Vehicle speed measuring device and method with self-checking function

Abstract

The present invention discloses a vehicle speed measuring device and method with a self-checking function, wherein the vehicle speed measuring device comprises at least two speed sensors and at least two speed measuring boards, each of which is connected to each speed sensor to form a redundant structure; the speed sensor is used to convert the speed information of the vehicle into a speed transmission signal; the speed measuring board is used to calculate the speed of the vehicle according to the speed transmission signal, and detect whether there is a fault inside the speed sensor and the speed measuring board. The present invention adopts a dual-system redundant structure to measure the vehicle speed, wherein if one speed sensor fails or a speed measuring board fails, the other speed sensor or speed measuring board with intact functions can still ensure that the train speed is correctly measured. At the same time, the present invention can accurately locate whether the fault is in the speed sensor or inside the speed measuring board, effectively improving the fault location capability of the vehicle speed measuring device.

Description

Technical Field

[0001] The invention relates to the field of traffic control, and in particular to a vehicle speed measuring device and method with a self-checking function. Background Art

[0002] With the rapid development of urban rail transit in my country, there is an urgent need for a vehicle control system that can ensure high-speed and safe operation of vehicles. Among them, the vehicle automatic protection system (ATP) is the core of the entire vehicle control system. Its main task is to prevent vehicles from speeding, collisions and other dangerous situations that may occur when the vehicle is driving. The basis for achieving all this is highly reliable and high-precision vehicle speed measurement. Based on comprehensive considerations of performance and cost, domestic vehicles mainly use wheel-shaped grating speed sensors to measure the vehicle's running speed in real time. The principle of speed measurement is to install the speed sensor on the wheel axle. When the vehicle is running, the speed sensor will generate a square wave pulse signal with a frequency of f=n×P (n is the speed, P is the number of pulses generated per revolution). The on-board speed measurement equipment will accurately calculate the vehicle's running speed by detecting the number of rotations of the wheel.

[0003] At present, the real-time measurement of vehicle speed by speed sensors has the following main technical defects: there is no effective detection measure for the square wave pulse signal generated by the speed sensor, so when the speed sensor fails or the square wave pulse signal is interfered, it cannot be discovered in time, which will eventually lead to erroneous speed measurement results; there is no effective detection measure for the working status of the on-board speed measuring equipment, and it is impossible to know whether the speed measuring equipment has failed. In the event of a failure, the speed measuring equipment is likely to send erroneous information to the system, thereby reducing system availability and even affecting driving safety; in actual use, due to the characteristics of the material, there is a certain probability that the on-board speed measuring equipment and speed sensors will fail due to aging after a long period of operation. Traditional devices perform poorly in fault detection and fault location, and cannot locate the fault point in a timely and accurate manner. Summary of the invention

[0004] The present invention proposes a vehicle speed measuring device and method with a self-checking function, which adopts a dual-system redundant speed measuring system to measure the vehicle speed. When one of the speed measuring systems fails, the other speed measuring system can still accurately measure the vehicle speed. At the same time, based on the perfect self-checking mechanism inside the speed measuring system, the fault point can be quickly located and an alarm signal can be generated.

[0005] In order to achieve the above object, the present invention proposes a speed measuring device with a self-checking function, comprising at least two speed sensors and at least two speed measuring boards, each of which is connected to each speed sensor, and each speed sensor outputs a speed transmission signal to each speed measuring board, forming a redundant structure;

[0006] The speed sensor is installed on the wheel of the vehicle, and is used to convert the speed information of the vehicle into a speed transmission signal;

[0007] The speed measuring board is used to calculate the speed of the vehicle according to the speed transmission signal and detect whether there is any fault inside the speed sensor and the speed measuring board.

[0008] Preferably, the speed measuring board comprises: a CPU, a register module, a reference signal generating module, a switching switch module, a signal checking module and a signal processing module;

[0009] The register module is connected to the CPU and is the interface between the CPU and the modules in the speed test board. It is used to store the data written by the CPU and save the processing results of the modules in the speed test board.

