CA1123496A - Locomotive wheel slip determination - Google Patents
Locomotive wheel slip determinationInfo
- Publication number
- CA1123496A CA1123496A CA307,760A CA307760A CA1123496A CA 1123496 A CA1123496 A CA 1123496A CA 307760 A CA307760 A CA 307760A CA 1123496 A CA1123496 A CA 1123496A
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- Canada
- Prior art keywords
- signal
- signals
- receiving
- representing
- motors
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
- B60T8/17—Using electrical or electronic regulation means to control braking
- B60T8/1701—Braking or traction control means specially adapted for particular types of vehicles
- B60T8/1705—Braking or traction control means specially adapted for particular types of vehicles for rail vehicles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L3/00—Electric devices on electrically-propelled vehicles for safety purposes; Monitoring operating variables, e.g. speed, deceleration or energy consumption
- B60L3/10—Indicating wheel slip ; Correction of wheel slip
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L2200/00—Type of vehicles
- B60L2200/26—Rail vehicles
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/64—Electric machine technologies in electromobility
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- Engineering & Computer Science (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Power Engineering (AREA)
- Electric Propulsion And Braking For Vehicles (AREA)
Abstract
Case 2558 ABSTRACT OF THE DISCLOSURE
Apparatus for determining and controlling wheel slip in a locomotive driven by d.c. motors has sensors which sense the wheel speeds of the different wheels and provide signals representing the different wheel speeds to a comparator. The comparator provides a signal representing the difference between the highest and lowest wheel speeds. A converter also acts on the signals representing the different wheel speeds to provide signals representing the acceleration of the different wheels and a selector selects the signal representing the largest acceleration. The signal representing the difference between the highest and lowest wheel speeds, and the signal representing the largest rate of acceleration are added together to provide a fault signal. A signal modifier modifies the fault signal to provide a controlled decay rate and the resulting signal is used to control the d.c.
motors.
Apparatus for determining and controlling wheel slip in a locomotive driven by d.c. motors has sensors which sense the wheel speeds of the different wheels and provide signals representing the different wheel speeds to a comparator. The comparator provides a signal representing the difference between the highest and lowest wheel speeds. A converter also acts on the signals representing the different wheel speeds to provide signals representing the acceleration of the different wheels and a selector selects the signal representing the largest acceleration. The signal representing the difference between the highest and lowest wheel speeds, and the signal representing the largest rate of acceleration are added together to provide a fault signal. A signal modifier modifies the fault signal to provide a controlled decay rate and the resulting signal is used to control the d.c.
motors.
Description
6 Case 255 This invention relates to the determination of a slipping condition of a wheel in a traction vehicle such as a locomotive and the providing of a control ~;
signal to prevent or limit slipping.
Traction vehicles, such as locomotives, commonly have a plurality of individually powered axles. For each wheel there is a coefficient of friction existing between that wheel and the surface on which ~
it is rolling. If the coeffieient of friction becomes ~ -less than that required to keep the wheel in rolling contact with the rail or other surface on which it is rolling, there will be a loss of adhesion and a slipping or skidding of the wheel. The present invention is primarily concerned with a determination of slipping.
Slipping occurs when the accelerating torque applied to a wheel becomes too large for the frictional forces existing between the wheel and the supporting surface and consequently the peripheral velocity of the wheel becomes greater than the corresponding vehicle velocity. ~ ;
In other words, the wheel turns faster than required to maintain rolling contact. Uncorrected slipping not ~;`
only causes loss of performance but may result in damage to the wheels or rails or other related apparatus. It is therefore desirable to detect the occurrence of slipping as soon as possible and to correct or control the slipping.
It is, in fact, desirable to detect slipping within less than a fraction of a wheel revolution, for example `
in 12 inches of a slip in a wheel of 40 inches in diameter, and then to correct the condition.
There are two types of slipping. In the first type the wheels of one of the individually powered axles of a vehicle may slip. In the second type, all the ~ ;
,'~ ;:
_ ,,:
1~3~6 Case 2558 wheels slip more or less simultaneously. This second type of slipping, referred to as synchronous slipping, tends to occur more frequently in systems where the source of driving power is alternating current (a.c.) motors where the speed of the motors is a function of the frequency of the electrical power supplied to the motors from a common source. When the source of driving power is direct current (d.c.) motors, it is possible for all the wheels to slip at the same time but due to small differences in individual motors, -coefficient of friction, etc., it is unlikely they will all start to ~lip at the same instant and maintain a more or less equivalent slip. The present invention takes advantage of this by detecting differences between the actions of the wheels as will be discussed hereinafter.
