IEEE TRANSACTIONS ON INDUSTRY AND GENERAL APPLICATIONS, VOL. IGA-7, NO. 6, NOVEMBER/DECEMBER 1971

Automatic Slow Speed Control for LocomotivesKENNETH 0. ANDERSON, SENIOR MEMBER, IEEE, AND WILLIAM E. KELLEY, SENIOR MEMBER, IEEE

Abstract-Special control apparatus has been developed and in-stalled on four 2500-hp 6-motor locomotives to automatically main-tain constant very low speeds for continuous loading of hopper carsin unit train service between coal mines and electric generatingplants. Speeds can be controlled in the span of 1/8 to 8 mi/h in threeranges (1/8 to 1/2 mi/h, 1/2 to 2 mi/h, and 2 to 8 mi/h) with exactadjustment possible in any of the ranges. Manual operation by anon-board crew directed by radio from the loading location is nowused. The special control apparatus presents the possibility of readilycontrolling train operation directly by radio from the loading loca-tion. The same locomotives are used in road service to haul the unittrains between mines and generating plants and may also be used forhumping and weighing in-motion operations.

BACKGROUND

THE SOLID-STATE computer-type apparatus for slowspeed control of diesel-electric locomotives was de-

veloped by the General Electric Company, primarily atthe request of the Pennsylvania Railroad, for very slowspeed handling of unit trains loading bulk commoditiessuch as coal and iron ore. The first application was for aunit coal train operation between a mine in westernPennsylvania and an electric generating plant in easternPennsylvania near Easton. These locations are approxi-mately 400 mi apart.

Locomotive units with conventional hump control sys-tems have been and are being used for this type of opera-tion with radio coaching from the tipple to the enginemanserving as the speed control. Since the control depends onthe reaction time of the engineman, there is a tendency toovershoot the desired speed and cause an erratic loadingoperation. The ability to control manually by hump con-trol becomes more difficult as tipple loading speeds andsize of unit trains are increased.

Investigation of several existing loading systems in-dicated an average tipple loading rate of 2500 ton/h. Atrain speed of 1/8 to 1/4 mi/h was found necessary to loada train of approximately 100 cars of 100-ton capacity in anacceptable time, which was considered to be on the orderof 4 h. Equipment was designed for slow speed loadingbased on these parameters.

Paper 71 TP 37-IGA, approved by the Land TransportationCommittee of the IEEE IGA Group for presentation at the 1967IEEE Industry and General Applications Group Annual Meeting,Pittsburgh, Pa., October 1-5. Manuscript received June 10, 1971.K. 0. Anderson is with the Transportation Systems Division,

General Electric Company, Erie, Pa. 16501.W. E. Kelley is with the Penn Central Transportation Company,

Philadelphia, Pa. 19086.

DESCRIPTION OF EQUIPMENTThe equipment for the automatic slow speed control is

packaged in several modules. The auxiliary control panelwith which the engineman selects the desired slow speedis shown in Fig. 1 as it is mounted on top of the air-brakestand. A detailed view of the face of this panel is shown inFig. 2. The speed sensor, which mounts on the journalbox to measure axle r/min and thus provide a feedbacksignal, is shown in Fig. 3. M\lechanical connection from theaxle is through an internally splined hose to the shaftshown in Fig. 4. Internal details of the sensor are illustratedin Fig. 5.To complete the equipment needed for a "lead unit" loco-

motive, three additional equipment modules are installedin available space immediately behind the operator's com-partment. The first of these, commonly called the "logicbox," contains solid-state components mounted on pull-out cards. This box, shown in Fig. 6, is easily transferablebetween units. A typical pull-out card is shown in Fig. 7.Each lead unit also has a permanently installed "basicbox," illustrated in Fig. 8. This box contains a group ofcontrol relays and resistors, and also includes the plugconnection to the transferable logic box. To operate in theslow speed mode, every unit must contain a "trail only"box of the sort depicted in Fig. 9. Included here is the powertransistor and its associated circuitry to directly feed theexciter field on that unit.The initial installation of this equipment was made on

four locomotive units. Two of the units had the trail onlybox installed. On the other two, all of the equipment, ex-cept the logic box, is permanently installed. Installation ofthis box, of which only one was furnished, completes theequipment needed for lead unit service. Either of the twolatter units can also function as a trail unit if desired. Thenet result of this method of packaging the equipmentkeeps the investment to a practical minimum and yetprovides adequate flexibility and continuity of the specialservice even though one unit may be temporarily out ofservice for inspection or maintenance.

