LACCELERATION Y @PINHIBIT
Contents
1. c a level detector circuit coupled to said absolute value circuit for detecting when the determined absolute value is less than said preselected value and d register means controlled by said level detector circuit for operating to a first and a second position as said absolute value is more or less than said preselected value respectively e said regulator means coupled to complete said integrator circuit and connect said integrator path in parallel with said first amplifier when in said second position UNITED ST TES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO 4 118 774 DATED October 3 1978 INVENTOR S Raymond C Franke It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below Column 14 line 67 delete output and insert input Column 16 line 38 delete regulator and insert register Signed and Sealed this Fifth Day o june 1979 SEAL Attest RUTH C MASON DONALD W BANNER Attesting Officer Commissioner of Patents and Trademarks UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO 4 118 774 DATED October 3 1978 INVENTOR S Raymond C Franke It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below Column 14 line 67 delete output and insert input Column 162. The speed control operates as a simple regulator when the velocity error is large to maintain the advantage of quick reaction to changes in speed The pulse width modulation arrangement shifts to a hybrid type network operation when the error signal is reduced to a preselected percentage of the selected speed with an automatic and smooth transition from the regulator to the hybrid operation However this hybrid circuit arrangement reduces the fast acting gain to improve the stability of the speed control It also provides better steady state speed accuracy due to the zero error seeking characteristic The arrangement of the invention thus efficiently and economically pro vides a locomotive speed contro system which is both accurate and stable Although I have shown and described but one spe cific embodiment of the locomotive speed control appa ratus embodying the invention it is to be understood that modifications and changes within the scope of the appended claims may be made without departing from the spirit and scope of my invention Having thus described the invention what I claim and desire to obtain by Letters Patent is 1 In a locomotive speed control system the combina tion comprising a a signal processing means operable for processing an input signal into a control signal at an output terminal and having a first operating condition for transferring an input signal without change to form an output control signal and a se
3. creases the locomotive will tend to go faster But the resulting velocity error will force the integrator to ad just the pulse width and reduce the corresponding ve locity error to zero Note that the output of the integra tor will remain fixed at any value whenever its input or signal V is zero Since the grade and load variations occur slowly enough the integrator can keep up and maintain signal V zat nearly zero The increase in the pulse width as control voltage CV becomes less negative is due in part to the decrease in the velocity error signal Vas signal V increases But the change in control voltage CV is also due in part to 4 118 774 7 the acceleration signal A applied through resistor R6 to the input summing junction for amplifier A4 This sig nal acts in anticipation of the achievement of or at least the approach to the desired speed Vs In the first condi tion signal A tends to shift voltage CV from a direct equality with signal V pin a plus or minus direction as A is positive acceleration or negative deceleration When relay IC releases signal V reduced to the prede termined percentage of signal Vs and puts the integra tor amplifier A2 into the loop the pulse width no longer bears its proportional relationship to the velocity error Instead the pulse width will assume an appropriate value to force the velocity error to zero This is true because if there is a velocity error the output of the integrator will
4. error signal to the zero level 9 Locomotive speed control apparatus as defined in claim 8 in which a said first amplifier circuit network includes a first and a second amplifier circuit connected in series said first amplifier circuit having a unity gain fac tor 1 said second amplifier conditioned by said level detection means in its first condition to also have a unity gain factor whereby said velocity error signal is transferred without change to the input of said modulating means and b said second amplifier circuit network includes said first and second amplifier circuits and an integrator amplifier circuit connected in parallel with said first amplifier circuit by said level detection means in its second condition for providing a slow acting gain function to said signal processing network to cause said control voltage to drive said velocity error toward a zero level 10 A hybrid signal processing circuit network for transferring a variable input signal from a selected source into a control voltage output comprising a a level detector means coupled to said source and responsive to the absolute value of an input signal to operate to a first or a second position for regis tering that input signal as greater than or less than a preselected level respectively b a first amplifier circuit having a unity gain and coupled to said source for receiving said variable input signal c an output amplifier circuit cond
5. plied as one input to a NOR gate G7 whose output is applied directly to the inhibit terminal of the counter A second input for gate G7 is received from the output of NAND gate G6 which has three inputs One of these inputs is received from gate G2 through an inverter gate G5 The other two inputs to gate G6 are received from the output terminals K1 and K2 of the counter It is to be noted that output Y from the acceleration classifier is also applied to a Level Translator circuit which pro duces a positive analog signal output when acceleration is excessive that is when a logic 0 output signal is re ceived from the acceleration classifier The output of this level translator is applied through resistor R16 as an additional source for charging capacitor C2 To discuss the operation of the apparatus it is as sumed that it is used on a hump locomotive which is to move a train up a classification yard hump starting from a stopped condition Briefly no throttle action and thus no propulsion power occurs until the locomotive brakes are released and relay BPR picks up After this initial positioning of the throttle to a preselected start ing point control is exercised depending upon a combi nation of the speed change required and acceleration If acceleration is in the low range the throttle will ad vance if necessary for increased speed However if acceleration is in the moderate range the throttle will remain unchanged while the detect