[0010] The reference signal generating module is connected to the register module and is used to output a reference signal according to the period, duty cycle and phase difference of the reference signal preset by the CPU;

[0011] The switching switch module is connected to the register module, the speed sensor and the reference signal generating module, and is used to switch the connection with the speed sensor or the reference signal generating module, so as to select the speed transmission signal output by the speed sensor or the reference signal output by the reference signal generating module;

[0012] The signal verification module is connected to the register module and the switching module, and is used to count the cycle time, high level time and phase difference time of the fast transmission signal or the reference signal output by the switching module, and store the count value in the register module;

[0013] The signal processing module is connected to the register module and the switch module, and is used to count the pulses of the fast transmission signal or the reference signal output by the switch module, and store the count value in the register module;

[0014] The CPU is connected to the register module. The CPU controls the operation of each module in the speed measuring board through the register module, and determines whether the input speed transmission signal or reference signal is valid according to the count value of the signal verification module, and calculates the speed of the vehicle according to the pulse count value of the speed transmission signal of the signal processing module.

[0015] Preferably, the number of channels of the reference signal output by the reference signal generating module is equal to the total number of channels of the speed transmission signals output by the at least two speed sensors.

[0016] Preferably, the switching switch module comprises two switching switches connected in series, each switching switch is controlled by an independent switching switch configuration register, the first switching switch is connected to the speed sensor and the reference signal generating module, and the second switching switch is connected to the first switching switch and the speed sensor.

[0017] The present invention also proposes a method for measuring vehicle speed using a vehicle speed measuring device, comprising the following steps:

[0018] The vehicle speed measuring device simulates the low-speed and high-speed running conditions of the vehicle, and performs low-speed and high-speed self-tests on the modules inside each speed measuring board;

[0019] Each speed measuring board verifies the validity of the speed transmission signal output by each speed sensor;

[0020] Each speed measuring board calculates the vehicle speed according to the speed transmission signal output by each speed sensor.

[0021] Preferably, the self-test of the speed measuring board includes the following steps:

[0022] The CPU sets the period, duty cycle and phase difference of the reference signal when the simulated vehicle is running at low or high speed according to the number of pulses generated by the speed sensor per revolution of the vehicle axle and the simulated vehicle running speed, and the reference signal generating module outputs the reference signal when the simulated vehicle is running at low or high speed;

[0023] The two switching switches in the switching switch module are both switched to connect to the reference signal generating module;

[0024] The signal checking module checks the input reference signal respectively, counts the cycle time, high level time and phase difference time of the reference signal, and stores the count values ​​in the register module respectively;

[0025] The CPU calculates the duty cycle and phase difference of the reference signal according to the count value of the signal inspection module, and compares it with the duty cycle and phase difference of the reference signal preset by the CPU when the vehicle is running at a low speed or a high speed. If the comparison result of the two is within the error range, the low-speed or high-speed self-test of the signal inspection module passes, otherwise the low-speed or high-speed self-test of the signal inspection module fails, and the CPU generates an alarm message;

[0026] The signal processing module counts pulses of the input reference signal respectively, and stores the count values ​​in the register module respectively;

[0027] The CPU reads the count value of the signal processing module. If the difference between the pulse count value of the reference signal read by the CPU in this cycle and the pulse count value of the reference signal read in the previous cycle meets certain conditions, the signal processing module passes the low-speed or high-speed self-test. Otherwise, the signal processing module fails the low-speed or high-speed self-test and the CPU generates an alarm message.

[0028] Preferably, the difference between the pulse count value of the reference signal read by the CPU in this cycle and the pulse count value of the reference signal read in the previous cycle must satisfy the following condition:

[0029] CPU reading cycle × simulated vehicle running speed × number of pulses generated by the speed sensor per rotation of the vehicle axle ± 1.

[0030] Preferably, the speed measuring board verifies the validity of the speed transmission signal output by the speed sensor, including the following steps:

[0031] The two switches in the switch module are both switched to connect the speed sensor;

[0032] The signal checking module checks the inputted fast transmission signal respectively, counts the cycle time, high level time and phase difference time of the fast transmission signal, and stores the count values ​​in the register module respectively;

[0033] The CPU calculates the duty cycle and phase difference of the speed transmission signal based on the count value of the signal inspection module, and compares it with the duty cycle and phase difference of the known speed sensor technical parameters. If the comparison results of the two are within the error range, the speed transmission signal input to the speed measurement board is valid, otherwise the input signal is invalid and the CPU generates an alarm message.

