Proceedings of the Institution of Mechanical
`Engineers, Part F: Journal of Rail and Rapid
`Transit
`
`http://pif.sagepub.com/
`
`
`Diesel Locomotive Reliability Improvement by System Monitoring
`K N Fry
`Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit
`DOI: 10.1243/PIME_PROC_1995_209_248_02
`
` 1995 209: 1
`
`The online version of this article can be found at:
`
` http://pif.sagepub.com/content/209/1/1
`
`Published by:
`
`http://www.sagepublications.com
`
`
`
`On behalf of:
`
`Institution of Mechanical Engineers
`
`
`
`  
`    
`
`Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid TransitAdditional services and information for
`
`
`can be found at:
`
`Email Alerts:
`
`
`http://pif.sagepub.com/cgi/alerts
`
`Subscriptions:
`
`http://pif.sagepub.com/subscriptions
`
`
`
`Reprints:
`
`
`http://www.sagepub.com/journalsReprints.nav
`
`
`
`http://www.sagepub.com/journalsPermissions.navPermissions:
`
`
`
`>>
`
`Version of Record
`
`- Jan 1, 1995
`
`What is This?
`
`
`
`
`
`Downloaded from Downloaded from
`
`
`
`pif.sagepub.compif.sagepub.com
`
`
`
` by guest on March 7, 2014 by guest on March 7, 2014
`
`1
`
`Mercedes-Benz USA, LLC, Petitioner - Ex. 1003
`
` 
`  
` 
` 
` 
` 
` 
`

`

`1
`
`Diesel a . locomotive
`
`monitoring
`
`a
`
`reliability improvement by system
`
`K N Fry, BSc
`British Rail Research, Railway Technical Centre, Derby
`
`System monitoring for reliability (SMR) involves monitoring critical parts of a vehicle and ir&orming the owning business of an
`impending fault. Diesel locomotives offer the largest opportunity for such systems and British Rail Research has developed a system
`designed to improve Class 47 locomotive reliability.
`The vehicle-mounted equipment comprises a computer that continuously monitors the condition of the vehicle through sensors at key
`points. The computer is connected to a radio telephone and modem and a GPS satellite navigator. The key elements in the success of
`the system are the automated analysis of data on-board the vehicle and its ability to call for help ahead of the occurrence of service
`failures. The business i n t e j i e is through a Windows based information display which runs on a personal computer connected to the
`public telephone network. This controls the display of messages from monitored vehicles and allows vehicles to be interrogated to check
`on current condition.
`When fully implemented, a reduction in technical casualties of 40 per cent is anticipated. There are additionalfinancial benejits from
`eflciency improvements and vehicle maintenance cost savings.
`Key words: system monitoring for reliability, diesel locomotives
`
`1 INTRODUCTION
`The Vehicle Systems Unit of British Rail Research has
`undertaken a series of projects over many years con-
`cerned with the development of condition monitoring
`for railway rolling stock and diesel locomotives in par-
`ticular. This work has recently concentrated on the
`development of systems to improve the reliability of
`vehicles. System monitoring for reliability (SMR) is the
`name given to monitoring critical parts of a vehicle in
`order to improve its reliability by informing the owing
`business of an impending fault.
`This paper describes the development of a system for
`monitoring Class 47 locomotives. It begins with the
`guiding philosophy for SMR. It then goes on to
`describe the component parts; the on-board equipment
`and analysis of data; the communication of information
`to and from the vehicle; and the information display
`system. Finally, there is a review of the current position.
`
`The MS was received on 25 November 1993 and was accepted for publication on
`22 December 1994.
`
`2 PHILOSOPHY OF SYSTEM MONITORING FOR
`RELIABILITY
`2.1 The ecooomic backgrouod
`Studies into maintenance and maintenance-related costs
`of typical types of rolling stock have been undertaken to
`determine the most cost-effective areas for the applica-
`tion of condition monitoring and diagnostic systems.
`The four main vehicle types used by British Rail have
`been examined; diesel locomotives, electric locomotives,
`diesel and electric multiple units.
`The costs have been broken down by vehicle system
`and subsystem into five areas, three directly associated
`with maintenance; exams, repairs and overhauls and
`two indirectly related; the cost of unreliability and
`unavailability. The results, given in Fig. 1, show that the
`largest total cost is for diesel locomotives, and the
`largest element of this total is the cost of unreliability.
`Examination of the reasons for unreliability showed
`that the total is made up of a small number of causes
`(see Fig. 2), many of which are easily monitored and
`
`0 Unavailability
`Reliability
`0 Overhauls
`Repairs
`Exams
`
`> .- - -
`
`2
`
`Diesel locomotive Electric locomotive
`
`Diesel
`multiple unit
`Vehicle type
`Fig. 1 Rolling stock maintenance and maintenance-affected costs
`
`Electric
`multiple unit
`
`F01693 Q IMcchE 1995
`
`Roc Instn Mech Engrs Vol 209
`
`Downloaded from
`
`pif.sagepub.com
`
` by guest on March 7, 2014
`
`2
`
`