6. Elsewhere in FIG 2 the reference B designates a connection to the positive terminal of this battery and the reference N a connection to the negative terminal A center or at least an intermediate terminal G is also used where a lower voltage is desirable for operating any of the appa ratus The terminal G may also be considered to be connected to the system ground in the usual manner At the upper left is the input from the operator s control panel providing a voltage signal Vs representing a se lected locomotive speed At the lower left is a symbol representing the tachometer which measures the actual locomotive speed here shown specifically as a fre quency signal This frequency signal is converted by conventional apparatus into an analog or voltage signal representing the actual speed signal V4 which is also differentiated in a conventional manner to provide a voltage signal A representative of the acceleration of the locomotive Signals Vs and V are compared or summed in the amplifier unit A1 to develop a velocity error signal Vy Signal Vx has a positive or negative characteristic as signal V is greater than or less than signal Vs respectively the inputs to amplifier A1 being ad justed and connected to provide this result The abso lute value of signal Vis determined in a conventional unit designated by the block V The output of unit Ve is a signal applied through a conventional level detector unit to energi
7. in ac 20 25 30 35 40 45 55 60 65 8 cordance with the existing count The decoding unit is of a type arrangement that the same reset pulse which returns the counter to zero will cancel or reset the logic to its at rest condition The clock network comprises an absolute value cir cuit CV a transistor Q a primary biasing resistor network including resistors R10 R11 and R12 capaci tor C2 a brake pressure release relay BPR a Pulse Shaper circuit and limiting resistors R13 and R14 The heart of the clock network is the programmed unijunc tion transistor Q illustrated by the conventional sym bol Gate electrode bias for this transistor is established by the resistor network including resistors R10 and R11 connected in series between terminals B and N of bat tery LB and resistor R12 This network determines the voltage required on the anode electrode to trigger tran sistor Q to its conducting condition The cathode of transistor Q is connected to terminal N through resistor R14 Anode voltage for transistor Q is established after the initial moment by the absolute value of the control voltage CV determined by the conventionally shown unit Voltage CV of course is supplied from the output of amplifier A4 in the manner previously discussed The voltage charge on capacitor C2 is also initially applied that is summed to the anode input of transistor Q over front contact a of relay BPR Relay BPR is
8. line 38 delete regulator and insert register Signed and Sealed this Fifth Day of June 1979 SEAL Attest DONALD W BANNER RUTH C MASON R p Attesting Officer Commissioner of Patents and Trademarks
9. moves to a throttle position sufficient to hold the train on the upgrade when the brake pressure is released The level of the acceleration of the train once the throttle is positioned is classified into one of three levels desig nated as low moderate and excessive The classifica tion output in logic form is combined with the sense or direction of the control voltage through a logic net work to enable or inhibit the counter The throttle posi tion thus varies only when the control voltage is of some magnitude When the control voltage approaches a dead band or the acceleration classification indicates an approach to the correct speed further counting is inhibited to hold the existing throttle position to elimi nate a speed overrun Under this condition the neces sary minor speed changes are controlled only by the pulse width modulator BRIEF DESCRIPTION OF THE DRAWINGS I shall now describe in broad outline the basic system including the invention and in greater detail one specific circuit arrangement embodying the details of my inven tion referring from time to time to the accompanying drawings in which FIG 1 is a conventional block diagram illustrating a basic locomotive speed control system into which the invention may be incorporated FIG 2 is a circuit diagram partly in schematic form of the speed control apparatus embodying the inven tion FIG 3 is a chart showing the relationship between selected functions in
10. normally deenergized and is controlled by a brake pressure switch BPS This switch is preset to release when the brake pipe pressure in the train is re duced to a predetermined value for example 5 psi When the brake pipe pressure is greater than this prede termined limit switch BPS is in the position to close the circuit through its contacts a so that a connection is made from terminal G of battery LB to a circuit leading to the reset terminals of the counter and the throttle decoding logic and also to resistor R15 When the brake pressure is reduced below this predetermined value switch BPS releases to close a circuit through its contacts b from terminal B to the winding of relay BPR and thence to terminal G This energizes the relay causing it to pick up and close its front contact a In the at rest condition with the circuit through contacts a of switch BPS closed capacitor C2 is charged to the volt age level of terminal G of battery LB which is consid ered in the illustrated system as the zero voltage or a logic 1 level A logic 1 on the reset line causes the counter to reset The up down and inhibit inputs to the counter are controlled through a logic network with inputs from an acceleration classifier device and a sense amplifier This latter unit receives the control voltage CV as an input and detects its positive or negative condition The out put signal from the sense amplifier is a logic 1 if an increase in speed is require
11. of this type system to act quickly to changes in requested speed Further the pulse width system automatically and smoothly transfers from the regulator to the hybrid operation when the speed error is reduced to a preset factor This reduces the fast acting gain with an atten 65 12 dant improvement in stability but retains a steady state speed accuracy due to the zero error seeking character istic of the integrator The system maintains its ability to make minor adjustments of the speed However the entire system uses the throttle adjustment for large and initial speed changes required to get the train underway under heavy load and difficult grade The locomotive speed control apparatus of my inven tion thus provides an improved contro with accuracy and stability in which the acceleration function is used to reduce the power in anticipation of the approach to the correct selected velocity Through a logic network and feedback control of the clock particularly when acceleration becomes excessive a counter device which determines the throttle position is inhibited or stepped back to hold or reduce the throttle when the accelera tion factor indicates the approach to the selected speed even though the locomotive may still be underspeed Control of the locomotive speed is adjusted in advance to prevent overshoot of the desired speed and for pro viding a control voltage to the pulse width modulator for finer speed adjustments
