A method and apparatus for measuring the speed and head warp of a billet

Abstract

This invention discloses a method and apparatus for measuring the speed and head warpage of a steel billet. The method includes: transmitting a symmetrical triangular linear frequency modulated continuous wave signal to the steel billet to be tested, wherein the symmetrical triangular linear frequency modulated continuous wave, as the local oscillator signal, is generated by a detection device installed at a preset position at the mill exit; after the linear frequency modulated continuous wave is emitted to the steel billet to be tested, an echo signal is generated; the local oscillator signal and the echo signal are mixed to obtain a difference frequency signal; the difference frequency signal is subjected to spectral analysis to measure the target distance of the steel billet to be tested; the difference between two target distances measured in the direction of travel of the steel billet to be tested is calculated, and it is determined whether the difference is within a first preset threshold range; if the difference is within the first preset threshold range, it is determined that the steel billet to be tested has no warpage. This method of the present invention uses linear frequency modulated continuous wave signal for distance and speed measurement, which is not easily affected by flowing water on the steel plate surface and water mist in the optical path, has strong anti-interference ability, and improves the accuracy and stability of steel plate warpage measurement.

Description

Technical Field

[0001] This invention relates to the field of steel smelting technology, and more specifically, to a method and apparatus for measuring billet speed and head warp. Background Technology

[0002] In the steel rolling process, billet head curvature (the billet head bending upwards) makes it prone to collisions with equipment or measuring instruments, potentially preventing strip from smoothly entering the mill and causing steel pile-up. Conversely, billet head curvature (the billet head bending downwards) can cause collisions with the mill stand rolls or roller table, leading to the billet embedding itself in the lower part of the roller table, causing numerous production problems. The accuracy of billet speed measurement directly affects the accurate operation of the flying shear system; inaccurate data leads to material waste and increased production costs. Therefore, real-time and accurate monitoring of billet speed and head curvature, and timely and accurate transmission of data to the control system, is of great significance for steel rolling control.

[0003] During the steel rolling process, extensive spraying is required to cool the mill rolls and wash away oxides generated on the surface of the rolled steel. Small amounts of flowing water easily remain on the surface of the intermediate billet, surrounded by a large amount of water mist. Furthermore, the rolling environment is harsh and subject to numerous interferences. Currently, there are two main methods for measuring billet speed and warpage: laser measurement and speed measuring roller measurement. Laser measurement offers high accuracy but is highly susceptible to the influence of flowing water on the steel plate surface and water mist in the optical path, easily leading to problems and lower reliability in harsh hot rolling applications. While speed measuring rollers are less affected by mist and flowing water on the steel plate surface, their measurement accuracy is easily affected by slippage and wear.

[0004] In summary, the above-mentioned methods for measuring billet speed and warpage have certain limitations and are difficult to obtain good measurement results, so improvements are necessary. Summary of the Invention

[0005] The present invention provides a method and apparatus for measuring billet speed and head warping, in order to overcome at least one problem existing in the prior art.

[0006] According to a first aspect of the embodiments of this specification, a method for measuring billet speed and head warpage is provided, comprising:

[0007] A symmetrical triangular linear frequency modulated continuous wave signal is emitted to the billet to be tested. The symmetrical triangular linear frequency modulated continuous wave signal is a linear frequency modulated continuous wave that changes in time in a triangular pattern and has a symmetrical slope. The symmetrical triangular linear frequency modulated continuous wave, as a local oscillator signal, is generated by a detection device installed at a preset position at the mill exit.

[0008] The linear frequency modulated continuous wave is emitted to the steel billet under test and generates an echo signal. The local oscillator signal and the echo signal are mixed to obtain a difference frequency signal.

[0009] The difference frequency signal is subjected to spectrum analysis to measure the target distance and traveling speed of the steel billet under test;

[0010] Calculate the difference between the two target distances measured in the direction of travel of the billet to be tested, and determine whether the difference is within a first preset threshold range. If the difference is within the first preset threshold range, then determine that the billet to be tested has no warping.

[0011] Optionally, the method for measuring the billet speed and head warpage further includes:

[0012] If the difference is not within the first preset threshold range, the test billet is determined to have either curled up or buckled based on the sign of the difference.

[0013] Optionally, the method for measuring the billet speed and head warpage further includes:

[0014] Determine whether the target distance is less than a first preset distance. If the target distance is less than the first preset distance, then determine that the steel billet under test has warped.

