A train impedance frequency response measurement device and method

Abstract

The application discloses a train impedance frequency response measuring device and measuring method, and relates to the technical field of train impedance measurement, which comprises the following steps: connecting the wheel and rail connecting part at the front and rear of the train as a two-port, connecting the two copper plates through the four-hole flange seat N-KF female head of the connecting device, connecting the lead wire of the two-port vector network analyzer port to the four-hole flange seat N-KF female head, measuring the scattering parameters of the two-port and the parallel two-port of the wheel and rail in the state of no train on the rail and the state of train on the rail, converting the two-port scattering parameters into admittance parameters and transmission parameters, removing the influence of the surrounding equipment such as the rail on the result according to the admittance parameter relationship in the parallel state of the two-port, and obtaining the admittance parameters of a single train; obtaining the transmission parameters of the connector between trains according to the transmission parameter relationship in the cascaded state of multiple two-ports, and converting the transmission parameters into impedance parameters, and obtaining the impedance frequency response of the train in the two-port state of the wheel and rail contact points in any frequency range.

Description

Technical Field

[0001] The present invention relates to the technical field of train impedance measurement, and in particular to a train impedance frequency response measurement device and a measurement method. Background Art

[0002] Measuring the impedance frequency response of high-speed train bodies is a key tool for assessing their electromagnetic compatibility, structural safety, and grounding performance, and is crucial for ensuring reliable train operation and passenger safety. As metal structures, high-speed train bodies must effectively shield against external electromagnetic interference (such as lightning and wireless signals) and suppress radiation from internal equipment. The impedance frequency response quantifies the body's reflection and absorption characteristics of high-frequency electromagnetic waves, optimizing shielding design and ensuring interference-free onboard communication systems. Furthermore, the body must dissipate lightning or fault currents through the grounding system. Impedance analysis can detect high-frequency resonant points in the ground loop to prevent voltage surges caused by sudden impedance changes during lightning strikes, thus protecting onboard electronic equipment. During high-speed travel, the body of a train is susceptible to lightning strikes. Impedance frequency response data is used to design surge protection circuits to ensure that lightning currents are safely discharged along low-impedance paths, minimizing the risk of potential rise within the body.

[0003] Trains are heavy, difficult to move, and difficult to separate from the tracks. Existing measurement methods ignore the connection between the train and the track. Instead, they measure the train's impedance directly while the train is positioned on the track. Because the wheels are in physical contact with the rails, the measurement results include not only the train's impedance but also the rails and their surrounding equipment. Furthermore, existing methods often only measure impedance at DC or power frequency. During train operation, situations such as offline pantographs and excessive phase shifts can cause high-frequency interference, leading to significant measurement errors. Summary of the Invention

[0004] The purpose of the present invention is to provide a train impedance frequency response measurement device and a measurement method to address the above-mentioned deficiencies in the prior art, so as to solve the problems in the prior art.

[0005] The present invention specifically provides the following technical solution: a train impedance frequency response measuring device, comprising:

[0006] A two-port vector network analyzer, used to input an excitation signal to a device under test and measure two-port scattering parameters; the device under test is a train;

[0007] A connecting device for connecting a two-port vector network analyzer and a device under test, the connecting device comprising:

[0008] Four-hole flange socket N-KF female connector, used to connect to a two-port vector network analyzer;

[0009] There are two sets of connectors, each set of connectors includes two copper plates, wherein the end of the first copper plate is provided with a hole for limiting the position of the four-hole flange seat N-KF type female connector shell, and the second copper plate is arranged below the first copper plate, and the end of the second copper plate is provided with a hole for connecting to the center conductor of the four-hole flange seat N-KF type female connector, and the other ends of the two copper plates are respectively connected to two terminals; the two terminals are respectively the connection points between the wheels and rails on the left and right sides of the train.

[0010] The present invention also provides a measurement method based on a train impedance frequency response measurement device, comprising:

[0011] The connections between the front left and right wheels and the rails of the train are used as the two terminals of the first port, and the connections between the rear left and right wheels and the rails of the train are used as the two terminals of the second port. The first and second ports are used to construct a parallel two-port connection between the train and the rails.