12. shift the processing network to a sec ond condition which incorporates an integrator circuit into the processing loop for the velocity error signal so that the operation becomes of a hybrid nature The control voltage now varies by three additive forcing functions In addition to acceleration acting in anticipa tion the control voltage varies directly proportional to the error signal but at one half the gain The integrator also acts to change the control voltage and correspond ing locomotive tractive effort to reduce the error to zero As the error signal becomes smaller the rate at which the control voltage changes becomes slower In the limit the control voltage will retain a finite value at zero error Thus the integrator may be thought of as having infinite but very slow acting gain 4 118 774 3 The control voltage and the acceleration signal are also applied to a second or throttle control network Here the control voltage drives a low frequency clock to operate a reversible counter network with the sense or direction that is the count up or down normally determined by the polarity of the velocity error as reflected by the control voltage The output of the counter is decoded to select the locomotive throttle position in accordance with the value of the control voltage During the time that the train brakes are en gaged that is before the humping operation starts the counter is held in its reset condition but immediately
13. United States Patent 11 Franke 54 LOCOMOTIVE SPEED CONTROL APPARATUS Raymond C Franke Shaler Township Allegheny County Pa 75 Inventor 73 Assignee Westinghouse Air Brake Company Swissvale Pa 21 Appl No 797 088 22 Filed May 16 1977 51 Int C12 aaa aa B60L 3 08 G05D 13 62 52 US Ooni 364 431 104 152 105 61 318 590 364 110 364 114 58 Field of Search 364 431 110 114 118 318 587 590 593 609 610 246 182 R 187 104 152 105 61 180 105 E 56 References Cited U S PATENT DOCUMENTS 3 218 456 11 1965 Matthews 246 187 3 601 605 8 1971 Elder etal 246 182 R 3 790 778 2 1974 Oster vw 105 61 R 3 946 297 4 1976 Bechtel 318 609 3 998 191 12 1976 Beyerlein et al 180 105 E 4 008 386 2 1977 ROSS 318 610 4 029 946 6 1977 Gaerstine et al sssi 318 609 OTHER PUBLICATIONS Westinghouse Air Brake Company Service Manual 5907 for Low Speed Locomotive Regulation System LSR 1 Nov 1974 Primary Examiner Felix D Gruber Attorney Agent or Firm A G Williamson Jr R W McIntire Jr SELECTED VELOCITY Vs V LEVEL VA FREQUENCY TO VOLTAGE CONVERTER TACHOMETER ACCELERATION g CLASSIFIER gt WIDTH Ra MODULATOR 11 4 118 774 45 Oct 3 1978 57 ABSTRACT An analog speed error signal develo
14. ach of actual speed to said se lected speed I 2 said other source also connected to said second speed control means for modifying the large step selection of locomotive speed when the accelera tion signal is such as to indicate a level of accel eration which may produce an overshoot of the selected speed 3 A speed control system as defined in claim 2 in which a said first speed control means includes a pulse width modulator coupled for receiving an output control signal from said signal processing means and responsive thereto for generating a series of pulses having a width proportional to the level of said control signal b said pulse width modulator further coupled for applying said pulses to a propulsion power source of the locomotive to vary the traction power out put to control locomotive speed 4 A speed control system as defined in claim 3 in which said second speed control means comprises a a clock means coupled to the output of said pro cessing means and responsive to said output con trol signal for generating periodic stepping pulses when the control signal voltage exceeds a predeter mined absolute value b a sense amplifier also coupled to the output of said processing means for determining in response to the control signal polarity a requirement for loco motive speed increase or decrease c an acceleration classifier means coupled to said other source and responsive to said acceleration signal fo
15. ain acceleration when the train starts may then become of the excessive classification Thus the output on leads X and Y from the acceleration classifier will each be a logic 0 signal Lead Z will also have a logic 0 but this is immaterial to the present operation Even though the sense amplifier output is a logic 1 calling for an in creased speed the outputs of gates G1 and G2 will be logic 1 signals The output of gate G4 thus becomes zero which applied to the counter actuates a DOWN count for reduced speed The logic 0 signal on lead Y is also applied to the Level Translator and results in a positive output from this unit Charging current thus flows through resistor R16 to capacitor C2 to reduce the clock time that is the interval between the succes sive clock pulses In other words under an excessive acceleration condition transistor Q is triggered more frequently These faster clock pulses reduce the time during which too high a throttle position is maintained 4 118 774 11 since the counter is reducing its count to cause the throttle decoding logic to set back the throttle The rate of approach to the selected speed is thus reduced to help reduce the amount of speed overshoot which may oc cur When the acceleration factor is reduced to the moderate range so that lead Z carries a logic 1 signal gate G3 output becomes zero since the sense amplifier is still outputting a logic 1 signal as more speed is needed NOR gate G7 no
16. change in a direction and hence change the pulse width to drive the velocity error to zero The output of the integrator will remain at the value it had to assume to drive the velocity error to zero The integrator amplifier A2 and its feedback capaci tor Cl are designed to have an infinite gain but to react slowly to change The constant of integration is chosen on the basis of making it fast enough to keep up with the long term propulsion demand changes which occur gradually as the weight of the train consist is decreased and the slope of the hump changes Minor propulsion command changes which occur quickly due to slight irregularities in track alignment are handled by the combined effect of the regulator system and the acceler ation feedback both of which act immediately to force a correction For example when moving at a constant speed a certain steady state propulsion effort is needed dependent upon the grade and load If a section of track of unusually tight gage is encountered or an unusual change in load occurs as an extra heavy cut is uncou pled over the hump the velocity will suddenly decrease or increase due to the change in track or load resistance respectively The velocity error reacts through ampli fier A3 and resistor R3 to immediately change the level of voltage CV Additionally the resultant deceleration or acceleration forces current through resistor R6 to also vary the control voltage Both of these actions will fo
