CN114701458A - Control system and control method for wheel rail braking - Google Patents

Control system and control method for wheel rail braking Download PDF

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Publication number
CN114701458A
CN114701458A CN202210326715.0A CN202210326715A CN114701458A CN 114701458 A CN114701458 A CN 114701458A CN 202210326715 A CN202210326715 A CN 202210326715A CN 114701458 A CN114701458 A CN 114701458A
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China
Prior art keywords
speed difference
adhesion
wheel
braking
speed
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CN114701458B (en
Inventor
陈波
常崇义
蔡园武
白鑫
李果
郭刚
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China Academy of Railway Sciences Corp Ltd CARS
Railway Science and Technology Research and Development Center of CARS
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China Academy of Railway Sciences Corp Ltd CARS
Railway Science and Technology Research and Development Center of CARS
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    • 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
    • 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
    • B60T8/171—Detecting parameters used in the regulation; Measuring values used in the regulation
    • 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
    • B60T8/172—Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters
    • 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
    • B60T8/176—Brake regulation specially adapted to prevent excessive wheel slip during vehicle deceleration, e.g. ABS
    • B60T8/1761—Brake regulation specially adapted to prevent excessive wheel slip during vehicle deceleration, e.g. ABS responsive to wheel or brake dynamics, e.g. wheel slip, wheel acceleration or rate of change of brake fluid pressure
    • 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
    • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
    • B60T8/34—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B61—RAILWAYS
    • B61H—BRAKES OR OTHER RETARDING DEVICES SPECIALLY ADAPTED FOR RAIL VEHICLES; ARRANGEMENT OR DISPOSITION THEREOF IN RAIL VEHICLES
    • B61H11/00—Applications or arrangements of braking or retarding apparatus not otherwise provided for; Combinations of apparatus of different kinds or types
    • B61H11/06—Applications or arrangements of braking or retarding apparatus not otherwise provided for; Combinations of apparatus of different kinds or types of hydrostatic, hydrodynamic, or aerodynamic brakes

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Transportation (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Regulating Braking Force (AREA)

Abstract

A control system for wheel-rail braking includes a control calculation unit; the brake system comprises a control calculation unit, an anti-skid valve and a brake cylinder; the control calculation unit is provided with a speed difference threshold value, and the value of the speed difference threshold value is set to enable the adhesion coefficient value in the braking process to enter an adhesion re-rising stage after the first peak point; and when the actual speed difference is larger than or equal to the threshold value of the speed difference in the braking process, triggering the system to perform braking antiskid, and sending an instruction by the control and calculation unit, wherein the instruction is to open an antiskid valve to reduce the pressure of a brake cylinder and enter an air exhaust stage. Through setting the threshold value of the speed difference, the adhesion curve has an adhesion re-rising stage along with the increase of the creep rate, the motor train can brake by utilizing the coefficient value of the adhesion force in the adhesion re-rising stage, the braking distance is better reduced, and the tread of the wheel can be effectively prevented from being scratched.

Description

Control system and control method for wheel rail braking
Technical Field
The invention relates to the field of bullet train control, in particular to a control system and a control method for wheel rail braking.
Background
At present, the brake of motor train units at home and abroad mainly adopts wheel-rail adhesion brake, namely, the brake is carried out by using the adhesion force between wheels and rail surfaces, the actual brake force is exerted depending on the magnitude of the adhesion force between the wheel rails, the available adhesion force coefficient between the wheel rails is reduced along with the improvement of the running speed of the motor train unit, and the wheel sliding probability is increased. Under the condition that the rail surface is wet, when the adhesive force between the wheel rails is smaller than the braking force actually required by the motor train unit, the wheel pair can slide or even scratch, and the braking distance is prolonged or even the risk of the motor train unit running is caused.
The brake anti-skid control is a control technology which is adopted for effectively utilizing adhesion between wheel rails to shorten the brake distance under the unfavorable adhesion condition and avoid the wheel set from being scratched as much as possible, is a core technology of a brake system of a motor train unit, and is also a key point and a difficulty point of the development of the brake system.
Specifically, in a state where "coasting" is not determined, the brake antiskid system does not operate; when the braking force is about to exceed the adhesive force (at the moment, the braking anti-skid system judges that the braking anti-skid system is in a 'sliding' state), the anti-skid device is triggered to exhaust air and reduce pressure of the brake cylinder, the braking force is reduced, the wheel is kept in a rolling (or rolling sliding) state, and the wheel is prevented from sliding; the antiskid device adopts a control means of a microprocessor, and repeatedly performs pressure reduction, pressure maintaining and pressure increase control on the pressure of a brake cylinder after being triggered to adjust the change of braking force, so that the adhesion between wheel rails is utilized to the maximum extent, and therefore, the braking antiskid system can control the braking force to prevent skidding without causing excessive loss of the braking force.
Therefore, the key point is that when the brake anti-skid system judges to be 'sliding', the judgment is early, the brake force loss is overlarge, the adhesion between wheel rails cannot be fully utilized, and the brake distance is prolonged greatly; later judgment, the sliding will occur, the tread is scratched, and the anti-skid function cannot be achieved. When the brake anti-skid system of the motor train unit judges whether the motor train unit slides, the brake anti-skid system mainly depends on speed difference, deceleration, slip rate, deceleration differential and the like, wherein the speed difference is more commonly adopted, the speed difference refers to the difference value between the speed of a train and the speed of a wheel pair shaft, and can be expressed as delta v ═ v-Vehicle with wheels-vWheel. When the speed difference exceeds a speed difference threshold value used as a sliding judgment basis, the speed difference is judged to be 'sliding', and then the antiskid device is triggered to execute antiskid actions.
However, the development of the current anti-skid braking system is based on the characteristics of wheel rail adhesion, and the threshold value of the speed difference according to the sliding judgment is set to be too small, generally limited within 30km/h-40km/h, and the wheel rail adhesion at the speed of over 300km/h cannot be fully utilized to shorten the braking distance.
In the future, the next generation of high-speed motor train unit with the speed of 400km/h can run on the existing high-speed railway, and in order to ensure the running safety, the emergency braking distance when the motor train unit runs at 400km/h is required to be equivalent to the index when the existing motor train unit with the renaissance number runs at 350km/h, namely 6500 m. The method provides a challenge for development and adhesion utilization of a braking system of a high-speed motor train unit with the speed of 400 kilometers. The adhesion and utilization of the brake under rain and snow weather of high-speed trains belong to the problem of large creep, however, the research on the characteristics and the generation mechanism of the large creep adhesion behavior of the brake under the speed of 400 kilometers per hour is almost blank at present.
