Method for evaluating unstable oscillation of current collector

Abstract

To provide an evaluation method of unstable vibration of a current collector for evaluating the presence or absence of unstable vibration generated in the current collector by a simple method without requiring parameter identification of the current collector.SOLUTION: A method of evaluating unstable vibration occurring in a current collector comprises: a step of dividing the whole system, which is the current collector when in sliding contact with an overhead line, into a plurality of sub-systems including a sub-system (1) including the current collector and a sub-system (2) including the overhead line; a step of acquiring the frequency response function of the sub-system (1) at the point of contact with the overhead line in contact with the current collector; a step of setting the stiffness, damping, and friction coefficient of the sub-system (2); a transfer function synthesis step of estimating the frequency response function of the whole system from the frequency response function of the sub-system (1) and the stiffness, damping, and friction coefficient of the sub-system (2); A process for identifying a mode characteristic based on a frequency response function of the whole system and identifying a mode damping ratio of the whole system, and stability evaluation of the whole system based on the mode damping ratio are performed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an unstable vibration evaluation method for evaluating the presence or absence of unstable vibration in a current collector attached to the top of a railway vehicle, and relates to an unstable vibration evaluation method for a current collector that can evaluate the stability of the current collector without requiring the identification of large-scale physical parameters. [Background technology]

[0002] Railway vehicles have current collectors attached to the top of the vehicles, and the current collectors slide over the overhead wires, obtaining power from the overhead wires to run.

[0003] Current collectors obtain power by sliding against the overhead wires, and it is known that this sliding can cause pitching in the current collectors of railway vehicles. This is a flapping phenomenon caused by an increase in the coefficient of friction between the contact strip and the contact wire that make up the current collector. This is also known as abnormal vibration or unstable vibration, and is known to have the potential to cause damage or malfunction to the equipment.

[0004] There are various known methods for reducing or detecting the occurrence of unstable vibrations in such current collectors. For example, Patent Document 1 proposes a structural method for reducing sliding friction between the current collector and the overhead wire, and Patent Document 2 proposes a method and device for detecting pitching vibrations based on multiple accelerations measured on the slider, assuming that unstable vibrations are caused by pitching vibrations of the slider. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-75063 [Patent Document 2] Japanese Patent Application Publication No. 2023-75529 Summary of the Invention [Problem to be solved by the invention]

[0006] When the coefficient of friction between the overhead wire and the collector slider increases, unstable vertical vibrations may occur in the collector due to forward and backward inputs caused by friction.To evaluate this, a stability evaluation method based on a mechanical model has been proposed.

[0007] In the conventional stability evaluation method, a mechanical model of a two-degree-of-freedom system is created to express the coupling between the pitching vibration and the up-and-down vibration of the contact strip, and the stability is evaluated numerically. This method makes it possible to evaluate whether or not unstable vibration occurs for any friction coefficient.

[0008] Conventional stability evaluation methods using complex eigenvalue analysis focus on the coupling of the vertical and pitching vibrations of the contact strip. A mechanical model is constructed to represent these motions. To simulate the partial contact between the contact strip and the overhead wire, a contact element is attached to the contact strip at a position offset from the center of the rigid body representing the contact strip to represent the contact force between the contact strip and the overhead wire. Coulomb friction is assumed in the friction model, and a friction force proportional to the contact force is applied in the horizontal direction of the contact point. The model parameters, such as mass, stiffness, and damping, of each part are obtained by, for example, measuring the frequency response function (FRF) through a pantograph vibration test and adjusting the model FRF so that it matches the measured FRF. In this specification, the pantograph in sliding contact is referred to as the "whole system."

[0009] Since the characteristic matrix of this mechanical model contains an asymmetric matrix due to the friction coefficient, its eigenvalues ​​are complex numbers (hereinafter referred to as "complex eigenvalues"), and their real parts indicate the negative values ​​of the modal damping ratios. Therefore, when the real part of the complex eigenvalue is positive, it means that the damping ratio is negative, and in that case, the system becomes unstable.

[0010] However, when using a mechanical model, it is necessary to identify the physical parameters (mass, stiffness, damping, etc.) of the current collector through vibration tests, which requires a great deal of effort and cost.

[0011] Therefore, in order to evaluate unstable vibrations occurring in a current collector, a method is required to evaluate the stability of an actual current collector without needing to identify the physical parameters of the current collector.