17. cond operating condition for producing a non proportional output control signal in response to a variable input signal b a speed signal source coupled for supplying said speed signal representing the difference between a selected locomotive speed and the actual locomo tive speed as an input signal to said processing means c a level detection means responsive to the absolute value of said speed signal and coupled for shifting said processing means between its first and second conditions as said speed signal is greater than or less than respectively a predetermined percentage of said selected speed d a first speed control means coupled to receive said output control signal from said processing means and operable in response thereto for varying the 4 118 774 13 locomotive speed in small adjustment steps to drive said difference speed signal to zero and e a second speed control means coupled to receive said output control signal from said processing means and operable in response thereto for varying the locomotive speed in large adjustment steps to quickly effect speed changes 2 A speed control system as defined in claim 1 which further includes a another source providing a locomotive accelera tion signal related to the actual locomotive speed 1 said other source connected to said processing means for modifying said output control signal in accordance with a level of acceleration which reflects an appro
18. d and a logic 0 if a decrease is required The acceleration classifier receives as an input the acceleration signal A and detects its level in accordance with predetermined limits If the accelera tion is low that is less than a predetermined minimum level the acceleration classifier outputs a logic 1 signal on lead X Above this level lead X carries a logic 0 signal If the acceleration is detected as being excessive that is greater than a predetermined upper level a logic signal 0 is output on lead Y which otherwise carries a logic 1 signal If the acceleration is in the moderate range that is greater than the predetermined minimum but less than this upper maximum above which it be comes excessive a logic 1 signal is output on lead Z which otherwise carries a logic 0 signal 4 118 774 9 The output of the sense amplifier is applied to one input of each of the NAND gates G1 G2 and G3 A second input to gate G1 is supplied from the accelera tion classifier by lead X which represents the low accel eration signal The output of gate G1 is applied as one input to a NOR gate G4 and thence to the UP DOWN input of the counter A second input to gate G4 is re ceived from the output of gate G2 which receives its second input from lead Y of the acceleration classifier that is the excess acceleration lead The Z output from the acceleration classifier is applied as the second input to NAND gate G3 The output of this last gate is ap
19. e is measured in a separate circuit to determine if it is more than or less than a predetermined portion or percentage of the selected speed for example in one installation a 10 ratio The level detected that is above or below the percentage is registered to select a condition of the processing net work When the error signal is greater than this prede termined portion the network is so connected that the resulting gain is equal to 1 In other words the transfer function of the network is unity so that the error signal is equal to the control voltage The acceleration signal is also incorporated into the final value of this control voltage to provide an anticipation of achieving the se lected speed This control voltage is then converted by a pulse width modulation means into a series of pulses each having a width proportional to the level of the control voltage signal This series of pulses is applied to control the output of the main locomotive propulsion source for example the main generator on a diesel elec tric locomotive As the locomotive speed increases the pulse width increases as the error signal decreases i e the actual speed approaches the selected speed The variation in the pulse width is also controlled in part by the acceleration signal to anticipate the achievement of the selected speed s When the velocity error is reduced to less than the predetermined portion of the selected speed the regis ter means acts to
20. e level and polarity of an input control voltage for varying the output of a locomotive power source to equalize said selected and actual speed signals e a level detection means coupled to receive said velocity error signal and operable to a first and a second condition for registering the absolute value of said signal as greater than or less than respec tively a predetermined percentage of said selected speed signal f a signal processing network coupled to receive said velocity error signal input and controlled by said level detection means for supplying said veloc ity error signal without change as a control voltage input to said modulating means when said level detection means is in its first condition and for generating a non proportional control voltage input in accordance with input and output varia tions when said level detection means is in its sec ond condition 6 Locomotive speed control apparatus as defined in claim 5 in which said signal processing network is further controlled by said acceleration signal for adjusting said con trol voltage input to said modulating means in ac cordance with the acceleration level to prevent overrun of the desired speed when achieved 7 Locomotive speed control apparatus as defined in claim 6 in which a said locomotive power source is an electric gener ator driven by a diesel engine and connected to supply power to traction motors and which further includes b thro
21. eed control mod ule provides two outputs The first in code format is to the throttle channel which through a throttle solenoid apparatus and a governor device sets the throttle posi tion to control the locomotive diesel engine speed This control channel is a rough speed adjustment and varies the locomotive speed in relatively large steps The second output designated PWM for pulse width modulation is in the form of pulse signals of selected width and acts through a field control module to further vary the output of the locomotive generator which is supplying power to the traction motors In one specific installation the longer the pulse width the greater the reduction in the generator power output so that if the speed control module fails full manual control is avail able The generator is thus controlled from two sources the diesel engine driving speed through the throttle adjustment and the field through the PWM channel The pulse width modulation or PWM channel provides fine adjustment of power or speed The feedback from the motors is through the gears and wheels to the ta chometer to generate the actual speed signal V4 Referring now to FIG 2 a circuit diagram partly in conventional block form illustrates a specific speed control module arrangement for the block illustrated in FIG 1 At the upper right by conventional symbol is illustrated a locomotive battery LB which supplies en ergy to the apparatus shown in FIG 2
