Note: Descriptions are shown in the official language in which they were submitted.
CROSS REFERENCE TO RELATED APPLICATIONS
me present application is related to the following
Canadian patent applications which are assigned to the same
assignee as the present application:
Serial Number 283,308, which was filed on July 21, 1977
by J. H. Franz and entitled Transit Vehicle Chopper Control
Apparatus And Method;
Serial Number 281,520, which was filed on June 28, 1977
by T. C. Matty and entitled Transit Vehicle Motor Effort Control
Apparatus And Method;
Serial Number 281,594, which was filed on June 28, 1977
by L. W. Anderson and J. H. Franz and entitled Transit Vehicle
Generated Voltage Control Apparatus And Method; and
Serial Number 283,312, which was filed on July 21f 1977
by T. C. Matty and J. H. Franz and entitled Transit Vehicle
Electrical Brake Control Apparatus And Method.
.......
'1~ 2 ~ 6,849
BACKGROUND_OF THE INVENTION
The present invention relates to the application
of thyristor chopper apparatus for determining the propul-
sion power and electric brake operations of a transit vehicle
having series propulsion motors, and more par-ticularly to
control apparatus including a microprocessor that is pro-
grammed for the desired control of such thyristor chopper
apparatus~
Direct current power has been supplied to the
series propulsion motors of a transit vehicle with a thyris-
tor chopper, such as disclosed in U.S, Patent ~,530,503
issued September 22, 1970 to H. C. Appelo et al, for con-
trolling the acceleration and speed of the vehicle by
turning the propulsion motor current ON and OFF in a pre-
determined pattern. The thyristor chopper can provide
either regenerative braking or d~namic braking when braking
is desired.
In an article entitled Automatic Train Control
Concepts Are Implemented By Modern Equipment published in
the Westinghouse Engineer for September 1g72 at pages 145
to 151, and in an article entitled "Propulsion Control For
Passenger Trains Provides High Speed Service" published in
the Westinghouse Engineer for September 1970 at pages 143
to 149, there is described the operation of the P signal
for controlling all powered vehicles in a train to contribute
the same amount of propulsion or braking ef~ort.
In an article entitled Alternative Systems For
Rapid Transit Propulsion And Electrical Braking~ published
in the Westinghouse Engineer for March, 1973, at pages 34-
41, there is described a thyristor chopper control system
for propulsion and electrical braking o~ transit vehicles.
Ll 6, ~34~
112~
~he thyristoI chopper provides a propulsion system that is
superior in smoothness and ease of maintaining a given
speed, which latter feature is desired for automatic train
control. Moreover, the thyristor system makes regenerative
braking practical because the response is fast enough to
continuously match regenerated voltage to line voltage, and
that matchirlg prevents excursions in braking current and
torque due to suddell transients ill line voltage. The reduc-
tion in power consumptioll that results from regenerative
braking can be significant 5 but another advantage is in
relation to minimizing heat input to tunnels otherwise
caused by dynamic braking.
The use of presently available microprocessor
devices~ such as the Intel 8080 family of devices~ is des-
cribed in a published article entitled "Microprocessors -
Designers Gain New Freedom As Option6 Multiply" in Electronics
Magazine for April 15, 1976 at page 78 and in a published
article entitled "Is There A High-Level Language In Your
Microcomputer's Future?" in EDN Magazine for May 20, 1976 at
page 62.
SUMMARY OF THE INVENTION
:
A programmed microprocessor apparatus establishes
at least one limit for each of a vehicle speed signal for
controlling the operation of the braking resistors to deter-
mine the motor electric braking effort in the brake mode and
the chopper phase angle signal for controlling the fleld
shunt operation of the motor to determine the motor tractive
effort in the power mode for more than one program cycle.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a functional showing of the present
--3--
~ 2 ~ 46,849
control apparatus in relation to the input signals and the
output signals operative with the control apparatus;
Figure 2 illustrates the input signal operations
and the output signal operations of the present control
apparatus;
Figures 3A and 3B illustrate schematically the
provided interface of the present control apparatus;
Figure 4 illustrates the coding of the program
listing included in the appendix;
Figure 5 shows a well Icnown operational charac-
teristic curve for a typical series propulsion motor opera-
tive with a train vehicle and the present control apparatus;
Figure 6 illustrates the speed signal determination
in accordance with the present invention;
Figure 7 illustrates the relationship of requested
current as a function o~ speed provided by the present
invention;
Figure 8 illustrates the provided electrical brake
fade out in relatlon to the operation of the mechanical
brake; and
Figure 9 illustrates the phase angle sensing
operation provided by the present invention.
DESCRIPTION OF A PREFERRED EMBODIMENT
In Figure l there is shown a functional illustra-
tion of the present control apparatus in relation to the
input signals and the output signals operative therewith,
and including a CPU microprocessor 94 operative with a PROM
programmable memory 96 and a scratch pad RAM random access
memory 98 used for intermediate storage. The application
program, in accordance with the program listing included in
'~ '
~ ~ 2~ ~ 9 46,849
the Appendix, is stored in the programmable memory 9~. The
microprocessor 94 can be an INTEI 8080, the random access
memory 98 can be an INTEL 8101, and the programmable memory
96 can be an INTEL 1702 programmable read only memory, which
items are currently available in the open marketplace.