[0034] Preferably, the speed measuring board calculates the speed of the vehicle according to the effective speed transmission signal including the following steps:

[0035] The signal processing module counts the pulses of the input effective speed transmission signals respectively, and stores the count values ​​in the register modules respectively;

[0036] The CPU reads the count value of the signal processing module and calculates the speed of the vehicle.

[0037] Preferably, the calculation formula for the duty cycle and phase difference between the reference signal and the fast transmission signal is:

[0038]

[0039] Preferably, the calculation formula of the vehicle speed is:

[0040]

[0041] In the formula, c(i) and c(i-1) are the pulse count values ​​of the speed transmission signal read by the CPU in the i-th reading cycle and the previous reading cycle respectively, D is the wheel diameter value of the vehicle axle, N is the number of pulses generated by the speed sensor per rotation of the vehicle axle, and T is the main cycle of the CPU accessing the register module to read the pulse count value of the speed transmission signal.

[0042] The present invention has the following advantages:

[0043] 1. The present invention adopts a dual-system redundant structure to measure the vehicle speed. The failure of one speed sensor or one speed measuring board will not cause the train speed measuring function to fail completely. The other speed sensor or speed measuring board with intact function can still ensure that the train speed is measured correctly.

[0044] 2. The signal verification module of the speed measuring board of the present invention will verify the period and phase difference of the speed transmission signal generated by the input speed sensor, so as to determine whether the input speed transmission signal is valid. If a fault is detected, an alarm will be issued in time to prevent the generation of erroneous speed measurement results.

[0045] 3. The present invention can not only verify the speed transmission signal generated by the input speed sensor, but also perform self-verification on the internal module of the speed transmission board. Therefore, once a fault occurs, it can be accurately located whether the fault is in the speed sensor or inside the speed measurement board, effectively improving the fault location capability.

[0046] 4. The switching switch module of the speed measuring board of the present invention adopts a design of two switching switches connected in series, which ensures that even if one of the switching switches fails, the reference signal used for testing will not be mistaken for the actual speed sensor pulse signal, thereby preventing the generation of erroneous speed measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A structural diagram of a vehicle speed measuring device with a self-checking function provided by an embodiment of the present invention;

[0048] Figure 2 A structural diagram of a speed measuring board provided by an embodiment of the present invention;

[0049] Figure 3 A classification diagram of register modules provided by an embodiment of the present invention;

[0050] Figure 4 A structural diagram of a switch module provided in an embodiment of the present invention;

[0051] Figure 5 The present invention provides a flow chart of a speed measuring method of a vehicle speed measuring device with a self-checking function according to an embodiment of the present invention. DETAILED DESCRIPTION

[0052] The following is a further detailed description of a vehicle speed measuring device and method with a self-checking function proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the accompanying drawings are in a very simplified form and use non-precise ratios, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0053] like Figure 1 As shown, the present invention proposes a vehicle speed measuring device with a self-checking function, comprising two speed sensors 1 and two speed measuring boards 2, each speed measuring board 2 is respectively connected to each speed sensor 1, and each speed sensor 1 outputs a speed transmission signal to each speed measuring board 2, forming a redundant structure;

[0054] The speed sensor 1 is installed on the front or rear wheel of the vehicle. The speed sensor 1 is used to convert the speed information of the vehicle into a two-channel speed transmission signal. The speed transmission signal is a square wave pulse signal.

[0055] The speed measuring board 2 is used to collect the speed transmission signal of the speed sensor 1 to calculate the speed of the vehicle, and to detect whether there is any fault inside the speed sensor 1 and the speed measuring board 2.

[0056] like Figure 2 As shown, the speed measuring board 2 comprises: a CPU 201, a register module 202, a reference signal generating module 203, a switching module 204, a signal checking module 205 and a signal processing module 206;

[0057] The register module 202 is connected to the CPU 201 and is the interface between the CPU 201 and the modules in the speed measurement board. Figure 3 The figure shows the types and functions of registers included in the register module. CPU201 controls the operation of each module of the speed measuring board by writing data into the corresponding register. At the same time, the processing results of each module of the speed measuring board are stored in the corresponding register for CPU201 to read.