Many ways have been devised in the past for detecting or determining wheel slip. As an example, one prior apparatus detects wheel slip by obtaining wheel speed from several wheels to determine an average wheel speed. Then the wheel speed from an individually monitored wheel (there may be several wheels that are individually monitored) is compared with the average speed to derive a difference signal. This difference signal is then compared with a reference signal which may be representative of either the speed of an individual wheel or the average wheel speed. The result of this comparison provides a control signal for controlling motor drive acceleration or braking deceleration. Thus, the reference signal and the resulting control signal have a dependency upon, or a relationship with, wheel speed. IIn other words, the control system response is
signal to prevent or limit slipping.
Traction vehicles, such as locomotives, commonly have a plurality of individually powered axles. For each wheel there is a coefficient of friction existing between that wheel and the surface on which ~
it is rolling. If the coeffieient of friction becomes ~ -less than that required to keep the wheel in rolling contact with the rail or other surface on which it is rolling, there will be a loss of adhesion and a slipping or skidding of the wheel. The present invention is primarily concerned with a determination of slipping.
Slipping occurs when the accelerating torque applied to a wheel becomes too large for the frictional forces existing between the wheel and the supporting surface and consequently the peripheral velocity of the wheel becomes greater than the corresponding vehicle velocity. ~ ;
In other words, the wheel turns faster than required to maintain rolling contact. Uncorrected slipping not ~;`
only causes loss of performance but may result in damage to the wheels or rails or other related apparatus. It is therefore desirable to detect the occurrence of slipping as soon as possible and to correct or control the slipping.
It is, in fact, desirable to detect slipping within less than a fraction of a wheel revolution, for example `
in 12 inches of a slip in a wheel of 40 inches in diameter, and then to correct the condition.
There are two types of slipping. In the first type the wheels of one of the individually powered axles of a vehicle may slip. In the second type, all the ~ ;
,'~ ;:
_ ,,:
1~3~6 Case 2558 wheels slip more or less simultaneously. This second type of slipping, referred to as synchronous slipping, tends to occur more frequently in systems where the source of driving power is alternating current (a.c.) motors where the speed of the motors is a function of the frequency of the electrical power supplied to the motors from a common source. When the source of driving power is direct current (d.c.) motors, it is possible for all the wheels to slip at the same time but due to small differences in individual motors, -coefficient of friction, etc., it is unlikely they will all start to ~lip at the same instant and maintain a more or less equivalent slip. The present invention takes advantage of this by detecting differences between the actions of the wheels as will be discussed hereinafter.
Many ways have been devised in the past for detecting or determining wheel slip. As an example, one prior apparatus detects wheel slip by obtaining wheel speed from several wheels to determine an average wheel speed. Then the wheel speed from an individually monitored wheel (there may be several wheels that are individually monitored) is compared with the average speed to derive a difference signal. This difference signal is then compared with a reference signal which may be representative of either the speed of an individual wheel or the average wheel speed. The result of this comparison provides a control signal for controlling motor drive acceleration or braking deceleration. Thus, the reference signal and the resulting control signal have a dependency upon, or a relationship with, wheel speed. IIn other words, the control system response is
- 2 -- - .. . ,. :. ~ ::. .-. . . .
- Case 2558
- Case 2558
3~
;.
adjusted to be more or less sensitive in accordance with speed. Reference is made to Canadian Patent No.
993,984 - Adde, issued July 27, 1976 for a description of this form of control system.
The present inven-tion does not re~uire an average wheel speed. The present invention, in its -basic form, compares signals representing speeds of all the desired wheels and derives a first signal representing the speed aifference between the highest and the lowest wheel speeds, and it derives a second signal representing the highest rate of acceleration of the wheels. The first and second signals may be compensated or modified, ~-and are then summed to provide a control signal to control ;
the driving torque. Thus, the response to wheel slip is adjusted to be~mor~ or less sensitive in accordance with acceleration. The present invention is able to detect wheel slip within a fraction of a revolution `~
of a slipping wheel.