22. he absolut value level detector path from amplifier Al Assuming first that V is greater than the selected percentage 0 1 of Vs for example during the underspeed condition at the start of a humping oper ation relay IC is picked up so that capacitor C1 is con nected by front contact a of this relay to maintain the voltage through resistor R4 equal to the output of am plifier unit A3 It is to be noted that the output connec tions from amplifier A2 are at this time disconnected at back contacts a and b of relay IC both of which are open Now the gain of amplifier A4 is expressed by the symbolic term R9 R2 R3 Given the value rela tionship between the resistors the gain of amplifier A4 thus equals 1 Since the gain of amplifier A3 is defined as being 1 the transfer function of this network is unity Therefore ignoring the effect of the acceleration signal A control voltage CV is equal to the error signal Vz when relay IC is picked up When the velocity error V is reduced so that it is equal to or less than the predetermined percentage of signal Vs herein 0 1 Vs relay IC releases and shifts the network to its second or hybrid operating condition This condition in humping operations generally occurs as the locomotive comes up to the desired speed Re lease of relay IC opens its front contacts a and b to interrupt all circuits through resistors R2 and R4 Back contacts a of relay IC closes to connect capacitor C1 t
23. ignal is used directly to con trol power and throttle of the locomotive when the difference exceeds a predetermined percentage of the 10 20 25 35 45 50 60 65 2 desired velocity and in which the difference signal is processed through an integrator network to provide hybrid control of the voltage signal controlling the power and throttle when the difference is less than the predetermined percentage of the desired velocity the acceleration signal being used as an advance indication of the achievement of the desired speed to eliminate overrun Other objects features and advantages of my inven tion will become apparent from the following descrip tion when taken in connection with the appended claims and accompanying drawings SUMMARY OF THE INVENTION The general system or arrangement embodying my invention includes a means for measuring the actual locomotive speed and converting this measurement into an analog voltage signal The actual speed voltage sig nal is differentiated to provide an acceleration signal and is compared with an equivalent signal representing a selected or desired speed to develop an error signal This erro signal is processed through a two condition hybrid network to provide a control voltage for a pulse width modulator and for a throttle control arrange ment The error signal of course may be positive or negative in accordance with the over or under speed condition Its absolute valu
24. ion level inhibits further counting and speed is then varied only by the pulse width modu lation network 12 Claims 3 Drawing Figures TO MAIN GENERATOR OUTPUT CONTROL 4B _ en BPS G 1 RELEASES WHEN TRAIN BRAKES RELEASED a THROTTLE 4 118 774 Sheet 1 of 3 U S Patent Oct 3 1978 SHOLOW S T33H AA NOI LOVtI L 3 L3AWOHOV L YOLWYANGS k 2913 TINON 3NON3 __ yonumnoosk SON31OS IOdLNOO 3s3lq JILLOYHL q33ds 4 118 774 Sheet 2 of 3 U S Patent Oct 3 1978 WAlsISSV TD NOILWW3T399V S3NI 1 1Od LNOO IIVLLOWHL e aasy 33d Save Niy dL E N3H A S3SV3139 sda otitis q IOULNOD LNdLNO HOLVYANSO NVW Z ZzZ WALAWOHOVL 3 Ld3ANOOS 3SV 1 TOA O L ADNSANDAVS SA ALIDOIGA g31237T3s 4 118 774 U S Patent Oct 3 1978 Sheet 3 of 3 HLAIM IS TNd q R g 9 amp amp Q SQNOO2O3S LNNOD NMOG N Q 0 Q N UP COUNT 0 SANODJS LNNOD dN 20 4 118 774 1 LOCOMOTIVE SPEED CONTROL APPARATUS BACKGROUND OF THE INVENTION My invention pertains to locomotive speed control apparatus More specifically the invention relates to an improved automatic speed control for locomotives which provides greater accuracy and stability of the locomotive speed as the load handled by this locomo tive varies Speed control apparatus for automaticall
25. ion of an excessive acceleration causes the throttle to retard The clock which initiates the throttle changes is controlled by control voltage CV instead of the velocity error signal V z Thus instead of throttle changes being on the basis of velocity error they are initiated on the basis of pulse width residing at either extremity that is at either maxi mum or minimum limit In oth r words not considering the overall supervision based on acceleration the throt tle will advance if the pulse width remains for a pro longed period at its minimum width and will retard if the pulse width remains at the maximum pulse width This is indicated in chart form in FIG 3 to which refer ence is also made Referring to the block diagram and the chart the graph shows a relationship of pulse width and the counting of clock pulses for positive and nega tive values of control voltage CV It is to be noted that there is a band of voltage CV to which the clock does not respond and which corresponds to the linear operat ing region of the pulse width control This is accom plished by the R10 R11 R12 resistor network which establishes the voltage to which capacitor C2 must charge before transistor Q is triggered The frequency of the clock i e the interval between the triggering of transistor Q is determined by the voltage output of the absolute value circuit CV Translated into dynamic speed regulation performance the control using accel eratio
26. itioned to have a unity gain when said level detector means occupies its first position and coupled in series with said first a 20 25 30 35 40 45 50 55 65 16 amplifier circuit for providing a unity transfer function for said input signal into said control volt age output d an integrator circuit completed when said level detector means occupies its second position and coupled to said source for receiving said variable input signal e said level detection means further coupled when occupying its second position for connecting said first amplifier circuit and said integrator circuit in parallel and said parallel circuits in series with said output amplifier circuit for providing a control voltage output which is non proportional to the corresponding variable input signal 11 A signal processing circuit network as defined in claim M which further includes a feedback circuit means coupling the control voltage output to said source for driving said variable input signal toward zero when said level detector means occupies said second position 12 A signal processing circuit network as defined in claim 11 in which a said variable input signal may have either polarity and in which said level detector means includes b an absolute value circuit coupled for receiving said input signal and responsive thereto for deter mining the absolute value of the received signal without regard to polarity