Disclosure of Invention
Object of the application
In view of the above, the invention provides a control system for wheel rail braking, so as to solve the problem that the technical requirement of a braking distance cannot be met any more in the braking process of a motor car on a wet rail surface, especially in the case that the speed of the motor car is greatly increased in the later period in the prior art.
(II) technical scheme
The application discloses a control system for wheel-rail braking, which comprises a control calculation unit, an anti-skid valve and a brake cylinder; when the actual speed difference in the braking process is larger than or equal to the threshold value of the speed difference, the system is triggered to execute braking antiskid, and the control calculation unit sends an instruction which is used for opening an antiskid valve to reduce the pressure of a brake cylinder and enter an air exhaust stage.
In a possible embodiment, said actual speed difference is the maximum of the differences between the peripheral speed of any one of the axles and the speed value of the railcar at the same moment in the braking process.
In a possible embodiment, a plurality of speed measuring devices are further included, which are respectively arranged on different wheel axles, for detecting the circumferential speeds of the different wheel axles, and the control and calculation unit receives the real-time detection of the circumferential speeds of the different wheel axles during braking and for calculating the actual speed difference.
In a possible embodiment, the velometer comprises a speed measuring gear and a sensor, the speed measuring gear is arranged on the wheel shaft and rotates along with the wheel shaft, the sensor collects the alternation of the tooth crest and the tooth trough of the rotating speed measuring gear in front of the sensor to generate a pulse signal, and the peripheral speed of the wheel shaft is calculated through the period of the pulse signal, the number of teeth of the test gear and the radius of the wheel on the wheel shaft.
In one possible embodiment, the upper limit value of the speed difference threshold value range when the vehicle speed is in the range of 300km/h-450km/h is 60km/h, and the lower limit value is 40 km/h.
In a possible implementation mode, when the vehicle speed is 350km/h, the range of the speed difference threshold value is 55km/h at the upper limit value and 40km/h at the lower limit value.
In a possible implementation mode, when the vehicle speed is 400km/h, the range of the speed difference threshold value is 60km/h at the upper limit value and 40km/h at the lower limit value.
In a possible implementation mode, when the vehicle speed is 450km/h, the range of the speed difference threshold value is 60km/h at the upper limit value and 40km/h at the lower limit value.
As a second aspect of the present application, there is also provided a control method for wheel rail braking, including the steps of:
setting a threshold value of the speed difference;
and detecting and calculating the actual speed difference in the braking process, and executing anti-skid braking when the actual speed difference in the braking process is greater than or equal to the threshold value of the speed difference, wherein the execution of anti-skid braking comprises opening an anti-skid valve to reduce the pressure of a brake cylinder and enter an air exhaust stage.
In a possible embodiment, said detecting and calculating said actual speed difference during braking comprises detecting in real time the peripheral speed of the different axles and receiving this data to calculate said actual speed difference; the actual speed difference is the maximum value of the difference between the peripheral speed of any one of the multiple wheel shafts and the speed value of the bullet train at the same moment in the braking process.
(III) advantageous effects
This application contrast prior art has following beneficial effect: by setting the threshold value of the speed difference, the adhesion curve has an adhesion re-rising stage along with the increase of the creep rate, and the motor train can brake by utilizing the adhesion coefficient value in the adhesion re-rising stage in the braking process, so that the braking distance can be better reduced, and the tread surface of the wheel can be effectively prevented from being scratched.
Additional advantages, objects, and features of the application will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the application.
The objectives and other advantages of the present application may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.
Drawings
The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining and illustrating the present application and should not be construed as limiting the scope of protection of the present application.
FIG. 1 is a system block diagram of the present application;
FIG. 2 is a schematic diagram of an interval of upper and lower limit values of a speed difference threshold value disclosed in the present invention;
FIG. 3 is a brake adhesion characteristic curve of a wheel rail with a maximum creep rate of 10% under a wet rail surface condition of 300 km/h;
FIG. 4 is a brake adhesion characteristic curve of a wheel rail with a maximum creep rate of 15% under a wet rail surface condition of 300 km/h;
FIG. 5 is a brake adhesion characteristic curve of a wheel rail with a maximum creep rate of 20% under a wet rail surface condition of 300 km/h;
FIG. 6 is a brake adhesion characteristic curve of a wheel rail with a maximum creep rate of 20% under a wet rail surface condition of 350 km/h;
FIG. 7 is a brake adhesion characteristic curve of a wheel rail with a maximum creep rate of 10% under a wet rail surface condition of 400 km/h;
FIG. 8 is a brake adhesion characteristic curve of a wheel rail with a maximum creep rate of 20% under a wet rail surface condition of 400 km/h;
FIG. 9 is a brake adhesion characteristic curve of a wheel rail with a maximum creep rate of 20% under a wet rail surface condition of 450 km/h;
FIG. 10 is a graph comparing conventional limits to new limits for an emergency braking speed of 300km/h at an initial speed under wet rail surface conditions, in accordance with the present disclosure;
in the figure: 1. a control calculation unit; 201. a first axle; 202. a second wheel axle; 203. a third wheel axle; 204. a fourth wheel axle; 301. a first speed measuring gear; 302. a second speed measuring gear; 303. a third speed measuring gear; 304. a fourth speed measuring gear; 401. a first sensor; 402. a second sensor; 403. a third sensor; 404. a fourth sensor; 501. a first anti-skid valve; 502. a second anti-skid valve; 503. a third prevention slide valve; 504. a fourth slide prevention valve; 601. a first brake cylinder; 602. a second brake cylinder; 603. a third brake cylinder; 604. and a fourth brake cylinder.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In the above description of the present invention, it should be noted that the terms "one side", "the other side" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings or orientations or positional relationships that the products of the present invention are conventionally placed in use, and are only used for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the device or the element to which the present invention is directed must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used merely to distinguish one description from another, and are not to be construed as indicating or implying relative importance.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
The embodiments of the control system for wheel rail braking provided by the invention are described in detail with reference to fig. 1-10, and are mainly applied to wheel rail braking antiskid, and based on the characteristics of braking creep adhesion behavior at a speed of 300-450km/h, a reasonable control range of detecting a speed difference of a key parameter by using the control system is provided, and corresponding operations are implemented, so that the wheel rail braking adhesion utilization level under a wet rail surface condition is improved, and the train braking distance is shortened.
