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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.
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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-
752
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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
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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.