[0015] Optionally, the method for measuring the billet speed and head warpage further includes:

[0016] Determine whether the target distance is greater than a second preset distance. If the target distance is less than the second preset distance, then determine that the steel billet under test has buckled.

[0017] Optionally, the target distance and the travel speed are obtained in the following way:

[0018] Calculate the signal to be transmitted to the billet under test according to formula (1). S S :

[0019] (1);

[0020] in, A The amplitude of the electromagnetic wave. f 0 For the center frequency, K The slope This is the initial phase;

[0021] Calculate the signal according to formula (2) S S The echo signal obtained after the light is incident on the steel billet under test and reflected back:

[0022] (2);

[0023] in, For transmission delay, ;

[0024] echo signal S r With transmitted signals S S After mixing and low-pass output, the echo signal is calculated according to formula (3). S r With transmitted signals S S Phase corresponding to the difference frequency:

[0025] (3);

[0026] Transform τ according to formula (4):

[0027] (4);

[0028] in, The time delay of the electromagnetic wave echoing from the original stationary object is considered, and the echo delay is superimposed on the motion of the steel billet. ;

[0029] Substituting formula (4) into formula (3), Transformed into formula (5):

[0030] = - + (5);

[0031] in, f b The frequency of the difference frequency signal; K b The slope of the difference frequency signal; This is the initial phase of the difference frequency signal; = ;

[0032] = ;

[0033] ;

[0034] = , The center frequency of the echo;

[0035] f dThis is due to the Doppler frequency shift caused by the movement of the steel billet;

[0036] Constructing the upslope and downslope of a symmetrical triangular linear frequency modulated continuous wave signal respectively f b 上 and f b 下 The two equations are used to determine the target distance and the travel speed of the billet to be measured.

[0037] Optionally, after mixing the local oscillator signal and the echo signal to obtain the difference frequency signal, and before performing spectral analysis processing on the difference frequency signal, the method further includes:

[0038] The difference frequency signal obtained from mixing is filtered, amplified, and sampled by an analog-to-digital converter (AD).

[0039] According to a second aspect of the embodiments of this specification, a measuring device for billet speed and head warpage is provided, comprising:

[0040] The local oscillator signal transmitting module is configured to transmit a symmetrical triangular linear frequency modulated continuous wave signal to the billet under test. The symmetrical triangular linear frequency modulated continuous wave signal is a linear frequency modulated continuous wave that changes in time in a triangular pattern and has a symmetrical slope. The symmetrical triangular linear frequency modulated continuous wave, as the local oscillator signal, is generated by a detection device installed at a preset position at the mill exit.

[0041] The difference frequency signal determination module is configured to generate an echo signal after the linear frequency modulated continuous wave is emitted to the steel billet to be tested, and to mix the local oscillator signal and the echo signal to obtain the difference frequency signal.

[0042] The distance and speed measurement module is configured to perform spectrum analysis processing on the difference frequency signal to measure the target distance and travel speed of the steel billet to be measured.

[0043] The first warping determination module is configured to calculate the difference between two target distances measured in the direction of travel of the billet to be tested, and determine whether the difference is within a first preset threshold range. If the difference is within the first preset threshold range, the billet to be tested is determined to be warped.

[0044] Optionally, the billet speed and head warpage measuring device further includes: a second warpage determination module;

[0045] The second warping determination module is configured to determine whether the steel billet under test has warped or buckled if the difference is not within the first preset threshold range.

[0046] Optionally, the billet speed and head warpage measuring device further includes: a third warpage determination module;

[0047] The third warping determination module is configured to determine whether the target distance is less than a first preset distance. If the target distance is less than the first preset distance, it is determined that the steel billet under test has warped.

[0048] Optionally, the billet speed and head warpage measuring device further includes: a fourth warpage determination module;

[0049] The fourth warping determination module is configured to determine whether the target distance is greater than the second preset distance. If the target distance is less than the second preset distance, it is determined that the steel billet under test has warped.

[0050] This specification describes an embodiment that uses a symmetrical triangular linear frequency-modulated continuous wave (FM-CW) signal to measure the distance to the billet in real time. The FM-CW signal is used for ranging and velocity measurement. Firstly, FM-CW has strong penetrating power and can operate normally even in foggy environments; small amounts of flowing water on the billet surface have minimal impact. Secondly, the FM-CW equipment operates at high frequencies, while rolling mill noise and interference are in the mid-to-low frequency range, resulting in strong adaptability and anti-interference capabilities, and providing real-time and accurate measurement data. Therefore, this measurement method can more accurately measure the speed and head warping of the billet in the harsh environment of rolling mill processes, facilitating accurate identification of abnormal conditions and effectively preventing equipment damage, billet defects, and reduced yield, thereby improving the level of automated steelmaking.