[0012] Before the train arrives, a two-port vector network analyzer is used to measure the scattering parameters of the rails under a single train in any frequency range. and the scattering parameters of the rails under the two trains When the train is approaching, measure the scattering parameters of the two parallel ports of the single train and the rail below Scattering parameters of the two ports in parallel with the two trains and the rails below , and the scattering parameters 、 Converted into the admittance matrix of a single train , the scattering parameters 、 Converted to the admittance matrix of two trains ;

[0013] For the admittance matrix and Convert them separately to obtain the transmission parameters of single-car train and two-car train T 1 and T , according to the transmission parameter relationship of multiple two-port cascade states, the transmission parameters of the train connector are obtained T 2; The transmission parameter relationship is: the transmission parameters of the two trains T Two single carriages T 1 Transmission parameters of the train connector T The product of 2;

[0014] The parameters will be transferred T 1 and transmission parameters T 2 are converted into the impedance of a single train and a workshop connector respectively Z 1 and Z 2.

[0015] Preferably, the scattering parameters 、 Converted into the admittance matrix of a single train , specifically:

[0016] The scattering parameters and scattering parameters Enter the admittance calculation formula to obtain the admittance matrix of the two rail ports under the single train section , the admittance matrix of a single train and its two parallel ports on the rail below Y , where the admittance calculation formula is:

[0017] ;

[0018] Among them, the conductivity matrix , conductivity , n =1,2, Re represents the real part, E is the identity matrix, , and are the characteristic impedances of the first port and the second port, respectively;

[0019] Get the admittance matrix of a single train , the specific expression is:

[0020] ;

[0021] in, Represents the admittance matrix of a single train, where the admittance matrix of two trains is And the admittance matrix of a single train The calculation formula is consistent.

[0022] Preferably, the admittance matrix and Convert them separately to obtain the transmission parameters of single-car train and two-car train T 1 and T , according to the transmission parameter relationship of multiple two-port cascade states, the transmission parameters of the train connector are obtained T 2. Specifically:

[0023] The admittance matrix and Convert to transfer parameters T The calculation formula is:

[0024] ;

[0025] Among them, the admittance matrix , is the self-admittance of the first port, represents the mutual admittance between the first port and the second port, represents the mutual admittance between the second port and the first port, is the self-admittance of the second port; where the admittance matrix They are and ;

[0026] The transmission parameters of the train connector are obtained based on the transmission parameter relationship under multiple two-port cascade states. T 2. The specific expression is:

[0027] ;

[0028] in, T is the transmission parameter when two trains are connected, T 1 is the transmission parameter of the first train, T 2 is the transmission parameter of the connector, T 3 is the transmission parameter of the second train. When the two trains are the same T 3= T 1.

[0029] Preferably, the transmission parameters T 1 and transmission parameters T 2 are converted into the impedance of a single train and a workshop connector respectively Z 1 and Z 2, the conversion formula between transmission parameters and impedance is used, and the specific expression is:

[0030] ;

[0031] in, , A, B, C and D are transmission parameters T The four matrix elements of .

[0032] Preferably, when the train has not arrived and when the train has arrived, the distance between the front wheel and the rear wheel of the train is used as the distance between the two ports, and the leads at the first port and the second port, and the copper plates connected to the four-hole flange seat N-KF type female connector shell are placed at the first terminal and the third terminal respectively, and the copper plates connected to the four-hole flange seat N-KF type female connector core wire are placed at the second terminal and the fourth terminal respectively; wherein the first terminal and the third terminal are located on the same rail, and the second terminal and the fourth terminal are located on the same rail.

