Friction test system for railway vehicles, computer-implemented friction test method for railway vehicles, computer program, and non-volatile data carrier

Abstract

In a railway vehicle (100), a control unit (140) controls a set of brake / traction units (101, 161; 102, 162; 103, 163; 104, 164) by control signals (B1, A1; B2, A2; B3, A3; B4, A4) so as to apply respective braking / traction forces to respective axles (131, 132, 133, 134) and decelerate / accelerate the railway vehicle (100). The control unit (140) obtains a first wheel speed signal (ω 1 ) indicating the rotational speed of at least one first wheel (121) and obtains a second wheel speed signal (ω a ) indicating the average rotational speed of at least one second wheel (122, 123, 124). The control unit (140) generates a first control signal (BF; A1) to the first brake / traction unit so that the first brake / traction unit (101, 161) applies an increasing braking / traction force to the first axle (131) until the absolute difference (|ω 1 - ω a |) between the first and second wheel speed signals (ω 1 ; ω a ) exceeds a threshold value. When the braking / traction force applied to the first axle (131) increases, these control signals are generated so that the average braking / traction force applied to at least one second axle (132, 133, 134) decreases. When the absolute difference (|ω 1 - ω a |) exceeds the threshold value, in response thereto, the control unit (140) obtains a parameter (μ e ) reflecting the friction coefficient (μ m ) between the wheels (121, 122, 123, 124) and the set of rails (181, 182) on which the railway vehicle (100) travels.

Description

Technical Field

[0001] The present invention generally relates to a safety device for a railway vehicle braking system. In particular, the present invention relates to a friction test system for railway vehicles according to the preamble of claim 1, and a corresponding computer-implemented method. The present invention also relates to a computer program and a non-volatile data carrier storing such a computer program.

Background Art

[0002] In the operation of electric railway vehicles, generally, on-board motors are adopted as generators for decelerating railway vehicles. However, for reasons of efficiency and safety, it is not possible to rely solely on this braking strategy. In particular, a dedicated braking function is always required to ensure the functionality of the emergency brake and to keep the railway vehicle stationary after it has been stopped. In many cases, the same brake unit is used for different types of braking functions such as service brakes, emergency brakes, and holding brakes.

[0003] To efficiently decelerate a railway vehicle, it is essential to have accurate knowledge of the predicted braking distance. Currently, the test frequency of the braking distance is relatively low, and the test results are generally reported at somewhat irregular intervals in the light of the potentially best values that are predicted. One reason for this methodology is that to estimate the braking distance, the railway vehicle needs to apply a known braking force, but due to mechanical wear and passenger comfort, it cannot be carried out very frequently. As a result, a safety margin must always be given to the estimated braking distance. As a result, the safety distance between consecutive trains must be set longer than what actually seems necessary. Therefore, the maximum capacity of a given railway cannot be utilized.

[0004] Patent Document 1 describes a test system and method for the adhesion state of a railway track. Here, at least one axle of the induced vehicle is accelerated to the adhesion limit between the wheels of this axle and the rail supporting this wheel, or above the adhesion limit, by applying a force to the axle and obtaining the adhesion coefficient from the measured value of the force at which the wheel starts to slip. Subsequently, this adhesion coefficient can be communicated to a central station that enables the creation and update of an adhesion coefficient map for other induced vehicles and / or the railway network.

[0005] By applying the above measures, it may be possible to roughly estimate the adhesion coefficient at various locations in the railway network. However, for a suitable implementation of this measure, since it involves independently controlling one or several motors simultaneously to independently accelerate the axles of various wheels according to various accelerations by applying a traction force to the axles of various wheels, there is a considerable risk that the railway vehicle will exhibit awkward behavior.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to solve the above problems and provide a solution that can smoothly operate a railway vehicle as a whole while frequently obtaining a highly reliable estimated value of the friction coefficient between the wheels and the rail of the railway vehicle during running.

Means for Solving the Problems

[0008] According to one aspect of the present invention, the above object is achieved by a friction test system for a railway vehicle including a set of brake / traction units and a control unit. Each unit of the set of brake / traction units receives respective control signals from the control unit and, in response thereto, is configured to apply respective brake / traction forces to respective axles of the railway vehicle in order to decelerate / accelerate the railway vehicle. The control unit is configured to obtain a first wheel speed signal indicating the rotational speed of at least one first wheel of a first axle among the above axles, wherein the first brake / traction unit of the set of brake / traction units is configured to apply a brake / traction force. The control unit is further configured to obtain a second wheel speed signal indicating the average rotational speed of at least one second wheel of at least one second axle among the above axles, wherein at least one second brake / traction unit of the set of brake / traction units is configured to apply respective brake / traction forces. The control unit is further configured to generate a first control signal to the first brake / traction unit such that the first brake / traction unit applies an increasing brake / traction force to the first axle until the absolute difference between the first wheel speed signal and the second wheel speed signal exceeds a threshold value. When the absolute difference exceeds the threshold value, in response thereto, the control unit is configured to determine a parameter reflecting the friction coefficient between the wheels and the set of rails on which the railway vehicle travels. Specifically, control signals are generated such that as the brake / traction force applied to the first axle increases, the average brake / traction force applied to at least one second axle decreases.