There are ~our illustrated categories of input and output
signals relative to the processor controlled operation of a
transit vehicle. The digital. input signals are supplied
through digital input. 100 from the transit vehicle and
include the slip slide signal SLIP, the thyristor temperature
sensor thermal overload signal THOUL, the effective value of
the line filter capacitor as indicated by the fuse counter
signal FUSE, the power circuit condition indication signal
LCOC, the power and brake feedback signal BFEED, the field
shunt feedback signal FS, the brake status signal BRKI and
the clock signal 218 Hz. The analog input signals are sup-
plied through analog input 102 and include the first pro-
: pulsion motor leg current Il, the second propulsion motor
leg current l2, the line curren~ IL, the line voltage LV,
the primary power request or brake request control signal P,the air pressure in the vehicle support bag members pro-
viding load weighed current request signal IRW, the analog
phase signal IP and the vehicle actual speed signal S1. The
digital output signals are supplied through digital output
104 to the controlled transit vehicle and include the line
switch control signal LS, the power brake mode control
signal P/B, the field shunt control signal FS, the first
braking resistor control signal BCl, the second braking
resistor control signal BC2, the third braking resistor
control signal BC3, the zero ohm field shunt control signal
--5--
~,
~ 46,843
BDC, the 10 kilometer per hour signal 10 KPH, the 25 kilometer
per hour signal 25 I~PH, the phase zero control signal 0O,
the timing signal BOOST, the ON suppress control signal SUPP
and the zero speed signal ZS. The analog output current
request signal I+ is supplied through analog output 106
going to an analog phase controller loS operative to supply
the control signal ON to fire the chopper thyristor Tl, the
control signal ~FF to fire the commut~ting chopper thyristor
T3, the control signal T~ for the T5 thyristor in the pro-
pulsion motor control c~lopper apparatus and the analog phaseindication signal IP going to analog input 102. The time
period associated with turning the chopper ON and OFF is at
a constant frequency of 218 Hz, that defines the clock time
interval for the program cycle and for checking the process
operation. During each of the 218 time intervals per second,
the program cycle operates through the application program.
It was necessary in the prior art for some of the input
signals to be filtered to slow down the effects of noise
transients and the like, but the computer program now sample~
the input signals 218 times every second, so if desired each
signal can be checked during each program cycle and if the
signal stays the same as it was before the proper response
can be provided. By sampling all the input signals every
program cycle and by addressing every output signal every
program cycle, if noise transients are received, their
effect can be minimized or eliminated. ~or the output
signals, a correct output can be given 5 milliseconds later,
faster than the power response time. For the input signals,
digi'al filtering by comparison with old data can eliminate
transient effects.
--6--
~ 2~ f 9 46,849
The train control system operative with each
vehicle provides a P signal which selects a desired propul-
sion effort and thi~ signal goes from O to 100 milliamps and
establishes how much propulsion power or braking effort is
desired by a particular train vehicle. The P signal is
decoded to determine the proper motor current to generate
the proper effort. In addition, there is a confirming
signal, called the ~RI~I signal which determines when pro-
pulsion power and when bralcing effort is applied. The
purpose of the ~RKI signal is to control the power switching
at the correct time to avoid one car braking while another
car is in propulsion. Contact closures in the power cir-
cuitry are detected to establish that the power contacts
have been made up properly and to read~ust the settings in
the logic. For instance, in field shunt operation, the
a~ount of motor current is adjusted to keep from getting an
undesired physical ~erk of the vehicle. A failsafe reading
of the P signal level is made such that, should the P signal
be lost, the train control automatically goes into a brake
mode. The present propulsion control apparatus determines
which switches to close and when to close them to modify the
power circuit pro~erly. A dynamic brake feedback signal is
sent to the mechanical brake control for providing the
blending of mechanical brake necessary to maintain the
- deceleration level required by the P signal. The P signal
is in reality a vehicle acceleration or deceleration request.
The propulsion control apparatus provides output
pulses to the main power thyristors to tell them when to
turn ON and when to turn OFF. When a command signal is
sensed, for example, if the vehicle is in propulsion or
--7--
,, ~ .
. ,
l6,849
~ 7 ~
power mode aIl~ t.ht' com~ar!d ~ignal d~sires the vehicle to
bral;e, the control apparatus senses any difference between
the desired motor current and the actual ~otor current and
ramps down the actual current as required. When the current
gets down to a desired level, the control apparatus opens
all the propulsion switches and reconnects for a brake
operation, thcn ranlps the nlotoI7 culrent back up again to the
level establishe~ by the desired brake operation.
In Figure 2 ther* is illustrated the input signal
operations and the output signal operations of the present
control apparatus, including the microprocessor 94 operative
with its random access memory 98 and its programmable memory
96. The analog input signals are supplied through the
analog input 102, through the multiplexer 120 and analog-to-
digital converter 122 and input port 124 of the micropro-
cessor 94 operative with a data bus 126 and address bus 128.
The address bus 128 and data bus 126 are operative through
an output port 130 to control the multip1exer 120 and the
analog-to-digital converter 122. The digital input signals
are supplied through the digital input 100 operating through
buffer 132 with the input port 136 operative with the data
bus 126 and the address bus 128. The digital output signals
are supplied through digital output 104 including output
ports 140 and 142 and respective isolation circuits 144 and
146 with drivers 148 and 150 in relat~on to the data bus 126
and the address bus 128. The analog output 106 is operative
through output ports 152 and 154 through a buffer 156 and a
digital-to-analog converter 158 with the analog phase con-
troller 108.
The central processor 94 addresses a particular
--8--
46 84g
1~2~6~9
input port or output port or memory location and then transmits
data to, or receives data from, that location on the data
bus 126. For example, the central processor 94 can address
an input port, such as input port 124 for the analog-to-
digital converter 122 and the multiplexer 120. First it
presents data to output 130 to tell the multiplexer 120
which analog circuit input signal is desired. Each analog
signal has some sort of bufferillg, such as a differential
amplifier or a low p~ss fllter. When the particular input
is addriessed, the analog-to-digital converter 122 cycles for
converting that data. The digital feedback signals from the
digital feedback 100 come in and can be read whenever desired.
A monitor or display panel 192 can be provided to indicate
the state of operation of the central processor 94. The
output port 153 is operative through digital-to-analog
converter and buffer amplifier 194 with the provided test
point 190 and is operative with display 192. The manual
switches 196 are operative with input port 137 as shown.
- The P signal goes through the multiplexer 120 to
request a particular vehicle operation. The control pro-
cessor 94 senses the various currents, the various voltages
apd the vehicle speed. It takes digital feedback signals
through buffers to know what is going on in the power cir-
cuit in relation to currents and voltages. The control
processor 94 provides output command signals to the power
circuit. Command signals go on the data bus and o~ltpUt
ports function as latches so the control processor 94 can
proceed to do other things while each latch remembers what
is on the data bus at a given address. The control pro-
cessor 94 outputs a signal to close whatever power switches
_g_
,
. ~,
1~2~ 4 ~, 8 4 9
are desired and also outputs a requested motor current. Therequested motor current is decoded in a digital-to-analog
converter. The analog motor control circuit, in response to
this current request, senses the actual motor current and
the commutating capacitor voltage, and if everything is
satisfactory, the motor control circuit appropriately fires
the drivers for the cl~opper apparatus.