[0033] Compared with the prior art, the present invention has the following significant advantages:

[0034] The connection device of the present invention is connected to the two-port vector network analyzer and the device under test through a four-hole flange socket N-KF female connector and two copper plates. It can connect one output port of the measuring device to the two terminals of the device under test while maintaining signal integrity, thereby achieving physical separation of the signal and the ground. Compared with the traditional double alligator clip, copper has good conductivity and a resistivity of only , which can reduce insertion loss and increase the reliability of measurement results. At the same time, by equivalently connecting the train and rail in parallel with two ports, a two-port vector network analyzer can be used in any frequency range to measure the scattering parameters of the two-port parallel train-rail connection and the two-port rail connection, respectively, with and without a train on the rail. The scattering parameters are converted into an admittance matrix and transmission parameters, eliminating the influence of peripheral equipment such as the rail on the results. The transmission parameters of a single train section and the inter-train connector are obtained, and the transmission parameters are converted into impedance to obtain the impedance frequency response of the train with the wheel-rail contact point as the two-port within any frequency range. This method can eliminate the influence of peripheral equipment such as the rail on the impedance measurement results, take into account the impedance changes at different frequencies, and provide a measurement solution with small measurement error and wide frequency coverage, providing a new direction for impedance measurement of large, difficult-to-move objects such as rail transit. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the connecting device of the present invention;

[0036] Figure 2 for Figure 1 A physical diagram of the connection device diagram;

[0037] Figure 3 This is a two-port parallel network diagram of a single train section and the rails below it; Figure 3 (a) is a schematic diagram of a two-port network terminal of a single train and the rail below it. Figure 3 (b) is a schematic diagram of a two-port parallel network;

[0038] Figure 4 This is a two-port parallel network diagram of two train sections and the rails below them; Figure 4 (a) is a schematic diagram of the two-port network terminal of two trains and the rails below them. Figure 4 (b) is a schematic diagram of a two-port parallel network;

[0039] Figure 5 This is a two-port cascade network diagram of the present invention; wherein Figure 5 (a) is a schematic diagram of the train port. Figure 5 (b) is a schematic diagram of three two-port cascade networks;

[0040] Figure 6 This is a schematic diagram of the rail measurement position below the train of the present invention;

[0041] Figure 7 This is a schematic diagram of the measurement position of a single train section and the rail parallel network below it according to the present invention;

[0042] Figure 8 This is a schematic diagram of the measurement positions of the parallel network of two train sections and the rails thereunder according to the present invention;

[0043] Figure 9 Flowchart of the measurement method of the present invention.

[0044] Figure markings: 1-four-hole flange seat N-KF type female connector, 2-first copper plate, 3-hole limited to the shell of the four-hole flange seat N-KF type female connector, 4-second copper plate, 5-hole connected to the center conductor of the four-hole flange seat N-KF type female connector, 6-first terminal, 7-second terminal, 8-third terminal, 9-fourth terminal, 10-carriage 1, 11-carriage 2, 12-connector, 13-fifth terminal, 14-sixth terminal, 15-seventh terminal, 16-eighth terminal. DETAILED DESCRIPTION

[0045] The following is a clear and complete description of the technical solutions of the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0046] This embodiment provides a train impedance frequency response measurement device, including: a two-port vector network analyzer and a connecting device.

[0047] Among them, the two-port vector network analyzer (VNA) is an instrument for measuring the frequency response of the device under test (DUT). It is used to input an excitation signal to the device under test and measure the scattering parameter measurement results, that is, the scattering parameter measurement results are obtained by calculating the vector amplitude ratio between the input signal and the transmitted signal or the reflected signal. The device under test is a train. The connecting device is used to connect the two-port vector network analyzer and the device under test. The connecting device includes: a four-hole flange socket N-KF type female connector 1 and two copper plates. According to Figure 1 and Figure 2As shown, a four-hole flange-mount N-KF female connector 1 is used to connect to a two-port vector network analyzer; two sets of connectors, each consisting of two copper plates, are shown. The first copper plate 2 has a hole 3 at its end for retaining the four-hole flange-mount N-KF female connector housing. The second copper plate 4 is located below the first copper plate 2 and has a hole 5 at its end for connecting to the center conductor of the four-hole flange-mount N-KF female connector. The other ends of the two copper plates are connected to two terminals, respectively; the two terminals are the connection points between the left and right wheels and the rails of the train. This connection device can connect one output port of a signal generator or measurement device to two terminals of the device under test while maintaining signal integrity, achieving physical separation of signal and ground.