It is therefore a feature of the present invention to provide an improved method and apparatus for determining wheel slip using a comparison of wheel speeds from a plurality of wheels and deriving a control signal related to the difference between the -highest and lowest.
In accordance with one form of the invention there is provided apparatus for determining and controlling wheel slip in a traction vehicle powered by d.c. motors, comprising sensor means for sensing the speed of individual wheels driven by different motors and providing ;
first signals representing individual wheel speeds, first comparison means for receiving said first signals and deriving a second signal representing the difference ;23~ i case 25S~
between the highest and lowest sensed wheel speeds, conversion means for receiving said first signals and deriving respective third signals representing rates of acc~leration of said individual wheels, selector means for receiving said third signals and providing a fourth signal representing the highest rate, summing means for receiving said second and fourth signals and providing a fifth signal representing a fault signal, and signal modifying means for receiving said fifth signal and providing as an output control signal for said motors a signal corresponding to said fifty signal with a controlled rate of decay. `
The invention will be described in one form `
with reference to the accompanying drawings, in which:
Figure 1 is a simplified block diagram of circuitry according to a basic form of the invention, ;~
and Figure 2 is a simplified circuit diagram of one embodiment of the invention.
Referring now to Figure 1, there are shown -three lines or conductors 10, 11 and 12 with a fourth ;
conductor 14 partly indicated with a broken line to show there may be any number, and these lines or conductors come from sensors (not shown) which,provide signals vl, v2, V3 - - vn each representing the velocity of an individual locomotive wheel. The sensores (not shown) ; ~ -may be any type that provide a voltage proportional to wheel speed, i.e. to rpm. For example, the sensors (not shown) may be a magnetic pick-up sensitive to teeth ~;
on a wheel that rotates with a locomotive wheel or drive wheel where the frequency of sensed pulses is proportional to wheel speed, and a frequency-to-voltage
;.
adjusted to be more or less sensitive in accordance with speed. Reference is made to Canadian Patent No.
993,984 - Adde, issued July 27, 1976 for a description of this form of control system.
The present inven-tion does not re~uire an average wheel speed. The present invention, in its -basic form, compares signals representing speeds of all the desired wheels and derives a first signal representing the speed aifference between the highest and the lowest wheel speeds, and it derives a second signal representing the highest rate of acceleration of the wheels. The first and second signals may be compensated or modified, ~-and are then summed to provide a control signal to control ;
the driving torque. Thus, the response to wheel slip is adjusted to be~mor~ or less sensitive in accordance with acceleration. The present invention is able to detect wheel slip within a fraction of a revolution `~
of a slipping wheel.
It is therefore a feature of the present invention to provide an improved method and apparatus for determining wheel slip using a comparison of wheel speeds from a plurality of wheels and deriving a control signal related to the difference between the -highest and lowest.
In accordance with one form of the invention there is provided apparatus for determining and controlling wheel slip in a traction vehicle powered by d.c. motors, comprising sensor means for sensing the speed of individual wheels driven by different motors and providing ;
first signals representing individual wheel speeds, first comparison means for receiving said first signals and deriving a second signal representing the difference ;23~ i case 25S~
between the highest and lowest sensed wheel speeds, conversion means for receiving said first signals and deriving respective third signals representing rates of acc~leration of said individual wheels, selector means for receiving said third signals and providing a fourth signal representing the highest rate, summing means for receiving said second and fourth signals and providing a fifth signal representing a fault signal, and signal modifying means for receiving said fifth signal and providing as an output control signal for said motors a signal corresponding to said fifty signal with a controlled rate of decay. `
The invention will be described in one form `
with reference to the accompanying drawings, in which:
Figure 1 is a simplified block diagram of circuitry according to a basic form of the invention, ;~
and Figure 2 is a simplified circuit diagram of one embodiment of the invention.
Referring now to Figure 1, there are shown -three lines or conductors 10, 11 and 12 with a fourth ;
conductor 14 partly indicated with a broken line to show there may be any number, and these lines or conductors come from sensors (not shown) which,provide signals vl, v2, V3 - - vn each representing the velocity of an individual locomotive wheel. The sensores (not shown) ; ~ -may be any type that provide a voltage proportional to wheel speed, i.e. to rpm. For example, the sensors (not shown) may be a magnetic pick-up sensitive to teeth ~;
on a wheel that rotates with a locomotive wheel or drive wheel where the frequency of sensed pulses is proportional to wheel speed, and a frequency-to-voltage
- 4 -. ~23~ Case 2558 converter to provide a voltage signal varying with wheel speed. Alternatively the sensors may be photo-tachmeters which are a sealed unit having a light source and an opposed photodetector with a transparent disc between.
