appearing in the interface means 16 and available at the test points are what may be described as control hardware management signals generated bythe computer, for example, clock and synchronising pulses. To minimise the number of connections between the real and simulated hardware these management signals may be generated by the monitor means.

It will be appreciated that in some circumstances fault determination in the interface means involves the running of special diagnostic programmes in the control computer 14. Information derived from the computer byway of l/O means 15may supplementor replace the information given by signal levels attest points.

Clearly effective operation of the dummy interface means as described relies upon the continued operation ofthe computer 14 and to caterforsuch circumstances a trainee input/output means 45, correspondingtothecomputercontrol I/O means 15 maybe connected to additional input/output ports ofthe computer, the computer being arranged to recognise inputs relating to fault diagnoses and provide appropriate outputs in accordancewiththefault being simulated. Such outputs may include providing different or no plant control outputstothe interface in accordance with the inputs at 45.

To complete the realism ofthe control hardware simulation a non functional representation 46 of the computer may be provided so that the trainee may be segregatedfrom the real control equipmentwhilst gainingfamiliaritywith plant control lay-out.

As described above the control maintenance training arrangement is limited to that electronic hardware, such as the interface means 16, external to the computer 14. However th e computer itself forms an important part of the control arrangement and comprises a hardware arrangement in the form of replaceable sub-assemblies (circuit cards) similarto the interface means 16.

Itwill be appreciated howeverthatacomputer hardware fault such as a processor or memoryfault cannot be simulated by tampering with the outputs thereofwhile retaining operation ofthecomputer.

Referring to Figure 3 which shows an arrangement generally similarto that of Figure 1 the dummy control computer 46 is provided with dummy su bassemblies 47 and monitor means 48 in a manner similarto that ofthe dummy interface means 30 and coupled to computer 14. The dummy computer also has an array of operation indicating lamps orthe like 49 corresponding to any appearing on the real computer. The dummy computer (and its dummy subassemblies) may also have a plurality oftest points 50. The dummy computer differs from the dummy interface means in that the test points 50 and indicating lamps are connected to receive special output signals from the computer on buses 51.

Thus a computer hardware fault may be simulated by providing appropriate outputs to the interface means 16 and the dummy computer 46 and trainee I/O means 45. Simulated responses to any inputfrom the I/O means 45 (e.g. diagnostic programs) orfrom the monitor means 48, indicative of removal of a dummy sub-assembly, cause outputs simulating the response to the action in accordance with the effects of the simulated fault.

Furthermore by using the trainee 1/O 45 and dummycomputerthetrainee is ableto adopt a procedure entailing shutting down and restoring the control computer in which this action and its effects on the other parts ofthe controlled plant are simulated by the real computerwhich continues to function.

The most comprehensive arrangement described above is particularlysuited tothe more complex types of plant 10. One example of such controlled plant is a simulatorfortheflight-deckofan aircraft or like complex vehicle. Such a flight simulator is employed to train pilots, the plant input means 12 being in the form aircraft flight deck controls and the plant output means 11 being in the form of aircraftflight deck instruments. The control computer programme containstheoperating parameters of an aircraft and produces outputs in accordance with the operation of the simulated flight controls.

Itwill be appreciated that such simulator operators will also be trainees operating underthe guidance of an instructorwho can create disturbances in the 'aircraft' by appropriate inputs to the computer. A separate simulator input/output means 52 may be provided to effect inputs to the control computer 14 by way ofthe plant and interface means or duplicating the I/O means 15.

In the above described embodiments the controller 13 has been described as comprising a computer.

Whilst it is envisagedthatfor most complex plantit will take this form it should be reiterated that for suitable plant it may also comprise a dedicated hard wired circuittowhich additional signal processing means 41 varies its operation to reproduce the effects of dummy sub-assemblies removal on the real hardware.