[0048] like Figure 9 As shown, in this embodiment, a measurement method is provided based on a train impedance frequency response measurement device, including the following steps:

[0049] Step S1: The connection points between the front left and right wheels and the rails of the train are used as the two terminals of the first port, and the connection points between the rear left and right wheels and the rails of the train are used as the two terminals of the second port. The first port and the second port are used as the two parallel ports of the train and the rails.

[0050] When measuring the impedance of a single train, it is difficult to obtain the train impedance directly by measuring the train when the train is placed on the rails in the on-site measurement environment. Figure 3 As shown in (a), the connection between the front left and right wheels and the rail is regarded as the two terminals of the first port (first terminal 6 and second terminal 7), and the connection between the rear left and right wheels and the rail is regarded as the two terminals of the second port (third terminal 8 and fourth terminal 9). The train and the rail together form the first and second ports. Figure 3 The two-port parallel network shown in (b).

[0051] Step S2: Connect the four-hole flange socket N-KF female connector to the two copper plates, and connect the leads of the two-port vector network analyzer ports to the four-hole flange socket N-KF female connector.

[0052] The copper plate was fixed with copper tape for all measurements. Leads were connected to ports 1 and 2 of the vector network analyzer.

[0053] Before measuring, the two-port vector network analyzer sets multiple sampling points and uses a logarithmic form on the horizontal axis. According to the test purpose, the scattering parameters to be measured are selected on the two-port vector network analyzer interface.

[0054] Step S3: Before the train arrives, use a two-port vector network analyzer to measure the scattering parameters of the rails under the single train in any frequency range. Scattering parameters of the lower rail of a single car train Scattering parameters of the lower rail of a single car train Scattering parameters of the lower rail of a single car train Scattering parameters of the lower rail of a single car train , , , , , .

[0055] , , , , Y ,

[0056] ;

[0057] , , , n =1,2, Re represents the real part, E , , , are the characteristic impedances of the first port and the second port, respectively.

[0058] , Figure 3 , ,

[0059] ;

[0060] , ,

[0061] , , , , Similarly, the admittance matrix of the two trains can be calculated The train and the rails below together form Figure 4 The two-port parallel network shown.

[0062] When the two train cars (carriage 1 and car 2, numbered 10 and 11 respectively) and the connector 12 between them are analyzed separately, the train consists of Figure 5 (b) shows three two-port cascade networks, where the specific layout of terminals and ports is shown in Figure 5 (a), wherein the first terminal 6 and the second terminal 7 constitute the first port (P1 of car 1), the third terminal 8 and the fourth terminal 9 constitute the second port (P2 of car 1) or the third port (P3 of the connector), the fifth terminal 13 and the sixth terminal 14 constitute the fourth port (P4 of the connector) or the fifth port (P5 of car 2), and the seventh terminal 15 and the eighth terminal 16 constitute the sixth port (P6 of car 2).

[0063] Step S4: Admittance matrix and Convert them separately to obtain the transmission parameters of single-car train and two-car train T 1 and T , according to the transmission parameter relationship of multiple two-port cascade states, the transmission parameters of the train connector are obtained T 2; The transmission parameter relationship is: the transmission parameters of the two trains T Two single carriages T 1 Transmission parameters of the train connector T The product of 2.

[0064] The known train admittance matrix and By converting, the transmission parameters of single-car train and two-car train can be obtained. T 1 and T , the calculation formula for converting the admittance matrix Y into the transmission parameter T is:

[0065] ;

[0066] Among them, the admittance matrix , is the self-admittance of the first port, represents the mutual admittance between the first port and the second port, represents the mutual admittance between the second port and the first port, is the self-admittance of the second port; where the admittance matrix They are and .

[0067] According to the fact that the composite two-port transmission parameter after cascading multiple two-ports is the product of the transmission parameters of each two-port before cascading, the transmission parameter of the train connector can be calculated. T 2, Figure 5 The transmission parameter matrix of the two-port cascade network shown in (b) satisfies:

[0068] ;

[0069] in, T 1 is the transmission parameter of the first train, T 2 is the transmission parameter of the train connector, T 3 is the transmission parameter of the second train. When the two trains are the same T 3= T 1.