The disc bears radial lines which interrupt the light to provide pulses from the photodetector. The pulses vary in frequency with speed. The pulses are applied to a frequency-to-voltage converter to obtain a voltage signal varying with wheel speed.
Conductors 10, 11, 12 and 14 are connected to a voltage comparator and summer 15 which compares the signals vl - - v to derive a signal representing the differnce between the highest and lowest and then ~ :~
sums the difference over a short term. The signal, appearing on conductor 16, will be zero or some other reference level when there is no slip. In a preferred form the velocity difference comparator and summer 15 includes a biasing or set point means which inhibits an output signal until a predetermined minimum level is reached to avoid causing an output signal with very minor and insignificant fluctuations.
The conductors 10 - 12 (and 14 as required) are connected to respective rate converters 20 - 22.
The rate converters 20 - 22 provide output signals on conductors 23 - 25 respectively, which represent the rate of acceleration, and these are applied to rate selector and summer 26. Rate selector 26 selects the ~ `~
signal representing the highest acceleration, sums the signal over a short term, and places this signal on a conductor 27. A rate compensator 28 is connected to rate selector and summer 26 to compensate or modify ;
the signal in any manner as required. For example, ;
~3~ Case 2558 it has been found desirable to be able to reduce the effect of acceleration on the final control signal under some circumstances and this can be done in the compensator 28. In other circumstances it may be desirable to increase the effect of acceleration on the final signal at the lower end of the acceleration range and decrease it at the higher end. In a preferred form the rate selector and summer 26 includes a biasing or set point means which inhibits the output signal until a predetermined minimum level is reached to avoid insignificant fluctuations in acceleration affecting the output.
Conductors 16 and 27 are connected as inputs ~-~
to a slip summer 33 which adds the signals and provides -a summed signal on conductor 34. In a preferred form the slip summer 33 may include an amplifier means whose gain may be set by a control 35 to adapt the ~;
apparatus for different conditions. Conductor 34 is connected to slope generator 36 which is used to control decay or recovery. As is well known in the control art, it may cause problems if a correcting ~-control signal is removed immediately the correction is applied. The fault may recur or an oscillation may start. The slope generator 36 provides the necessary `
controlled delay in reducing the control signal after the fault is corrected. When a wheel slip is detected ;
a fault signa:L appears on conductor 34 and a corresponding control signal is applied via conductor 37 to the driving motors (not shown) to reduce the torque. The torque is reduced and the wheel slip stops but the correcting control signal on conductor 37 is not imme-diately removed. The slope generator 36 provides a . . ~
~,' '.:
~ 6 Case 2558 sloped signal that reduces with time, that is the signal ~reduces at a controlled rate or slope. The slope generator has two controls 40 and 41. Control 40 sets the decay rate or rate of decrease (i.e. the slope), and control 41 sets the starting point for the decay or decrease.
That is, the starting point for the controlled decrease may be set at the maximum control signal that can be achieved, or it can be set at a lower value.
It is believed that the operation of the Figure 1 circuit will be apparent from the preceding description. Very briefly, ~f a locomotive is accelerating and one wheel begins to slip and that wheel accelerates very quickly, there will be a difference in velocity between that wheel and the rest of the wheels.
This is detected by comparator 15 and the difference summed. Also there will be a rapid increase in acceleration for one wheel which will provide an increasing signal, selected by selector 26 and summed. ~-It will be recalled that the locomotive was itself accelerating and there would consequently be a signal ;
representing this on conductor 27. However rate ~ ;
compensator`28 may be set or arranged to reduce this comparatively low level acceleration below the limit of acceleration set into rate selector and summer 26 so that the locomotive acceleration, i.e. the slow accelera-tion of all wheels of the locomotive, does not cause a signal on conductor 27. The rapid acceleration of the single wheel is high there will be a large signal on conductor 27 and if it is a more moderate acceleration the signal on conductor 27 will be more moderate to adapt the con-trol response to the severity of the slip.