`

`2
`
`K N F R Y
`
`E
`I2 P
`ii
`
`. . . . . . . . . .
`
`.
`
`.
`
`.
`
`.
`
`.
`
`.
`
`.
`
`.
`
`.
`
`
`
`Not preventable
`Preventable
`
`. . . . . . .
`
`Battery
`condition
`
`Traction control -
`
`interlocks
`
`”
`
`I
`and low oil
`Brake condition
`pressure
`Fig. 2 Causes of Class 47 failures in service
`
`allow warning to be given. About 40 per cent are con-
`sidered preventable through appropriate monitoring
`and notification of impending failure.
`
`2.2 Reliability emphasis
`The factors described in Subsection 2.1 led to the
`concept of system monitoring for reliability which is
`specifically aimed at reducing in-service failure of
`equipment rather than reducing maintenance costs or
`increasing availability. This very specific approach gives
`a number of advantages:
`(a) the number of measurands is significantly reduced;
`(b) the maintenance philosophy of the vehicles does not
`change, so it is quicker and easier to implement;
`(c) data analysis is generally easier since faults severe
`enough to cause a vehicle to fail are more easily
`identified than the comparatively smaller changes
`associated with a need for maintenance.
`
`2.3 Importance of on-board analysis
`Most approaches to vehicle monitoring have involved
`fitting data logging equipment and analysing the data
`after they have been downloaded. This requires the
`routine download of a large amount of data, the major-
`ity of which will indicate that the vehicle is healthy. It
`also introduces a delay in fault identification and will
`miss the majority of faults likely to affect service reli-
`ability on a daily basis.
`An emphasis on reliability improvement requires that
`in order to achieve a fast response to developing faults,
`the analysis of data must be automated and done on-
`board the vehicle; the vehicle must also be able to call
`for help. It is this requirement for a high degree of
`vehicle system ‘intelligence’, in conjunction with a com-
`munications system where the vehicle can call for help
`or be called at any time that is the key to successful
`SMR.
`The move towards an ‘intelligent vehicle’ gives two
`other major benefits. Firstly, it considerably reduces the
`Part F: Journal of Rail and Rapid Transit
`
`amount of data requiring transmission, which is partic-
`ularly advantageous where communication is by radio.
`Secondly, it opens up the possibility of providing infor-
`mation to the driver or train crew in those situations
`where it can be usefully acted upon.
`The provision of a continuous communications link
`between the owning business and an ‘intelligent vehicle’
`allows information on condition to be provided on
`demand. Such vehicle interrogation may be useful as a
`check on condition just prior to assignment or for mon-
`itoring the development of a fault already reported.
`
`2.4 Information required
`System monitoring is really only half the story. In order
`for the service reliability to be improved not only must
`information about a fault be provided, but the informa-
`tion must be suitably acted upon in order to remedy the
`situation. If appropriate action is not carried out, the
`vehicle will fail just as it would without monitoring. In
`this respect the presentation of information to the end
`user is of paramount importance.
`An important part is the information content. The
`majority of rolling stock is maintained by means of
`component replacement to facilitate rapid return to
`service and so the information provided should support
`this philosophy. In other words, faults in equipmerit
`need only be diagnosed down to the level of ‘replaceable
`unit’ or the level of action required to allow the vehicle
`to continue running, such as ‘top up with coolant’.
`Diagnosis to this depth is particularly important in the
`case of a vehicle reporting a developing fault but a long
`way from a repair depot. Should the vehicle be brought
`back to the depot, repaired at an outstation, repaired by
`a mobile maintenance team or left for a while? If the
`vehicle does need to return to depot, diagnosis to
`replaceable unit level allows an indication beforehand
`of what spares and depot resources are required (for
`example, under cover, crane, pit, manpower etc.) This
`speeds up repair time considerably. Similarly, if a
`mobile maintenance team needs to be sent to the vehicle
`they will know what equipment to take with them.
`
`Q IMechE 1995
`
`Downloaded from
`
`pif.sagepub.com
`
` by guest on March 7, 2014
`
`3
`
`

