Laser length measuring instrument based on dynamic cold detection distance

Abstract

The present invention relates to a laser length measurement system based on dynamic cold-detection distance. The system comprises a laser velocity measurement unit, a cold-detection unit that triggers the laser velocity measurement unit, and a data processing unit that communicates with the laser velocity measurement unit. The system also includes a cold-detection unit tracking module. The laser length measurement system based on dynamic cold-detection distance can dynamically configure the spacing between two cold-detection units, achieving high measurement accuracy for both long and short materials, typically achieving a ±2mm error range.

Description

Technical Field

[0001] The present invention belongs to the field of measuring equipment characterized by adopting optical methods, and in particular relates to a laser length measuring instrument which is specially used for measuring the length of an object when the object is moving. Background Art

[0002] Online length measurement systems for measuring the length of moving cold steel plates have been reported. For example, Chinese patent CN213021446 U discloses a tool for measuring the width of hot billets during continuous casting. This patent utilizes an electrical dimension measurement structure. Related reports also describe a method combining multiple photoelectric switches and encoders for measuring cold billets, and a method combining two displacement sensors and pressure detection switches for measuring hot billets. However, regardless of the method, existing length measurement systems cannot guarantee ideal measurement accuracy for both long and short steel plates, with measurement errors often exceeding 0.5%. Summary of the Invention

[0003] To address the above-mentioned issues, the present invention relates, on one hand, to a laser length measurement system based on dynamic cold detection distance, comprising a laser speed measurement unit, a cold detection unit that triggers the laser speed measurement unit, and a data processing unit that communicates with the laser speed measurement unit. The system may comprise three or more cold detection units. The system may further comprise a cold detection unit tracking module, which is configured to:

[0004] Obtain the pre-measurement length of the material being measured;

[0005] Get the distance between any two cold inspection units;

[0006] Calculate the difference between the pre-measurement length of the material being measured and the distance between any two cold inspection units;

[0007] The two cold detection units with the smallest difference are used to trigger the laser speed measurement unit. The two cold detection units with the smallest difference include a front cold detection unit located in front of the laser speed measurement unit and a rear cold detection unit located behind the laser speed measurement unit according to the moving direction of the moving material to be measured.

[0008] A second aspect of the present invention relates to a laser length measurement method based on dynamic cold detection distance, the laser length measurement method comprising the following steps:

[0009] The cold inspection unit tracking step includes:

[0010] a. Obtain the pre-measurement length of the material being measured;

[0011] b. Get the distance between any two cold inspection units, where the number of cold inspection units is 3 or more;

[0012] c. Calculate the difference between the length of the material before measurement and the distance between any two cold inspection units;

[0013] d. The two cold detection units with the smallest difference are used to trigger the laser speed measurement unit. The two cold detection units with the smallest difference are arranged in the direction of travel of the moving material to be measured, including a front cold detection unit located in front of the laser speed measurement unit and a rear cold detection unit located behind the laser speed measurement unit;

[0014] a laser speed measuring unit speed measuring step, wherein the laser speed measuring unit obtains the speed of the material to be measured according to the trigger instructions of the two cold detection units with the smallest difference;

[0015] The data processing unit calculates the length step, and the data processing unit calculates the length step includes the data processing unit calculating the shortest required measuring length of the measured material according to the speed of the measured material.

[0016] The beneficial effect of the present invention is that the laser length measurement system based on dynamic cold detection distance of the present invention can dynamically configure the spacing of the dual cold detections, while achieving good measurement accuracy for both long and short materials, and the measurement accuracy can usually reach within the error range of ±2mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 .Known laser length measurement systems;

[0018] Figure 2 .Topology diagram of the laser length measurement system with dynamic cold detection distance;

[0019] Figure 3 .Communication schematic diagram of the laser length measurement system that can trigger logic errors;

[0020] Figure 4 .Display panel of the laser length measurement system with dynamic cold detection distance;

[0021] Figure 5 .Flowchart of the laser length measurement method for dynamic cold detection distance;

[0022] Figure 6 . Flowchart of cold inspection unit tracking steps;

[0023] Figure 7 .Schematic diagram of the data processing unit. DETAILED DESCRIPTION

[0024] The term "material" in the present invention includes but is not limited to steel plates, and the two can sometimes be used interchangeably.