[0012] Therefore, the present invention has been made in consideration of the above problems and findings, and aims to provide a method for evaluating unstable vibration of a current collector, which can evaluate the presence or absence of unstable vibration occurring in the current collector in a simple manner, without requiring parameter identification of the current collector. [Means for solving the problem]

[0013] The method for evaluating unstable vibrations of a current collector according to the present invention is a method for evaluating unstable vibrations that occur in a current collector, and is characterized by the steps of: dividing the entire system, which is the current collector when in sliding contact with an overhead wire, into a plurality of divisional systems, including divisional system 1 including the current collector and divisional system 2 including the overhead wire; acquiring the frequency response function of divisional system 1 at the contact point between the current collector and the overhead wire; setting the stiffness, damping, and friction coefficient of divisional system 2; a transfer function synthesis step of estimating the frequency response function of the entire system from the frequency response function of divisional system 1 and the stiffness, damping, and friction coefficient of divisional system 2; identifying modal characteristics based on the frequency response function of the entire system and identifying the modal damping ratio of the entire system; and evaluating the stability of the entire system based on the modal damping ratio.

[0014] In the method for evaluating unstable vibration of a current collector according to the present invention, it is preferable that the step of acquiring the frequency response function of the first branch system comprises performing a vibration test on the current collector.

[0015] In addition, in the method for evaluating unstable vibration of a current collector according to the present invention, it is preferable that the step of acquiring the frequency response function of the division system 1 includes a noise removal step of reconstructing the frequency response function obtained by the vibration test based on the mode characteristics identified using a differential iterative method.

[0016] In addition, in the method for evaluating unstable vibration of a current collector according to the present invention, the step of setting the stiffness, damping and friction coefficient of the division system 2 is preferably performed by measuring the free vibration when the current collector is collided with a rigid wall, and adjusting parameters including stiffness and damping so that they match the values ​​reproduced by simulation.

[0017] In addition, in the method for evaluating unstable vibration of a current collector according to the present invention, it is preferable that the stability evaluation of the entire system is performed by evaluating that the entire system is unstable when the modal damping ratio is a negative value.

[0018] The above summary of the invention does not list all of the necessary features of the present invention, and subcombinations of these features may also constitute inventions. [Effects of the Invention]

[0019] The method for evaluating unstable vibration of a current collector according to the present invention includes a step of acquiring the frequency response function of the divisional system 1 at the contact point between the current collector and the overhead wire, a step of setting the stiffness, damping, and friction coefficient of the divisional system 2, a transfer function synthesis step of estimating the frequency response function of the entire system from the frequency response function of the divisional system 1 and the stiffness, damping, and friction coefficient of the divisional system 2, a step of identifying modal characteristics based on the frequency response function of the entire system and identifying the modal damping ratio of the entire system, and a step of evaluating the stability of the entire system based on the modal damping ratio. This makes it possible to evaluate unstable vibration without identifying the physical parameters of the current collector, which requires a great deal of effort and cost. [Brief explanation of the drawings]

[0020] [Figure 1] 1 shows the complete system of current collectors and contact elements. [Figure 2] FIG. 3 is a flow chart of a method for evaluating unstable vibration of a current collector according to an embodiment of the present invention. [Figure 3] A simple model that separates the contact element and current collector systems to represent unstable vibrations. [Figure 4] Diagram showing division into system 1 and contact elements. [Figure 5] 1 is a table showing modal characteristics obtained by the method for evaluating unstable vibration of a current collector according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Preferred embodiments for carrying out the present invention will be described below with reference to the drawings. Note that the following embodiments do not limit the inventions according to the claims, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0022] Figure 1 is a diagram showing the entire system consisting of a current collector and contact elements, Figure 2 is a flow chart of a method for evaluating unstable vibration of a current collector according to an embodiment of the present invention, Figure 3 is a simple model in which the contact elements that express unstable vibration and each system of the current collector are divided, Figure 4 is a diagram showing the division into sub-system 1 and contact elements, and Figure 5 is a table showing the modal characteristics obtained by the method for evaluating unstable vibration of a current collector according to the present invention.

[0023] Generally, unstable vibration is a phenomenon that occurs mainly due to the dynamic characteristics of the pantograph, and the phenomenon can be reproduced, for example, by performing a sliding test at low speed using a known high-speed pantograph testing device. However, a problem with sliding tests is that it is difficult to precisely control the friction coefficient.

[0024] Therefore, in the method for evaluating unstable vibration of a current collector according to this embodiment, the FRF of the entire system in a sliding contact state is estimated from the FRF of the pantograph alone, as a method that can evaluate whether unstable vibration occurs in the pantograph without conducting a sliding test or constructing a mechanical model. In this method, the FRF during sliding contact is estimated, and the unstable vibration is evaluated using the sign of the modal damping ratio identified based on this.