`

`DIESEL LOCOMOTIVE RELIABILITY IMPROVEMENT BY SYSTEM MONITORING
`3
`Information from the system must be sent to the
`puter knows the vehicle's position through connection
`to a GPS satellite navigator.
`business maintenance controllers. They respond to calls
`The equipment is housed in three rugged steel enclo-
`from outstations reporting problems with vehicles and
`arrange repair or a replacement vehicle.
`sures sealed to IP66 and protected against the electro-
`magnetic environment of the locomotive. Also fitted are
`For fault diagnosis, messages should be sent from the
`a number of transducers mounted directly on to existing
`vehicle immediately, but this is not necessarily the case
`when prognosis is involved. There are situations where,
`components, some small enclosures containing trans-
`ducers and appropriate interconnection via high specifi-
`if the existing set of circumstances were to continue, the
`vehicle would fail, but the fault may be naturally reme-
`cation cable sealed into flexible conduit. Two aerials are
`also used, a short whip aerial mounted on the end of the
`died before it occurs. For example, a battery draining
`with the engine stopped may be just about to be
`vehicle, and a small flat antenna mounted on the roof
`charged following an engine start, or a vehicle with a
`for the GPS navigator. This equipment is designed to
`coolant leak may be just running on to a depot to have
`retrofit into the vehicle without interfering with its
`its coolant topped up. In these circumstances the
`normal operation and maintenance. A general sche-
`matic is shown in Fig. 3.
`approach has been to define a failure limit and make
`predictions of the remaining time to failure. Messages
`can then be generated a set time before failure is esti-
`mated. The maintenance controller can then decide on
`whether the fault will require action based upon the
`duty of the vehicle.
`
`3.1.1 Computer
`Hardware. The on-board computer is an industry stan-
`dard VME bus-based system made up of single height
`eurocards. The use of the VME bus standard allows a
`system to be made up in a very modular and flexible
`way using equipment from one or a number of s u p
`pliers. The system can be easily expanded to include
`additional processing power, memory, communications
`or monitoring channels.
`Software. Most computers use an operating system as
`the master supervisor of their resources; memory, pro-
`cessing time and input/output devices such as sensors,
`modems and disk drives. The operating system also
`provides an interface between the computer and the
`
`3 ON-BOARD SYSTEM
`3.1 Equipment fitted
`The vehicle-mounted equipment comprises a computer
`that continuously monitors the condition of the vehicle
`through sensors at key points. The computer is con-
`nected to a radio telephone and modem allowing the
`system to ring out with fault messages or be inter-
`rogated by the owning business at any time. The com-
`
`Cubicle end
`........... ;- Battery1
`Battery V
`Turbine temperature
`
`j
`
`..
`
`j
`
`Fuel
`level
`
`Computer
`
`PC logic
`
`c 6 PRS
`3
`P E Ambient temperature (internal)
`
`[ Navigator @
`
`Navigator aerial
`".__..\
`(roof cL)
`
`---"^
`
`FI
`
`4121208
`
`From governor end - - - +(=
`
`i 1 ioi-vl
`- - - - - - - - -
`
`: I
`/ I
`i I M
`i l E
`
`i
`i
`!
`
`._.......................-._..........._I
`: MIC mom end
`1 Hydraulic oil level (6W PLY FXD SKT)
`i Oil temperature (6W PLY FXD SKT)
`i Water level (6W PLY FXD SKT)
`1 Oil pressure in (manifold)
`8 Oil pressure out (manifold)
`j Governor air (manifold)
`i Crankcase pressure
`: (6W PLY FXD SKT)
` .......................
`
`I .
`
`.
`
`.
`
`.
`
`PRS
`
`' 6w
`
`i FXD SKT 0- Engine speed
`
`I
`1
`
`.......
`; Cubicle
`
`1
`
`I
`!
`b
`1 Fig. 3 Monitoring equipment general arrangement
`
`8 IMechE 1995
`
`Proc lnstn Mech Engs Vol209
`
`Downloaded from
`
`pif.sagepub.com
`
` by guest on March 7, 2014
`
`4
`
`