In relation to effort versus motor current, at up
to about 100 amps, a typical series propulsion motor as
shown by Figure 5 provides little practical effort, and
above 100 amps the characteristic looks more or less like a
straight line. As speed increases there is wind resistance,
so the effective effort available is actually less in power,
and in braking, the reverse is true. When power is re~uected
motor current comes up to the P signal requested level at a
jerk limited rate. The vehicle increases its speed because
of the effort supplied. ~he phase increases with speed, and
when the phase approaches almost 100%, the full field opera-
tion is completed and the field shunt is used to weaken the
motor field, and this provides a transient response problem;
a very fast controller is required, such that it can pro-
perly control the phase on the thyristors. In actual prac-
tice, propulsion power is easier to control because in power
a particular phase angle sets a percentage of line volts on
the motor and this will give a particular amount of motor
current, such that if the phase is set at 50%, a particular
amount of current is provided in power operation for a given
speed. In brake operation, this same relationship is not
true since brake operation is more unstable. If the phase
3G is held at a desired place in power operation, the motor
--10--
~ 6~ 9 46,849
current is stable; if a particular phase setting is held in
brake operation, the motor may go to overload or to zero.
If it is desired to initiate brake operation, the control
apparatus has to command brake which ramps down the motor
current on a jerk limit, then opens up the power switches
and reconnects the power swit:ches for brake operation;
thereafter, the control apparatus goes into brake operation
and ramps up the motor current to give the torque necessary
to get the desired brake effort. The motor may be generating
a considerable voltage that goes baclc intc, the supply line
so a resistor is put into the circuit to dissipate the
excess voltage. As the vehicle comes down in speed, the
motor counter EMF drops and the chopper can no longer sus-
tain the motor current, so switches are operated to change
the resistors to maintain the desired motor current. If
the line voltage exceeds a particular value to indicate that
the line is not receptive and will not accept the generated
current, the motor current is reduced if no dynamic braking
resistor is used with dynamic resistors in the circuit, if
the line voltage becomes excessive, the motor current is
shunted into the dynamic braking resistor.
In Figures 3A and 3B there is schematically illus-
trated the provided interface of the present chopper logic
control apparatus. The digital input 100 is shown in Figure
-~ 3B operative through the buffers 132 with the input port
136. The analog input 102 is shown in Figure 3A operative
through multiplexer 120 and the analog to digital converter
122 with the input port 124 of the microprocessor. The
output port 130 is operative with the register 131 to con-
trol the multiplexer 120 and the analog to digital converter
_ ....
~ 6 ~ ~ 46,349
122. The output port 152 is shown in Figure 3~ operative
with the digital to analog converter 158 and the analog
phase controller 10~; the output port 106 is shown in Figures
3A and 3B operative through buffer amplifiers 156 with the
drivers 109, 111 and 113 for controlling the respective
thyristors Tl, T2 and T5. The output port 142 is shown in
Figure 3B operative wi~h the isolation amplifiers 146. The
output port 140 is shown in Figure 3B operative with the
isolation amplifiers 144. The output port 153 is shown in
Figure 3B operative with isolation amplifiers 194 and test
point 190 and operative with display 192.
The pump circuit 151 operates to verify the proper
working of the present control apparatus including the
microprocessor 94 before the line switch is picked up and
the desired propulsion motor control operation takes place.
A dummy boost signal is initially put out at program line 16
to enable the line switch to be picked up, and during the
main program operation if something goes wrong the boost
signal disappears and the line switch drops out. The Y
carrier shown in Figure 4 has added to it the boost bit, and
then time is called to wait as shown by the code sheet; the
Y carrier indicates whether the OFF suppress or the ON
suppress is called for.
The load weighed current request signal is output
by amplifier 153. Then the buffer 155 leads to the phase
controller amplifier 157, which takes the current request
signal from buffer 155 and the motor current signals Il and
I2 from lines 159 and 161. The output of controller ampli-
fier 157 is the requested OFF pulse position or the phase
angle IP. The output of the amplifier 157 is compared by
-12-
. . .
~ ~ 2Z~ 9 )-16,~49
comparator 163 ~ith the timing ramp from amplifier 165 which
is reset by the computer each 218 Hz. The comparator 163
establishes when phase angle signal IP has exceeded the
timing ramp, and this would determine at the output of
comparator 163 where the OFF pulse is positioned. The logic
block 167 determines whether or not the OFF pulse position
output of comparator 163 is actually used. For example, if
comparator 169 determines there is too much current in the
s~stem, the OFF pulse wi]l be fired and might inhibit or
suppress the ON pulse in lo~ic bloclc 1~1 which is operative
with the ON pulse. The boost pulse comes from the computer
and goes into the logic bloclc 167 on line 173, and will fire
an OFF pulse on the leading edge if comparator 169 has not
already fired a pulse and suppress any further action out of
the control system. The logic block 167 includes a flip-
flop operative such that if an OFF pulse is fired once
during a given program cycle, a second OFF pulse is not
fired during that same program cycle. The power up restart
circuit 175 suppresses pulses with the control system has
time to operate properly. The circuit 177 is a monostable
to assure that only a pulse is output, and circuit amplifier
111 drives the OFF pulse going to the gated pulse amplifier
for thyristor T2. In power mode the FET switch 179 is
~; closed to provide the desired motor characteristics com-
pensation signal, and in brake mode, this switch is opened
to provide a faster controller operation. The amplifier 181
checks the phase controller 157 to see if the signal IP is
all the way up against the bottom stop to indicate too much
current, and if so, the circuit 171 suppresses the ON pulses;
this is used when starting up in power to skip ON pulses.
-13-
~ 7 ~ 46,849
The ON pulses are suppressed by the power up circuit 183.
The ON pulses use the monostable 185 and the driver 109 as
in the operation for the OFF pulses. The safety enable
signal or pump circuit 151 will stop the firing of an ON
pulse if repetitive boost signals are not provided. The FET
switch 187 energi2es the line switch output, such that if
there is no activity on boost signal line 173, then the pump
circuit 151 will cause FE~ switch 1~7 to keep the line
switch dropped. The T5 signal comes from the computer to
fire the ~5 thyristor, and monostable 189 drives the driver
circuit 19i going outside to the ~ated pulse amplifier for
the ~5 thyristor. The phase controller 108 includes the
operational amplifier 157, with its attendant compensation
for power and brake operations. The computer can force the
controller 108 from output port 3-0 to zero for startup.