[0025] In order to estimate the FRF for the entire system of the actual current collector 10, consider the entire system in which the contact spring and damping element representing the contact element 20 is attached to the top surface of the collector head 13 of the current collector 10 as shown in Figure 1. We will estimate the FRF that represents the input-output relationship for point i of this entire system.

[0026] Next, each step of the method for evaluating unstable vibration of a current collector according to this embodiment will be described in detail.

[0027] As shown in FIG. 2, the method for evaluating unstable vibration of a current collector according to this embodiment includes the steps of: dividing the entire system including the current collector 10 when it is in sliding contact with the contact element 20 into multiple sub-systems (S101), including sub-system 1 including the current collector and sub-system 2 including the contact element 20; acquiring the frequency response function of sub-system 1 at the contact point between the current collector 10 and the contact element 20 (S102); setting the stiffness, damping, and friction coefficient of sub-system 2 (S103); synthesizing a transfer function (S104) to estimate the frequency response function of the entire system from the frequency response function of sub-system 1 and the stiffness, damping, and friction coefficient of sub-system 2; identifying modal characteristics based on the frequency response function of the entire system and identifying the modal damping ratio of the entire system (S105); and evaluating the stability of the entire system based on the modal damping ratio (S106).

[0028] In the step (S101) of dividing the entire system including the current collector 10 when it is in sliding contact with the contact element 20 into a plurality of sub-systems including a sub-system 1 including the current collector and a sub-system 2 including the contact element 20, the entire system is divided into a sub-system 1 including the current collector 10 and a sub-system 2 including contact elements such as overhead wires, as shown in Fig. 3. In this step, the contact point between the contact strip 11 of the current collector 10 and the contact element 20 is set as a contact point 12.

[0029] In the step (S102) of acquiring the frequency response function of the division system 1 at the contact point with the contact element 20 that contacts the current collector 10, the FRF of the division system 1 is acquired by performing an impulse vibration test on the current collector 10. Specifically, it is preferable to install a pantograph on a surface plate and perform the impulse vibration.

[0030] As for the excitation points and acceleration measurement points, it is preferable to fix aluminum blocks of a specified size to two locations on the top surface of the contact strip with adhesive, attach accelerometers to the aluminum blocks, and vibrate any location on the aluminum blocks with an impulse hammer. By using the aluminum blocks to perform excitation and acceleration measurement, it becomes possible to perform excitation and acceleration measurement in the y direction, which is difficult to perform on the top surface of the contact strip. The aluminum blocks are preferably installed at the contact point 12 with the contact element 20, designated as point j, which is the center of the contact strip in the sleeper direction and the end of the contact strip in the rail direction, and point i, which is the location to be estimated for FRF, located a specified distance from point j in the x direction, designated as points j and i.

[0031] Furthermore, after acquiring the FRF of the division system 1, it is preferable to have a noise removal step in which, in order to remove noise components contained in the acquired FRF, the FRF is reconstructed based on the mode characteristics identified using the differential iterative method, and the FRF is used to estimate the FRF.

[0032] The process (S103) of setting the stiffness, damping and friction coefficient of the system 2 involves measuring the free vibration when the pantograph collides with a rigid wall or the like, reproducing it through simulation, and adjusting the parameters so that the two match. c , and decay c c The friction coefficient μ can be set to any value.

[0033] The transfer function synthesis step (S104) for estimating the frequency response function of the entire system from the frequency response function of the sub-system 1 and the stiffness, damping, and friction coefficient of the sub-system 2 is carried out by dividing the entire system into the sub-system 1 and the contact element as shown in FIG. 4, and then calculating the z-direction displacement Z at point i of the sub-system 1. i , the z-direction displacement Z at point j, which is the contact point with the contact element j、 y-direction displacement Y j is expressed as follows using FRF and external forces:

[0034] Z i =G zi F zi +G zizj F zj+G ziyj F yj (Equation 1) Z j =G zjzi F zi +G zj F zj +G zjyj F yj (Equation 2) Y j =G yjzi F zi +G yjzj F zj +G yjyi F yi (Equation 3)

[0035] Here, F zi is the external force acting on point i in the z direction, G zi is the self-compliance in the z direction at point i, G zjzi represents the mutual compliance between the z-direction input at point i and the z-direction response at point j.