[0025] Known laser length measurement systems include Figure 1As shown, this system is based on the externally triggered length measurement principle and consists of an LSV laser velocimeter and two cold barriers (photoelectric switches, light barriers) LB1 and LB2. The LSV laser velocimeter operates in externally triggered mode. When the material (object) passes through the length measurement device, measurement begins when both cold barriers LB1 and LB2 detect the material (object). Measurement ends when either cold barrier loses its signal. Material length is calculated as follows: Material length = measured length (dual cold barrier effective period) + distance between the two cold barriers (Division X). As can be seen, the distance between the two cold barriers in conventional laser length measurement systems is fixed and cannot be changed. This results in lower measurement accuracy for longer materials than for shorter ones. Improving the measurement accuracy of longer materials may also make it impossible to measure shorter materials. Therefore, conventional laser length measurement systems have at least the following issues: 1. The length measurement device itself has an error of 0.05%, which increases with the measured length. 2. Measurement is impossible when the total length of the material is less than the distance between the two cold barriers. 3. When the total length of the material is much longer than the "double cold inspection distance", the error will increase.

[0026] Furthermore, the spacing between the dual cold detectors in existing technology is fixed and cannot be changed, but the materials to be measured vary in length. To improve measurement accuracy, it is necessary to select an appropriate cold detector installation distance that ensures that all materials can be measured while keeping the measurement distance as short as possible. Therefore, no matter how the dual cold detectors are installed, it is impossible to guarantee high-precision measurement of materials of all lengths.

[0027] In response to the technical problems in the prior art, an embodiment of the present invention uses multiple cold detectors to dynamically configure the spacing of double cold detectors to achieve the purpose of reducing the measurement distance and improving the measurement accuracy. Therefore, both long and short materials can achieve good measurement accuracy at the same time.

[0028] The following describes the technical solution of the system embodiment of the first aspect of the present invention.

[0029] In some embodiments, a laser length measurement system based on dynamic cold detection distance includes a laser speed measurement unit, a cold detection unit that triggers the laser speed measurement unit, and a data processing unit that communicates with the laser speed measurement unit. The cold detection units may be three or more. The system also includes a cold detection unit tracking module, which is configured to:

[0030] Obtaining the pre-measurement length of the moving material being measured;

[0031] Get the distance between any two cold inspection units;

[0032] Calculate the difference between the pre-measurement length of the moving material being measured and the distance between any two cold inspection units;

[0033] The two cold detection units with the smallest difference are used to trigger the laser speed measurement unit. The two cold detection units with the smallest difference include a front cold detection unit located in front of the laser speed measurement unit and a rear cold detection unit located behind the laser speed measurement unit according to the moving direction of the moving material to be measured.

[0034] It can be seen from these embodiments that one advantage of the embodiments of the present invention is that when the material to be tested (such as a steel plate) passes through these cold inspection units, the cold inspection unit tracking module (also known as a hardware circuit board) will consider which two cold inspection units to use as the "initial length accumulation value".

[0035] In a further laser length measurement system, the two cold detection units with the smallest difference are used to trigger the laser speed measurement unit, including the following steps:

[0036] The distance between the two cold inspection units with the smallest difference is taken as the initial cumulative value;

[0037] When the front cold inspection unit senses the leading end of the moving material to be tested, it triggers the laser speed measurement unit to start measuring;

[0038] When the rear cooling inspection unit senses the tail end of the moving material to be tested, the laser speed measurement unit is triggered to end the measurement.

[0039] It can be seen from these embodiments that another advantage of the embodiments of the present invention is to inform the laser speed measurement unit LSV that it only needs to measure the distance from cold inspection 2 to the tail end of the steel plate plus the initial cumulative value to obtain the full length of the steel plate. The present invention does not specifically limit the number of hardware circuit boards. It is preferred to connect 6 cold inspection units. When the steel plate passes through these cold inspection units, the hardware circuit board will consider which 2 cold inspections to use as the "initial length cumulative value." For example: using cold inspections 1 and 2, the initial cumulative value is the distance between 1 and 2. Subsequently, it is necessary to inform LSV that it only needs to measure the distance from cold inspection 2 to the tail end of the steel plate to obtain the full length of the steel plate. For another example: using cold inspections 1 and 3, the initial cumulative value is the distance between 1 and 3. Subsequently, it is necessary to inform LSV that it only needs to measure the distance from cold inspection 3 to the tail end of the steel plate to obtain the full length of the steel plate.