Claims

1. For electronically controlled plant having a con troller and interface means for converting between plant control data generated and/or utilised by the controller and electrical signals utilised and/orgenerated bythe plantand wherein said controllerand/or interface means has a plurality of replaceable circuit sub-assemblies a control maintenance training arrangement comprising a simulated control hardware arrangement including a plurality of replaceable dummy sub-assemblies corresponding to at least some of said replaceable circuit sub-assemblies, monitor means operableto providemonitorsignals indicative ofthe presence or absence of each of said replaceable dummy sub-assemblies, and signal processing means responsive to the monitor signals to cause said controllerto produce outputs consistent with said real sub-assemblies having the same pre sence status as the dummy sub-assembly.

2. Acontrol maintenance training arrangement as claimed in claim 1 in which the monitor means includes switching means associated with each replaceable dummy sub-assembly operable to detect the physical presence or absence ofthe associated dummy sub-assemblies.

3. Acontrol maintenance training arrangement as claimed in claim 2 in which the monitor means comprises an electrical circuit operable to scan the status of each switching means and responsive to a change of statues of any switching means to provide a signal to the processing means indicative ofthe status and ofthe sub-assembly location in the dummy control hardware.

4. Acontrol maintenance training arrangement as claimed in claim 3 in which each dummy sub- assembly contains encoding means operable to iden tifythe functional nature ofthe sub-assembly it simulates.

5. Acontrol maintenance training arrangement as claimed in claim 4 in which the monitor means is responsive to said encoding means to provide also a sub-assembly identification signal to the processing means.

6. Acontrol maintenance training arrangement as claimed in claim 4 or claim 5 in which the encoding means is carried by the dummy sub-assembly and electrical signals therefrom are connected to the monitor means byway of a connector simulating a circuit connector between the simulated subassembly and hardware.

7. Acontrol maintenacnetraining arrangementas claimed in claim 6 in which the encoding means comprises a plurality of switches selectively set to define, in combination, a code characteristic ofthe subassembly.

8. Acontrol maintenance training arrangement as claimed in any one ofthe preceding claims in which said controller comprises a control computer having programmed therein the sequence of instructions for operation ofthe plant and in which the signal processing means comprises the control computer containing a program run in addition to the plant operating program to effect said outputs in accordance with the signals received from the monitor means.

9. Acontrol maintenance training arrangement as claimed in anyone ofthe preceding claims in which the simulated hardware includes accessible circuit test points.

10. Acontrol maintenance training arrangement as claimed in claim 9 in which the corresponding real hardware is external of the controller, said accessible circuit test points of the simulated hardware being electrically connected to corresponding test points of the real hardware and providing at said test points the appropriate signal levels.

11. A control maintenance training arrangement as claimed in claim 10 in which the controller is responsive to detection of removal of a dummy subassembly by the monitor means to maskthe signal levels at the real sub-assembly contacts with the levels consistent with said sub-assembly having been removed.

12. A control maintenance training arrangement as claimed in claim 11 when dependent from claim 8 in which control hardware management signals provided by the computer and detectable in said control hardware at said test points are, for the simulated hardware, generated therein by the monitor means.

13. Acontrol maintenance training arrangement as claimed in claim 9when dependent from claim 8 in which the corresponding real hardware is part of the control computer and accessible circuit test points on the simulated hardware are provided with specially generated signals simulating a computer hardware state consistent with the presence status ofthe dum my sub-assemblies thereof.

14. A control maintenance training arrangement as claimed in the preceding claims for electronically controlled plant in which said controller comprises a control computer having programmed therein a sequence of instructions for plant operation and including a simulated computer operating input/output means comprising real computer operating input/ output means coupled to the control computer such that instructions and data entered thereby and out puts thereto are operated on by the computer in accordance with the simulated condition ofthe hardware.

15. Acontrol maintenance training arrangement as claimed in any one ofthe preceding claims in which only those parts ofthe simulated hardware corresponding to the real hardware are accessible in operation.

16. Amaintenancetrainingarrangementsub- stantially as herein described with reference to, as shown in, Figures 1 and 2(b) or in Figures 2(b) and 3 of the accompanying drawings.

17. Electronically controlled plant including a control maintenance training arrangement as claimed in any one of the preceding claims.