The signals on conductors 16 and 27 are summed . `,~
- 7 - ~ `
. "r~
~3~ Case 2558 by summer 33 to provide a control signal on conductor 37 to reduce the driving torque of the motors. The gain control 35 is set to ensure the control signal will be adequate for all situat:ions. As explained previously, the slope generator 36 controls the rate of return of the control signal to normal.
Assuming now that the locomotive moves on to a section of track with a lesser coefficient of friction and all the wheels begin to slip. Because the different wheels are driven by different d.c. motors the torque will not be precisely the same and the condi-tions will not be identical. Consequently the wheels will not all slip at identical speeds. There~ore ' there will be a difference in wheel velocity between the wheels and the velocity comparator 15 will ~' , detect the difference and provide a signal representative of the difference between the highest and the lowest wheel speeds as previously described. There will, ~,,' of course, be acceleration as the wheels begin to slip and the rate selector and summer 26 will provide a '7 signal representative of the highest rate of wheel acceleration. The two signals will be summed and a control ,, signal applie~ via conductor 37 to reduce the driving ~,'' torque from the d.c. motors to stop the slip. Thus -;', the slipping condition will be corrected whether one wheel is slipping~,or more than one wheel is slipping.
If desired, as an added precaution in case all wheels ~;~
should slip in abso1~ute synchronism (an unlikely ' ,~
occurrence in a d.c. drive), the wheel speed may be ~
monitored and when wheel speed exceeds that which ' corresponds to maximum locomotive velocity a warning '~ ', : . . -or control device could be activated. `, Case 2558 As will be apparent from Figure 1, signals, such as the fault or velocity signals, are available and these signals could be used for auxiliary purposes. For example, the fault signal or conductor 34 might be used to initiate operation of a sanding device. The signal for the slowest wheel speed, available from velocity comparator/summer 15, might be used to drive a locomotive speed indicator. The speed indicator might be driven by a signal directly from the front axle as is done on some locomotives at present, and this signal would be available on one of the conductors 10-14.
It is believed that the invention will be clearly understood from the description thus far.
However, one specific circuit is included in Figure ;~
2 as an example of one form or embodiment of the ;
invention.
Referring to Figure 2, the conductors 10, 11 and 12 are shown connected to pairs of oppositely poled diodes 42-47 as shown. The diodes are connected to provide on conductors 50 and 51 the highest and the lowest signals as inputs to an operational amplifier circuit 52 connected as a difference summer. A biasing voltage is applied via resistor 53 to inhibit signals below a certain level. The output is on conductor 16a and represents the sum of the difference between the highest and lowest wheel speeds.
The conductors 10, 11 and 12 are connected --by capacitors 54, 55 and 56 to rate converters 20a, ;~
20b and 20c respectively. The rate converters 20a, 20b and 20c provide output signals representative of the rate of acceleration of the respective wheels and these ~- :.-,~ ., are applied via diodes 57, 58 and 59 and conductor 60.
~:~l23~; Case 2558 The signal or conductor 60 will thus represent the largest accleration of the wheels whose speed is sensed.
This signal is applied as one irnput to operational amplifier 61 which sums the signal and provides an output on conductor 27a. A selectable bias can be set into the summer via conductor 62 as shown.
The signal representing the summed velocity difference on conductor 16a appears across potentiometer 64 and a selected portion of the signal is applied via resistance 74 to an input of operational amplifier 65. Similarly, the signal representing the summed greatest rate of accele~;ration on conductor 27a appears B across potentiometer ~ and a selected portion' of the signal is applied via resistance 67 to the same input of amplifier 65. Amplifier 65 is connected as `
an amplifier/summer whose gain is controlled by gain control 35a. This portion of the circuitry is indicated as being generally equivalent to slip summer 33 of ;Figure 1.
The signal form amplifier 65 ~the fault signal) is applied over conductor 34a to circuitry including operational amplifier 68. This circuitry, generally equivalent to slope generator 36 of Figure 1, provides `
the desired decay rate. Th~ feedback control 40a-controls the rate of decay and the voltage selected by voltage ,~
:. ~:,." :
control 41a controls the starting level. The conductor 37 carries the control signal as in Figure 1.