[0058] A reference signal generating module 203, which is connected to the register module 202, is used to output a four-channel reference signal according to the period, duty cycle and phase difference of the reference signal preset by the CPU 201;

[0059] The switching switch module 204 is connected to the register module 202, the speed sensor 1 and the reference signal generating module 203, and is used to switch the connection with the speed sensor 1 or the reference signal generating module 203, so as to select the speed transmission signal output by the speed sensor or the reference signal output by the reference signal generating module; Figure 4As shown, the switch module 204 includes two switches connected in series, each switch is controlled by an independent switch configuration register, the first switch is connected to the speed sensor 1 and the reference signal generating module 203 respectively, and the second switch is connected to the first switch and the speed sensor 1 respectively; the series design of the two switches ensures that even if one of the switches fails, the reference signal for the test will not be mistaken as the actual speed measurement signal, thereby preventing the generation of erroneous speed measurement results;

[0060] The signal verification module 205 is connected to the register module 202 and the switching switch module 204, respectively, and is used to count the cycle time, high level time and phase difference time of the four-way reference signal or the four-way fast transmission signal output by the switching switch, and store the count value in the corresponding register for the CPU 201 to read;

[0061] The signal processing module 206 is connected to the register module 202 and the switch module 204, respectively, and is used to count the pulses of the four-way reference signal or the four-way fast transmission signal output by the switch, and store the count value in the corresponding register for the CPU 201 to read;

[0062] The CPU 201 controls the operation of each module in the speed measuring board through the register module 202 , determines whether the input signal is valid according to the count value of the signal checking module 205 , and calculates the speed of the vehicle according to the count value of the signal processing module 206 .

[0063] The speed sensor in the embodiment of the present invention takes the photoelectric speed sensor DF16 / 1.200badk assembled and produced by Shanghai DEUTA as an example. The dual-channel square wave pulse output by the speed sensor meets the following technical parameters:

[0064] Pulse duty cycle: 50% ± 10%

[0065] Pulse phase difference: 90°±45°

[0066] The parameters of the vehicle in the embodiment are:

[0067] The number of pulses generated by the speed sensor for each rotation of the vehicle axle is N = 100;

[0068] Vehicle wheel diameter D = 0.8m;

[0069] The main cycle of CPU accessing the speed test board register module is T = 50ms;

[0070] The running speed of the vehicle is 10m / s.

[0071] like Figure 5As shown, the present invention provides a speed measuring method of a vehicle speed measuring device with a self-checking function, comprising the following steps:

[0072] S1. The vehicle speed measuring device simulates the low-speed and high-speed running conditions of the vehicle, and performs low-speed self-test and high-speed self-test on the modules inside each speed measuring board;

[0073] After the vehicle speed measuring device is started, it will be initialized, including: CPU initialization, initialization of each module of the speed measuring board, initialization of the local bus, initialization of interrupts, etc. Each speed measuring board simulates the low-speed operation of the vehicle (axle 1r / s):

[0074] Since the number of pulses N generated by the speed sensor 1 for each rotation of the vehicle axle is 100, the reference signal should be 100 pulses per second, that is, the period of the reference signal should be set to 10ms, so CPU201 writes 10000 to the reference signal period configuration register; at the same time, in order to set the duty cycle of the reference signal to 50%, the CPU writes 5000 to the reference signal high level configuration register; in order to set the phase difference of the reference signal to 45°, CPU201 writes 1250 to the reference signal phase difference configuration register; the reference signal generation module 203 generates a four-channel low-speed reference signal according to the preset period, duty cycle and phase difference of the reference signal under the condition of low-speed operation of the vehicle;

[0075] The CPU 201 writes data into the first switch configuration register and the second switch configuration register, and switches both switches to connect to the reference signal generating module 203;

[0076] The signal verification module 205 counts the cycle time, high level time and phase difference time of the input four-channel low-speed reference signal respectively, and stores the count values ​​in the corresponding reference signal cycle count register, reference signal high level count register and reference signal phase difference count register respectively; CPU201 reads the count values ​​of the reference signal cycle count register, the reference signal high level count register and the reference signal phase difference count register at a period of T=50ms; since the reference signals are all generated inside the speed measuring board 2, the signal processing module 206 and the signal verification module 205 are also inside the speed measuring board 2, so CPU201 reads the count values ​​of the reference signal cycle count register, the reference signal high level count register and the reference signal phase difference count register according to the signal verification module 20 The duty cycle and phase difference of the low-speed reference signal calculated by the count value of 5 will only have a clock error with the duty cycle and phase difference of the reference signal preset by CPU201 during the simulated vehicle operation, so the error range is within ±1; therefore, when the value of the reference signal cycle count register read by CPU201 satisfies 10000±1, the value of the reference signal high level count register should satisfy 5000±1, and the value of the reference signal phase difference count register satisfies 1250±1, it means that the signal inspection module 205 has passed the low-speed self-test and enters the next step, otherwise it means that the signal inspection module 205 has failed the low-speed self-test and CPU201 generates an alarm message;