[0009] With the proposed brake / traction control, the non-uniform distribution of the brake / traction force is smoothed out, and the friction test procedure becomes hardly noticeable to the passengers of the railway vehicle. Therefore, the friction test system has advantages. Thus, it does not essentially affect the comfort of the passengers. Also, the friction test system only causes minor mechanical wear of the related equipment. As a result, the friction test can be carried out quite frequently. By the periodically updated friction evaluation, ultimately, the dynamic adaptation of the safe distance between successive railway vehicles becomes possible. As a result, the average throughput capacity of a given railway network can be expanded without compromising safety.

[0010] Also, the proposed friction test system is flexible because it can evaluate the friction coefficient when the railway vehicle brakes and accelerates.

[0011] According to one embodiment of this aspect of the present invention, the control unit is further configured to generate a control signal such that the gradual decrease in the average brake / traction force applied to at least one second axle corresponds to the gradual increase in the brake / traction force applied to the first axle at each point in time. That is, this smooths out the variation in the brake / traction force and makes the friction test procedure even less noticeable to the passengers of the railway vehicle.

[0012] According to another embodiment of this aspect of the present invention, the friction test system includes a set of rotational speed sensors configured to generate a first wheel speed signal and a respective wheel speed signal for at least one second wheel of at least one second axle. For example, these rotational speed sensors may include respective tachometers provided on or near the first axle and / or on or near at least one second axle.

[0013] According to one embodiment of this aspect of the present invention, at least one of these rotational speed sensors includes a first accelerometer provided on a frame element of a railway vehicle, and this first accelerometer is configured to generate at least one first vector signal representing the acceleration of the railway vehicle in at least one dimension, for example linearly along the rail. Also, at least one second accelerometer is provided eccentrically with respect to the rotation axis of at least one wheel of the railway vehicle. The at least one second accelerometer is configured to generate at least one second vector signal representing the movement of the at least one second accelerometer in a plane orthogonal to the rotation axis of the at least one wheel. Here, the control unit is configured to obtain a first wheel speed signal and / or at least one second wheel speed signal based on the first and second vector signals. Such measurement of the accelerometer-based wheel speed signal has the advantage of avoiding the need for conventional sensors that are generally susceptible to the influence of dust and mechanical action.

[0014] According to another embodiment of this aspect of the present invention, a set of brake / traction units specifically has a plurality of brake units, and each of these brake units applies a respective braking force to a respective axle in response to a respective control signal to decelerate the railway vehicle. Therefore, the friction coefficient can be evaluated in any type of service brake operation.

[0015] According to still another embodiment of this aspect of the present invention, a set of brake / traction units specifically has a plurality of traction motors, and each of the traction motors is configured to apply a respective traction force to a respective axle in response to a respective control signal to accelerate the railway vehicle. Therefore, the friction coefficient can be evaluated at any time during the running of the railway vehicle.

[0016] According to another embodiment of this aspect of the present invention, the friction test system comprises a data bus configured to send control signals from the control unit to each of the brake / traction units of a set of brake / traction units. By doing so, the brake / traction units can be controlled efficiently and with high reliability.

[0017] According to another aspect of the present invention, the above object is achieved by a computer-implemented friction test method for a railway vehicle. The method includes generating respective control signals configured to be received by respective brake / traction units of a set of brake / traction units of a railway vehicle. Each brake / traction unit is configured to apply a respective brake / traction force to a respective axle of the railway vehicle in response to the control signal to decelerate / accelerate the railway vehicle. The method further includes obtaining a first wheel speed signal indicating the rotational speed of at least one wheel of a first axle of the axles, wherein a first brake / traction unit of the set of brake / traction units is configured to apply a brake / traction force. Additionally, the method includes obtaining a second wheel speed signal indicating the average rotational speed of at least one second wheel of at least one second axle of the axles, wherein at least one second brake / traction unit of the set of brake / traction units is configured to apply a respective brake / traction force. The method also includes generating a first control signal to the first brake / traction unit such that the first brake / traction unit applies an increasing brake / traction force to the first axle until the absolute difference between the first wheel speed signal and the second wheel speed signal exceeds a threshold value. The method includes determining a parameter reflecting the coefficient of friction between the wheel and a set of rails on which the railway vehicle travels in response to the absolute difference exceeding the threshold value. In particular, the control signal is generated such that as the brake / traction force applied to the first axle increases, the average brake / traction force applied to at least one second axle decreases. The advantages of the method and its preferred embodiments are apparent from the above considerations with reference to the proposed friction test system.