The Figure 2 circuit is included only as an example of one embodiment and various alternatives are `-~
30 available as is apparent from the preceding description.
'~:
- 1 0 - :' ' '''' - . . . .. . . -
The disc bears radial lines which interrupt the light to provide pulses from the photodetector. The pulses vary in frequency with speed. The pulses are applied to a frequency-to-voltage converter to obtain a voltage signal varying with wheel speed.
Conductors 10, 11, 12 and 14 are connected to a voltage comparator and summer 15 which compares the signals vl - - v to derive a signal representing the differnce between the highest and lowest and then ~ :~
sums the difference over a short term. The signal, appearing on conductor 16, will be zero or some other reference level when there is no slip. In a preferred form the velocity difference comparator and summer 15 includes a biasing or set point means which inhibits an output signal until a predetermined minimum level is reached to avoid causing an output signal with very minor and insignificant fluctuations.
The conductors 10 - 12 (and 14 as required) are connected to respective rate converters 20 - 22.
The rate converters 20 - 22 provide output signals on conductors 23 - 25 respectively, which represent the rate of acceleration, and these are applied to rate selector and summer 26. Rate selector 26 selects the ~ `~
signal representing the highest acceleration, sums the signal over a short term, and places this signal on a conductor 27. A rate compensator 28 is connected to rate selector and summer 26 to compensate or modify ;
the signal in any manner as required. For example, ;
~3~ Case 2558 it has been found desirable to be able to reduce the effect of acceleration on the final control signal under some circumstances and this can be done in the compensator 28. In other circumstances it may be desirable to increase the effect of acceleration on the final signal at the lower end of the acceleration range and decrease it at the higher end. In a preferred form the rate selector and summer 26 includes a biasing or set point means which inhibits the output signal until a predetermined minimum level is reached to avoid insignificant fluctuations in acceleration affecting the output.
Conductors 16 and 27 are connected as inputs ~-~
to a slip summer 33 which adds the signals and provides -a summed signal on conductor 34. In a preferred form the slip summer 33 may include an amplifier means whose gain may be set by a control 35 to adapt the ~;
apparatus for different conditions. Conductor 34 is connected to slope generator 36 which is used to control decay or recovery. As is well known in the control art, it may cause problems if a correcting ~-control signal is removed immediately the correction is applied. The fault may recur or an oscillation may start. The slope generator 36 provides the necessary `
controlled delay in reducing the control signal after the fault is corrected. When a wheel slip is detected ;
a fault signa:L appears on conductor 34 and a corresponding control signal is applied via conductor 37 to the driving motors (not shown) to reduce the torque. The torque is reduced and the wheel slip stops but the correcting control signal on conductor 37 is not imme-diately removed. The slope generator 36 provides a . . ~
~,' '.:
~ 6 Case 2558 sloped signal that reduces with time, that is the signal ~reduces at a controlled rate or slope. The slope generator has two controls 40 and 41. Control 40 sets the decay rate or rate of decrease (i.e. the slope), and control 41 sets the starting point for the decay or decrease.
That is, the starting point for the controlled decrease may be set at the maximum control signal that can be achieved, or it can be set at a lower value.
It is believed that the operation of the Figure 1 circuit will be apparent from the preceding description. Very briefly, ~f a locomotive is accelerating and one wheel begins to slip and that wheel accelerates very quickly, there will be a difference in velocity between that wheel and the rest of the wheels.
This is detected by comparator 15 and the difference summed. Also there will be a rapid increase in acceleration for one wheel which will provide an increasing signal, selected by selector 26 and summed. ~-It will be recalled that the locomotive was itself accelerating and there would consequently be a signal ;
representing this on conductor 27. However rate ~ ;
compensator`28 may be set or arranged to reduce this comparatively low level acceleration below the limit of acceleration set into rate selector and summer 26 so that the locomotive acceleration, i.e. the slow accelera-tion of all wheels of the locomotive, does not cause a signal on conductor 27. The rapid acceleration of the single wheel is high there will be a large signal on conductor 27 and if it is a more moderate acceleration the signal on conductor 27 will be more moderate to adapt the con-trol response to the severity of the slip.