[0051] Compared with the prior art, the inventive points of the embodiments in this specification include at least:

[0052] 1. This invention uses a symmetrical triangular linear frequency modulated continuous wave signal to measure the distance and speed of the steel billet, and determines the warping based on the distance measurement. The linear frequency modulated continuous wave has strong penetration ability and can still work normally in foggy environments. The small amount of flowing water on the surface of the steel billet has little effect on it. It has strong anti-interference ability and is suitable for steel rolling processes in harsh environments. It can quickly, continuously and in real time detect more accurate steel plate warping information, which is one of the inventive points of this invention.

[0053] 2. This invention employs a triangular linear frequency-modulated continuous wave signal with a symmetrical slope. Frequency formulas corresponding to the difference frequency signal are constructed using its upper and lower slopes to determine the target distance and traveling speed of the billet under test. By calculating the difference between two target distances measured along the billet's traveling direction, and determining whether the billet is warped, this invention provides a simple, efficient, and reliable online detection method for billet warping. This is one of the inventive aspects of this invention. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a schematic diagram of the composition of steel rolling process equipment;

[0056] Figure 2 This is a schematic flowchart illustrating a method for measuring billet speed and head warp according to an embodiment of the present invention.

[0057] Figure 3 This is a schematic diagram of the component structure of a probe according to an embodiment of the present invention;

[0058] Figure 4 This is a schematic diagram of the probe installation according to an embodiment of the present invention;

[0059] Figure 5 This is a schematic diagram of another installation of the probe according to an embodiment of the present invention;

[0060] Figure 6 This is a schematic diagram of the module composition of a billet speed and head warping measuring device according to an embodiment of the present invention. Detailed Implementation

[0061] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] It should be noted that the terms "comprising" and "having," and any variations thereof, in the embodiments and drawings of this specification are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0063] This specification discloses a method and apparatus for measuring billet speed and head warpage. These will be described in detail below.

[0064] This embodiment uses the steel rolling process as an example. It should be noted that the billet speed and head warpage measurement methods provided in this embodiment are not limited to the steel rolling process, but are also applicable to other production processes, such as chemical production processes. Figure 1 This is a schematic diagram of the steel rolling process equipment. (For example...) Figure 1 As shown, the main equipment for steel rolling processes includes a heating furnace, descaling box, roughing mill, hot coil box, continuous rolling mill, laminar flow cooling, and coiler. The corresponding steel rolling production process consists of multiple production processes such as heating, descaling, roughing, flying shear, hot coiling, finishing, laminar flow cooling, and coiling, forming a long product processing flow with a series structure from raw materials to the final product.

[0065] Figure 2 This is a schematic flowchart illustrating a method for measuring billet speed and head warpage according to an embodiment of the present invention. Figure 2 As shown, a method for measuring billet speed and head warpage includes the following steps:

[0066] Step S201: A symmetrical triangular linear frequency modulated continuous wave signal is transmitted to the billet to be tested. The symmetrical triangular linear frequency modulated continuous wave signal is a linear frequency modulated continuous wave that changes in time in a triangular pattern and has a symmetrical slope. The symmetrical triangular linear frequency modulated continuous wave is generated as a local oscillator signal by a detection device installed at a preset position at the mill exit.

[0067] In one implementation, the detection device includes a probe for transmitting a symmetrical triangular linear frequency modulated continuous wave signal. Figure 3 This is a schematic diagram of the component structure of a probe according to an embodiment of the present invention. Figure 3 As shown, the probe includes a triangular wave generator, a voltage-controlled oscillator (VCO), a power amplifier, a transmitting antenna, a receiving antenna, a filtering and amplification module, an AD sampling module, and a signal processing module. The symmetrical slope triangular wave generator provides the required modulation signal, which, under VCO control, generates a continuous high-frequency, constant-amplitude wave whose frequency varies in a triangular pattern over time—a linear frequency modulated (LFM) continuous wave. As an example, the LFM continuous wave can operate in the 60GHz band (wavelength 5mm, bandwidth 50MHz). Part of the LFM continuous wave is amplified and radiated through the transmitting antenna, while the other part serves as the local oscillator signal. When the radio wave encounters the target, it returns to the receiving antenna. At this point, the echo signal's frequency differs from the local oscillator signal, and the resulting signal after mixing is the difference frequency signal. The frequency of the difference frequency signal is related to the target's distance and velocity. The main task of signal processing is to extract the frequency of the difference frequency signal and obtain information such as the target's actual distance and velocity from it.