In the application, adhesion is a phenomenon that the position of the part on both sides of the contact surface of the wheel rail and the position of the force transmission side part are not changed in the rolling process of the wheel. The adhesion force is the force transmitted by the contact part between the wheel and the rail along with the micro-slip, and when the wheel rolls along the wheel and the rail, the braking force can be applied only under the condition that the contact surface has relative motion in the longitudinal (tangential) direction. When the braking force exceeds the limit value of the adhesive force, the adhesion state between the wheel rails is changed, namely the static friction is converted into sliding friction, the size of the sliding friction is reduced sharply, the phenomenon is called 'sliding', the generation of sliding causes the braking force to be reduced, and the requirement of the parking distance cannot be met.
The wheel-rail adhesion characteristics are generally expressed by using an adhesion coefficient and a longitudinal creep rate change curve. Wherein the adhesion coefficient μ is generally defined as the ratio of the tangential moving force F to the normal force Q at the contact surface between the wheel and the rail, i.e.:
Figure RE-GDA0003675590690000071
the creep rate is also called slip rate, and when a wheel sends out traction force or braking force, relative motion occurs between the wheel and a track, and the creep rate is the proportion of a sliding component in the motion of the wheel. As mentioned above, the speed v of the trainVehicle with wheelsSpeed v of wheel pair shaftWheelThe difference of (a), i.e., the speed difference, can be expressed as Δ v ═ vVehicle with wheels-vWheelThe creep rate can be set as xi ═ Δ v/vVehicle with wheelsTo indicate. The speed difference is more direct and accurate than the creep rate, becauseIn the actual anti-skid control, the speed difference of key parameters detected by a control system is used as a criterion.
In the present embodiment, the control system includes a control calculation unit 1; wherein the control calculation unit is provided with a threshold value of the speed difference; the value of the threshold value of the speed difference is set to enable the value of the adhesion coefficient in the braking process to enter an adhesion re-rising stage after the first peak point; and when the actual speed difference is larger than or equal to the threshold value of the speed difference in the braking process, triggering the system to perform braking antiskid, and sending an instruction by the control and calculation unit, wherein the instruction is to open an antiskid valve to reduce the pressure of a brake cylinder and enter an air exhaust stage.
Here, the threshold value of the speed difference may be set to perform control of braking antiskid when the vehicle is coasting; when the adhesion between the wheel rails is low, the wheel can be effectively prevented from sliding, after adhesion recovery, the requirement of braking distance can be met, re-adhesion control is realized, the sliding probability is reduced, adverse consequences caused by sliding of the vehicle are avoided, and the abrasion of the wheel rails is reduced. The control of the braking skid resistance is closed in a normal state, and is started only when the sliding occurs. Therefore, the threshold value of the speed difference is the judgment basis for determining whether the brake anti-skid control is triggered.
The invention sets the values of the speed difference threshold value as follows: so that the adhesion coefficient in the braking process can enter the adhesion re-rising stage. As described above, the wheel-rail adhesion characteristic can be represented by a brake adhesion characteristic curve, which is a variation curve between the longitudinal creep rate and the adhesion coefficient, and the brake adhesion characteristic curve has a first peak point, which is the highest point of the first rising stage of the adhesion characteristic curve, and the first peak point of the first rising stage of the adhesion coefficient is used in the conventional train braking process. The threshold value of the speed difference is set to enable the value of the adhesion coefficient in the braking process to enter an adhesion re-rising stage after the first peak point, and the adhesion re-rising stage comprises at least one other peak point with the adhesion coefficient value higher than the first peak point.
As shown in fig. 2, the value interval of the speed difference threshold value specifically includes: when the vehicle speed is 300km/h-450km/h, the upper limit value of the value range of the speed difference threshold value is 60km/h, and the lower limit value is 40 km/h. Among them, as shown in Table 1, the more preferable value is that when the vehicle speed is 300km/h, the upper limit value of the range of the speed difference threshold value is 50km/h, and the lower limit value is 40 km/h. When the vehicle speed is 350km/h, the upper limit value of the value range of the speed difference threshold value is 55km/h, and the lower limit value is 40 km/h. When the vehicle speed is 400km/h, the upper limit value of the value range of the speed difference threshold value is 60km/h, and the lower limit value is 40 km/h. When the vehicle speed is 450km/h, the upper limit value of the value range of the speed difference threshold value is 60km/h, and the lower limit value is 40 km/h.
TABLE 1 Range of value ranges for speed Difference threshold values
Figure RE-GDA0003675590690000081
Figure RE-GDA0003675590690000091
By setting the threshold value of the speed difference, the adhesion curve has an adhesion re-rising stage along with the increase of the creep rate, and the motor train can brake by utilizing the coefficient value of the adhesion force in the adhesion re-rising stage, so that the braking distance can be better reduced, and the tread of the wheel can be effectively prevented from being scratched.
The actual speed difference is the maximum value in the difference value between the peripheral speed of any one of the multiple wheel shafts and the speed value of the bullet train at the same moment in the braking process; the control system for acquiring the peripheral speeds of different axles further comprises a plurality of speed measuring devices, the plurality of speed measuring devices are respectively arranged on different axles and are used for detecting the peripheral speeds of different axles, the control calculation unit receives the real-time detected peripheral speeds of different axles in the braking process and is used for calculating the actual speed difference, and the bullet train speed value can be obtained through an ultrasonic radar or other technical means; the velometer comprises a speed measuring gear and a sensor, the speed measuring gear is arranged on a wheel shaft and rotates along with the wheel shaft, the sensor collects the alternation of tooth crests and tooth valleys of the rotating speed measuring gear in front of the sensor to generate pulse signals, and the peripheral speed of the wheel shaft is calculated through the period of the pulse signals, the number of teeth of the testing gear and the radius of wheels on the wheel shaft: the peripheral speed calculation formula of the wheel axle is v ═ rw; wherein: r is the radius of the wheel on the axle and w is the angular velocity of the axle. The speed measuring gear is arranged on the wheel shaft and rotates along with the wheel shaft, and the sensor generates pulse signals through the alternation of tooth crests and tooth troughs of the rotating speed measuring gear in front of the sensor, so that the angular speed of the wheel shaft is calculated:
w＝2*f*3.6*π/Z；
wherein: w is the angular velocity of the axle;
f is the frequency of the pulse signal;
and z is the number of the speed measuring gear teeth.