[0018] According to a further aspect of the present invention, the above object is achieved by a computer program that can be mounted on a non-volatile data carrier communicably connected to a processing unit. This computer program includes software for executing the above method when the program runs in the processing unit.

[0019] According to another aspect of the present invention, the above object is achieved by a non-volatile data carrier including the above computer program.

[0020] Further advantages, beneficial features, and applications of the present invention will become apparent from the following description and the dependent claims.

[0021] The present invention will now be described in detail by way of preferred embodiments disclosed herein by way of example and with reference to the accompanying drawings.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0023] FIG. 1 is a schematic view of a railway vehicle 100 equipped with a friction test system according to an embodiment of the present invention.

[0024] The friction test system includes a set of brake units 101, 102, 103, 104, and / or a set of traction units 161, 162, 163, 164, each configured to receive respective control signals B1, B2, B3, and B4, and / or control signals A1, A2, A3, and A4. In response to the control signals, the brake / traction units are configured to apply respective brake / traction forces to respective axles 131, 132, 133, 134 of the railway vehicle 100 to decelerate / accelerate the railway vehicle 100.

[0025] The control unit 140 is configured to generate respective control signals B1 / A1, B2 / A2, B3 / A3, and / or B4 / A4. In FIG. 1, the control unit 140 is illustrated as a separate unit. However, according to the present invention, the control unit 140 can be suitably arranged together with any other unit of the system. For example, the control unit 140 can be incorporated into any of the brake units 101, 102, 103, or 104, or the traction units 161, 162, 163, or 164.

[0026] Also, the control unit 140 is configured to obtain a first wheel speed signal ω indicating the rotational speed of at least one first wheel 121 of the first axle 131 of the set of axles, and the first brake / traction unit 101 / 161 of the set of brake / traction units is configured to apply a brake / traction force to this first axle 131. Further, the control unit 140 is configured to obtain a second wheel speed signal ω indicating the average rotational speed of at least one second wheel 122, 123, 124 of at least one second axle 132, 133, 134 of the set of axles, and at least one second brake / traction unit of the set of brake / traction units is configured to apply respective brake / traction forces to this at least one second axle. 1 a

[0027] Also, the control unit 140 is configured to generate a first control signal BF or A1 to the first brake / traction unit 101 or 161, respectively, such that the first brake / traction unit applies an increasing brake / traction force to the first axle 131. This increase continues until the absolute difference between the first wheel speed signal ω 1 and the second wheel speed signal ω a exceeds a threshold value. That is, the absolute difference |ω 1 −ω a |. When the absolute difference |ω 1 −ω a | exceeds the threshold value, in response thereto, the control unit 140 determines a parameter μ e reflecting the coefficient of friction μ m between the wheels 121, 122, 123, 124 and the set of rails 181, 182 on which the railway vehicle 100 travels.

[0028] It should be noted that the above-mentioned first axle 131 does not have to be the foremost or the rearmost axle of the railway vehicle 100. In fact, it is preferable that all the axles of the railway vehicle 100 represent the first axle at different times. That is, there is an advantage in performing the above procedure, whether static or dynamic, according to a schedule, in which case each axle of the railway vehicle 100 alternately represents the first axle or is included in a set of at least one second axle. Thus, the entire railway vehicle 100 is involved in the friction test, which is an advantage with respect to component wear. Also, such a measure makes it easier to identify abnormalities in individual brake units and / or traction units.

[0029] FIG. 3 is a graph showing an example of how the dynamic coefficient of friction μ k is represented as a function of the wheel slip ratio s, where in this specification, the slip ratio is understood to refer to a general term for the sliding or spinning motion of the wheel with respect to the rail. That is, the wheel slip ratio s applies to both deceleration and acceleration.

[0030] Characteristically, the dynamic coefficient of friction μ kincreases relatively in proportion to the increase in the slip ratio s of the wheel. However, as it approaches the peak value μ e the coefficient of dynamic friction μ k becomes somewhat flat. This peak value of the coefficient of friction μ e is associated with the optimal wheel slip ratio s e and after the peak value, when the wheel slip ratio s further increases, as a result, the coefficient of dynamic friction μ k gradually decreases.