[0068] In one implementation, the detection device can be installed between the outlet of the roughing mill and the hot coil box, or at a certain distance from the flying shear system. Figure 4 This is a schematic diagram of the probe installation according to an embodiment of the present invention. Figure 4 As shown, the probe is installed 2m above the center line of the billet and 2m from the exit of the roughing mill. The signal transmission direction is vertically downward, using a linear frequency modulated continuous wave signal for ranging, with a measurement accuracy down to the micrometer level. The probe is protected by a heat-insulating material box, cooled by flowing air and water. It can be installed using a hanging type or a structural frame. Figure 5 This is a schematic diagram illustrating another installation method for the probe according to an embodiment of the present invention. Figure 5 As shown, the probe is installed 2m above the center line of the billet and 10m from the flying shear system. The signal transmission direction is obliquely downward at a 45° angle to the horizontal plane. Linear frequency modulated continuous wave signal is used for ranging and velocity measurement, and the measurement accuracy can reach the micrometer level.

[0069] This invention uses a symmetrical triangular linear frequency modulated continuous wave signal to measure the distance and speed of steel billets, and determines warping based on the distance measurement. The linear frequency modulated continuous wave has strong penetration ability and can still work normally in foggy environments. The small amount of flowing water on the surface of the steel billet has little effect on it. It has strong anti-interference ability and is suitable for steel rolling processes in harsh environments. It can quickly, continuously and in real time detect more accurate steel plate warping information, which is one of the inventive points of this invention.

[0070] Step S202: After the linear frequency modulated continuous wave is shone onto the steel billet to be tested, an echo signal is generated. The local oscillator signal and the echo signal are mixed to obtain a difference frequency signal.

[0071] Step S203: Perform spectrum analysis on the difference frequency signal to measure the target distance and travel speed of the steel billet to be tested;

[0072] In one implementation, the target distance and the travel speed are obtained in the following way:

[0073] Calculate the signal to be transmitted to the billet under test according to formula (1). S S :

[0074] (1);

[0075] in, A The amplitude of the electromagnetic wave. f 0 For the center frequency, K The slope This is the initial phase; neglecting attenuation during electromagnetic wave propagation, when encountering a distance of... R When the steel billet is in the process of being reflected, its reflected echo is calculated according to formula (2): that is SS The echo signal obtained after the light is incident on the steel billet under test and reflected back:

[0076] (2);

[0077] in, For transmission delay, ;

[0078] echo signal S r With transmitted signals S S After mixing and low-pass output, the echo signal is calculated according to formula (3). S r With transmitted signals S S Phase corresponding to the difference frequency:

[0079] (3);

[0080] According to formula (4) Perform the transformation:

[0081] (4);

[0082] in, The time delay of the electromagnetic wave echoing from the original stationary object is considered, and the echo delay is superimposed on the motion of the steel billet. , f d This is due to the Doppler frequency shift caused by the movement of the steel billet;

[0083] Substituting formula (4) into formula (3), since Therefore, some smaller items can be discarded, and Transformed into formula (5):

[0084] = - + (5);

[0085] It can be seen that the difference frequency signal obtained is still a linear frequency modulated signal. Among them, f b The frequency of the difference frequency signal; K b The slope of the difference frequency signal; This represents the initial phase of the difference frequency signal; where,

[0086] = ;

[0087] = ;

[0088] ;

[0089] = , The center frequency of the echo can be derived from the time-frequency triangle using similar triangles; f b It contains the range and motion information of the target. If the transmitted signal is a linear frequency modulated continuous wave with a single slope, a range-velocity coupling problem exists when the target's range and velocity are unknown. This device uses a triangular wave with a symmetrical slope, constructing the range and velocity information through the upper and lower slopes respectively. f b 上 and f b 下 The two equations can be used to decouple the target distance and determine the travel speed of the billet under test.