[0040] In a further laser length measurement system, the cold inspection units are arranged in sequence according to the travel direction of the moving material to be measured, including the first cold inspection unit located in front of the laser speed measurement unit and several second cold inspection units located behind the laser speed measurement unit.

[0041] Still taking the aforementioned 6-way cold inspection unit as an example, you can also use: cold inspection 1 and 4; cold inspection 1 and 5; cold inspection 1 and 6; among them, cold inspection 1 is the first cold inspection unit, cold inspection 4, cold inspection 5, and cold inspection 6 are the second cold inspection units.

[0042] In a further laser length measurement system, the signal between the cold detection unit tracking module and the laser speed measurement unit is determined based on a number of the cold detection units.

[0043] For example, there's only one signal, Trig2, connecting the hardware circuit board to the LSV. Whether Trig2 is 0 or 1 is determined by the status of the six input cold-check signals. Specifically, Trig2 is the output signal to the LSV and also serves as the "measuring in progress" signal. Photoelectric switches 1 through 6 are input signals to the hardware circuit board. Essentially, Trig2's output is determined by the six inputs. For example, using cold-checks 1 and 2 is suitable for measuring the shortest steel plates; using 1 and 3 is suitable for slightly longer steel plates; using 1 and 4 is suitable for longer steel plates; using 1 and 5 is suitable for even longer steel plates; and using 1 and 6 is suitable for the longest steel plates.

[0044] The present invention does not restrict how the distance between any two cold-test units is acquired; it can be pre-programmed into the system or captured using a data acquisition device. Because the system knows which cold-test unit triggers the laser velocity measurement unit, the laser velocity measurement unit only needs to measure a very short distance to determine the total length of the steel plate. Furthermore, due to the short measurement distance, the measurement accuracy typically remains within a ±2mm error range.

[0045] The method in which the data processing unit of the present invention calculates the distance based on the information of the laser speed measuring unit is a known technology. For example, the speed value is integrated and calculated based on the effective signal to obtain the moving distance value.

[0046] The laser length measurement system based on dynamic cold detection distance of the present invention improves the measurement accuracy by shortening the distance to be measured, and the spacing between different cold detection sections is known (the error does not exceed 1mm), so a very good accuracy can be achieved in the end.

[0047] In a further laser length measurement system, the cold inspection unit tracking module is further configured to:

[0048] receiving a direction signal and a motion signal obtained by a data processing unit from the laser speed measuring unit;

[0049] Determine whether there is a cold check trigger logic error;

[0050] If it exists, assist in decision making;

[0051] The difference between the pre-measurement length of the material being measured and the distance between any two cold inspection units is calculated based on the auxiliary decision.

[0052] The present invention does not specifically limit the method for triggering logic errors. To avoid cold inspection triggering logic errors caused by factors such as steel plate backflow and manual roller operation, in a preferred embodiment, the system's display terminal may also be equipped with a side head fault prompt. The data processing unit of the present invention may be implemented in any known computer processing device. The present invention does not specifically limit decision support. Any method for enhancing the accuracy of logical judgments is within the scope of the present invention, such as transmitting the length gauge's "direction and motion signals" back to the circuit board to assist in decision-making. These technical solutions further enhance the stability of system measurements. Furthermore, decision support is primarily intended to address abnormal errors in the field, such as steel plate backflow or interference signals during cold inspection that cause unexplained jumps between 0 and 1. These abnormalities can affect circuit board decisions. However, the addition of direction and motion signals can effectively avoid some common errors.

[0053] In some other embodiments of the laser length measurement system, the cold detection unit is a photoelectric switch. Preferably, the photoelectric switches are arranged linearly and evenly.

[0054] In some other embodiments of the laser length measurement system, the data processing unit includes a material length calculation unit, which is used to add the dynamic cold inspection spacing and the shortest length to be measured to obtain the total length of the measured material, wherein the spacing between the two cold inspection units with the smallest difference is the dynamic cold inspection spacing, and the length measured by the two cold inspection units with the smallest difference triggering the laser speed measurement unit is the shortest length to be measured.