[0077] The signal processing module 206 counts the pulses of the input low-speed four-channel reference signals respectively, and stores the count values ​​in the corresponding reference signal pulse count registers; CPU201 reads the count value of the reference signal pulse count register with a period of T=50ms; the difference between the pulse count value of the reference signal read by CPU201 in this period and the pulse count value of the reference signal read in the previous period must meet the following conditions: CPU reading period×simulated vehicle running speed×the number of pulses generated by the speed sensor per rotation of the vehicle axle±1; therefore, when the difference between the value c(i) of the reference signal pulse count register read by CPU201 in this period and the value c(i-1) of the reference signal pulse count register read in the previous period satisfies 5±1, it indicates that the signal processing module 206 has passed the low-speed self-test and enters the next step, otherwise, the signal processing module 206 has failed the low-speed self-test and the CPU generates an alarm message.

[0078] Each speed measuring board simulates the high-speed operation of the vehicle (axle 100r / s):

[0079] Since the number of pulses N generated by the speed sensor 1 for each rotation of the vehicle axle is 100, the reference signal should be 10,000 pulses per second, that is, the period of the reference signal should be set to 100us, so CPU201 writes 100 to the reference signal period configuration register; at the same time, the duty cycle of the reference signal is set to 40%, and the CPU writes 40 to the reference signal high level configuration register; the phase difference of the reference signal is set to 90°, and CPU201 writes 25 to the reference signal phase difference configuration register; the reference signal generation module 203 generates a four-channel high-speed reference signal according to the preset period, duty cycle and phase difference of the reference signal under the condition of high-speed operation of the vehicle;

[0080] The CPU 201 writes data into the first switch configuration register and the second switch configuration register, and switches both switches to connect to the reference signal generating module 203;

[0081] The signal verification module 205 counts the cycle time, high level time and phase difference time of the input four-channel high-speed reference signal respectively, and stores the count values ​​in the corresponding reference signal cycle count register, reference signal high level count register and reference signal phase difference count register respectively; CPU201 reads the count values ​​of the reference signal cycle count register, the reference signal high level count register and the reference signal phase difference count register with a cycle of T=50ms; when the value of the reference signal cycle count register read by CPU201 satisfies 100±1, the value of the reference signal high level count register should satisfy 40±1, and the value of the reference signal phase difference count register satisfies 25±1, it indicates that the signal verification module 205 high-speed self-test has passed, otherwise it indicates that the signal verification module 205 high-speed self-test has failed, and CPU201 generates an alarm message;

[0082] The signal processing module 206 counts the pulses of the input four-channel high-speed reference signals respectively, and stores the count values ​​in the corresponding reference signal pulse count registers respectively; the CPU 201 reads the count value of the reference signal pulse count register at a period of T = 50ms. When the difference between the value c(i) of the reference signal pulse count register read by the CPU 201 in this period and the value c(i-1) of the reference signal pulse count register read in the previous period satisfies 500±1, it indicates that the high-speed self-test of the signal processing module 206 has passed, otherwise, the high-speed self-test of the signal processing module 206 has failed, and the CPU 201 generates an alarm message.

[0083] S2. Each speed measuring board verifies the validity of the speed transmission signal output by each speed sensor;

[0084] CPU201 writes data to the first switching switch configuration register and the second switching switch configuration register, and switches both switches to connect to the speed sensor 1; the signal verification module 205 of the two speed measuring boards 2 counts the cycle time, high level time and phase difference time of the input four-channel fast transmission signal respectively, and stores the count values ​​in the corresponding fast transmission signal cycle count register, fast transmission signal high level count register, and fast transmission signal phase difference count register respectively. CPU201 reads the count values ​​of the cycle time, high level time and phase difference time of the four-channel fast transmission signal respectively, and calculates the duty cycle and phase difference of each channel fast transmission signal. The calculation formula for the duty cycle and phase difference of the fast transmission signal is:

[0085]

[0086] The duty cycle and phase difference of the four-way high-speed transmission signal both meet the following requirements: the duty cycle value is within the range of 50%±10%, and the phase difference value is within the range of 90°±45°. Then the four-way high-speed transmission signals input to the signal verification module 205 are all valid signals. Otherwise, CPU201 generates an alarm signal.