The pumping circuit 151 checks the activity of the computer
by looking at the boost line 173 for snubbing the provision
of ON pulses and thereby controls the line switch. If the
line switch is out, the propulsion and brake control system
cannot operate the chopper apparatus, so if something is
wrong, it is important to snub the ON pulses quickly, be-
cause the line switch takes time to drop out; for this
reason an effort is made to stop the ON pulses when some
control apparatus malfunction occurs and is sensed by the
boost signals no longer being provided.
Figure 4 illustrates a code sheet that was used to
de~elop the program listing included in the Appendix. As
shown in Figure 4 and in reference to Figure 2, output port
1 ~shown in Figure 2 as 153) was used for a test mode,
30 output port 3 (shown in Figure 2 as 154) was used for analog
-14-
~ 6,849
n~nipulation, output port 4 (shown in Figure 2 as 152) was
used for analog command si~nal output, output port 5 (shown
in Figure 2 as 142) and output port 6 (shown in Figure 2
divided into four bits each for 140 and 130) were used for
digital command signal outputs, input port 4 (shown in
Figure 2 as 136~ was used for digital input data, input port
5 (shown in Figure 2 as 124) was used for analog input data
and input port 6 (shown in Figure 2 as 137) was used for
test purposes in relation to manual input switches.
In Figure 5 there ls shown a motor characteristic
for a well-known series Westinghouse traction ~otor of Type
1463 operative through a 5.58 to 1 gear ratio with 30 inch
vehicle wheels.
SPEED SIGNAL HYSTERESIS
The values of the brake resistors are selected for
inherent stability of the system operation during brake mode.
In reference to Figure 5 for a given supply line voltage as
seen by the vehicle motor, reali~ing that Figure 5 relates
to one motor and for two motors connected in series an 800
volts su~ply line would provide in the order of 400 volts
across each motor, when the chopper is switched off the
circuit should cause a motor current decrease in brake mode
of operation. When the chopper is switched ON, the motor
current should increase. For an 800 volts power supply
line, about 400 volts is applied across each motor, and if a
well-known load line is applied to Figure 5, the slope of
that line ~ould be a function of the resistance of the motor
circult with the motor considered to be a generator in the
brake mode, the motor circuit includes ~ resistance and the
voltage across the motor is determined by the spced of the
-]5-
~ 2 ~ 46,8ll9
motor and the requested motor current. On an average basis
of the chopper operatio~, the voltage generated by the motor
minus the motor circuit resistance IR drop must be equal to
the supply line voltage. If the generated voltage minus the
IR drop exceeds the supply line voltage, then a larger
current will resul~ and a lesser current will result if the
opposite is true. The ~otor is operating as a generator, so
the more current requested from the motor causes the motor
voltage to go higher, since more current will cause more
volts to be generated. In e~fect the generator is operat~ng
as a negative impedance device, and to assure stability o~
the circuit the positive resistance added to the circuit has
to be greater than the negative resistance of the generator.
Thusly, this limits the requested brake current available to
avoid having the generated voltage exceed the line voltage
and bring about an unstable system operation. In an effort
to obtain the desired brake current magnitude, resistors are
inserted into the circuit to provide a different slope to
the load line in relation to the vehicle speed. When the
chopper is OFF, the line voltage plus the IR drop should be
greater than the generated motor voltage. When the chopper
is ON, it more-or-less shorts the supply line and the ap-
plled supply line voltage goes down to near zero volts and a
net positive voltage results. A chopper ad~usts the time
spent OFF at the higher applied supply line voltage compared
to the time spent ON at the lower applied near zero supply
line ~oltage, so the average voltage intercepts the speed
characteristic curve at the desired motor current ~or the
desired brake effort operation. As the vehicle slows down,
the chopper has to be ON more to maintain this brake motor
-16-
~ ~ ~2 ~ ~ ~ 46,849
current until ~he chopper is ON full time and with no other
action then the current would begln to decrease. The motor
circuit resistance value can now be changed at some point as
a function of vehicle speed, to change the slope of the load
line and this permits the chopper to operate at a lower
speed. Thusly, the brake resistors are inserted into the
motcr circuit ~or the u~per speed operatio1l of the motor,
and when the motor speed gets below a determined value the
resistors are switched out of the circuit to improve the
controi range of the chopper circuit. The resistors have to
dissipate a considerable amount o~ energy as heat loss in
the regenerative brake mode and this should be minimized by
changing the resistance as soon as practicable in relation
to a reasonable number of brake resistors and switches and
the time required to do this. In the operation of the Sao
Paulo equipment at about 70 MPH the ~irst resistor is
, changed, at about 60 MPH another reslstor is changed, and at
about 40 MPH the last resistor is switched out.
The speed signal sensing operation for this pur- -
2~ pose requires a stable speed signal to determine the switch-
ing of these brake resistors, and further it is not deslred
to switch these resistors into and then back out of the
motor circuit as a result of noise signal effects and the
like. The whole motor circuit would be significantly dis-
turbed by such a practice. For each resistor change that is
made, the motor is generating so many volts, the supply line
is providing so many volts and a sudden resistor change
creates a delta voltage condition in the motor circuit, and
to reestablish the desired circuit operation level the
3P cho~per phase angle is changed. The chopper operates to
-17-
.,~
~:~2~67~ 46,849
determllle the net voltage across the motor circuit, in-
cluùing inducta1-lce. Tl~e current rate of change is deter-
mined by the voltage across that inductance.
The measured vehicle actual speed Sl varies as
required b~ the desired tr~nsit vchicle performance. The
internal prograll) spee~ S shown in Figure 6 as curves 160 and
162 is made to rollow ll~e ~easured a~t;ual speed Sl shown by
curve lG4. The progralll speed S sllown by curve 160 follows
in the up direction of the actual speed and the program
speed S shown by curve 164 follows in the down direction of
the actual speed. Wherl the actual speed Sl shown by curve
164 and on line 166 is increasing, the program speed S shown
by curve 160 is at a predetermined di~ference such as 1 KPH
less; and when the actual speed Sl shown by curve 164 and on
line 166 is decreasing, the program speed S shown by curve
162 is at a predetermined difference such as 1 KPH greater.