[0090] This invention employs a triangular linear frequency-modulated continuous wave signal with a symmetrical slope. Frequency formulas corresponding to the difference frequency signal are constructed using its upper and lower slopes to determine the target distance and traveling speed of the billet under test. By calculating the difference between two target distances measured sequentially along the billet's traveling direction, and using this difference to determine whether the billet is warped, a simple, efficient, and reliable online detection of billet warping is achieved. This is one of the inventive aspects of this invention.

[0091] Step S204: Calculate the difference between the two target distances measured in the forward and backward directions of the billet to be tested, and determine whether the difference is within the first preset threshold range. If the difference is within the first preset threshold range, then determine that the billet to be tested has no warping.

[0092] In one implementation, the two target distances measured forward and backward along the direction of travel of the billet to be tested are denoted as H. 前 and H 后 Let the difference between the two be denoted as ΔH, and let ΔH = H 后 -H 前 When ΔH fluctuates within a specified range of 0 or around 0, the billet is free from warping.

[0093] The billet speed and head warpage measurement method provided in this specification achieves real-time measurement of the billet distance by transmitting a symmetrical triangular linear frequency-modulated continuous wave signal to the billet under test and using frequency-modulated continuous wave ranging and velocity measurement. On the one hand, frequency-modulated continuous waves have strong penetrating power and can still operate normally in foggy environments; small amounts of flowing water on the billet surface have minimal impact. On the other hand, the frequency-modulated continuous wave equipment operates in the high-frequency band, while the noise and interference in steel rolling mills are in the mid-to-low frequency range, resulting in strong adaptability and anti-interference capabilities, and real-time and accurate measurement data. Therefore, this measurement method can more accurately measure the billet speed and head warpage in the harsh environment of steel rolling processes, facilitating accurate identification of abnormal conditions, effectively preventing equipment damage and billet defects that could lead to reduced yield, and improving the level of automated steelmaking.

[0094] In one implementation, the method for measuring the billet speed and head warpage further includes:

[0095] If the difference is not within the first preset threshold range, the test billet is determined to have either curled up or buckled based on the sign of the difference.

[0096] Throughout the ranging process, the previous measurement data H can be used. 前 Next adjacent measurement data H 后 The difference is continuously calculated to obtain ΔH, and a ΔH curve is generated by computer. When ΔH fluctuates in the negative region, it is called a "head up"; when ΔH fluctuates in the positive region, it is called a "head down".

[0097] In one implementation, the method for measuring the billet speed and head warpage further includes:

[0098] Determine whether the target distance is less than a first preset distance. If the target distance is less than the first preset distance, then determine that the steel billet under test has warped.

[0099] In one implementation, the method for measuring the billet speed and head warpage further includes:

[0100] Determine whether the target distance is greater than a second preset distance. If the target distance is less than the second preset distance, then determine that the steel billet under test has buckled.

[0101] The rolling process requires that the maximum allowable target distance for the billet head to curl upwards is denoted as H1, and the maximum allowable target distance for the billet head to buckle is denoted as H2. When the real-time measured target distance H < H1, the degree of billet head curling upwards exceeds the specified value H1, triggering an alarm system or transmitting the data to the flying shear system for positioning and shearing; when H > H2, the degree of billet head buckling exceeds the specified value H2, triggering an alarm system or transmitting the data to the flying shear system for positioning and shearing.

[0102] In one implementation, to reduce computational load and improve measurement accuracy, after mixing the local oscillator signal and the echo signal to obtain the difference frequency signal, and before performing spectral analysis processing on the difference frequency signal, the method further includes:

[0103] The difference frequency signal obtained from mixing is filtered, amplified, and sampled by an analog-to-digital converter (AD).

[0104] Filtering and amplification can remove low- and mid-frequency interference signals from the signal, improving measurement accuracy. A / D sampling can ensure rich data sampling while reducing computational load.

[0105] Figure 6 This is a schematic diagram of the module composition of a billet speed and head warping measuring device according to an embodiment of the present invention. Figure 6 As shown, a measuring device 60 for billet speed and head warpage includes:

[0106] The local oscillator signal transmitting module 601 is configured to transmit a symmetrical triangular linear frequency modulated continuous wave signal to the steel billet to be tested. The symmetrical triangular linear frequency modulated continuous wave signal is a linear frequency modulated continuous wave that changes in time in a triangular pattern and has a symmetrical slope. The symmetrical triangular linear frequency modulated continuous wave, as the local oscillator signal, is generated by a detection device installed at a preset position at the mill exit.

[0107] The difference frequency signal determination module 602 is configured to generate an echo signal after the linear frequency modulated continuous wave is emitted to the steel billet to be tested, and to mix the local oscillator signal and the echo signal to obtain the difference frequency signal.