27. ly its output will remain at the value it assumed in driving the velocity error to zero The hybrid network is thus re sponsive to the long term propulsion demand changes which occur gradually as the weight of the consist is decreased and the slope of the hump changes Once a reasonably steady state of the locomotive speed is achieved through the throttle and pulse width functions minor propulsion changes which occur are handled by the combined effect of the regulator system and the acceleration feedback Both act immediately to force a correction For example when moving at a constant speed a certain steady state propulsion effort of the locomotive is needed dependent upon the grade and the consist load If there is a change in velocity due to external conditions such as a sudden speed decrease due to a section of tight gage track the velocity error signal reacts through amplifiers A3 and resistor R3 to increase propulsion current Additionally the resulting deceleration forces current through resistor R6 to in crease the propulsion current Thus no change in the throttle position is required and the pulse width is ad justed in whatever minor amount is necessary to correct the speed variation The portion of the system for pulse width control of minor changes in the speed can be characterized as operating as a simple regulator system when the veloc 20 25 40 45 55 60 ity error is very large to maintain the advantage
28. n for supervision insures that the appropriate throttle notch is achieved for accelerating the train 15 25 30 35 40 45 50 55 60 65 10 The explanation of the throttle logic sequence starts with the train at rest which is the condition shown in the circuit arrangement of FIG 2 With the brakes applied switch BPS is picked up so that its contacts a complete the circuit for voltage to flow from terminal G through resistor R15 to charge capacitor C2 This is considered the zero voltage or logic 1 level in the sys tem so that the application of this to the reset terminals of the counter and the throttle decoding logic holds these units in their at rest no count condition When the brakes are released on the train or at least the brake pipe pressure reduces below the preselected pressure 5 Psi switch BPS releases closing the circuit through its contacts b to energize relay BPR When front contact a of relay BPR closes the existing voltage charge on capacitor C2 is applied to transistor Q This exceeds the threshold voltage set by resistors R10 R11 and R12 so that the transistor immediately conducts When the transistor conducts a pulse is applied to the clock input of the counter through the Pulse Shaper network con nected to the transistor cathode The counter steps to its first position and immediately advances the throttle to notch 3 which on most diesel locomotives is the lowest acceptable operating
29. o the output of amplifier A2 so that the capacitor now forms an integrating feedback circuit path that is am plifier A2 becomes an integrator At the instant of trans fer by contact b or relay IC the current through resistor R2 to the summing junction input of amplifier A4 is interrupted However since resistor R1 is equal to resis tor R2 in value and capacitor C1 has been maintained at the output voltage of amplifier A3 there is no instanta neous change in control voltage CV at the output of amplifier A4 Therefore the transition from the simple regulator control to the hybrid form of operation in volving the integrator including amplifier A2 is made smoothly without instantaneous change in the locomo tive speed control The control voltage CV desi which pro cessing circuit form is active is converted to a series of pulses having a proportional pulse width by the Pulse Width Modulator unit shown by the conventional block The main generator responds to the PWM sig nals to derive a proportional output to vary the locomo tive speed The pulse width or duration of each pulse in other words the percent on time varies in accordance with the level and polarity of control voltage CV For example when signal CV has a negative characteristic 10 25 30 35 40 45 60 65 6 during underspe d conditions the pulse width duration is at a low level As signal CV becomes more positive the pulse width or duration inc
30. ottle when necessary to exercise manual control A speed control system which eliminates these and other limitations is thus extremely desirable Accordingly an object of my invention is an im proved automatic locomotive speed control system Another object of the invention is a speed control system for hump locomotives which provides good speed regulation and improved operating stability A further object of my invention is automatic loco motive speed control apparatus with improved regula tion of selected speed and a higher degree of stability Yet another object of the invention is speed control apparatus for a hump locomotive in which the concept of processing the error signal is shifted when the speed error is reduced below a predetermined percentage of the selected speed to achieve a more accurate response while retaining stability Still another object of my invention is a locomotive speed control system which obtains a desired speed by controlling a master power source output on the loco motive and also the locomotive throttle position in proportion to a selected ratio of a desired speed with an operational shift from a first to a second type processing when the speed error is reduced below a predetermined percentage of the desired speed A further object of the invention is an arrangement for controlling speed of a locomotive in which the dif ference between the actual and selected speeds modi fied by the acceleration s
31. ped by comparing actual and desired speeds is processed into a control voltage through a two condition circuit network When the error signal is more than a predetermined percent age of the desired speed the network has a unity gain and the control voltage equals the error signal When the error signal becomes less than the predetermined percentage the network is shifted into a hybrid form by inserting an integrator loop into the gain circuit so that the control voltage and error signal are not directly proportional The control voltage is converted into a series of proportional width pulses which are applied to vary the generator output to control locomotive speed The pulse width varies in part from the error signal variation but also in part from an acceleration signal to anticipate the achievement of desired speed When the hybrid network is in use the pulse width speed control feeds back to drive the error signal to zero The control voltage and acceleration signal are also applied to a clock and reversible counter network which controls the locomotive throttle position The counter steps up or down to increase or decrease the throttle at a clock frequency established by the absolute value of the con trol voltage whose polarity further designates the re quirement for speed increase or decrease A high level of acceleration however overrides to reverse the count direction to prevent overshooting the desired speed A moderate accelerat