The control system also comprises an anti-skid valve and a brake cylinder; when the speed difference is larger than or equal to the threshold value of the speed difference, the brake cylinder is controlled to exhaust to reduce the braking force, and wheels of the wheel axle with the speed difference larger than or equal to the threshold value of the speed difference are enabled to be adhered to the rail from the new position. The method comprises the following specific steps: the control calculation unit issues an instruction: opening the anti-skid valve to reduce the pressure of the brake cylinder and enter an air exhaust stage; then the antiskid valve is closed, the pressure of the brake cylinder stops decreasing, and a pressure maintaining state is formed; and (4) charging air into the brake cylinder, and increasing the pressure of the brake cylinder to restore the normal braking state before sliding. Taking a car as an example, fig. 1 shows a specific configuration of the control system: the axles comprise a first axle 201, a second axle 202, a third axle 203 and a fourth axle 204; the speed measuring gear envelopes the first speed measuring gear 301, the second speed measuring gear 302, the third speed measuring gear 303 and the fourth speed measuring gear 304; the sensors include a first sensor 401, a second sensor 402, a third sensor 403, and a fourth sensor 404; the antiskid valves include a first antiskid valve 501, a second antiskid valve 502, a third antiskid valve 503, and a fourth antiskid valve 504; the brake cylinders comprise a first brake cylinder 601, a second brake cylinder 602, a third brake cylinder 603 and a fourth brake cylinder 604; the first speed measuring gear and the first wheel shaft are coaxially arranged on the first wheel shaft and synchronously rotate along with the first wheel shaft, the first sensor collects the alternative change of the tooth tops and the tooth valleys of the first speed measuring gear in front of the sensor to generate pulse signals, and the pulse signals are transmitted into the control calculation unit and are used for calculating the angular speed of the first wheel shaft through the control calculation unit so as to calculate the peripheral speed of the first wheel shaft; in a similar way the control calculation unit may also calculate the peripheral speed of the second axle, the peripheral speed of the third axle and the peripheral speed of the fourth axle. When the motor car sends a braking instruction, the control calculation unit sets a threshold value of the speed difference, detects and calculates the actual speed difference in the braking process, and continuously acquires the speed value of the motor car, the peripheral speed of the first wheel shaft, the peripheral speed of the second wheel shaft, the peripheral speed of the third wheel shaft and the peripheral speed of the fourth wheel shaft at the same moment in the braking process; the control calculation unit respectively calculates the difference between the peripheral speed of the first wheel shaft and the speed value of the motor train, the difference between the peripheral speed of the second wheel shaft and the speed value of the motor train, the difference between the peripheral speed of the third wheel shaft and the speed value of the motor train, and the difference between the peripheral speed of the fourth wheel shaft and the speed value of the motor train, wherein the maximum value of the differences is the actual speed difference.
The adhesion characteristic curve of the wheel rail under the large creep condition (such as the wet rail surface working condition) in the vehicle speed range of 300-450km/h obtained by the adhesion test is described below, so as to demonstrate the variation condition of the adhesion coefficient under the above speed difference threshold value. The adhesion test utilizes the high-speed wheel-rail relation experiment table to be composed of a track wheel system, a test wheel pair system, a hydraulic vibration excitation system, a track contact interface environment simulation system, a track wheel profile numerical control selective repairing device, a high-pressure hydraulic supply unit, a lubricating unit, electrical equipment, a measurement and data acquisition system, a control system and the like, and performance parameters such as wheel pair rotating speed, track wheel rotating speed, wheel-rail contact force, braking torque and the like can be measured in the test process. The test bed is used for large creep adhesion characteristic tests in braking at different speeds under the condition of a wet rail surface working condition. Wherein, the test defines the longitudinal adhesion coefficient as:
Figure RE-GDA0003675590690000111
wherein Fx is longitudinal adhesion of the wheel rail, and Fn is contact force of the wheel rail. Longitudinal creep rate xixCan be calculated as follows:
Figure RE-GDA0003675590690000112
in the formula: rwAnd RrRadius of contact point of wheel and rail wheel, nwAnd nrThe rotational speeds of the vehicle and the rail wheel, respectively.
Experiment one: an adhesion characteristic curve of an adhesion coefficient and a longitudinal creep rate in the loading and unloading processes during 300km/h speed braking.
Comparative example 1: when the maximum creep rate is controlled to be 10% (i.e. the speed difference is controlled to be within 30 km/h), it can be seen from fig. 3 that the longitudinal creep rate is increased from 0% to less than 1% during the loading process, and the adhesion coefficient is increased rapidly in an approximately linear manner along with the longitudinal creep rate; when the longitudinal creep rate is increased to 1%, the adhesion coefficient reaches the point A in the loading process, and the adhesion coefficient at the moment is the highest and is called as a first peak point A; thereafter, the adhesion coefficient decreases with increasing longitudinal creep rate until reaching the point of inflection B when the maximum longitudinal creep rate is 10%; the longitudinal creep rate is reduced from 10% during unloading, the adhesion coefficient is reduced along with the reduction of the longitudinal creep rate until the longitudinal creep rate reaches a point C, which is a peak point C, and the peak point C is smaller than a first peak point A; thereafter, the adhesion coefficient rapidly decreases approximately linearly with increasing longitudinal creep rate until the longitudinal creep rate is 0%.
The speed adhesion characteristics are distinct: when the longitudinal creep rate is increased from 0% to 1%, a first peak point A appears, the adhesion coefficient of the first peak point A is consistent with that in a wheel-rail small creep experiment, and the adhesion coefficient is rapidly increased in an approximately linear mode along with the increase of the longitudinal creep rate at the stage; from the first peak point A to the inflection point B, the adhesion coefficient decreases with increasing longitudinal creep rate; the peak point C also appears in the unloading process, the adhesion coefficient of the peak point C is far smaller than the value of the first peak point A, the adhesion characteristic curve in the form belongs to an unstable stage in the process from the first peak point A to the turn-back point B and from the turn-back point B to the peak point C, and the adhesion is avoided during the wheel-rail adhesion utilization; the adhesion belongs to a stable stage from the beginning to the first peak point a, that is, the adhesion rising stage in fig. 3, which is beneficial to improve the utilization of the wheel-rail adhesion, but since the maximum creep rate is controlled to be 10% (i.e., the speed difference is controlled to be within 30 km/h), the adhesion coefficient in the whole process is not higher than the first peak point a.