This results in the program speed S following ~ehind the
actual speed by the 1 KPH difference until the actual speed
Sl reverses and begins to decrease, at which time the pro-
gram speed S would stay at the same value until the actualspeed Sl decreased to 1 KPH below the program speed, and the
program speed S would then follow at 1 I~PH above the actual
speed. If, for some reasonl a noise perturbatlon of the
speed vehicle actual reading taken from a tachometer opera-
tive with a wheel axle should occur, this might otherwise
needlessly trip the switch contactors in the brake resistor
circuits, and a considerable number of other speed relzted
decisions are made in the course of the program operation.
If the actual speed Sl is greater than the program speed S
plus three units (about 1 KPH) in program line 91 then the
-18~
, ., -,
", ~
~ 2 ~6 ~ ~ 46,~L19
program sp~ed S ~s incremented by olle, and if the program
speed S is greater than the actual speed Sl plus three in
program line 92 then thc program speed S is decremented by
one, which provides 11l efrect a two K~H speed signal hystere~is
band. It was known in the prior art to provlde a hysteresis
effect for each speed sigllal decision operatio~al amplifler,
but not to involve mal~y runctions of the same speed variable
and put the hysteresis Oll the speed variable before making
the many desired fun~tional decisions.
Bec~use there are a number of decisions that are
made throughout the whole program in response to vehicle
speed, by providing this hysteresis eff`ect, the general
problem of oscll~ating decisions in relation to sensed speed
is avoided. Every time a decis1on level in speed is reached,
the speed has to be determined by this provided hysteresls
band before the control action responds ~or the rest of the
program operation.
The internal artificial parameter S is established
in relation to Sl the currently read actual speed, so the
parameter inside the program is related to the actual speed.
At program line 91, if the actual speed Sl is greater than S
3~ such that the new value of speed or the currently read
value of speed is greater by a magnitude of 3 more than the
progr~m speed S, then the program speed S is incremented by
1 once every program cycle. First, this operation gives a
bulk hysteresis on all decisions made on measured actual
speed and secondly it acts as a f`ilter because the internal
~peed S is changed only one increment per program cycle. If
there is any noise in the measured speed, the program speed
S will only change by a small amount once per cycle. A
--19--
~ 6 7 ~ 1~6,~49
hysteresis condition is put on measured speed by requiring
that the newly measured actual speed changed by an amount
greater than 3 units, and then only allows a one unit change
to the speed S seen by the program.
Since the program speed moves faster than the
vehicle speed S only ncise is filtered ou~, and the actual
speed is not a~fected.
ELECTRIC BRAKE EFFORT FADE OUT
The brake fade out OCCUI'S after all the brake
resistors are out of the motor circuit, and the thyristor
chopper is full ON, and the speed is going down such that
current can no longer be maintained. The purpose is to
adapt the faster electrical brake effort characteristic to
the known slower mechanical bralce effort characteristlc. It
is desired to slow the electrical fade so that together with
the mechanical brakes no ~erk is not~ced in the net brake
effort. This permits the slower mechanical brake effort to
keep up with the drop off o~ the electrical brake effort.
The minimum circuit resistance is known and the operating
- 20 characteristic of the chopper apparatus is known. There is
a motor current point of minimum voltage for the chopper at
maximum ON time. The brake effort request determines the
motor current. If the speed goes down beyond this current
po~nt, the motor current cannot be sustained and electrical
brake effort control will be lost. The mechanical brake
must satisfy the ~erk limit rate of change of' deceleration
or how f'ast the mechanical brakes can be applied, and it is
known to require a certain time pçriod to apply the mech~ni-
cal brakes from zero to maximum levels of operation. Xnow-
ing the accelerating rate of the vehicle, the time for a
-20-
., ., ~
~ 7 ~ 4~,849
change in speed determines the speed value at which thecomputed electric bralce fade out should start, and the
program line 85 states this vehicle speed is in the range of
60 hexadecimal to 10 hexadecimal. ~ speed range of 0 to 100
KPH ln Sao Paulo is re~resented by a binary relationship of
0 to 256, and 60 hexadecimal represents 37 percent or 37 KPH
and 10 hexadecinlal repre~etlts 4 percent or 4 KPH. Program
line 86 states that if the requested current P0 is greater
than twice the value of speed ~inu~ 20 hexadecimal, then P0
is set equal ~o the latter. I~ Figure ~ the speed versus
requested current relationship is shown to illustrate how
the value of P0 ralls off as a function of speed reduction
~ until the speed reaches a value of 11 hexadecimal in program
line 88 where P0 is set at a ~ixed value.
The provided taper allows the mechanical brakes to
build up in effort to compensate ~or the reduction in the
electric brake effort.
In Figure 8 curve 194 shows the provided electri-
cal brake fade out and curve 196 shows the friction mechanl-
cal brake effort build-up, and the sum of these two curves
194 and 196 is the desired constant value curve of resulting
net brake effort 198. Without the here provided controlled
~ electric brake fade out, the curve 190 illustrates the
- uncontrolled electric brake fade out that would otherwise
result.
The dynamic brake feedback signal to the mechani-
cal brake system causes the mechanical brake to build up
early and follow the controlled decrease of the dynamic
electric brake system. The program line 86 operates to
reduce the P signal current request as a function of speed,
-21-
~Zt~7~ 1l6, 8l~g
and t}-lis collt;rols t;~e gellerated brake curren-t in the re-
generating motors. A false motor current fade out is pro-
vlded while the vehicle speed is adequate to malntain the
motor current as desired.
FIELD SH~NT CONTROL
-
Motor operation characteristic c~rves such as
those shown in Figure 5, but related to tracti~e effort for
full field operation and field shunt operation, are well
known to persons skilled ill this art. For a given motor
current, the tractive effort; of the motor with full field
operation and for shunt f`ield operation can be determined.