[0036] Also, the contact force F acting on point j in the entire system c and friction force F yj is expressed by the following equation:

[0037] F c =-F zj =(k c +jωc c )(G zjzi F zi +G zj F zj +G zjyj F yj ) (Equation 4) F yj =-μ(k c +jωc c )(G zjzi F zi +G zj F zj +G zjyj F yj ) (Equation 5)

[0038] Combining the above equations 1 to 5 in matrix notation gives the following equation:

number

[0039] An estimate of the FRF of the entire system is obtained by solving the column vector on the left side of Equation 6. To estimate the FRF of the entire system using this method, it is necessary to measure the various FRFs of subsystem 1. These various FRFs can be measured, for example, by impulse vibration testing.

[0040] In the step (S105) of identifying modal characteristics based on the frequency response function of the entire system and identifying the modal damping ratio of the entire system, the modal damping ratio is identified from the FRF of the entire system. The identified modal characteristics are obtained as shown in Fig. 5. As a specific technique for identifying modal characteristics, various conventionally well-known methods can be used, and for example, the differential iterative method is preferably used.

[0041] In the step (S106) of evaluating the stability of the entire system based on the modal damping ratios, if all the modal damping ratios identified in the step (S105) of identifying the modal damping ratios of the entire system are positive, it is evaluated that unstable vibrations will not occur (the system is stable), and if even one modal damping ratio is negative, it is evaluated that unstable vibrations will occur (the system is unstable).

[0042] Specifically, for example, in the case of a single-arm pantograph, in the case of an anti-sway condition where the intermediate hinge slides in a direction toward the rear of the traveling direction, Figure 5 shows that when the friction coefficient μ exceeds 0.8 and reaches 1.0, the modal damping ratio of a certain natural mode (natural frequency of approximately 10.6 Hz) becomes negative, causing unstable vibration.

[0043] Furthermore, sliding tests of a single-arm pantograph using a high-speed pantograph testing device confirmed that unstable vibrations occur when the friction coefficient is approximately 0.75 under anti-swing conditions, confirming that the conditions for the occurrence of unstable vibrations can be roughly estimated using the method for evaluating unstable vibrations in a current collector according to this embodiment.

[0044] As described above, the method for evaluating unstable vibration of a current collector according to this embodiment includes a step of acquiring the frequency response function of the division 1 at the contact point between the current collector and the overhead wire, a step of setting the stiffness, damping, and friction coefficient of the division 2, a transfer function synthesis step of estimating the frequency response function of the entire system from the frequency response function of the division 1 and the stiffness, damping, and friction coefficient of the division 2, a step of identifying modal characteristics based on the frequency response function of the entire system and identifying the modal damping ratio of the entire system, and a stability evaluation of the entire system based on the modal damping ratio, so that it is possible to evaluate unstable vibration without identifying the parameters of the current collector. [Explanation of symbols]

[0045] 10 current collector, 11 contact strip, 12 contact point, 20 contact element.

Claims

1. A method for evaluating unstable vibrations occurring in a current collector, comprising: a step of dividing the entire system, which is the current collecting device when in sliding contact with the overhead wire, into a plurality of division systems, including a division system 1 including the current collecting device and a division system 2 including the overhead wire; acquiring a frequency response function of the system 1 at a contact point between the power collector and the overhead wire; setting the stiffness, damping and friction coefficient of the system 2; a transfer function synthesis step of estimating a frequency response function of the entire system from the frequency response function of the first subsystem and the stiffness, damping, and friction coefficient of the second subsystem; performing modal characteristic identification based on a frequency response function of the entire system to identify a modal damping ratio of the entire system; A method for evaluating unstable vibrations occurring in a current collector, comprising evaluating the stability of the entire system based on the modal damping ratio.

2. 2. The method for evaluating unstable vibrations occurring in a current collector according to claim 1, A method for evaluating unstable vibrations occurring in a current collector, wherein the step of acquiring the frequency response function of the first division system comprises performing a vibration test on the current collector.

3. 3. The method for evaluating unstable vibrations occurring in a current collector according to claim 2, A method for evaluating unstable vibrations occurring in a current collector, characterized in that the step of acquiring the frequency response function of the division system 1 includes a noise removal step of reconstructing the frequency response function obtained by the vibration test based on the mode characteristics identified using a differential iterative method.

4. 2. The method for evaluating unstable vibrations occurring in a current collector according to claim 1, A method for evaluating unstable vibrations that occur in a current collector, characterized in that the process of setting the stiffness, damping and friction coefficient of the division system 2 is performed by measuring the free vibration when the current collector collides with a rigid wall and adjusting parameters including stiffness and damping so that they match the values ​​reproduced by simulation.

5. 2. The method for evaluating unstable vibrations occurring in a current collector according to claim 1, A method for evaluating unstable vibrations occurring in a current collector, characterized in that the stability evaluation of the entire system is performed by evaluating the entire system as being unstable when the modal damping ratio has a negative value.

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