Experimental example 1: when the maximum creep rate is controlled to be 15% (i.e. the speed difference is controlled to be within 45 km/h), it can be seen from fig. 4 that the longitudinal creep rate is increased from 0% to less than 1% during the loading process, and the adhesion coefficient is increased rapidly in an approximately linear manner along with the longitudinal creep rate; when the longitudinal creep rate is increased to 1%, the adhesion coefficient reaches a point A in the loading process, and the adhesion coefficient at the moment is a first peak point A; thereafter, the adhesion coefficient decreases with an increase in the longitudinal creep rate, and reaches point D when the longitudinal creep rate increases to 8%; then the adhesion coefficient begins to slowly increase along with the increase of the longitudinal creep rate until the adhesion coefficient reaches a folding point B when the longitudinal creep rate is 15 percent; when unloading, the longitudinal creep rate is reduced from 15%, and the adhesion coefficient is increased along with the reduction of the longitudinal creep rate; until the longitudinal creep rate reaches a point E, and the adhesion coefficient at the moment is a second peak point E; thereafter, the adhesion coefficient decreased with increasing longitudinal creep rate until the longitudinal creep rate was 0%.
The adhesion characteristics at speed are distinguished as follows: when the longitudinal creep rate of the adhesion coefficient is increased from 0% to 1%, a first peak point A appears, and from the beginning to the first peak point A, the adhesion coefficient is rapidly increased in an approximately linear way along with the increase of the longitudinal creep rate; from the first peak point a to point D, the adhesion coefficient decreases slightly with increasing longitudinal creep rate; from the point D to the point B of the reverse turn, the adhesion coefficient is slightly and stably increased along with the increase of the creep rate; a second peak point E appears in the unloading process, the second peak point E is 2-3 times of the first peak point A, and from the turning point B to the second peak point E, the adhesion coefficient is stably increased along with the increase of the creep rate; the adhesion characteristic curve of this type, from the first peak point A to the point D, belongs to the unstable stage, and should be avoided when the wheel rail adhesion is used; the adhesion from point D to point B of turn-back and from point B of turn-back to point E of second peak belongs to the stable stage, namely the first adhesion rising stage and the second adhesion rising stage in fig. 4, which is favorable for improving the utilization of wheel rail adhesion. And, the maximum creep rate is controlled to be 15% (i.e., the speed difference is controlled to be within 45 km/h), the adhesion coefficient can enter the adhesion re-rising stage after the first peak point, i.e., the second adhesion rising stage, and the second peak point E having the adhesion coefficient higher than the first peak point a is included according to the brake adhesion characteristic curve of fig. 4.
Experimental example 2: controlling the maximum creep rate to be 20% (i.e. controlling the speed difference to be within 60km/h), it can be seen from fig. 5 that the longitudinal creep rate is increased from 0% to be less than 1% during the loading process, and the adhesion coefficient is increased rapidly in an approximately linear manner along with the longitudinal creep rate; when the longitudinal creep rate is increased to 1%, the adhesion coefficient reaches a point A in the loading process, and the adhesion coefficient at the moment is a first peak point A; thereafter, the adhesion coefficient decreases with an increase in the longitudinal creep rate, and reaches a point F when the longitudinal creep rate increases to 8%; then the adhesion coefficient begins to slowly increase along with the increase of the longitudinal creep rate until the adhesion coefficient reaches a point E in the loading process when the longitudinal creep rate is 17 percent (the speed difference is 51km/h), the adhesion coefficient at the moment is a second peak point E, and when the longitudinal creep rate reaches 20 percent, the adhesion coefficient reaches a folding point B; when unloading, the longitudinal creep rate is reduced from 20%, and the adhesion coefficient is increased along with the reduction of the longitudinal creep rate; until the longitudinal creep rate reaches a point G, the adhesion coefficient at the moment is a third peak point G; thereafter, the adhesion coefficient decreased with increasing longitudinal creep rate until the longitudinal creep rate was 0%.
The speed adhesion characteristics are distinct: when the longitudinal creep rate of the adhesion coefficient is increased from 0% to 1%, a first peak point A appears, and from the beginning to the first peak point A, the adhesion coefficient is rapidly increased in an approximately linear way along with the increase of the longitudinal creep rate; from the first peak point a to point F, the adhesion coefficient decreases slightly with increasing longitudinal creep rate; from point F to a second peak point E, the adhesion coefficient increases with increasing longitudinal creep rate; from the second peak point E to the inflection point B, the adhesion coefficient decreases with the increase of the creep rate; a third peak point G appears in the unloading process, the second peak point E and the third peak point G are 2-3 times of the first peak point A, and the adhesion coefficient is stably increased along with the increase of the creep rate from the folding point B to the third peak point G; the adhesion special curve in the form belongs to an unstable stage from a first peak point A to a point F and from a second peak point B to a turn-back point B, and is avoided when the wheel rail is used for adhesion; the adhesion from point F to the second peak point B and the back-folding point B to the third peak point G belongs to a stable stage, that is, the first adhesion rising stage and the second adhesion rising stage in fig. 5, which is beneficial to improving the utilization of wheel-rail adhesion. It can be seen that the adhesion coefficient can also enter the adhesion re-rising stage after the first peak point, and includes the second and third peak points with the adhesion coefficient higher than the first peak point a.
Experiment two: an adhesion characteristic curve of an adhesion coefficient and a longitudinal creep rate in the loading and unloading processes during 350km/h speed braking.
Experimental example 3: when the maximum creep rate is controlled to be 20% (i.e. the speed difference is controlled to be within 70 km/h), it can be seen from fig. 6 that the longitudinal creep rate is increased from 0% to less than 1% during the loading process, and the adhesion coefficient is increased rapidly in an approximately linear manner along with the longitudinal creep rate; when the longitudinal creep rate is increased to 1%, the adhesion coefficient reaches the point A in the loading process, and the adhesion coefficient at the moment is a first peak point A; thereafter, the adhesion coefficient decreases with increasing longitudinal creep rate, and after increasing the longitudinal creep rate to point I of 6%, the adhesion coefficient starts to increase again with increasing longitudinal creep rate until reaching a second peak point E at a longitudinal creep rate of 15% (i.e., a speed difference of 52.5 km/h); then, the adhesion coefficient is gradually reduced along with the increase of the longitudinal creep rate, and the longitudinal creep rate coefficient is unloaded after reaching a turning point B; during unloading, the longitudinal creep rate is reduced from 20%, and the adhesion coefficient is stably reduced along with the reduction of the longitudinal creep rate until the longitudinal creep rate reaches a peak point J, wherein the value of the peak point J is smaller than the values of a first peak point A and a second peak point E; thereafter, the adhesion coefficient decreased with increasing longitudinal creep rate until the longitudinal creep rate was 0%.