`

`K N FRY
`able amount of software has been necessary to ensure
`reliable phone management across the two-way link.
`
`4
`user, managing the basic operations of the system,
`loading and executing programs, managing input/
`output, managing a directory of files and allocating
`memory. Application programs performing data
`analysis, data storage and communications all sit on
`top of the operating system and call on it to perform
`low-level tasks.
`The operating system used in the on-board computer
`is 0s-9. This is a multi-tasking operating system similar
`to UNIX but specifically developed for use in real time
`embedded systems.
`Multi-tasking means that several programs may run
`apparently simultaneously, by rapidly switching from
`one program to the next many times per second. This
`capability is used extensively for the on-board software.
`It considerably simplifies the task of managing data
`analysis, allowing for example, communications over
`the radio telephone to occur while analysing data from
`the oil system, while reading the position from the navi-
`gator, while storing vehicle operating data to file, etc.
`Each task can be written as a separate program sim-
`plifying development and testing, and removing any risk
`of programs interfering with each other.
`
`3.1.3 GPS satellite navigator
`The vehicle is equipped with a ‘Navstar’ XR5 GPS
`receiver which gives satellite-based positioning. Position
`information from the receiver, accurate to a mean error
`of 28 metres, is available to the on-board computer
`through a serial data link. The latitude and longitude is
`converted to eastings and northings by the computer.
`
`3.2 Data analysis
`The general structure of the data analysis performed is
`shown in Fig. 4. This structure separates the data
`analysis from the hardware allowing more generalized
`program modules to be produced.
`The program ‘logger’ reads all the sensors and the
`vehicle location from the satellite navigator and writes
`the data to a global buffer. The buffer holds all the mea-
`surements made over the last minute.
`The program ‘validate’ takes information from the
`measurement buffer and places it in a second, similar
`buffer after :
`(a) converting it to engineering units;
`(b) adjusting it for the value of supply voltage existing
`at the time;
`(c) checking it against limits to ensure validity
`‘Validate’ also sets ‘flags’ to identify engine operating
`status and transducer and power supply faults.
`The analysis programs for individual systems then
`simply extract data from this buffer when their own cri-
`teria for analysis are met, for example the engine has
`
`3.1.2 Cellular radio telephone and modem
`The computer is connected to a Racal Vodafone cellular
`radio telephone and modem. Modems for cellular radio
`require a special error correction protocol, cellular data
`link control (CDLC), which gives 100 per cent error-free
`data transmission at speeds up to 2400 bits per second.
`The modem is configured for auto-dial and auto-answer
`allowing the vehicle to call out or be called at any time.
`Development of additional hardware and a consider-
`
`- :
`
`_
`
`_
`
`_
`
`Data logging
`, . . . . . . _ . .
`.
`_
`Data analysis
`
`8
`
`.
`
`_
`
`(-)
`
`4
`
`4
`
`Data stored at 4 Hz as ‘bits’
`values to continuously updated
`60 second ring buffer
`
`Data convened to engineering
`units, supply voltage
`compensated and checked for
`sensor faults
`
`I
`Current status information
`
`I
`
`*
`
`. Data analysis
`Communications
`; ,
`
`CDLC modem
`
`. . . . _ _ . . . . . . . _ . _ _ . . . _ _ _ _ . _ _ _ _
`
`,
`
`Fault message files
`
`Part F: Journal of Rail and Rapid Transit
`
`Q IMechE 1995
`
`Fig. 4 Structure of DEMON SMR47 software
`
`Downloaded from
`
`pif.sagepub.com
`
` by guest on March 7, 2014
`
`5
`
`