[0055] The following combination Figure 2 Some embodiments of the present invention are described as follows. Figure 2 As shown, the laser length measurement system 10 based on dynamic cold detection distance includes a laser speed measurement unit 11, a photoelectric switch 12 for triggering the laser speed measurement unit 11, and a data processing unit ( Figure 2 Not shown, refer to Figure 7 ), there are five photoelectric switches 12, which are linearly arranged in the running direction of the steel plate 1 at a spacing N, and the photoelectric switches 12 sense the steel plate 1 through light 16; the system also includes a photoelectric switch tracking module 13, which communicates with the five photoelectric switches 12 through a signal line 14 and communicates with the photoelectric switch tracking module 13 through a signal line 15. Figure 2 It can be seen that the “actual length to be measured” is much smaller than the length of the steel plate 1 (about 3.6N).

[0056] Continue to refer Figure 2As shown, to ensure that the laser length measurement system 10 based on dynamic cold-check distance can adapt to steel plates 1 of varying lengths and improve measurement accuracy, a corresponding set of photoelectric switches 12 is used to measure steel plates 1 of varying lengths, and the spacing between the two cold-checks is dynamically configured to reduce the measurement distance and improve measurement accuracy. Furthermore, a photoelectric switch tracking module 13 (e.g., a circuit board) is used to control which two photoelectric switches 12 are used to trigger the length measuring instrument. The algorithm for calculating the actual total length of the steel plate is:

[0057] The actual total length of the steel plate = the spacing of the dynamic cold test + the shortest length to be measured.

[0058] The following combination Figure 3 Some embodiments of the present invention are described as follows. Figure 3 As shown,

[0059] The photoelectric switch tracking module 13 receives the LSV direction signal and motion signal obtained by the data processing unit 17 from the laser speed measurement unit 11 (LSV), and sends a measurement trigger signal to the LSV.

[0060] The LSV receives the measurement trigger signal from the photoelectric switch tracking module 13 and the data request instruction from the data processing unit 17 , and feeds back the LSV direction signal and motion signal to the data processing unit 17 in 16 bytes.

[0061] The data processing unit 17 sends a data request instruction to the LSV, receives the cold detection status and dynamic cold detection distance sent by the photoelectric switch tracking module 13, and the LSV direction signal and motion signal fed back in 16 bytes from the LSV, and sends the LSV direction signal and motion signal to the LSV receiving photoelectric switch tracking module 13.

[0062] The following combination Figure 4 Some embodiments of the present invention are described as follows. Figure 4 As shown,

[0063] The photoelectric switch tracking module 13 (circuit board) and LSV are located on the same local area network (Board: 192.168.108.9, LSV: 192.168.108.150). Once both are successfully connected, measurement can begin. During Trig 2, photoelectric switches 0, 1, and 2 trigger LSV. The system prompts "Measuring" and the current status is "Valid." The relevant parameters are as follows: Counter: 605; Status: 0x14; Speed: 0.000; Length: 0.014; Signal-to-Noise Ratio: 55.5; Data Rate: 2860; Quality: 89; Sensor: 0x00; Temperature: 32; Trig 2 614. LSV recording can also be selected via the display panel.

[0064] The meanings of the relevant parameters are as follows:

[0065] Counter: records the number of data outputs; Status: information such as steel / no steel / probe failure; Speed: measured steel plate speed; Length: accumulated length after triggering;

[0066] Data rate: the amount of data obtained within the LSV;

[0067] Quality: numerical expression of measurement quality;

[0068] Sensor: sensor abnormality flag;

[0069] Temperature: probe temperature

[0070] "111000, 1" represents the instantaneous value of the input and output IOs. In this embodiment, a maximum of six cold inspection units can be connected, and the current steel plate blocks three, so the input is: 111000. The final ", 1" is the output signal to the LSV, instructing it to enable length measurement.

[0071] The following describes the technical solution of the method embodiment of the second aspect of the present invention.

[0072] In some embodiments, a laser length measurement method based on dynamic cold detection distance is involved, such as Figure 5 、 Figure 6 As shown, the laser length measurement method includes the following steps:

[0073] S1: cold detection unit tracking step, the cold detection unit tracking step comprising:

[0074] a. Obtain the pre-measurement length of the material being measured;

[0075] b. Get the distance between any two cold inspection units, where the number of cold inspection units is 3 or more;

[0076] c. Calculate the difference between the length of the material before measurement and the distance between any two cold inspection units;

[0077] d. The two cold detection units with the smallest difference are used to trigger the laser speed measurement unit;

[0078] S2: a laser speed measuring unit speed measuring step, wherein the laser speed measuring unit obtains the speed of the material being measured according to the triggering instructions of the two cold detection units with the smallest difference;

[0079] S3: a data processing unit calculating the length step, wherein the data processing unit calculating the length step includes the data processing unit calculating the shortest length to be measured of the material to be measured according to the speed of the material to be measured.