32. position With a notch 3 throttle position sufficient tractive effort is provided to at least hold the train on the hump grade so that no roll back occurs Thus switch BPS may be set at a relatively low brake pressure for example 5 psi and still prevent train roll back prior to the step up of the throttle This avoids any problems in handling the train due to a high brake pressure setting on this switch At this point the throttle can either advance retard or remain at notch 3 depending upon the acceleration Since at the beginning the locomotive is greatly under speed output of amplifier A4 that is voltage CV is high but with a negative characteristic so that the sense amplifier output is a logic 1 The next clock pulse refer ring to FIG 3 will be in the UP direction and will occur in approximately 5 to 10 seconds in this specific showing If the train does not begin to move or at least acceleration is extremely low the X and Y leads of the acceleration classifier are at the logic 1 signal level The outputs of NAND gates G1 and G2 are then at logic 0 so that NOR gate G4 outputs a logic 1 to cause the counter to count UP when the next clock pulse occurs Frequently a static friction condition makes it diffi cult to get a train moving up the hump grade and re quires a higher throttle position to start the train than is necessary after movement actually begins If for exam ple the throttle advances to notch 4 to start the tr
33. r providing a selected plurality of output signals in accordance with the detected level of acceleration d a reversible counter means coupled to a locomo tive power source for varying the speed in accor dance with a recorded count e said counter means controlled by said clock means said sense amplifier and said acceleration classifier means for normally stepping up or down in accordance with a registered speed increase or decrease requirement respectively when a step ping pulse is generated by said clock means 1 said classifier means responsive to an excessive acceleration input level for overriding control of said counter means by said sense amplifier for reversing the normal stepping direction 2 said classifier means further responsive to a moderate acceleration input as said locomotive approaches the selected speed for inhibiting op eration of said counter means while maintaining 14 locomotive speed control by said pulse width speed control 5 Locomotive speed control apparatus comprising in combination a a source of a selected speed signal representing desired speed b a source of an actual speed signal and an associ ated acceleration signal c means connected to both said sources for compar ing the received speed signals to generate a veloc ity error signal representing the level and direction of the difference between the actual and desired speeds d modulating means responsive to th
34. ractive effort If zero error happens to produce the proper pulse width and corresponding tractive effort the system can operate at zero error 1f as is more frequently the case zero error does not pro duce the proper pulse width then the system will as sume whatever error is necessary to run at a constant speed The amount of error that is acceptable deter mines the gain If it is desired to operate with very little error it is necessary to use very high gain There are limits however to how high the gain can be raised because of system stability If the gain is increased too much the system becomes unstable The novelty in the system disclosed herein is that control voltage CV be comes an independent function of error forcing the error to zero For example assume a system for which zero error produces 50 power If the selected speed is 2 mph and if the particular grade and load is such that 50 power is exactly correct for 2 mph the system will operate at zero error On the other hand if 50 is too much power an error signal will develop because the train speed V is too high and the power is reduced It will be necessary for the system to operate at some velocity error velocity will be a little on the high side in order to produce an acceptable tractive effort In this disclosed system however the pulse width is independent of the velocity error in the steady state condition It is true that as the demand for power de
35. rce the pulse width to vary sufficiently to change the generator output to accommodate the change in veloc ity and force the velocity error again towards zero The throttle control network shown in the lower half of FIG 2 will now be described This network com prises a clock circuit a direction sensor an acceleration logic network a counter means decoding logic for the throttle control lines and various associated apparatus The counter shown by the block at the lower right is any conventional apparatus of the reversible counting type A pulse applied to the clock input terminal actu ates the stepping of the counter the pulse frequency determining the counting rate Input to the UP DOWN terminal determines the count direction that is whether to add or subtract the count pulse For exam ple in one specific type assumed herein a logical one input causes the counter to count up that is increase the count while a logical zero input causes a reduction in the count that is a down counting action A logical One input to the inhibit terminal causes the counter to cease operation i e not respond to any clock input pulses but to hold the existing count level An input to the reset terminal causes the counter to reset to its at rest or zero condition The counter output that is the count status appears at terminals K1 and K2 and is applied to the throttle decoding logic a conventional network which determines the throttle position
36. reases This occurs as the actual speed V increases A specific example is shown in the chart of FIG 3 which is taken from one specific installation of the apparatus on a hump locomotive of the diesel electric type In this specific installation the locomotive main generator output decreases as the pulse width increases It is to be understood however that other arrangements may be used depending upon the characteristics of the diesel locomotives to which the speed control apparatus is being applied Referring to the straight line designated as the pulse width it is to be noted that minimum and maximum values of pulse width are in effect at the extreme values of voltage CV in both the positive and negative directions That is the pulse width has a maximum of 70 when voltage CV is greater than a predetermined positive value while a minimum value of 10 is in effect when voltage CV is below a predetermined negative value Normally speed control is initiated with the locomotive at stop just prior to the start of the humping operation The control voltage CV is thus at its maximum negative value under these conditions In humping operations however rarely will voltage CV get to the maximum positive condition where the maximum pulse width is in effect A value of zero for voltage CV is no more ideal than any other value Most speed regulation systems for this purpose must operate with some finite error in order to develop the proper t