`

`DIESEL LOCOMOTIVE RELIABILITY IMPROVEMENT BY SYSTEM MONITORING
`5
`been at full power for a set time, or is idling, or has just
`A comprehensive software test environment was
`created. The physical outputs from the sensors on the
`been turned off.
`vehicle were replaced by a program that wrote data from
`If the results of the analysis require a message to be
`a file into either of the data buffers in Fig. 3. The data
`sent from the vehicle this is instigated by creating a file
`file format used to seed the buffer was the same as that
`containing the message. This file forms the interface
`used for data storage. This gave an easily controlled
`between the analysis program and the software control-
`and repeatable means of testing the response of the
`ling the communications link. A separate program iden-
`analysis programs to either previously collected real
`tifies that a fault file has been created, establishes
`data or simulated fault data, designed to test the
`communications, via cellular telephone, with the infor-
`analysis under a particular set of circumstances.
`mation display system and passes over the information.
`The complexity of on-board analysis varies with the
`parameter or vehicle system in question. There are a
`number of factors that lead to the task being more
`complex than is initially apparent, such as the effects of
`varying duty, the need to normalize for ambient condi-
`tions and the requirement to provide prognostic infor-
`mation.
`The use of out-of-limit alarms is in general too sim-
`plistic for many parameters and will not provide the
`level of decision support needed if the system is to
`succeed. It is far more useful to know that failure is
`likely at a particular time as this then allows the con-
`troller to make a decision based upon the remaining
`duty requirement and the best point of repair. In other
`words the primary requirement is not one of simple
`diagnostics but of prognostics.
`Prognostic estimates will always have a level of
`uncertainty. The approach that has been taken through-
`out has been to base all time to failure estimates on 95
`per cent confidence limits. The statistics are obviously
`transparent to the information receiver who just sees an
`upper and lower time to failure. The information is
`given in absolute time so that it is not affected by any
`communication delays, it does not require the receiver
`to make mental calculations of likely failure time and it
`compares easily with operating schedules.
`
`3.2.2 Coolant monitoring
`The level of water in the header tank is measured by a
`potentiometer attached to a pivoted float arm. During
`periods when the engine is off or idling the level stays
`fairly constant, provided there is no leak. However,
`when the engine is running under power, the level fluc-
`tuates due to vehicle movement. The level also changes
`due to expansion and contraction of the water with
`temperature. As the temperature of the water is mea-
`sured and the capacity of the system is known, the level
`can be corrected for temperature. Prognostic analysis
`predicts the time at which the tank will be empty and
`sends out a message when this time is less than two
`hours away.
`Refills need to be detected in order that predictions
`can be reset. Data have shown that sudden increases in
`level can occur normally when the engine is running,
`and the engine is not always stopped in order to refill
`the tank, so the refill detection method used depends on
`whether the engine is running at the time.
`
`3.2.3 Fuel monitoring
`A locomotive running out of fuel is a very rare
`Occurrence so analysis simply involves sending a
`warning message if the level in the tank drops below ten
`per cent.
`Fuel efficiency information is also calculated. The
`power output of the main generator is integrated to give
`the total energy provided and this is divided by the
`calorific value of the fuel used, over a reasonable time
`period.
`Measurement errors occur while the vehicle is in
`motion due to acceleration or deceleration. Addi-
`tionally, because of the arrangement of the fuel supply
`system, track gradients or cant can cause the engine to
`draw fuel from only one tank while the vehicle is sta-
`tionary. Fortunately these effects are not significant
`when measuring engine efficiency over a tank of fuel
`since the amount of fuel burnt is quite large in compari-
`son with the errors.
`One problem with efficiencies calculated in this way is
`that the measured power output from the vehicle
`includes only that provided by the main generator.
`Therefore, power produced for auxiliary equipment
`(battery charging, electric train heating, etc.) is ignored.
`
`3.2.4 Battery monitoring
`There are two problems that occur with the battery
`system :
`(a) flat batteries due to poor battery health;
`
`Proc lnstn Mech Engrs Voi 209
`
`3.2.1 System development and testing
`The first stage in the development of data analysis pro-
`grams was the collection of data to see how the oper-
`ation of the vehicle affected the results. It is easy to be
`‘swamped’ in data by condition monitoring systems, so
`to avoid this it was decided that data collection would
`be targeted specifically for each of the systems of inter-
`est. Using past experience of condition monitoring data
`collection and analysis, specific data collection pro-
`grams were written for each monitored system. These
`stored, at the appropriate time or engine condition and
`at an appropriate sampling and averaging rate, only the
`measurements considered relevant.
`This resulted in completely different data collection
`programs for each monitored system, all running
`together at the same time. The data collected was auto-
`matically downloaded from the vehicle each night to a
`microVAX computer network where it was archived.
`The data collected were stored in files compatible
`with standard spreadsheet programs. This meant that
`downloaded data could be placed straight into a
`spreadsheet where they could be plotted and manipu-
`lated with ease. Spreadsheet functions and macros were
`used to experiment with analysis possibilities before
`they were finally programmed. When a suitable method
`of analysing the data was decided upon, a program was
`written for inclusion on the vehicle.
`
`Q IMechE 1995
`
`Downloaded from
`
`pif.sagepub.com
`
` by guest on March 7, 2014
`
`6
`
`