The speed adhesion characteristics are distinct: when the longitudinal creep rate of the adhesion coefficient is increased from 0% to 1%, a first peak point A appears, and from the beginning to the first peak point A, the adhesion coefficient is rapidly increased in an approximately linear way along with the increase of the longitudinal creep rate; after the first peak point a, the adhesion coefficient decreases with increasing longitudinal creep rate; then, the creep rate enters into the rising again along with the increase of the longitudinal creep rate until reaching a second peak point B; from point B to the inflection point C, the adhesion coefficient decreases with the increase of the creep rate; after the self-turning point C, the adhesive coefficient continuously decreases in the unloading process; the adhesion characteristic curve of this type, from the first peak point A to the point D, belongs to the unstable stage, and should be avoided when the wheel rail adhesion is used; the adhesion from the point D to the second peak point B belongs to a stable stage, and the adhesion coefficient can enter an adhesion re-rising stage after the first peak point, so that the utilization of wheel rail adhesion is improved.
Experiment three: adhesion characteristic curve of adhesion coefficient and longitudinal creep rate in the loading and unloading process during 400km/h speed braking.
Experimental example 4: when the maximum creep rate is controlled to be 10% (i.e. the speed difference is controlled to be within 40 km/h), it can be seen from fig. 7 that the longitudinal creep rate is increased from 0% to less than 1% during the loading process, and the adhesion coefficient is increased rapidly in an approximately linear manner along with the longitudinal creep rate; when the longitudinal creep rate is increased to 1%, the adhesion coefficient reaches the point A in the loading process, and the adhesion coefficient at the moment is a first peak point A; thereafter, the adhesion coefficient decreases with an increase in the longitudinal creep rate, and reaches a point H when the longitudinal creep rate increases to 6%; then the adhesion coefficient begins to increase along with the increase of the longitudinal creep rate until the adhesion coefficient reaches a folding point B when the longitudinal creep rate is 10 percent; when unloading, the longitudinal creep rate is reduced from 10%, and the adhesion coefficient is increased along with the reduction of the longitudinal creep rate; until the longitudinal creep rate reaches a point E, and the adhesion coefficient at the moment is a second peak point E; thereafter, the adhesion coefficient decreased with increasing longitudinal creep rate until the longitudinal creep rate was 0%.
The speed adhesion characteristics are distinct: when the longitudinal creep rate of the adhesion coefficient is increased from 0% to 1%, a first peak point A appears, and from the beginning to the first peak point A, the adhesion coefficient is rapidly increased in an approximately linear way along with the increase of the longitudinal creep rate; from the first peak point a to the point H, the adhesion coefficient decreases with increasing longitudinal creep rate; from point H to point B of inflection, the coefficient of adhesion increases with the increase of creep rate; a second peak point E appears in the unloading process, the second peak point E is 2-3 times of the first peak point A, and from the turning point B to the second peak point E, the adhesion coefficient is stably increased along with the increase of the creep rate; the adhesion characteristic curve of this form belongs to an unstable stage from the first peak point A to the point H, and should be avoided when the wheel rail is used for adhesion; the adhesion from the point H to the turn-back point B and from the turn-back point B to the second peak point E belongs to a stable stage, that is, the first adhesion rising stage and the second adhesion rising stage in fig. 6, which is beneficial to improving the utilization of the wheel rail adhesion. It can be seen that the adhesion coefficient can also enter the adhesion re-rising stage after the first peak point, and includes a second third peak point where the adhesion coefficient is higher than the first peak point a.
Experimental example 5: when the maximum creep rate is controlled at 20% (i.e., the speed difference is controlled at 80km/h), it can be seen from fig. 8 that the longitudinal creep rate increases from 0% to less than 1% during the loading process, and the adhesion coefficient increases rapidly in an approximately linear manner with the longitudinal creep rate; when the longitudinal creep rate is increased to 1%, the adhesion coefficient reaches a point A in the loading process, and the adhesion coefficient at the moment is a first peak point A; thereafter, the adhesion coefficient decreases with increasing longitudinal creep rate, and reaches point I when the longitudinal creep rate increases to 6%; then the adhesion coefficient starts to increase again along with the increase of the longitudinal creep rate until the adhesion coefficient reaches a point E in the loading process when the longitudinal creep rate is 15 percent (the relative sliding speed is 60km/h), the adhesion coefficient at the moment reaches a second peak point E, and then the adhesion coefficient decreases along with the increase of the longitudinal creep rate until a folding point B is reached; when unloading, the longitudinal creep rate is reduced from 20%, and the adhesion coefficient is reduced along with the reduction of the longitudinal creep rate; until the longitudinal creep rate reaches a peak point J, the value of the peak point J is smaller than the values of the first peak point A and the second peak point B; thereafter, the adhesion coefficient decreased with increasing longitudinal creep rate until the longitudinal creep rate was 0%.
The speed adhesion characteristics are distinct: when the longitudinal creep rate of the adhesion coefficient is increased from 0% to 1%, a first peak point A appears, and from the beginning to the first peak point A, the adhesion coefficient is rapidly increased in an approximately linear way along with the increase of the longitudinal creep rate; from the first peak point a to point I, the adhesion coefficient decreases with increasing longitudinal creep rate; from point I to a second peak E, the adhesion coefficient increases with increasing creep rate; from the second peak point E to the turning point B, the adhesion coefficient decreases with the increase of the longitudinal creep rate; a peak point J appears during the unloading process, but the peak point J is smaller than the first peak point a and the second peak point E; the adhesion characteristic curve in the form belongs to an unstable stage from a first peak point A to a point I, and is avoided when the wheel rail is adhered and utilized; the adhesion from the point I to the second peak point E belongs to a stable stage, that is, in fig. 7, the first adhesion rising stage and the second adhesion rising stage are favorable for improving the utilization of the wheel rail adhesion. It can be seen that the adhesion coefficient can also enter the adhesion re-rising phase after the first peak point and includes a second peak point with an adhesion coefficient higher than the first peak point a.