[0031] According to the present invention, a parameter μ m reflecting the coefficient of friction between the wheels of the railway vehicle 100 and the rails on which the railway vehicle 100 travels is determined. Ideally, the peak value μ e should be derived. For example, the peak value μ e can be derived as follows. When the absolute difference |ω 1 −ω a | between the first wheel speed signal ω 1 and the second wheel speed signal ω a exceeds a threshold value, this corresponds to a situation where a wheel slip ratio s e close to the optimal wheel slip ratio s m occurs in at least one wheel 121 of the first axle 131. The coefficient of dynamic friction μ k is represented by the following formula

Equation

[0032] Assuming that the wheel slip ratio s m is close to the optimal wheel slip ratio s e the peak value μ k of the coefficient of dynamic friction μ e can be estimated relatively accurately.

[0033] According to one embodiment of the present invention, the control unit 140 generates control signals B1 / A1, B2 / A2, B3 / A3, or B4 / A4, and is configured such that when the braking / traction force applied to the first axle 131 gradually increases, the average braking / traction force applied to at least one of the second axles 132, 133, and 134 gradually decreases. In other words, at least one of the second axles 132, 133, and 134 cancels out the excessive force applied to the first axle 131.

[0034] Preferably, this cancellation is made to coincide in time. This means that the control unit 140 generates control signals B1 / A1, B2 / A2, B3 / A3, B4 / A4, and at each point in time, the average braking / traction force applied to at least one of the second axles 132, 133, 134 gradually decreases in correspondence with the gradual increase in the braking / traction force applied to the first axle 131. That is, thereby, the deviation in the braking / traction force applied to the first axle 131 is made less noticeable by the deviation in the opposite direction represented by the braking / traction force applied to at least one of the second axles 132, 133, and 134.

[0035] Figure 2 shows a brake unit 101 according to an embodiment of the present invention. The brake unit 101 is configured to receive, for example, a control signal representing a brake command B1 from a control unit 140 via, for example, a data bus 150. In response to this signal, the brake unit 101 is configured to perform a braking operation. The brake unit 101 may include a rotatable member 111, first and second pressing members indicated herein by reference numeral 211, a brake actuator 220, a gear assembly (not shown), and an electric motor 230. The rotatable member 111, which may be represented by a brake disk or a brake drum, is mechanically coupled to at least one wheel 121 of the railway vehicle 100. Specifically, in response to the brake command B1, the brake actuator 220 is preferably configured to generate a brake force signal BF1 to the electric motor 230, whereby the electric motor 230 moves the first and second pressing members 211 relative to the rotatable member 111.

[0036] According to the present invention, the electric motor 230 may be replaced with a pneumatically actuated piston cylinder structure configured to actuate the first and second pressing members.

[0037] Furthermore, for overall efficiency, it goes without saying that the data bus 150 may be configured to transmit all control signals B1, A1; B2, A2; B3, A3; B4, and / or A4 from the control unit 140 to each brake / traction unit of the set of brake / traction units 101, 161; 102, 162; 103, 163, 104, and / or 164.

[0038] Each of the first and second pressing members 211 is configured to perform a braking operation by moving relative to the rotatable member 111. Usually, the braking operation includes applying a specific braking force to the rotatable member 111. However, the braking operation may also include reducing or releasing a braking force that has already been applied.

[0039] Referring back to FIG. 1, an embodiment of the present invention will be described here, in which a friction test is performed during acceleration of the railway vehicle 100 by respectively adopting the traction units 161, 162, 163, and 164.

[0040] Here, the control unit 140 is configured to acquire a first wheel speed signal ω indicating the rotational speed of at least one first wheel 121 of a first axle among a plurality of axles, and for this first axle, a first traction unit 161 among a set of traction units is configured to apply a traction force. 1 Here, the control unit 140 is configured to acquire a first wheel speed signal ω indicating the rotational speed of at least one first wheel 121 of a first axle among a plurality of axles, and for this first axle, a first traction unit 161 among a set of traction units is configured to apply a traction force.

[0041] Furthermore, the control unit 140 is configured to acquire a second wheel speed signal ω indicating the average rotational speed of at least one second wheel, that is, 122, 123, 124, of each of at least one second axle 132, 133, 134 among the plurality of axles, and for each of the at least one second axle 132, 133, 134, at least one second traction unit 162, 163, 164 among the set of traction units is configured to apply respective traction forces. a Furthermore, the control unit 140 is configured to acquire a second wheel speed signal ω indicating the average rotational speed of at least one second wheel, that is, 122, 123, 124, of each of at least one second axle 132, 133, 134 among the plurality of axles, and for each of the at least one second axle 132, 133, 134, at least one second traction unit 162, 163, 164 among the set of traction units is configured to apply respective traction forces.