[0070] Therefore, the transmission parameters of the train connector can be calculated by the above formula: T 2.

[0071] Step S5: Transmit parameters T 1 and transmission parameters T 2 are converted into the impedances Z1 and Z2 of the single train section and the workshop connector respectively; Z1 and Z2 are the two-port impedance frequency responses of the single train section and the workshop connector respectively.

[0072] The transmission parameters of the single train and the workshop connector are known T 1. T 2. They can be converted into impedances. Here we need to use the conversion formula between transmission parameters and impedances. The specific expression is:

[0073] ;

[0074] in, , A, B, C and D are transmission parameters T The four matrix elements of .

[0075] Thus, the impedance frequency responses of the single train section and the workshop connector with the wheel-rail contact point as the two ports in any frequency range are obtained respectively.

[0076] The measurement steps also include:

[0077] (1) Connect 20-meter-long leads to Port 1 and Port 2 of the vector network analyzer.

[0078] (2) Set the initial frequency, end frequency and number of sampling points of the vector network analyzer as required. The horizontal axis uses a logarithmic form. According to the test purpose, select the scattering parameters S11 and S21 to be measured on the instrument interface.

[0079] (3) Use standard calibration components (Open, Short, Load, and Through) to calibrate the test path ports to eliminate the system errors of the test system.

[0080] (4) Connect the center conductor and shell of the N-type female connector to the two copper plates respectively, and connect the lead of the port of the vector network analyzer to the N-type female connector.

[0081] (5) When the train is placed on the rails, the distance between the train and the rails is limited, and the copper plate cannot be fixed with a clamp. In order to keep consistent with the measurement when the train is placed on the rails, the copper plate is fixed with copper tape in all measurements.

[0082] (6) If the car does not arrive, follow Figure 6 The layout shown measures the scattering parameters of the rails under a single train section. The distance between the front and rear wheels of the train is used as the distance between the two ports. The vector network analyzer is connected to the first and second ports respectively. The copper plates connected to the four-hole flange socket N-KF female connector shell are placed at the first terminal 6 and the third terminal 8 respectively. The copper plates connected to the four-hole flange socket N-KF female connector core wire are placed at the second terminal 7 and the fourth terminal 9 respectively. Among them, the first terminal 6 and the third terminal 8 are located on the same rail (the distance is L), and the second terminal 7 and the fourth terminal 9 are also located on the same rail. According to Figure 6 The layout shown measures the scattering parameters of the rails beneath two carriages. The distance between the two ports is the distance between the frontmost and rearmost wheels of the two carriages.

[0083] (7) When the car comes, follow Figure 7 The layout shown measures the scattering parameters of the two-port parallel network of the train and the rails below it. Connect the vector network analyzer to the first and second ports respectively, and place the copper plates connected to the four-hole flange socket N-KF female connector shell at the first terminal 6 and the third terminal 8 respectively. The copper plates connected to the four-hole flange socket N-KF female connector core wire (the first copper plate 2 and the second copper plate 4) are placed at the second terminal 7 and the fourth terminal 9 respectively. Figure 8 The layout shown measures the scattering parameters of the parallel network of two train cars (carriages 1 and 2, numbered 10 and 11, respectively) and the rails beneath them; in each figure, the rails are connected to the train via an axle-end grounding device (grounding carbon brushes), and a grounding resistor is installed on each train.