In power more current is requested as the speed increases
whereas in brake less current is reguested as the speed is
increased. When the field is shunted~ this shi~ts the motor
characteristics and if a given tractive effort is required
to give the acceleration rate desired, as the speed increases
for a given current the full field operation is suitable up
to some speed. If it is desired to keep the same tractive
effort level~ it becomes necessary to shunt the ~ield and
increase the motor current to a new level corresponding to
the shunt field operation. At this new current level, the
desired tractive effort can be obtained up to a higher speed
of motor operation. This additional speed is obtained by
paralleling the motor fields in-to shunt operation, to pro-
vide one-half the motor armature current in each motor
field. Once the 95% ON duty cycle of the chopper is reached,
before the field shunt is ch~nged, a predetermined time
delay is provided by countin~ a number of clock pulses to
avoid lnstability of field shunt change. When the field
shunt ls changed, this significantly changes the motor
-22~
..~
~:~ 2~G79 ~1 6, ~ 4 9
characteristics and the chopper has to ad~ust from the 957O
ON duty cycle to a new phase angle ol operation, such as in
the order of 70~ ON duty cycle of` the chopper. It is desired
to assure that the chopper operation is actually stable at
the 95% ON duty cycle and not an anomaly of noise pertur-
bation to only momentarily bring the chopper to the 95% ON
duty cycle level. The ph~se angle controller 1s very fast
in oper~tion ~nd it is n~t desired to respond to a momentary
high phase angle condition and change the field shunt before
the chopper is at a steady-sta~e 95% ON duty cycle of opera-
tion, and then have to unshunt the 1ields when the chopper
returns to its stable op~ration below the 95% on dùty cycle
condition. This would require going from a parallel field
connection back to a series field connection and this is
ob~ectionable in relation to the switches and the motor
operation. Once the 95% ON duty cycle condition is main-
tained for the provided time period, the switches are
operated to shunt the motor fields and this causes the
chopper to phase back to about a 75% ON duty cycle. There-
fore, the decision point has to be moved now from the pre-
vious 95~ ON level to a lower value of about a 60% ON duty
cycle level, so the motor fields do not unshunt by the
expected phase back of the chopper operation. This provides
a hysteresis conditioning of the response to the chopper
phase angle, including a time element in the response, to
improve and malce more stable the motor field shunt control
operation.
At program line 128 if the phase angle PH is
greater than OE5 hcxadecimal, then a timer TP is incremented
at program line 129 by one per program cycle if the phase
-23-
~. ,,
.
~ 6 ~ ~ 45,8L~
angle stays continuous. If TP becomes greater than 1~ hexa-
decimal then TP is forced to ha~re a maximum of 13 hexa-
decimal. At program line 130 i~ TP is greater than 10
hexadecimal, the field shunt switches are operated. The
program line 128 senses when the phase angle exceeds about
95,~ ON duty cycle, and the operation of timer TP to incre-
ment by one for each program cycle provides a desired time
characteristic for the phase angle to remain above this
upper limit of about 95% ON duty cycle. This operation is
shown in Figure 9 ~here the phase angle 191 has to remain
above the provided upper limit 193 for a desired time period
before the field shunt operation is effected. When the
field shunt changes, then the phase angle of the chopper
drops to about a 70% ON duty cycle. The available dynamic
range of the full field operation was about finished since
- with a full field the motor was generating a lot of back
EMF which was equalizing the supply line voltage and this
required the chopper to be ON most of the time. When some
of the field is shunted, this weakens the magnetic ~ield in
the motor and reduces the back EMF, and to get more current
at the same torque the chopper is phased back towards the
OFF position to give more dynamic range again. At program
line 131 if the phase angle goes below a minimum limit of
about 60% ON duty cycle~ then at program line 132 the timer
TP is decremented by one for each program cycle. This
recognizes when the phase angle is below some limit for a
given number o~ program cycles, and when the time TP is less
than 10 hexadec~mal at program line 130 this opens the field
shunt contactor. .4t program line 116 the input 4 is read to
bring back the status of field sh~nt FSs to indicate whether
-24-
~226~9 46,849
or not the field shunt has actually closed because this is a
non-time related thing; that is, whenever the request is
made to close the field shunt~ there is a time ~ ement
involved in the mechanics, so it takes a certain amount of
time for it to happen, and the program waits after the
request is put out for the response that says the field
shunt has actually closed; and when it is actually closed,
at program line 116 an increment of current of 49 hexa-
decimal is added to the current request.
The program listing included in the Appendix is
written in a language called PLM which was developed ~or use
with the INTEL microprocessor, such as the central processor
94. This is a high level assembly language which can be
compiled into machine language. me numbers used in the
listing are in the hexadecimal number system, which is a
base 16 number system. me first part af the listing in
lines 1 to 6 is for bookkeeping purposes and identifies for
the program the variables, the constants and the labels used
in the course o~ the program. More specifically, K is an
art~ficial constant that is set in the brake mode for con-
trolling the brake build-up. IRW is the current request
that has been load weighed to compensate for the weight of
the car. I0 is the old current, I1 is one of the motor
circuit currents and I2 is the other motor circuit current.
IR is the current request. LVL is the modified line vol-
tage. PR is the permission to regenerate. RE is the retard
the effort due to a number of conditions such as overline
voltage or overcurrent or the like. TI is a timer. IL is
line current. LV is l~ne voltage. M is the mode of the
external equipment. M0 is the old mode and M1 is the tran-
-25-
. ,.~
~ 46,849
sitory mode as determined by the mode request and the posi-
tion of the power brake switch. N is a counter. PH is the
phase that the external analog controller is controlling and
that is brought back in to establish the field shunting. PI
is the P signal that is used internally to do mode changes,
PN is the new presently read P signal and P0 is the jerk
limited P signal. TT is a timer. SI is the speed after the
hysteresis has been applied. TOS is blank. ZI and Q are
carriers to the external analog controller and establishes
certain modes of operation. S is the currently read speed
signal and SS is the speed signal after it has been modified
for the taper on the power and brake modes. T is a timer,
TP is a timer and TS is a timer. X, Xl, X2, Y and Z are
external controls for the analog controller. The three
upper lines in the program listing are the variables used in
the program. The next three lines are labels that identify
in the program certain starting points where the program can
jump to if needed. The compiler assigns memory locations
for each variable, and any time a given variable is read,
the computer knows the memory location. The mode labels are
used to assign locations in the program.