In operation, the engineman positions the train with thefirst hopper car in place to start loading. He will then turnthe selector switch on the auxiliary control panel to theappropriate speed range, which turns on the automatic slowspeed equipment, as indicated by the pilot light. The speedadjustment potentiometer knob will also be adjusted tothe approximate desired speed within the selected range.The engineman then releases the brakes, pulls the throttle

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ANDERSON AND KELLEY: SPEED CONTROL

Fig. 1. Auxiliary control panel for slow speed operation as mountedon air-brake stand.

Fig. 3. Speed sensor mounted on locomotive journal box.

Fig. 2. Face of auxiliary control panel.

out to notch 1/2 or higher (exact throttle position makesno difference), and proceeds with loading. By means ofvoice radio from the tipple, instructions to speed up orto slow down, as they are needed, are relayed to him. Theloading proceeds in this manner until it has been com-pleted.The automatic speed regulation equipment controls

application of power only. No interconnection with thebraking system is provided. In use, loading on a slight up-grade is desirable. Experience has shown that a com-pensated grade of about 1/4 percent is near optimum. Ifit were necessary to control a precise slow speed on a down-grade, this could be done by making a small brake pipereduction with the automatic air-brake equipment andletting the locomotive units pull the train against thebrakes. At this very low speed no damage or undue wearon wheels or brakeshoes would occur.

Fig. 10 is a block diagram of the automatic slow speedequipment. At the upper left are the speed range selectorswitch and the exact speed control potentiometer on theengineman's auxiliary control panel. Setting of these deter-mines the output pulsewidth of the pulse generator,which is the "desired speed" signal, with this signal further

Fig. 4. Drive end of speed sensor.

Fig. 5. Internal details of speed sensor.

IEEE TRANSACTIONS ON INDUSTRY AND GENERAL APPLICATIONS, NOVEMBER/DECEMBER 1971

Fig. 8. Basie box for lead(-ullit locomotive, showing plug connectionto logic box.

Fig. 6. Logic box containinhg pill-out panels; plug connection onfar side is hidden from view.

Fig. 7. Typical pull-out card from logic box showing solid-statemounting.

squared and amplified by the combination of gated timer1 and flip-flop 2.

Principal components of the speed sensor are a light-emitting diode shining through a slotted rotating disc(driven from the axle) onto a light-sensing diode. Electricaloutput of this diode is an ac voltage, essentially sinusoidalin waveshape, alternati.g at a frequency proportional tothe axle r/min. Also mounted in the speed sensor is an

Fig. 9. Trail only box which is installed on both lead- and trail-unit locomotives that are equipped for automatic slow speedoperation.

amplifying and squaring circuit that shapes the detectoroutput and amplifies it to a level that can be transmittedthrough the flexible cable to the other equipment in thecab without spurious signals being introduced by electricalnoise.Even though the automatic slow speed control equip-

ment is used only at low locomotive speeds, no damage isdone to the speed sensor rotating elements at the maxi-

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ANDERSON AND KELLEY: SPEED CONTROL

. -7ENGINEMAN'CONTROL PANEL

PiEXACT ,,--"SPEED --_CONTROLPOT. SPEED

RANGESELECTORSWITCH

SLOTTEDLIGHT DISCEMITTING.> r-t \ --lil

IC RC IT I

SPEED SENSOR /(MOUNTED ONJOURNAL BOX)

DESIREDSPEEDSIGNAL

TOO SLOW TOO FASTWAVE FORM WAVE FORM

AND -NOR4 LOGIC

PANELS I

EXCITERFIELD

-

LEAD UNIT 1UNIT(S)-

Fig. 10. Automatic slow speed control equipment.

mum road-haul speeds of 70 mi/h since the slotted disc isformed by the etching of a metallic surface on a glassplate. This disc has a total of 360 slots, each one 1/2 deg inwidth.

Because of the severe mechanical shocks to which thespeed sensor is subjected in operation, particularly at highspeeds, no miniature lamp available would stand up. Thelight source chosen is a type LED-10 light-emitting diode,which provides sufficient intensity for the type 14A501light-sensing diode to produce a usable signal.The signal transmitted from the speed sensor through the

flexible cable goes first to a Schmitt trigger circuit, whichmakes it a nearly perfect square wave of the same fre-quency as the sensor frequency, then into flip-flop 1, whichcuts this frequency in half. This output then goes toflip-flop 2 to turn on the reference time base signal. Theturn-off signal comes from gated timer 1, as previouslydescribed. Outputs of flip-flop i 1 and 2 are compared inlogic panels Al and A2 to determine the sense of the speederror and its magnitude, with pulsewidth being propor-tional to error.