`

`K N FRY
`6
`tion of low-pressure faults since a reduction in pressure
`(b) flat batteries due to excessive discharge over a
`can be caused by a reduction in engine speed or a
`period.
`reduction in oil viscosity (due to either fuel dilution or
`Battery health. Battery health and state of charge can
`an increase in oil temperature).
`be determined by measuring the voltage drop under
`Neural networks can be envisaged as a ‘black box’
`load. The load needs to be of reasonable magnitude and
`that can be trained to provide an output related to
`should last for some time. For the Class 47 locomotive
`certain
`inputs. Work conducted by British Rail
`the necessary conditions are met when the electrically
`Research has shown that neural networks can be suc-
`powered fuel, oil and water triple pump runs with the
`cessfully used to normalize oil pressure data for oil tem-
`engine turned off. This situation occurs before engine
`perature and the engine speed. The neural network is
`start-up and also after shutdown for a short time.
`used to predict inlet and outlet pressures, and two new
`It is anticipated that battery health will deteriorate
`parameters are then produced, the difference between
`slowly, so that occasions when insufficient running to
`the measured and predicted inlet and outlet pressures.
`fully charge the battery happen (thus prohibiting the
`Using these new parameters a considerable increase in
`determination of condition) should not severely affect
`diagnostic sensitivity to genuine low-pressure faults can
`the prediction of battery maintenance need.
`be obtained. These parameters are used to identify
`The fact that battery health and state of charge cause
`potential low oil pressure while the engine is still
`the same effect on the voltage drop under load means
`warming up and correct for the filter pressure drop
`that the effect of battery deterioration on voltage drop
`variation with temperature.
`can be determined from laboratory tests. Tests have
`A neural network was quickly and easily trained
`been conducted to determine the voltage drop under an
`using data from the system in good condition. The
`equivalent triple pump load for a good battery at
`network was then generated as computer code and
`known states of charge. A voltage drop equivalent to a
`embedded within the on-board analysis program for the
`value of health below 70 per cent generates a fault
`oil system.
`message.
`Discharge monitoring and ability to start engine. The
`system predicts the time when the available energy will
`just meet the energy required to start the engine and
`then sends out a warning one hour before. The battery
`capacity available depends upon the amount of charg-
`ing before engine shutdown, the amount of discharge
`since shutdown, the rate of the discharge, and the
`battery state of health. The amount of energy required
`to start the engine depends upon the engine tem-
`perature and condition.
`As mentioned, the initial capacity of the battery can
`be determined when the engine is turned off by measur-
`ing the voltage drop due to the triple pump load. From
`the known initial charge it is possible to calculate the
`theoretical charge at any point in time by counting out
`the ampere-hours discharged. By assuming that the
`present discharge rate will remain unchanged, the
`battery capacity at any time in the future can be pre-
`dicted.
`The battery capacity required to start the engine at
`different temperatures is well defined as it is a value
`used in the vehicle design for battery sizing. These data
`relate only to the severest design case, where a loco-
`motive is to be started ’from cold after an overnight
`stand. They do not cover the case where a vehicle has
`stood for a short time and is then required to start. In
`this case the energy required to start the engine will be
`much less and using the data above will be very conser-
`vative, resulting in unnecessary warning messages. To
`allow for warm start cases, the temperature-start capac-
`ity relationship has been extrapolated to higher tem-
`peratures and the engine oil temperature is used.
`
`3.2.6 Engine monitoring
`The engine monitoring program carries out two tasks.
`Firstly, it monitors the engine to provide a record of its
`duty. Secondly, it identifies the cause of engine power
`loss due to isolation of the engine power control.
`Engine monitoring. When the engine is running, the gov-
`ernor air pressure, effectively a measure of engine power
`demand, is monitored and divided up into ten bands.
`The total amount of time spent in each band is calcu-
`lated and stored.
`Control relay monitoring. Power from the engine is con-
`trolled by the power control relay coil. Only when 110
`V is supplied to this coil can power be provided by the
`main generator. When the engine is started the coil is
`directly supplied with 110 V. After this, when the engine
`is running normally, the 110 V is supplied via a number
`of other contacts. These contacts are controlled by the
`correct operation of the power control relay, the power
`earth fault relay, the load regulator, the auto air gover-
`nor, the equipment governor and the control governor.
`When intermittent faults on these devices occur, the
`supply to the power relay coil is broken and the trac-
`tion power is cut off. If this happens while the engine is
`running under power, power is cut off to the traction
`motors, and cannot be reapplied for at least 30 seconds.
`This type of occurrence is obviously very inconvenient
`for the driver:
`When any of these devices has an intermittent fault it
`is very difficult to detect which one of them it is,
`because once power has been lost all of the healthy
`systems will react by opening their contacts as well. By
`the time the driver is able to examine the contacts it will
`not be possible to determine which contact opened first.
`It may also be difficult for the maintenance staff to iden-
`tify the causes of such faults.
`The analysis program monitors the voltage at each of
`the contacts, which control the supply to the power
`control relay, to see which contact opens first. When the
`state of any of the contacts changes the new condition is
`
`3.2.5 Oil monitoring
`Experience has shown that idling is the best condition
`under which to analyse oil system data because this
`condition is the most critical with respect to possible
`engine shutdowns. Oil pressure is affected by the oil
`temperature and engine speed, complicating the detec-
`
`Part F: Journal of Rail and Rapid Transit
`
`Q IMcchE 1995
`
`Downloaded from
`
`pif.sagepub.com
`
` by guest on March 7, 2014
`
`7
`
`