The program defines the desired sequence of steps
to be followed in controlling the propulsion and electric
braking operation of a transit vehicle. The safe mode of
operation is the brake mode. Therefore, the present control
program listing always starts up through the brake mode. If
an abnormal condition is detected, the program operation
returns to the beginning and resequences through the brake
mode. In comparison, the prior art control systems shut the
chopper OFF and did not try to reinitialize the equipment or
-26-
~ 46,849
to make sure the start of the operation was always from the
same base.
In line 8 and mode 1 of the program an output port
is directed to take a certain state, which is output port 1,
and the constant Q is initialized to equal zero. In lines 9
to 14 of mode 1 the program sets the output line switch out
and checks if it is satisfactory and then reads the line
voltage. The program looks at the inputs, the slip slides,
and so forth to see that they are in proper form and then
tests for line voltage. If the line voltage at line 14 is
not satisfactory, the program goes back to line 8 and the
start. If the line voltage is satisfactory, a false boost
signal is output at line 16 of the program because the line
switch cannot be picked up until a boost is provided, so a
false boost is provided for this purpose. ~he motors will
not be energized at this time because the ON and OFF pulses
for the thyristors have been suppressed. If the line vol-
tage is all right, then in line 17 of mode 2 of the program
the line switch is closed for charging the commutating
capacitors and a check is made at line 18 to see if all the
inputs are as desired, and if they are satisfactory, the
program at lines 20 and 21 initializes certain timer vari-
ables.
In line 24 of mode 3 of the program the program
waits for a pulse from an external clock at 218 Hz from a
crystal oscillator and when the program sees the rising edge
of the clock pulse, it provides the front end of the boost
to fire the ON pulse and puts the ON pulse positioner up to
output the request through output port 106 shown in Figure
3 3-
-27-
4 G , & 4 9
Lines 26 to 30 of mode 4 of the program are con-
troll~ng the ~ternal analog phase controller 108 to provide
a boost interval for ~nterpreting the curren~ signals and
other things as to where the ON pulse will be and whether or
not it is allowed, and providing the ON suppress and the OFF
suppress.
In mode 5 llnes 40 to 64, the progra~ reads analog
inputs and sets some variables. The P signal which is a
line~r monotonic type signal is converted to effort. When
the P signal ls above 60 milliamps this is a power request,
when the P slgnal is below 60 milllamps it is a brake request,
and below 20 mllliamps it is superbrake. If the line vol-
tage LVL is less than some predetermined number then the
operator RE is set to retard the effort. In addition, a
speed taper is provided whereby the speed signal S is read
in the outside world and is modified so that the lnternal
speed signal SS stays at the given level as long as the
external speed signal is within predetermined limits. The
external speed S is the actual vehicle speed and the in-
ternal speed SS is the value that the program is uslng forlts operations. In effect a window is put on the real
vehicle speed and then used inslde the program as a bracketed
speed such that as the outside speed starts moving up~ then
the lnside speed SS does not change for as long as the
outslde speed S is within this provided wlndow, thereby lf
the outside speed S has noise interference, this provldes a
dead band for filtering the noise and other dlsturbances out
of the actual speed signal S.
In lines 32 to 38 of mode 6, a determination is
made to go to power or go to brake and to conflrm that the
-~8-
~i
, .
~2 ~6 ~ ~ 45,81~9
control is in power or the control is in brake for the
purpose o~ setting up the request.
Starting at line 65 of mode 7, the P signal is
considered, which P signal has a value from 0 to 100, for
the generation of requested effort. If the control is in
power and the P signal is above 60 milliamps, this requires
more effort. If the P signal is below 50 milliamps and the
control is in power, this n-aintains a minimum effort. If
the control is set in brake and the P signal is below 60
milliamps, this re~uests an increased brake effort down to
20 milliamps, at which time the same effort is held. If the
P signal is above 60 milliamps but the BRK signal does not
allow the control to go into power, a minimum brake effort
is maintained. In addition, a jerk limit is provided in
lines 75 to 82 of the program because the P signal can
change instantly to a full 100 milliamps and must be jerk
limited such that the effort signal has to increase on a
ramp in one program cycle step at a time. The ~erk limited
P signal is incremented by one unit each program cycle to
provide the desired ramp and repeatedly incrementing one at
a time determines how quick the effort increasesl. When
going into brake to prevent an abrupt fade-out of the elec-
tric motors and to permit a smoother blending of the fric-
tiQn brakes, a false fade-out is provided in lines 84 to 89
of the program so the electric braking fades out on a softer
slope to permit the friction brakes to maintain a smooth and
total braking effort.
Lines 94 to 98 of mode 8 of the program provides a
check for a zero speed when ~he actual speed is less than a
defined amount such that the vehicle is considered tc be
-29-
G~ 46,8l19
standing still at zero speed. In addition, zero speed
clears the Z carrier ~ithin the program used in a situation
when there is too much current in brake, which indicates an
overload and the operation should be shut down. In line 9g
of the program, if the vehicle is at zero speed and a re-
quest for power is received, then the Z carrier is cleared
to go back into power. ~ chech is made at line 100 to see
i~ the line voltage is too low, and if it is too low, the
program returns to the bee;innin~ of the program since there
is notienough ener~y for the c.ommutating capacitor and the
present control apparatus is not required to operate below a
predetermined voltage level, which could mean that the
vehicle is operating in a rail gap and the normal mode is to
shut down the equipment when going into a rail gap. In
addition in line 101 of mode ~, a check is made for excess-
ive line voltage which is used for incrementing the RE
request. If the voltage is too high, the Y carrier is set
for the purpose of skipping ON pulses, and the RE request
starts reducing the motor current and this reduces the line
current. A check is made for LCOC which is a signal that
indicates that all the power circuitry is made up properly.
If any of the conditions, such as a thermal overload or a
slip/slide signal or the like, indicates improper action,
the effort request is reduced and a suppression of the ON
pulse is effected. The Y carrier controls the ON pulse, the
OFF pulse and the T5 pulse. A check is made to see if motor
current Il is greater than motor current I2 or vice versa to
maintain the desired balance in the motors. A check is made
at line 105 to see that I0, which is a sum of 11 and I2, is
not exceeding the request IR by more than a certain amount;
-30-
.~
~ 6 ~ 9 46,849
and if it is, t;he ON pulses are skipped.