[0042] Furthermore, the control unit 140 generates a first control signal A1 to the first traction unit 161, and this unit is configured to apply an increasing traction force to the first axle 131 until the absolute difference |ω 1 - ω a | between the first wheel speed signal ω 1 and the second wheel speed signal ω a exceeds a threshold value. As described above, when the absolute difference |ω 1 - ω a | exceeds the threshold value, in response thereto, the control unit 140 determines a parameter μ e reflecting the friction coefficient μ m between the wheels 121, 122, 123, 124 and each of the set of rails 181, 182 on which the railway vehicle 100 travels.

[0043] According to an embodiment of the present invention, different combinations of brake units 101, 102, 103, 104 and traction units 161, 162, 163, 164 can be adopted for the friction test. For example, while the railway vehicle 100 is running at a constant speed, that is, while neither accelerating nor decelerating, the control unit 140 generates a first control signal A1 to the first traction unit 161, and this unit is configured to apply an increasing traction force to the first axle 131. At the same time, the control unit 140 generates, here, at least one second control signal B2, B3, B4, and these units are configured to apply an increasing braking force to at least one of the second axles 132, 133, 134 respectively. The control unit 140 is configured to continue generating the first control signal A1 and at least one second control signal B2, B3, B4 until the absolute difference |ω 1 - ω a | between the first wheel speed signal ω 1 and the second wheel speed signal ω a exceeds a threshold value. When the absolute difference |ω 1 - ω a | exceeds the threshold value, in response, the control unit 140 is configured to determine a parameter μ e reflecting the coefficient of friction μ m between the wheels 121, 122, 123, 124 and the set of rails 181 and 182 on which the railway vehicle 100 runs respectively. This parameter can be obtained based on the knowledge of the respective traction forces and braking forces applied to a plurality of axles when the absolute difference |ω 1 - ω a | exceeds the threshold value.

[0044] Of course, the reverse approach is also possible, i.e., the control unit 140 generates a first control signal B1 for the first brake unit 101, and this unit applies an increasing braking force to the first axle 131. Parallel to this, the control unit 140 generates at least one second control signal A2, A3, A4 for at least one of the second traction units 162, 163, 164, and these units apply an increasing traction force to at least one of the second axles 132, 133, 134.

[0045] According to an embodiment of the present invention, the friction test system is a set of rotational speed sensors 215, 235, 425, which generates a first wheel speed signal ω 1 and the respective wheel speed signals ω 2 、ω 3 、ω 4 of at least one of the at least one second wheel 122, 123, 124 of the at least one second axle 132, 133, 134, respectively. For example, this rotational speed sensor may include a tachometer 215 installed on or near the first axle 131 and / or on or near at least one of the at least one second axles 132, 133 and / or 134.

[0046] FIG. 4 schematically shows an accelerometer 425 according to an embodiment of the present invention.

[0047] According to an embodiment of the present invention, the friction test system includes a first accelerometer 425 and at least one second accelerometer 235.

[0048] The first accelerometer 425 is installed on the frame element 110 of the railway vehicle 100. The first accelerometer 425 is typically in at least one dimension in three spatial directions a x 、a y 、and a z each, and each rotation a R 、a p 、and aw configured to generate at least one first vector signal VS1 representative of the acceleration of the railway vehicle 100 therein.

[0049] Each of the at least one second accelerometer 235 is disposed eccentrically with respect to the axis of rotation of at least one wheel, i.e., wheel 121 shown in FIG. 2 of the railway vehicle 100. The at least one second accelerometer 235 is configured to generate at least one second vector signal VS2 representative of the movement of the at least one second accelerometer 235 in a plane orthogonal to the axis of rotation of the at least one wheel 121.

[0050] Furthermore, the control unit 140 is configured to obtain the first wheel speed signal ω 1 and / or at least one second wheel speed signal ω 2 , ω 3 , and / or ω 4 using mechanical calculations, based on each of the first vector signal VS1 and the second vector signal VS2.

[0051] Generally advantageous is the case where the above braking procedure automatically takes effect by executing one or more computer programs. Thus, the brake actuator 120 preferably includes a processing circuit and a programmed memory unit, and its design will be briefly described below with reference to FIG. 5.

[0052] FIG. 5 shows a block diagram of a control unit 140 according to an embodiment of the present invention. The control unit 140 includes a processing circuit in the form of at least one processor 530 and a memory unit 520, i.e., a non-volatile data carrier storing a computer program 525, and this memory unit 520 in turn includes software that causes the at least one processor 530 to execute the operations referred to in the present disclosure when the computer program 525 runs on the at least one processor 530.