Corrective feedbacks are also provided for extremes ofspeed condition. A feedback from flip-flop 2 normallyprevents gated timer 2 from firing. If not, its output,through flip-flop 4, turns on logic panel OR to ensure that a

true "too slow" signal is at the output of this panel. Thisis the condition that will govern when the locomotive isstopped since output from the speed sensor will be zerofrequency at that time. Alternatively, a false "too slow"signal could be generated if the locomotive is operating atmore than twice desired speed. A feedback from the "toofast" channel through flip-flop 3 as an auxiliary input tologic panel Al acts as a lockout for thlis false "too slow"signal.

Corrected and verified output signals from the logicpanels, still in two channels, are delivered to the propor-tional panel and to the integrator panel. In the former, anoutput signal is produced which is proportional to theamount of error in speed. In the latter, an output signalis produced which is the integration of the speed errorwith respect to time. By this means, correction in speed isproduced more quickly than if the integrated signal onlywere available. The integrated signal provides a constantexcitation signa]; Both of these outputs are fed intowindings of the reactor in the pulsewidth modulatorpanel which directly controls the power transistor on eachunit feeding the exciter field. Typical waveforms, showingschematically too slow and too fast shapes, as they mightappear on an oscilloscope, are included Fig. 10. A part ofthe circuitry in the proportional panel provides for a slow

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IEEE TRANSACTIONS ON INDUSTRY AND GENERAL APPLICATIONS, NOVEMBER/DECEMBER 1971754

turn-on feature so that initial increase in speed from astopped condition is gradual.Those portions of the slow speed control equipment

dealing with excitation, as previously described, are en-tirely solid-state devices. Several control relays are used toestablish the proper circuitry at time of setup and inselecting the desired speed range, as well as to control dieselengine speed, which is at the fifth notch in the lower twospeed ranges and at the eighth notch in the 2-8 mi/h range.Three multiple-unit trainline wires are used for this specialequipment. This number could be reduced with some lossin operating convenience.Problems encountered during development of this equip-

ment were those normally expected. It was found necessaryto provide additional shielding against electrical noise andmeans to keep harmful spikes out of the solid-state devices.Some problems in stability, common to most servo-mechanism circuitry, were encountered. These were over-come in the normal process of testing and circuit modifica-tion.

RESULTS AND EVALUATION

The slow speed control equipment does the job as in-tended, providing accurate automatic speed regulation ata very low speed with adequate range of adjustment. Theincreasing weight of the train as it is loaded does not pro-duce an inaccuracy. When loaded, the train is ready to goon the line haul to the generating station. No need existsto change motive power, to make an air-brake test, or doother operations which could result in a prolonged delay.As a result of the successful experience on these four

units, similar equipment has been installed on several in-dustrial locomotives used in both loading and unloadingoperations. These have a radio link giving a remote opera-tor full control; consequently, no on-board crew is used.This equipment is also being considered for hump loco-motives in large new railroad classification yards, where aconstant speed at the hump is highly desirable and constantcoaching of the engineman by the tower operator producescongestion on the yard radio circuits.

Kenneth 0. Anderson (M'48-SM'54) was born in Oskaloosa, Iowa, on December 7, 1923.He received the B.S. degree in electrical engineering from Iowa State University, Ames, in1947.Following graduation, he joined the General Electric Company as a Test Engineer with

training assignments in several plants and departments. He also pursued that company's Ad-vanced Engineering Program and is a graduate of the Creative Engineering Program. Since1950 he has been with the Locomotive Products Department of the Transportation SystemsDivision, Erie, Pa., in various locomotive sales and service assignments. He is presentlyManager, Maintenance Engineering and Education.Mr. Anderson is a member of Tau Beta Pi, Eta Kappa Nu, and Phi Kappa Phi.

William E. Kelley (M'41-SM'51) was born in Altoona, Pa., on July 29, 1918. He received theB.S. degree in electrical engineering from Pennsylvania State University, University Park, andthe M.S. degree in electrical engineering from the Drexel Institute of Technology, Philadelphia,Pa.He joined the Pennsylvania Railroad in June 1940 as a Junior Engineer in the Maintenance

of Equipment Department. He has remained with that company and its successor, the PennCentral Transportation Company, to the present. Since 1947 he has held various positionsin connection with engineering for locomotive and car equipment and fixed facilities in theElectrical Engineering and Equipment Engineering Offices, Philadelphia. He is presentlySenior Electrical Engineer-Equipment.Mr. Kelley is a member of Eta Kappa Nu, Tau Beta Pi, the Association of American Rail-

roads, and the Locomotive Maintenance Officers' Association.