[0084] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. For those skilled in the art to which the present invention belongs, several simple deductions or replacements can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A method for measuring a train impedance frequency response measuring device, characterized in that: The measuring device comprises: A two-port vector network analyzer, used to input an excitation signal to a device under test and measure two-port scattering parameters; the device under test is a train; A connecting device for connecting a two-port vector network analyzer and a device under test, the connecting device comprising: A four-hole flange socket N-KF type female connector (1) for connecting to a two-port vector network analyzer; Two groups of connectors, each group of connectors includes two copper plates, wherein the end of the first copper plate (2) is provided with a hole (3) for limiting the position of the four-hole flange seat N-KF type female connector shell, the second copper plate (4) is arranged below the first copper plate (2), the end of the second copper plate (4) is provided with a hole (5) for connecting to the central conductor of the four-hole flange seat N-KF type female connector, and the other ends of the two copper plates are respectively connected to two terminals; the two terminals are respectively the connection points between the wheels and the rails on the left and right sides of the train; The measuring method comprises: The connections between the front left and right wheels and the rails of the train are used as the two terminals of the first port, and the connections between the rear left and right wheels and the rails of the train are used as the two terminals of the second port. The first and second ports are used to construct a parallel two-port connection between the train and the rails. Before the train arrives, a two-port vector network analyzer is used to measure the scattering parameters of the rails under a single train in any frequency range. and the scattering parameters of the rails under the two trains When the train is approaching, measure the scattering parameters of the two parallel ports of the single train and the rail below Scattering parameters of the two ports in parallel with the two trains and the rails below , and the scattering parameters 、 Converted to the admittance matrix of a single train , the scattering parameters 、 Converted to the admittance matrix of two trains ; For the admittance matrix and Convert them separately to obtain the transmission parameters of single-car train and two-car train T 1 and T , according to the transmission parameter relationship of multiple two-port cascade states, the transmission parameters of the train connector are obtained T 2; The transmission parameter relationship is: the transmission parameters of the two trains T Two single carriages T 1 Transmission parameters of the train connector T The product of 2; The parameters will be transferred T 1 and transmission parameters T 2 are converted into the impedance Z1 and Z2 of the single train and workshop connector respectively.

2. The measuring method according to claim 1, wherein The scattering parameters 、 Converted to the admittance matrix of a single train , the scattering parameters 、 Converted to the admittance matrix of two trains , specifically: The scattering parameters and scattering parameters Enter the admittance calculation formula to obtain the admittance matrix of the two rail ports under the single train section , the admittance matrix Y of the two parallel ports of a single train and the rail below it, where the admittance calculation formula is: ； Among them, the conductivity matrix , conductivity , n =1,2, Re represents the real part, E is the identity matrix, , and are the characteristic impedances of the first port and the second port, respectively; Get the admittance matrix of a single train , the specific expression is: ； in, Represents the admittance matrix of a single train, where the admittance matrix of two trains is And the admittance matrix of a single train The calculation formula is consistent.

3. The measuring method according to claim 1, wherein: For the admittance matrix and Convert them separately to obtain the transmission parameters of single-car train and two-car train T 1 and T , according to the transmission parameter relationship of multiple two-port cascade states, the transmission parameters of the train connector are obtained T 2. Specifically: The admittance matrix and Convert to transfer parameters T The conversion formula is: ； Among them, the admittance matrix , is the self-admittance of the first port, represents the mutual admittance between the first port and the second port, represents the mutual admittance between the second port and the first port, is the self-admittance of the second port; where the admittance matrix They are and ; The transmission parameters of the train connector are obtained based on the transmission parameter relationship under multiple two-port cascade states. T 2. The specific expression is: ； in, T 1 is the transmission parameter of the first train, T 2 is the transmission parameter of the connector, T 3 is the transmission parameter of the second train. When the two trains are the same T 3= T 1.

4. The measuring method according to claim 1, wherein The parameters will be transmitted T 1 and transmission parameters T 2 are converted into the impedance of a single train and a workshop connector respectively Z 1 and Z 2, the conversion formula between transmission parameters and impedance is used, and the specific expression is: ； in, , A, B, C and D are transmission parameters T The four matrix elements of .

5. The measuring method according to claim 1, wherein: When the train has not yet arrived and when the train has arrived, the distance between the front wheel and the rear wheel of the train is used as the distance between the two ports, and the copper plates connected to the leads at the first port and the second port, and the four-hole flange seat N-KF type female connector shell are placed at the first terminal and the third terminal respectively, and the copper plates connected to the four-hole flange seat N-KF type female connector core wire are placed at the second terminal and the fourth terminal respectively; wherein, the first terminal and the third terminal are located on the same rail, and the second terminal and the fourth terminal are located on the same rail.

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