[0053] The control unit 140 includes an input unit configured to receive wheel speed signals ω 1 ω 2 ω 3 ω 4 . Optionally or additionally, the control unit 140 may also include an input unit configured to receive a first vector signal VS1 and a second vector signal VS2 respectively. Further, the control unit 140 includes an output unit configured to provide control signals B1, B2, B3, B4, and / or control signals A1, A2, A3, A4. According to an embodiment of the present invention, one or more of the above input signals and / or output signals may be communicated via the data bus 150.

[0054] For the sake of summary, with reference to the flowchart of FIG. 6, a computer-implemented friction test method for a railway vehicle implemented by the control unit 140 will be described here.

[0055] In a first step 610, for example, in response to the expiration of a timer function or in response to an operator command, a check is made as to whether a friction test should be performed. If it is determined in step 610 that a friction test should be performed, then the process proceeds to steps 620 and 630, which may be executed in parallel or may not be executed in parallel. If it is determined in step 610 that a friction test should not be performed, the procedure returns or remains at step 610.

[0056] In step 620, the control unit 140 obtains a first wheel speed signal ω 1 indicating the rotational speed of at least one first wheel 121 of the first axle 131 among the plurality of axles, and for this first axle 131, the first brake / traction unit 101 / 161 among the set of brake / traction units is configured to apply a brake / traction force.

[0057] In step 630, the control unit 140 obtains a second wheel speed signal ωa respectively indicating the average rotational speed of at least one second wheel 122, 123, and / or 124 on at least one second axle 132, 133, and / or 134, and for this at least one second axle, at least one second brake / traction unit of a set of brake / traction units is configured to apply its respective brake / traction force.

[0058] In step 640 following step 620, the control unit 140 generates a first control signal for each of the first brake / traction units 101 or 161 so that the first brake / traction unit 101 or 161 applies an increasing brake / traction force to the first axle 131.

[0059] In step 650 following step 630, the control unit 140 generates at least one second control signal for at least one second brake / traction unit 102, 103, 104, or 162, 163, 164 so that at least one second brake / traction unit 102, 103, and 104, or 162, 163, and 164 applies a decreasing brake / traction force to each of at least one second axle 132, 133, and 134. Accordingly, the non-uniform distribution of the brake / traction force is smoothed, the procedure of the friction test becomes hardly noticeable to the passengers of the railway vehicle, and of course the comfort of the passengers is increased.

[0060] In step 660 following steps 640 and 650, the absolute difference |ω 1 - ω a | between the first and second wheel speed signals ω 1 and ω a is checked to see if it exceeds a threshold value. If it exceeds the threshold value, the process proceeds to step 670, but if not, the procedure returns to steps 620 and 640.

[0061] In step 670, the friction coefficient μ between the wheels 121, 122, 123, 124 and a set of rails 181, 182 during the running of the railway vehicle 100e parameter μ reflecting this m is determined. Thereafter, the procedure returns to step 610.

[0062] All process steps and sub-sequences of steps described with reference to FIG. 6 can be controlled by a programmed processor. Also, the embodiments of the present invention described above with reference to the drawings include a processor and a process executed in at least one processor. However, the scope of the present invention therefore also extends to a computer program, in particular a computer program on or in a carrier adapted for the implementation of the present invention. This program can be in source code, object code, intermediate source code and intermediate object code in a partially compiled form, or any other form suitable for use in the implementation of the process according to the present invention. The above program can be part of an operating system or a separate application. The above carrier can be any entity or device capable of holding the program. For example, the above carrier can include a storage medium such as a flash memory, ROM (read-only memory), such as a DVD (digital video / versatile disc), CD (compact disc), or semiconductor ROM, EPROM (erasable programmable read-only memory), EEPROM (electrically erasable programmable read-only memory), or a magnetic recording medium such as a floppy disk or a hard disk. Further, the above carrier can be a transmissible carrier such as an electrical signal or an optical signal transmitted via an electrical cable or an optical cable, or by radio waves or other means. When the above program is embodied in a signal that can be directly transmitted using a cable or other device or means, the above carrier may be constituted by such a cable or other device or means. Alternatively, the above carrier may be an integrated circuit in which the above program is embedded and adapted for performing the related process or for use in performing the related process.

[0063] As used herein, the terms "comprises" and "comprising" are to be construed as specifying the presence of the stated features, integers, steps, or components. These terms do not preclude the presence or addition of one or more further elements, features, integers, steps, or components, or groups thereof. The indefinite articles "a" or "an" do not preclude the plural. In the claims, the term "or" is not to be construed as exclusive or exclusive disjunction (sometimes called "XOR"). On the contrary, expressions such as "A or B" cover all cases of "A and not B", "B and not A", and "A and B", unless otherwise specified. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the claims.

[0064] It should also be noted that the features of the various embodiments described herein can be freely combined unless explicitly stated to be inappropriate.