`

`DIESEL LOCOMOTIVE RELIABILITY IMPROVEMENT BY SYSTEM MONITORING
`7
`latched in hardware just after the change. The computer
`practice this means radio is the only option for cost-
`effective communications.
`then reads the status of the contacts and the analysis
`program decides whether the change was due to a
`Data communications between the vehicle and the
`maintenance controller are provided through the Voda-
`normal set of circumstances, such as the driver shutting
`fone mobile data service. Communications are generally
`down the engine, or a fault on one of the interlocking
`systems.
`good, though like any radio-based communications
`system, they are subject to certain limitations. Contact
`may not be possible if the land line to cellular conver-
`sion service is busy or if the vehicle is not in radio
`range, which can happen if it is located in a tunnel or a
`deep cutting, also if it is surrounded by high buildings
`or situated in a remote area not covered by the cellular
`network.
`For these reasons communications are generally
`better if the vehicle is stationary, provided it lies in an
`area of good radio reception. Communication with
`moving vehicles works with a reliability dependent
`upon the geography of the surrounding area. In practice
`this limits call duration, the line being lost as the vehicle
`moves into areas of poor reception.
`The required contact duration depends upon the
`amount of information to be transferred. For system
`development large quantities of logged data were down-
`loaded, this being done at night when the vehicle was
`most likely to be stationary and the Vodafone network
`was not busy. The contact duration for fault message
`transfer and vehicle interrogation is quite short (less
`than a minute), so loss of line does not affect per-
`formance too frequently.
`
`3.2.7 System self-monitoring
`In order to provide reliable information it is important
`that the monitoring system is able to identify faults with
`itself and ensure that such faults do not result in mis-
`diagnosis. Experience has shown that the automatic
`identification of monitoring system faults is vitally
`important if false messages are not to be produced and
`that in the majority of cases this can be handled fairly
`easily.
`A comprehensive set of self-monitoring procedures
`are set up that cover the detection of transducer/
`channel faults, the detection of power supply faults, the
`detection of clock faults and the detection of computer
`faults.
`
`4 DATA COMMUNICATIONS
`There is an advantage to having a continuous link
`available in order to receive fault messages from a