37. the operations of the circuit ar rangement of FIG 2 In each of the drawings similar reference characters refer to the same or similar apparatus and or functions DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Referring first to FIG 1 shown therein in block diagram form is an automatic speed control system for a locomotive by way of a specific example a diesel electric locomotive used for humping in a classification yard It is thus a low speed service for example moving at a fixed speed in the range of 1 to 5 mph in pushing the train upgrade to the hump where the cars are released to move by gravity to the proper classification track In effect the entire arrangement is a servo loop but with two control links to the locomotive propulsion At the extreme left the block represents the control panel in the locomotive cab on which the engineer or operator selects the desired humping speed This is a voltage signal V5 which is supplied to the speed control module shown here as a conventional block but which will be shown and described in detail in connection with FIG 2 A second input to the speed control module is an actual speed signal V from a tachometer apparatus which measures the actual speed in any known manner 20 25 30 35 40 45 55 60 65 4 Signal V is provided as or at least is converted to an analog signal so that it becomes a voltage input similar to the selected speed signal V s The sp
38. ttle control apparatus coupled for controlling the throttle position of said diesel engine to vary the power driving said electric generator c said throttle control apparatus coupled to said signal processing network and responsive to said control voltage for positioning said throttle in ac cordance with the level and polarity of said control voltage d said throttle control apparatus also coupled to said acceleration signal source and responsive to said acceleration signal for modifying the throttle posi tion to prevent overrun as the actual speed ap proaches the desired speed 8 Locomotive speed control apparatus as defined in claim 7 in which said signal processing network com prises a a first amplifier circuit network coupled for re ceiving said velocity error signal and completed by said level detection means only when in its first condition to have a unity transfer function for sup plying the input velocity error signal as an output control voltage 5 bt 0 25 35 45 50 55 60 65 4 118 774 15 b a second amplifier circuit network also coupled for receiving said velocity error signal and com pleted by said level detection means only when in its second condition to include an integrating cir cuit path and to have a slow acting gain function for supplying an input control voltage which is nonproportional to the input velocity error signal to cause the control voltage to drive the velocity
39. w has at least one input at logic 0 and provides an inhibit signal to the counter Thus when acceleration becomes moderate even though the loco motive is underspeed the throttle is held in its existing position While the throttle control portion of the apparatus is functioning as the train starts up the pulse width modu lation of the main generator is also functioning Initially with a large underspeed condition control voltage CV is equal to velocity error signal Vz and has a negative polarity Voltage CV is converted into a proportional pulse width and the generator responds to develop a proportional output The pulse width is at the prese lected minimum under these conditions for example 10 as shown in FIG 3 As the actual velocity signal V increases voltage CV becomes less negative that is approaches the zero position or point of the FIG 3 chart The acceleration signal also affects the value of voltage CV As the error signal Vz decreases to the predetermined percentage for example 10 of the selected speed Vs the hybrid network is created When relay IC releases amplifier A2 with the feedback path through capacitor C1 acts as an integrator network As previously explained with this integrator in the loop the pulse width no longer has a direct proportional relationship to the velocity error but assumes an appro priate value to force the velocity error to zero Since the integrator has infinite gain but reacts very slow
40. y control ling the speed of humping locomotives is known in the railroad art However the known systems have limita tions in retaining stability within the system while main taining the speed within a selected band In these sys tems regulation of speed within a given tolerance re quires a corresponding gain of the velocity error That is the closer the tolerance desired the greater the gain required However as this gain is increased the possi bility of instability becomes greater In hump locomo tive applications the load being pushed varies over a large range For example it is not uncommon to start with a train weighing 10 000 tons As the cars are dropped over the hump the load continues to decrease until the last car which may weigh only 10 tons or so Since the tractive capability of the locomotive is con stant it can be realized that the overall system gain continues to increase as cars are humped Thus in one prior system due to the increased gain as the consist becomes lighter instability occurs typically with 10 or fewer cars so that it is necessary to operate the locomo tive manually Another problem or limitation is the high setting on the brake pressure switch necessary to allow the locomotive operator to hold the train on the hump until a throttle position is achieved which will move the train upgrade This high pressure setting hinders later operation as it requires excessive brake application to shut off the thr
41. ze integrator control relay IC Sufficient energy is output to pick up relay IC only if signal V is greater than a predetermined portion of the selected velocity signal Vs For example in one specific installation relay IC is sufficiently energized to pick up only when V zis greater than 10 of Vs Relay IC is shown in its released position but obviously when the locomotive is halted as it is initially before humping begins relay IC is picked up to close its front contacts a and b 4 118 774 5 The processing network for signal V includes ampli fiers A2 A3 and A4 capacitor C1 contacts a and b of relay IC and various resistors designated R1 through R9 This network processes the input signal V z at the output of amplifier A1 into a control voltage CV at the output of amplifier A4 It is to be noted that by prese lection of the elements of the network the gain of am plifier A3 is fixed at 1 and resistors R1 R2 and R3 are of equal value which is also twice the resistance of resistor R9 The signal processing network has two operating conditions depending upon whether signal Ve is greater than or less than the predetermined por tion or percentage of signal Vs that is in this present example 10 or 0 1 Vs In other words two operating conditions for the processing network are established as relay IC is picked up or released that is as its front or back contacts close due to the level of energy received through t
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