[0065] Variations of the disclosed embodiments will be understood and practicable by those skilled in the art in implementing the invention recited in the claims by considering the drawings, the specification, and the appended claims. The invention is not limited to the described embodiments and can be freely modified within the scope of the claims.

Claims

1. A friction test system for a railway vehicle (100), wherein the system comprises a set of brake / traction units (101, 161; 102, 162; 103, 163; 104, 164), each receiving a respective control signal (B1, A1; B2, A2; B3, A3; B4, A4) and configured to apply a respective brake / traction force to respective axles (131, 132, 133, 134) of the railway vehicle (100) in response to the control signal to decelerate / accelerate the railway vehicle (100), a control unit (140) configured to generate each of the control signals (B1, A1; B2, A2; B3, A3; B4, A4), wherein the control unit (140) is configured to A first wheel speed signal (ω 1 ) indicating a rotational speed of at least one first wheel (121) of a first axle (131) of the wheel axles, wherein a first brake / traction unit (101, 161) of the set of the brake / traction units is configured to apply a brake / traction force, is obtained At least one second wheel (122, 123, 124) of at least one second axle (132, 133, 134) of the axles, wherein at least one second brake / traction unit of the set of brake / traction units is configured to apply its respective brake / traction force, to indicate an average rotational speed of the at least one second wheel, a second wheel speed signal (ω a ) is obtained, the first wheel speed signal (ω 1 ) and the absolute difference between the second wheel speed signal (ω a ), i.e., (|ω 1 - ω a |), until it exceeds a threshold value, a first control signal (BF; A1) is generated for the first brake / traction unit (101, 161) so that the first brake / traction unit (101, 161) applies an increasingly increasing brake / traction force to the first axle (131). When the absolute difference (|ω 1 - ω a |) exceeds the threshold value, in response thereto, The coefficient of friction (μ e ) between the wheels (121, 122, 123, 124) and the set of rails (181, 182) on which the railway vehicle (100) travels m ) is determined, and generate the control signals (B1, A1; B2, A2; B3, A3; B4, A4) such that when the brake / traction force applied to the first axle (131) increases gradually, the average brake / traction force applied to the at least one second axle (132, 133, 134) decreases gradually, characterized in that the friction test system is configured as such.

2. The friction test system according to claim 1, wherein the control unit (140) is configured to generate the control signals (B1, A1; B2, A2; B3, A3; B4, A4) such that the gradual decrease in the average brake / traction force applied to the at least one second axle (132, 133, 134) corresponds to the gradual increase in the brake / traction force applied to the first axle (131) at each point in time.

3. The friction test system, the first wheel speed signal (ω 1 ), and the respective wheel speed signals (ω 2 , ω 3 , ω 4 ) of the at least one second wheel (122, 123, 124) of the at least one second wheel axle (132, 133, 134), a set of rotational speed sensors (215; 235, 425) configured to generate, the friction test system according to claim 1 or 2.

4. The friction test system according to claim 3, wherein at least one of the set of rotational speed sensors comprises a tachometer provided on or near the first axle (131) and / or on or near the at least one second axle (132, 133, 134).