[0080] In a further laser length measurement method,

[0081] The cold inspection unit tracking step further includes:

[0082] receiving a direction signal and a motion signal obtained by a data processing unit from the laser speed measuring unit;

[0083] Determine whether there is a cold check trigger logic error;

[0084] If it exists, assist in decision making;

[0085] The difference between the pre-measurement length of the material being measured and the distance between any two cold inspection units is calculated based on the auxiliary decision.

[0086] In a further laser length measurement method, the cold detection unit is a photoelectric switch. In a preferred embodiment, the photoelectric switches are arranged linearly and evenly.

[0087] A further laser length measurement method, the length calculation step of the data processing unit also includes a material length calculation step, the material length calculation step is to add the dynamic cold inspection spacing and the shortest length to be measured to obtain the total length of the measured material, wherein the spacing between the two cold inspection units with the smallest difference is the dynamic cold inspection spacing, and the length measured by the two cold inspection units with the smallest difference triggering the laser speed measurement unit is the shortest length to be measured.

[0088] With the further laser length measurement method, the spacing difference of dynamic cold inspection in different sections does not exceed 1mm.

[0089] The embodiments and functional operations of the subject matter described in this specification may be implemented in digital electronic circuitry, tangibly implemented computer software or firmware, computer hardware including the structures disclosed in this specification and their structural equivalents, or a combination of more than one of the foregoing. The embodiments of the subject matter described in this specification may be implemented as one or more computer programs, i.e., one or more modules of computer program instructions encoded on one or more tangible, non-transitory program carriers, for execution by, or to control the operation of, a data processing apparatus.

[0090] Alternatively or additionally, the program instructions may be encoded on an artificially generated propagated signal, such as a machine-generated electrical, optical, or electromagnetic signal, which is generated to encode information for transmission to an appropriate receiver device for execution by a data processing device. The computer storage medium may be a machine-readable storage device, a machine-readable storage substrate, a random or serial access memory device, or a combination of one or more of the foregoing.

[0091] The term "data processing unit" encompasses all types of equipment, devices, and machines for processing data, including, by way of example, a programmable processor, a computer, or multiple processors or multiple computers. Equipment may include specialized logic circuitry, such as an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit). In addition to hardware, equipment may also include code that creates an execution environment for the associated computer program, such as code constituting processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of these.

Claims

1. A laser length measurement system based on dynamic cold detection distance, comprising a laser speed measurement unit, a cold detection unit for triggering the laser speed measurement unit, and a data processing unit for communicating with the laser speed measurement unit, characterized in that: The number of the cold detection units is three or more; the system further comprises a cold detection unit tracking module, and the cold detection unit tracking module is configured to: Obtain the pre-measurement length of the material being measured; Get the distance between any two cold inspection units; Calculate the difference between the pre-measurement length of the material being measured and the distance between any two cold inspection units; The two cold detection units with the smallest difference are used to trigger the laser speed measurement unit. The two cold detection units with the smallest difference include a front cold detection unit located in front of the laser speed measurement unit and a rear cold detection unit located behind the laser speed measurement unit according to the moving direction of the moving material to be measured.

2. The laser length measurement system according to claim 1, wherein: The two cold detection units with the smallest difference are used to trigger the laser speed measurement unit, including the following steps: The distance between the two cold inspection units with the smallest difference is taken as the initial cumulative value; When the front cold inspection unit senses the leading end of the moving material to be tested, it triggers the laser speed measurement unit to start measuring; When the rear cooling inspection unit senses the tail end of the moving material to be tested, the laser speed measurement unit is triggered to end the measurement.

3. The laser length measurement system according to claim 2, wherein: The cold inspection units are arranged in sequence according to the traveling direction of the moving material to be inspected, and include a first cold inspection unit located in front of the laser speed measurement unit and a plurality of second cold inspection units located behind the laser speed measurement unit.