[0087] S3. Each speed measuring board calculates the vehicle speed according to the speed transmission signal output by each speed sensor.

[0088] The signal processing module 206 counts the pulses of the input four-channel speed transmission signals respectively, and stores the count values ​​in the corresponding speed transmission signal pulse counting registers respectively. The CPU reads the calculated value of any speed transmission signal pulse calculation register to calculate the vehicle speed. The calculation formula of the vehicle speed is:

[0089]

[0090] In the formula, c(i) and c(i-1) are the pulse count values ​​of the speed transmission signal read by the CPU in the i-th reading cycle and the previous reading cycle respectively, D is the wheel diameter value of the vehicle axle, N is the number of pulses generated by the speed sensor per rotation of the vehicle axle, and T is the main cycle of the CPU accessing the register module to read the pulse count value of the speed transmission signal.

[0091] The assumptions of this embodiment are: N = 100, T = 50ms, D = 0.8m, and the train is running at a speed of 10m / s. The difference between the value c(i) of the pulse counting register read by the CPU in this cycle and the value c(i-1) of the pulse counting register read in the previous cycle is 20. The vehicle speed calculated using the vehicle speed calculation formula is: 10.048m / s. The error between the calculated result and the assumed value meets the requirements.

[0092] The present invention adopts a dual-system redundant structure to measure the vehicle speed. If one speed sensor or one speed measuring board fails, the train speed measuring function will not be completely invalid. The other speed sensor or speed measuring board with intact function can still ensure that the train speed is correctly measured. At the same time, the switching switch module of the speed measuring board adopts a design of two switching switches in series, which ensures that even if one of the switching switches fails, the reference signal used for testing will not be mistaken as the actual speed sensor pulse signal, thereby preventing the generation of erroneous speed measurement results. The signal verification module of the speed measuring board will verify the period and phase difference of the speed transmission signal generated by the input speed sensor, so as to determine whether the input speed transmission signal is valid. If a fault is detected, an alarm will be issued in time to prevent the generation of erroneous speed measurement results. The present invention can verify the speed transmission signal generated by the input speed sensor, and can also perform self-verification on the internal module of the speed transmission board. Therefore, once a fault occurs, it can accurately locate whether the fault is in the speed sensor or inside the speed measuring board, effectively improving the fault location capability.

[0093] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A vehicle speed measuring device with a self-checking function, characterized in that: It includes at least two speed sensors and at least two speed measuring boards, each speed measuring board is respectively connected to each speed sensor, and each speed sensor outputs a speed transmission signal to each speed measuring board respectively, forming a redundant structure; The speed sensor is installed on the wheel of the vehicle, and is used to convert the speed information of the vehicle into a speed transmission signal; the speed transmission signal is a square wave pulse signal; The speed measuring board is used to calculate the speed of the vehicle according to the speed transmission signal and detect whether there is any fault inside the speed sensor and the speed measuring board; The speed measuring board comprises: a CPU, a register module, a reference signal generating module, a switching module, a signal checking module and a signal processing module; The register module is connected to the CPU and is the interface between the CPU and the modules in the speed test board. It is used to store the data written by the CPU and save the processing results of the modules in the speed test board. The reference signal generating module is connected to the register module and is used to output a reference signal according to the period, duty cycle and phase difference of the reference signal preset by the CPU; The switching switch module is connected to the register module, the speed sensor and the reference signal generating module, and is used to switch the connection with the speed sensor or the reference signal generating module, so as to select the speed transmission signal output by the speed sensor or the reference signal output by the reference signal generating module; The signal verification module is connected to the register module and the switching module, and is used to count the cycle time, high level time and phase difference time of the fast transmission signal or the reference signal output by the switching module, and store the count value in the register module; The signal processing module is connected to the register module and the switch module, and is used to count the pulses of the fast transmission signal or the reference signal output by the switch module, and store the count value in the register module; The CPU is connected to the register module. The CPU controls the operation of each module in the speed measuring board through the register module, and determines whether the input speed transmission signal or reference signal is valid according to the count value of the signal verification module, and calculates the speed of the vehicle according to the pulse count value of the speed transmission signal of the signal processing module.