5. The friction test system further comprises A first accelerometer (425) provided on a frame element (110) of the railway vehicle (100), the first accelerometer (425) being configured to generate at least one first vector signal (VS1) representing an acceleration (a x , a y , a z , a R , a p , a w ) of the railway vehicle (100) in at least one dimension; At least one second accelerometer (235) provided eccentrically with respect to the rotation axis of at least one wheel (121) of the railway vehicle (100), the at least one second accelerometer (235) being configured to generate at least one second vector signal (VS2) representing the movement of the at least one second accelerometer (235) in a plane orthogonal to the rotation axis of the at least one wheel (121); and at least one second accelerometer (235). The control unit (140) is configured to obtain the first wheel speed signal (ω 1 ), and / or at least one of the second wheel speed signals (ω 2 , ω 3 , ω 4 ) based on the first vector signal (VS1) and the second vector signal (VS2). The friction test system according to claim 3 or 4. **Claim 6** The set of brake / traction units comprises a plurality of brake units (101, 102, 103, 104), each of the brake units being configured to apply a respective braking force to a respective axle (131, 132, 133, 134) in order to decelerate the railway vehicle (100) in response to the respective control signals (B1, B2, B3, B4). The friction test system according to any one of claims 1 to 5. **Claim 7** The set of brake / traction units comprises a plurality of traction motors (161, 162, 163, 164), each of the traction motors being configured to apply a respective traction force to a respective axle (131, 132, 133, 134) in order to accelerate the railway vehicle (100) in response to the respective control signals (A1, A2, A3, A4). The friction test system according to any one of claims 1 to 5. **Claim 8** The friction test system comprises a data bus (150) configured to transmit the control signals (B1, A1; B2, A2; B3, A3; B4, A4) from the control unit (140) to each brake / traction unit of the set of brake / traction units (101, 161; 102, 162; 103, 163; 104, 164). The friction test system according to any one of claims 1 to 7. **Claim 9** A friction test method for a railway vehicle (100) implemented on a computer, the method comprising: A process of generating respective control signals (B1, A1; B2, A2; B3, A3; B4, A4), each configured to be received by a respective brake / traction unit of a set of brake / traction units (101, 161; 102, 162; 103, 163; 104, 164) of a railway vehicle (100), wherein each of the respective brake / traction units is configured to apply a respective brake / traction force to respective axles (131, 132, 133, 134) of the railway vehicle (100) to decelerate / accelerate the railway vehicle (100) in response to the control signals, and the method further comprises A first wheel speed signal (ω) indicating the rotational speed of at least one first wheel (121) of a first axle (131) of the axles, wherein a first brake / traction unit (101, 161) of the set of the brake / traction units is configured to apply a brake / traction force 1 is obtained; At least one second wheel (122, 123, 124) of at least one second axle (132, 133, 134) of the axles, wherein at least one second brake / traction unit of the set of brake / traction units is configured to apply its respective brake / traction force, and indicating an average rotational speed of the at least one second wheel, a second wheel speed signal (ω a ) is obtained; the first wheel speed signal (ω 1 ), and until the absolute difference (|ω a −ω 1 |) of the first wheel speed signal and the second wheel speed signal (ω a |) exceeds a threshold value, generating a first control signal (BF; A1) to the first brake / traction unit (101, 161) so that the first brake / traction unit (101, 161) applies an increasingly increasing brake / traction force to the first axle (131); and when the absolute difference (|ω 1 −ω a |) exceeds the threshold value, in response thereto, A coefficient of friction (μ) between the wheels (121, 122, 123, 124) and a set of rails (181, 182) on which the railway vehicle (100) travels e ), and a parameter (μ m ) for determining the same generating the control signals (B1, A1; B2, A2; B3, A3; B4, A4) such that when the brake / traction force applied to the first axle (131) increases gradually, the average brake / traction force applied to the at least one second axle (132, 133, 134) decreases gradually, a friction test method for a railway vehicle, characterized by comprising this step.

10. The method according to claim 9, comprising generating the control signals (B1, A1; B2, A2; B3, A3; B4, A4) such that the gradual decrease in the average brake / traction force applied to the at least one second axle (132, 133, 134) corresponds to the gradual increase in the brake / traction force applied to the first axle (131) at each point in time.

11. said first wheel speed signal (ω 1 ), and said at least one second wheel (122, 123, 124) of said at least one second axle (132, 133, 134) of said railway vehicle (100) from a set of rotational speed sensors (215; 235, 425) thereof, each wheel speed signal (ω 2 , ω 3 , ω 4 ), the method according to claim 9 or 10, comprising the step of obtaining.

12. The method according to claim 11, wherein at least one tachometer (215) provided on or near the first axle (131) and / or on or near the at least one second axle (132, 133, 134) is included in the set of rotational speed sensors.

13. The railway vehicle (100) is A first accelerometer (425) provided on a frame element (110) of the railway vehicle (100), the first accelerometer (425) being configured to generate at least one first vector signal (VS1) representing an acceleration (a x , a y , a z , a R , a p , a w ) of the railway vehicle (100) in at least one dimension. at least one second accelerometer (235) provided eccentrically with respect to the rotation axis of at least one wheel (121) of the railway vehicle (100), configured to generate at least one second vector signal (VS2) representing the movement of the at least one second accelerometer (235) in a plane orthogonal to the rotation axis of the at least one wheel (121), and the method comprises Based on the first vector signal (VS1) and the second vector signal (VS2), the first wheel speed signal (ω 1 ), and / or at least one of the second wheel speed signals (ω 2 , ω 3 , ω 4 ) is obtained, the method according to claim 11 or 12.

14. The railway vehicle (100) comprises a data bus (150), and the method comprises A method according to any one of claims 9 to 13, including the step of transmitting the control signals (B1, A1; B2, A2; B3, A3; B4, A4) to each braking / traction unit of a set of the braking / traction units (101, 161; 102, 162; 103, 163; 104, 164) via the data bus (150).

15. A computer program (525) installable on a non-volatile data carrier (520) communicably connected to at least one processor (530), the computer program (525) including software for executing the method according to any one of claims 9 to 14 when the computer program (525) is executed on the at least one processor (530).

16. A non-volatile data carrier (520) including the computer program (425) of claim 15.

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