The signals on conductors 16 and 27 are summed . `,~
- 7 - ~ `
. "r~
~3~ Case 2558 by summer 33 to provide a control signal on conductor 37 to reduce the driving torque of the motors. The gain control 35 is set to ensure the control signal will be adequate for all situat:ions. As explained previously, the slope generator 36 controls the rate of return of the control signal to normal.
Assuming now that the locomotive moves on to a section of track with a lesser coefficient of friction and all the wheels begin to slip. Because the different wheels are driven by different d.c. motors the torque will not be precisely the same and the condi-tions will not be identical. Consequently the wheels will not all slip at identical speeds. There~ore ' there will be a difference in wheel velocity between the wheels and the velocity comparator 15 will ~' , detect the difference and provide a signal representative of the difference between the highest and the lowest wheel speeds as previously described. There will, ~,,' of course, be acceleration as the wheels begin to slip and the rate selector and summer 26 will provide a '7 signal representative of the highest rate of wheel acceleration. The two signals will be summed and a control ,, signal applie~ via conductor 37 to reduce the driving ~,'' torque from the d.c. motors to stop the slip. Thus -;', the slipping condition will be corrected whether one wheel is slipping~,or more than one wheel is slipping.
If desired, as an added precaution in case all wheels ~;~
should slip in abso1~ute synchronism (an unlikely ' ,~
occurrence in a d.c. drive), the wheel speed may be ~
monitored and when wheel speed exceeds that which ' corresponds to maximum locomotive velocity a warning '~ ', : . . -or control device could be activated. `, Case 2558 As will be apparent from Figure 1, signals, such as the fault or velocity signals, are available and these signals could be used for auxiliary purposes. For example, the fault signal or conductor 34 might be used to initiate operation of a sanding device. The signal for the slowest wheel speed, available from velocity comparator/summer 15, might be used to drive a locomotive speed indicator. The speed indicator might be driven by a signal directly from the front axle as is done on some locomotives at present, and this signal would be available on one of the conductors 10-14.
It is believed that the invention will be clearly understood from the description thus far.
However, one specific circuit is included in Figure ;~
2 as an example of one form or embodiment of the ;
invention.
Referring to Figure 2, the conductors 10, 11 and 12 are shown connected to pairs of oppositely poled diodes 42-47 as shown. The diodes are connected to provide on conductors 50 and 51 the highest and the lowest signals as inputs to an operational amplifier circuit 52 connected as a difference summer. A biasing voltage is applied via resistor 53 to inhibit signals below a certain level. The output is on conductor 16a and represents the sum of the difference between the highest and lowest wheel speeds.
The conductors 10, 11 and 12 are connected --by capacitors 54, 55 and 56 to rate converters 20a, ;~
20b and 20c respectively. The rate converters 20a, 20b and 20c provide output signals representative of the rate of acceleration of the respective wheels and these ~- :.-,~ ., are applied via diodes 57, 58 and 59 and conductor 60.
~:~l23~; Case 2558 The signal or conductor 60 will thus represent the largest accleration of the wheels whose speed is sensed.
This signal is applied as one irnput to operational amplifier 61 which sums the signal and provides an output on conductor 27a. A selectable bias can be set into the summer via conductor 62 as shown.
The signal representing the summed velocity difference on conductor 16a appears across potentiometer 64 and a selected portion of the signal is applied via resistance 74 to an input of operational amplifier 65. Similarly, the signal representing the summed greatest rate of accele~;ration on conductor 27a appears B across potentiometer ~ and a selected portion' of the signal is applied via resistance 67 to the same input of amplifier 65. Amplifier 65 is connected as `
an amplifier/summer whose gain is controlled by gain control 35a. This portion of the circuitry is indicated as being generally equivalent to slip summer 33 of ;Figure 1.
The signal form amplifier 65 ~the fault signal) is applied over conductor 34a to circuitry including operational amplifier 68. This circuitry, generally equivalent to slope generator 36 of Figure 1, provides `
the desired decay rate. Th~ feedback control 40a-controls the rate of decay and the voltage selected by voltage ,~
:. ~:,." :
control 41a controls the starting level. The conductor 37 carries the control signal as in Figure 1.
The Figure 2 circuit is included only as an example of one embodiment and various alternatives are `-~
30 available as is apparent from the preceding description.