Experiment four: adhesion characteristic curve of adhesion coefficient and longitudinal creep rate in the loading and unloading process during 450km/h speed braking.
Experimental example 6: when the maximum creep rate is controlled at 20% (i.e., the speed difference is controlled at 90km/h), it can be seen from fig. 9 that the longitudinal creep rate increases from 0% to less than 1% during the loading process, and the adhesion coefficient increases rapidly in an approximately linear manner with the longitudinal creep rate; when the longitudinal creep rate is increased to 1%, the adhesion coefficient reaches a point A in the loading process, and the adhesion coefficient at the moment is a first peak point A; thereafter, the adhesion coefficient decreases with increasing longitudinal creep rate, reaching point I when the longitudinal creep rate increases to 6%; then the adhesion coefficient starts to increase again along with the increase of the longitudinal creep rate until the adhesion coefficient reaches a point E in the loading process when the longitudinal creep rate is 15 percent (the relative sliding speed is 60km/h), the adhesion coefficient at the moment reaches a second peak point E, and then the adhesion coefficient decreases along with the increase of the longitudinal creep rate until a folding point B is reached; when unloading, the longitudinal creep rate is reduced from 20%, and the adhesion coefficient is reduced along with the reduction of the longitudinal creep rate; until the longitudinal creep rate reaches a peak point J, the value of the peak point J is smaller than the values of the first peak point A and the second peak point B; thereafter, the adhesion coefficient decreased with increasing longitudinal creep rate until the longitudinal creep rate was 0%.
The adhesion characteristics at speed are distinguished as follows: when the longitudinal creep rate of the adhesion coefficient is increased from 0% to 1%, a first peak point A appears, and from the beginning to the first peak point A, the adhesion coefficient is rapidly increased in an approximately linear way along with the increase of the longitudinal creep rate; from the first peak point a to point I, the adhesion coefficient decreases with increasing longitudinal creep rate; from point I to a second peak E, the adhesion coefficient increases with increasing creep rate; from the second peak point E to the turning point B, the adhesion coefficient decreases with the increase of the longitudinal creep rate; a peak point J appears in the unloading process, but the peak point J is smaller than the first peak point A and the second peak point E; the adhesion characteristic curve in the form belongs to an unstable stage from a first peak point A to a point I, and is avoided when the wheel rail is adhered and utilized; the adhesion from the point I to the second peak point E belongs to a stable stage, that is, in fig. 7, the first adhesion rising stage and the second adhesion rising stage are favorable for improving the utilization of the wheel rail adhesion. It can be seen that the adhesion coefficient can also enter the adhesion re-rising phase after the first peak point and includes a second peak point with an adhesion coefficient higher than the first peak point a.
The experimental effect is as follows:
a large number of experiments prove that when the maximum creep rate control value (namely the speed difference threshold value) is too small, the adhesion coefficient may only generate a peak point in a small creep interval within 1%; the maximum creep rate control value (also aiming at the speed difference threshold value) is properly enlarged, the adhesion coefficient not only has a first peak point in a small creep interval, but also has a second peak point in a large creep interval, and has the second peak point or a third peak point in a turn-back stage; the second peak point and the third peak point can reach 2-3 times of the first peak point; the adhesion re-ramp-up phase may be during loading of creep rate, and may also be during unloading.
II, experimental result surface: under the working condition of a wet rail surface and the same braking pressure, the adhesion force coefficient in the braking process can enter an adhesion and re-rise stage by increasing the speed difference threshold value, the utilization of the adhesion of the wheel rail is enhanced, the braking distance can be shortened by 30-40%, the temperature of a brake disc is within the limit value of 750 ℃, and the surface of the wheel is free of scratches and other abnormal conditions.
FIG. 10 is a graph comparing a conventional threshold with a new threshold, where the conventional threshold is a speed difference threshold with a value range of 30km/h to 40 km/h; the new limit value is an interval value in which the upper limit of the value range of the speed difference threshold value is 60km/h and the lower limit is 40km/h, for example: when the vehicle speed is within the range of 300km/h, the value range of the speed difference threshold value is 40km/h-50 km/h; when the vehicle speed is in the range of 350km/h, the value range of the speed difference threshold value is 40km/h-55 km/h; when the speed is within the range of 400km/h, the value range of the speed difference threshold value is 40km/h-60 km/h; when the vehicle speed is 450km/h, the upper limit value of the value range of the speed difference threshold value is 40km/h-60 km/h.
TABLE 2 comparison of Emergency braking distance and brake disc temperature for wet rail surface conditions
Figure RE-GDA0003675590690000191
As can be seen from the comparison between the emergency braking distance under the wet rail surface working condition and the brake disc temperature in the table 2, when the vehicle speed is 300km/h, the speed difference adopting the traditional limit value is 30km/h, the emergency braking distance is 4890m, and the speed difference adopting the new limit value is 45km/h, the emergency braking distance is 3447m, compared with the traditional limit value, the emergency braking distance is 1443m shorter, although the temperature of the brake disc is increased by 52 ℃, the increased temperature is smaller and belongs to a controllable range, and the abrasion between the wheel and the rail also belongs to a reasonable range;
when the vehicle speed is 350km/h, the speed difference adopting the traditional limit value is 30km/h, the emergency braking distance is 5810m, and the speed difference adopting the new limit value is 45km/h, the emergency braking distance is 4027m, compared with the traditional limit value, the 1783m is shortened, although the temperature of a brake disc rises by 10 ℃, the rising temperature is small and belongs to a controllable range, and the abrasion between the wheels and the track also belongs to a reasonable range;
when the speed is 400km/h, the speed difference adopting the traditional limit value is 30km/h, the emergency braking distance is 9885m, and the speed difference adopting the new limit value is 45km/h, the emergency braking distance is 5985m, compared with the traditional limit value, the 3900m is shortened, although the temperature of a brake disc is increased by 48 ℃, the increased temperature is smaller and belongs to a controllable range, and the scratch between the wheel and the track also belongs to a reasonable range;
therefore, the speed difference threshold value is increased, the wheel and rail adhesion can be more fully utilized, the braking distance is shortened, the temperature of the brake disc is within the threshold value, the surface of the wheel is not scratched or has no other abnormal conditions, and the wheel and rail adhesion at the speed of 300 and 450 kilometers per hour can be fully utilized to shorten the braking distance.