4. The laser length measurement system according to claim 3, wherein: The signal between the cold detection unit tracking module and the laser speed measurement unit is determined based on a number of the cold detection units.

5. The laser length measurement system according to claim 4, characterized in that: The cold inspection unit tracking module is further configured to: receiving a direction signal and a motion signal obtained by a data processing unit from the laser speed measuring unit; Determine whether there is a cold check trigger logic error; If it exists, assist in decision making; The difference between the pre-measurement length of the material being measured and the distance between any two cold inspection units is calculated based on the auxiliary decision.

6. The laser length measurement system according to claim 5, characterized in that: The cold detection unit is a photoelectric switch, and the photoelectric switches are arranged linearly and evenly.

7. The laser length measurement system according to claim 6, wherein: The data processing unit includes a material length calculation unit, which is used to add the dynamic cold inspection spacing and the shortest length to be measured to obtain the total length of the material to be measured, wherein the spacing between the two cold inspection units with the smallest difference is the dynamic cold inspection spacing, and the length measured by the laser speed measurement unit triggered by the two cold inspection units with the smallest difference is the shortest length to be measured.

8. The laser length measurement system according to claim 7, wherein: The spacing difference between different sections of dynamic cold inspection shall not exceed 1mm.

9. A laser length measurement method based on dynamic cold detection distance, characterized in that: The laser length measurement method comprises the following steps: The cold inspection unit tracking step includes: a. Obtain the pre-measurement length of the material being measured; b. Get the distance between any two cold inspection units, where the number of cold inspection units is 3 or more; c. Calculate the difference between the length of the material before measurement and the distance between any two cold inspection units; d. The two cold detection units with the smallest difference are used to trigger the laser speed measurement unit. The two cold detection units with the smallest difference are located in the direction of travel of the moving material being measured, including a front cold detection unit located in front of the laser speed measurement unit and a rear cold detection unit located behind the laser speed measurement unit; a laser speed measuring unit speed measuring step, wherein the laser speed measuring unit obtains the speed of the material to be measured according to the trigger instructions of the two cold detection units with the smallest difference; The data processing unit calculates the length step, and the data processing unit calculates the length step includes the data processing unit calculating the shortest required measuring length of the measured material according to the speed of the measured material.

10. The laser length measurement method according to claim 9, wherein: The two cold detection units with the smallest difference are used to trigger the laser speed measurement unit, including the following steps: The distance between the two cold inspection units with the smallest difference is taken as the initial cumulative value; When the front cold inspection unit senses the leading end of the moving material to be tested, it triggers the laser speed measurement unit to start measuring; When the rear cooling inspection unit senses the tail end of the moving material to be tested, the laser speed measurement unit is triggered to end the measurement.

11. The laser length measurement method according to claim 10, wherein: The cold inspection units are arranged in sequence according to the traveling direction of the moving material to be inspected, and include a first cold inspection unit located in front of the laser speed measurement unit and a plurality of second cold inspection units located behind the laser speed measurement unit.

12. The laser length measurement method according to claim 11, wherein: The signal between the cold detection unit tracking module and the laser speed measurement unit is determined based on a number of the cold detection units.

13. The laser length measurement method according to claim 12, wherein: The cold inspection unit tracking step further includes: receiving a direction signal and a motion signal obtained by a data processing unit from the laser speed measuring unit; Determine whether there is a cold check trigger logic error; If it exists, assist in decision making; The difference between the pre-measurement length of the material being measured and the distance between any two cold inspection units is calculated based on the auxiliary decision.

14. The laser length measurement method according to claim 13, wherein: The cold detection unit is a photoelectric switch.

15. The laser length measurement method according to claim 14, wherein: The photoelectric switches are arranged linearly and evenly.

16. The laser length measurement method according to claim 15, wherein: The data processing unit length calculation step also includes a material length calculation step, which is to add the dynamic cold inspection spacing and the shortest length to be measured to obtain the total length of the material to be measured, wherein the spacing between the two cold inspection units with the smallest difference is the dynamic cold inspection spacing, and the length measured by the laser speed measurement unit triggered by the two cold inspection units with the smallest difference is the shortest length to be measured.

17. The laser length measurement method according to claim 16, wherein: The spacing difference between different sections of dynamic cold inspection shall not exceed 1mm.

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