The line ~urrent llmit check in line 103 of mode 8
is provided to establish that the respective currents in
each o~ the motor circuits are within a prede~ermined match
of each other in relation to balance; i~ they are, the
operation is satisfactory; and if not, corrective action is
taken. Towing protection is provided in line 104 to enable
a train vehicle to be pulled or ~owed; if there is a failure
in the external equipment of a giverl ~ehicle, it is desired
that this be recognized and the ~e~licle operated such that
the other operating cars in the train can tow the disabled
vehicle.
In lines 110 to 113 of mode 9 of the program the
current request is generated from the PR signal from which
the retard effort RE is subtracted to get the IR request
signal, and a speed tilt is provided in relation to a power
~ode or brake mode of operation to change the current
request IR on the field shunt and check of the inputs. The
~effort request is the modified P signal which has been
-20 modified, then a speed tilt is added to the modified P
signal by looking at the speed and tilting the P signal plus
when power operation is desired and tilting the P signal
negative for brake operation. The speed tilt is provided in
lines 114 and 115 by chopping off a l~ttle bit of the
requested current to compensate for the effort required to
maintain acceleration as speed increases; in effect, the
requested current is added to or subtracted from, depending
upon whether the control is in power or in brake, and this
adds or subtracts an increment of vehicle speed. In this
3~ regard, during brake, the motor is dragging and the car is
-31-
46,~4~
dragging, so less effort is needed from the motor current
because the drag is additive; however, in power operation,
the drag is against the propulsion effort, so additional
motor current and effort is provided to compensate for the
needed extra power to properly operate the vehicle. The
provided speed tilt accomplishes this function in relation
to the speed of the vehicle. For the change of the current
request on field shullt in lines 116 to 118, if in field
shunt o~eration, then the motor characteristics are dif-
ferent; the field shullt is field weakening, and there is a.dlf~erent current level needed to get the desired motor
torque. The input check is provided at lines 120 to 123 to
make sure that all the switches and so forth are set where
they should be. The input 4 relates to the temperature of
the semiconductors; this temperature in the prior art was
sensed and if too high was previously used to shut everything
down as an irrevocable control move. In the present system,
restarting of the program is permitted after a too high
semiconductor temperature is sensed. Input 4 is presently
checked to see if the temperature i8 not too high, if it is
satisfactory the ON pulse for the chopper is allowed~ and
the incremental loop timer goes to mode 10. If the semi-
conductor temperature is too high, the program goes to mode
10 and if necessary, a T5 pulse is fired; for a given cycle
of program operation, it may be desired to cancel the ON
pulse for that cycle or suppress the OFF pulse or shut o~f
the T5 pulse, or even to turn on the T5, ~epending on what
is desired. If the semiconductor temperature ln the next
cycle ~s back to a desired level, the program continues as
~- 30 nor~al to avoid a total shut-down and permit the transit
-32-
46,~49
1~2~67~
vehicle to continue runnin~. The present control provides a
lessening of thc provided effort to permit the equipment to
continue running within capabilities and contrlbuting some
partial desired effort to the train movement.
~ ode 10 of the program includes four selectable
control operations--namely, CYCPP which is confirmed power,
CYCBB which is confirmed brake, CYCBP which is cycling from
brake to power, and CYCP~ which is cycling from power to
brake. These relate to di~ferences i~ the desired vehicle
1~ control as to when a particular control is desired and what
kind of control is desired. More specifically, for the
first control operation of CYCPP which is confirmed power,
it is desired to stay in power and to confirm that the
control is presently in power; the field shunt is closed in
lines 129 to 132 in relation to phase angle and the line
volta~e is cut back in line 134 in relation to low voltage.
The close of the field shunt is provided to increase the
train speed. To keep the current flowing in the motor, it
is necessary to keep turning the chopper ON for longer
periods of time to keep increasing the percentage of voltage
to counteract the counter EMF of the motor. At some control
polnt, it is desired to move to field weakening, and the
control approach taken here senses the chopper being ON for
95% of the time and field weakening is then pro~ided.
In the second operation of CYCBB which is conf~rmed
brake, the request is to be in brake and the control opera-
tion is confirmed to be already in brake. This portion of
the program permits improved control in the braking mode in
relation to regeneration of power, wherein a sequence of
30 control steps is provided in lines 147 to 151 taking pro-
-33-
~226~ 46,849
gressively stronger action if the line voltage gets beyond
defined limits in an effort to control the maximum level of
line voltage. If the line voltage starts getting above a
predetermined first limit CE~ then the request is cut back
by two; if the line volta~e gets above a predetermined
second limit D4, then the previous action has added to it a
stronger reduction and so ~orth through greater predeter-
mined limits to effect progressively increased current
reductions due to excess line volts by suppressing ON pulses
for the chopper to provide this current reduction.
A hysteresis for brake build-up is provided at
lines 152 to 156 by trying to get at least a minimum prede-
- termined current level in the brake mode after the motor
armature current has been reversed for braking; this portion
of the program provides the requested brake effort in con-
junction with a minimum effort to assure an adequate brake
current. The problem is to assure after the propulsion
motors are established in the proper way to start generating
brake current, that the armature current is built up in time
to prevent loss of the armature current because when changing
from power to electric braking, the braking armature current
results from the residual magnetism left over in the field
circuits of the motor. If the control apparatus does not
operate fast enough and lets this residual magnetism go to
zero, the armature current will not build up. In relation
to a contribution to regenerative braking or electrical
braking, the present control apparatus enables a build up of
brake current after going to the brake mode~ such that when
the build up contactor is closed thereafter only ON pulses
are provided with a defeat of O~F pulses until a minimum
-34-
~ 6 1~ ~ 4 6 ~ 8 4 9
armature current is present in an effort to assure that the
armature currel1t gets started as quickly as it can and
before there occurs a loss of the residual field magnetism.
The propulsion motor is a series motor, so the armature and
field windings are in series. After cutting the armature
current to go into a brake operation, it takes a while for
the field to be reenergi~ed and this is the residual mag
netism that is involved in this operation; the armature
circuit is reversed for brake operation, but the field does
not go to zero instantl~ because of residual magnetism.
~hen it is desired to go into the brake mode of operation,
the program maintains a minimum level of current in the
- brake mode and permits the armature current build up in the
opposite direction to an adequate level to maintain the
field magnetism and still reverse the current flow in the
armature; the control operation desires a current above a
certain value and assures that at least this value of
armature current is maintained.
. .~