'~:
- 1 0 - :' ' '''' - . . . .. . . -
Claims (4)
1. Apparatus for determining and controlling wheel slip in a traction vehicle powered by d.c. motors, comprising sensor means for sensing the speed of individual wheels driven by different motors and providing first signals representing individual wheel speeds, comparison means for receiving said first signals and deriving a second signal representing the difference between the highest and lowest sensed wheel speeds, conversion means for receiving said first signals and deriving respective third signals representing rates of acceleration of said individual wheels, selector means for receiving said third signals and providing a fourth signal representing the highest rate, summing means for receiving said second and fourth signals and providing a fifth signal representing a fault signal, and signal modifying means for receiving said fifth signal and comprising a slope generator to provide a slope governing said rate of decay of said fifth signal, said slope generator including a slope control to adjust said slope and consequently said rate of decay and a level control to adjust a fixed level at which said decay commences, said signal modifying means providing an output control signal for said motors.
2. Apparatus as defined in claim 1 and further comprising first biasing means connected between said comparison means and said summing means to provide a bias inhibiting said second signal when said second signal is below a first predeter-mined level.
3. Apparatus as defined in claim 2 and further comprising a second biasing means connected between said selector Case 2558 means and said summing means to provide a bias inhibiting said fourth signal when said fourth signal is below a second predetermined level.
4. Apparatus for determining wheel slip in a traction vehicle powered by d.c. motors, comprising sensor means for sensing the speed of individual wheels driven by different d.c. motors and providing first signals whose voltage varies as the speed of the respective wheels, a voltage comparator for receiving said first signals and deriving a second signal representing the difference between the highest and the lowest voltage of said first signals, first summing means for receiving said second signal and summing said second signal over a short term, conversion means for receiving said first signals and deriving respective third signals whose voltage varies as the rates of acceleration of the respective wheels, selector means for receiving said third signals and providing a fourth signal representing the highest voltage of said third signals, second summing means for receiving said fourth signal and summing said fourth signal over a short term, third summing means for receiving the summed second and fourth signals and providing as an output a fifth signal which is the algebraic sum of said summed second and fourth signals, and a decay rate slope generator for receiving said fifth signal and providing as an output control signal to reduce the driving torque of said motors when said fifth signal indicates wheel slip a sixth signal corresponding to said fifth signal with a controlled rate of decay.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA307,760A CA1123496A (en) | 1978-07-20 | 1978-07-20 | Locomotive wheel slip determination |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA307,760A CA1123496A (en) | 1978-07-20 | 1978-07-20 | Locomotive wheel slip determination |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1123496A true CA1123496A (en) | 1982-05-11 |
Family
ID=4111932
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA307,760A Expired CA1123496A (en) | 1978-07-20 | 1978-07-20 | Locomotive wheel slip determination |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1123496A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4463289A (en) * | 1982-03-11 | 1984-07-31 | General Electric Company | Wheel slip control using differential signal |
| US4773714A (en) * | 1985-12-27 | 1988-09-27 | Akebono Brake Industry Co., Ltd. | Anti-skid control system for motor vehicles |
| US4924395A (en) * | 1989-04-13 | 1990-05-08 | Caterpillar Inc. | Synchronous wheel slip strategy for a locomotive governor |
| US4950964A (en) * | 1989-04-13 | 1990-08-21 | Caterpillar Inc. | Locomotive differential wheel slip control |
| WO2023151458A1 (en) * | 2022-02-11 | 2023-08-17 | 长城汽车股份有限公司 | Motor torque control method and apparatus, electronic device, and vehicle |
-
1978
- 1978-07-20 CA CA307,760A patent/CA1123496A/en not_active Expired
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4463289A (en) * | 1982-03-11 | 1984-07-31 | General Electric Company | Wheel slip control using differential signal |
| US4773714A (en) * | 1985-12-27 | 1988-09-27 | Akebono Brake Industry Co., Ltd. | Anti-skid control system for motor vehicles |
| US4924395A (en) * | 1989-04-13 | 1990-05-08 | Caterpillar Inc. | Synchronous wheel slip strategy for a locomotive governor |
| US4950964A (en) * | 1989-04-13 | 1990-08-21 | Caterpillar Inc. | Locomotive differential wheel slip control |
| WO2023151458A1 (en) * | 2022-02-11 | 2023-08-17 | 长城汽车股份有限公司 | Motor torque control method and apparatus, electronic device, and vehicle |
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