There is also provided, as a second aspect of the present application, a control method for wheel-rail braking: the method comprises the following steps:
setting a threshold value of the speed difference; the value of the threshold value of the speed difference is set to enable the value of the adhesion coefficient in the braking process to enter an adhesion re-rising stage after the first peak point; the adhesion re-rise phase includes at least one other peak having an adhesion coefficient value higher than the first peak. When the vehicle speed is 300km/h-450km/h, the upper limit value of the value range of the speed difference threshold value is 60km/h, and the lower limit value is 40 km/h; more specifically: when the vehicle speed is 300km/h, the upper limit value of the value range of the speed difference threshold value is 50km/h, and the lower limit value is 40 km/h; or when the vehicle speed is 350km/h, the upper limit value of the value range of the speed difference threshold value is 55km/h, and the lower limit value is 40 km/h; or when the vehicle speed is 400km/h, the upper limit value of the value range of the speed difference threshold value is 60km/h, and the lower limit value is 40 km/h; or when the vehicle speed is 450km/h, the upper limit value of the value range of the speed difference threshold value is 60km/h, and the lower limit value is 40 km/h.
When the actual speed difference is larger than or equal to the threshold value of the speed difference in the braking process, triggering the system to perform anti-skid braking, wherein the step of performing anti-skid braking comprises opening an anti-skid valve to reduce the pressure of a brake cylinder and enter an air exhaust stage, and the actual speed difference is the maximum value of the difference value between the peripheral speed of any one of the plurality of wheel shafts and the speed value of the bullet train under the condition of the same moment in the braking process, and specifically comprises the following steps: detecting peripheral speeds of different wheel shafts, receiving the real-time detected peripheral speeds of the different wheel shafts in a braking process and calculating the actual speed difference, wherein the speed measurer comprises a speed measuring gear and a sensor, the speed measuring gear is arranged on the wheel shafts and rotates along with the wheel shafts, the sensor collects the alternation of tooth tops and tooth valleys of the rotating speed measuring gear in front of the sensor to generate pulse signals, and the peripheral speeds of the wheel shafts are calculated according to the pulse signal period, the number of teeth of the testing gear and the radius of wheels on the wheel shafts: the peripheral speed calculation formula of the wheel axle is v ═ rw; wherein: r is the radius of the wheel on the axle and w is the angular velocity of the axle. The speed measuring gear is arranged on the wheel shaft and rotates along with the wheel shaft, and the sensor generates pulse signals through the alternation of tooth crests and tooth troughs of the rotating speed measuring gear in front of the sensor, so that the angular speed of the wheel shaft is calculated:
w＝2*f*3.6*π/Z；
wherein: w is the angular velocity of the axle;
f is the frequency of the pulse signal;
and z is the number of speed measuring gear teeth.
When the vehicle speed is 300km/h-450km/h, the upper limit value of the value range of the speed difference threshold value is 60km/h, and the lower limit value is 40 km/h; more specifically: when the vehicle speed is 300km/h, the upper limit value of the value range of the speed difference threshold value is 50km/h, and the lower limit value is 40 km/h; or when the vehicle speed is 350km/h, the upper limit value of the value range of the speed difference threshold value is 55km/h, and the lower limit value is 40 km/h; or when the vehicle speed is 400km/h, the upper limit value of the value range of the speed difference threshold value is 60km/h, and the lower limit value is 40 km/h; or when the vehicle speed is 450km/h, the upper limit value of the value range of the speed difference threshold value is 60km/h, and the lower limit value is 40 km/h.
Finally, although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the present application, which is defined by the claims.

Claims (10)

1. A control system for wheel-rail braking is characterized by comprising a control calculation unit, an antiskid valve and a brake cylinder; the control calculation unit is provided with a threshold value of the speed difference and detects and calculates the actual speed difference in the braking process; and when the actual speed difference is larger than or equal to the threshold value of the speed difference in the braking process, triggering the system to perform braking antiskid, and sending an instruction by the control calculation unit, wherein the instruction is used for opening an antiskid valve to reduce the pressure of the brake cylinder and enter an air exhaust stage.
2. A control system for wheel track braking according to claim 1, wherein said actual speed difference is the maximum of the differences between the peripheral speed of any one of the plurality of axles and the railcar speed value at the same instant in the braking process.
3. A control system for wheel-track braking according to any one of claims 1 or 2, further comprising a plurality of speed detectors respectively disposed on different axles for detecting peripheral speeds of different axles in real time, wherein the control calculating unit receives the detected peripheral speeds of different axles in real time during braking and calculates the actual speed difference.
4. The control system according to claim 3, wherein the tachometer comprises a tachometer gear and a sensor, the tachometer gear is arranged on the axle and rotates with the axle, the sensor collects the alternation of the tooth tops and the tooth valleys of the tachometer gear before the sensor to generate a pulse signal, and the circumferential speed of the axle is calculated according to the period of the pulse signal, the number of the tooth tops and the tooth valleys of the tachometer gear and the radius of the wheel on the axle.
5. A control system for wheel-track braking according to claim 1, wherein the upper limit value of the range of the threshold value of the speed difference when the vehicle speed is 300km/h to 450km/h is 60km/h, and the lower limit value is 40 km/h.
6. A control system for wheel track braking according to claim 5, wherein when the vehicle speed is 350km/h, the upper limit value of the range of the speed difference threshold value is 55km/h, and the lower limit value is 40 km/h.
7. A control system for wheel track braking according to claim 5, characterized in that when the vehicle speed is 400km/h, the upper limit value of the range of the speed difference threshold value is 60km/h, and the lower limit value is 40 km/h.
8. A control system for wheel track braking according to claim 5, characterized in that when the vehicle speed is 450km/h, the upper limit value of the range of the speed difference threshold value is 60km/h, and the lower limit value is 40 km/h.
9. A control method for wheel-rail braking, characterized by comprising the steps of:
setting a threshold value of the speed difference;
and detecting and calculating the actual speed difference in the braking process, and executing anti-skid braking when the actual speed difference in the braking process is greater than or equal to the threshold value of the speed difference, wherein the execution of anti-skid braking comprises opening an anti-skid valve to reduce the pressure of a brake cylinder and enter an air exhaust stage.
10. A control method for wheel-track braking, characterized in that said detecting and calculating said actual speed difference during braking comprises detecting in real time the peripheral speeds of the different wheel axles and receiving this data to calculate said actual speed difference; the actual speed difference is the maximum value of the difference between the peripheral speed of any one of the multiple wheel shafts and the speed value of the bullet train at the same moment in the braking process.
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