2. A vehicle speed measuring device with a self-checking function as claimed in claim 1, characterized in that: The switching switch module includes a first switching switch and a second switching switch connected in series, wherein the first switching switch and the second switching switch are respectively controlled by an independent switching switch configuration register, the first switching switch is connected to a speed sensor and a reference signal generating module, and the second switching switch is connected to the first switching switch and the speed sensor.

3. A vehicle speed measuring device with a self-checking function as claimed in claim 1, characterized in that: The number of channels of the reference signal output by the reference signal generating module is equal to the total number of channels of the speed transmission signals output by at least two speed sensors.

4. A method for measuring vehicle speed using a vehicle speed measuring device with a self-checking function as claimed in any one of claims 1 to 3, comprising the following steps: The vehicle speed measuring device simulates the low-speed and high-speed running conditions of the vehicle, and performs low-speed and high-speed self-tests on the modules inside each speed measuring board; Each speed measuring board verifies the validity of the speed transmission signal output by each speed sensor; Each speed measuring board calculates the vehicle speed according to the speed transmission signal output by each speed sensor.

5. A vehicle speed measurement method with self-checking function as claimed in claim 4, characterized in that: The self-test of the speed test board includes the following steps: The CPU sets the period, duty cycle and phase difference of the reference signal when the simulated vehicle is running at low or high speed according to the number of pulses generated by the speed sensor per revolution of the vehicle axle and the simulated vehicle running speed, and the reference signal generating module outputs the reference signal when the simulated vehicle is running at low or high speed; The two switching switches in the switching switch module are both switched to connect to the reference signal generating module; The signal verification module verifies the input reference signal respectively, counts the cycle time, high level time and phase difference time of the reference signal, and stores the count values ​​in the register module respectively; The CPU calculates the duty cycle and phase difference of the reference signal according to the count value of the signal verification module, and compares it with the duty cycle and phase difference of the reference signal when the vehicle is running at low speed or high speed, which is preset by the CPU. If the comparison result of the two is within the error range, the low-speed or high-speed self-test of the signal verification module passes, otherwise the low-speed or high-speed self-test of the signal verification module fails, and the CPU generates an alarm message; The signal processing module counts pulses of the input reference signal respectively, and stores the count values ​​in the register module respectively; The CPU reads the count value of the signal processing module. If the difference between the pulse count value of the reference signal read by the CPU in this cycle and the pulse count value of the reference signal read in the previous cycle meets certain conditions, the signal processing module passes the low-speed or high-speed self-test. Otherwise, the signal processing module fails the low-speed or high-speed self-test and the CPU generates an alarm message.

6. A vehicle speed measurement method with self-checking function as claimed in claim 5, characterized in that: The condition that the difference between the pulse count value of the reference signal read by the CPU in this cycle and the pulse count value of the reference signal read in the previous cycle must meet is: CPU reading cycle × simulated vehicle running speed × number of pulses generated by the speed sensor per rotation of the vehicle axle ± 1.

7. A vehicle speed measurement method with self-checking function as claimed in claim 6, characterized in that: The speed measurement board verifies the validity of the speed transmission signal output by the speed sensor, including the following steps: The two switches in the switch module are both switched to connect the speed sensor; The signal verification module verifies the input fast transmission signal respectively, counts the cycle time, high level time and phase difference time of the fast transmission signal, and stores the count values ​​in the register module respectively; The CPU calculates the duty cycle and phase difference of the speed transmission signal based on the count value of the signal verification module, and compares it with the duty cycle and phase difference of the known speed sensor technical parameters. If the comparison results of the two are within the error range, the speed transmission signal input to the speed measurement board is valid, otherwise the input signal is invalid and the CPU generates an alarm message.

8. A vehicle speed measurement method with self-checking function as claimed in claim 4, characterized in that: The speed measuring board calculates the speed of the vehicle based on the valid speed transmission signal, including the following steps: The signal processing module counts the pulses of the input effective speed transmission signals respectively, and stores the count values ​​in the register modules respectively; The CPU reads the count value of the signal processing module and calculates the speed of the vehicle.

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