[0108] The distance and speed measuring module 603 is configured to perform spectrum analysis processing on the difference frequency signal to measure the target distance and travel speed of the steel billet to be measured.

[0109] The first warping determination module 604 is configured to calculate the difference between two target distances measured in the direction of travel of the billet to be tested, and determine whether the difference is within a first preset threshold range. If the difference is within the first preset threshold range, the billet to be tested is determined to be warped.

[0110] Optionally, the billet speed and head warpage measuring device further includes: a second warpage determination module;

[0111] The second warping determination module is configured to determine whether the steel billet under test has warped or buckled if the difference is not within the first preset threshold range.

[0112] Optionally, the billet speed and head warpage measuring device further includes: a third warpage determination module;

[0113] The third warping determination module is configured to determine whether the target distance is less than a first preset distance. If the target distance is less than the first preset distance, it is determined that the steel billet under test has warped.

[0114] Optionally, the billet speed and head warpage measuring device further includes: a fourth warpage determination module;

[0115] The fourth warping determination module is configured to determine whether the target distance is greater than the second preset distance. If the target distance is less than the second preset distance, it is determined that the steel billet under test has warped.

[0116] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0117] Those skilled in the art will understand that the modules in the apparatus of the embodiments can be distributed in the apparatus of the embodiments as described in the embodiments, or they can be located in one or more devices different from this embodiment with corresponding changes. The modules of the above embodiments can be combined into one module, or they can be further divided into multiple sub-modules.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for measuring billet speed and head warpage, characterized in that, include: A symmetrical triangular linear frequency modulated continuous wave signal is emitted to the billet to be tested. The symmetrical triangular linear frequency modulated continuous wave signal is a linear frequency modulated continuous wave that changes in time in a triangular pattern and has a symmetrical slope. The symmetrical triangular linear frequency modulated continuous wave, as a local oscillator signal, is generated by a detection device installed at a preset position at the mill exit. The linear frequency modulated continuous wave is emitted to the steel billet under test and generates an echo signal. The local oscillator signal and the echo signal are mixed to obtain a difference frequency signal. The difference frequency signal is subjected to spectrum analysis to measure the target distance and traveling speed of the steel billet under test; Calculate the difference between the two target distances measured in the direction of travel of the billet to be tested, and determine whether the difference is within a first preset threshold range. If the difference is within the first preset threshold range, then determine that the billet to be tested has no warping.

2. The method for measuring billet speed and head warpage according to claim 1, characterized in that, Also includes: If the difference is not within the first preset threshold range, the test billet is determined to have either curled up or buckled based on the sign of the difference.

3. The method for measuring billet speed and head warpage according to claim 2, characterized in that, Also includes: Determine whether the target distance is less than a first preset distance. If the target distance is less than the first preset distance, then determine that the steel billet under test has warped.

4. The method for measuring billet speed and head warpage according to claim 3, characterized in that, Also includes: Determine whether the target distance is greater than a second preset distance. If the target distance is less than the second preset distance, then determine that the steel billet under test has buckled.

5. The method for measuring billet speed and head warpage according to claim 4, characterized in that, The target distance and the travel speed are obtained in the following way: Calculate the signal to be transmitted to the billet under test according to formula (1). S S : （1）； in, A The amplitude of the electromagnetic wave. f 0 For the center frequency, K The slope This is the initial phase; Calculate the signal according to formula (2) S S The echo signal obtained after the light is incident on the steel billet under test and reflected back: （2）； in, For transmission delay, =2(R 0 -υ 0 t) / c ; echo signal S r With transmitted signals S S After mixing and low-pass output, the echo signal is calculated according to formula (3). S r With transmitted signals S S Phase corresponding to the difference frequency: （3）； According to formula (4) Perform the transformation: (4)； in, The time delay of the electromagnetic wave echoing from the original stationary object is considered, and the echo delay is superimposed on the motion of the steel billet. ; Substituting formula (4) into formula (3), Transformed into formula (5): = - + (5); in, f b The frequency of the difference frequency signal; K b The slope of the difference frequency signal; This is the initial phase of the difference frequency signal; = ; = ； ； = , The center frequency of the echo; f d This is due to the Doppler frequency shift caused by the movement of the steel billet; Constructing the upslope and downslope of a symmetrical triangular linear frequency modulated continuous wave signal respectively f b 上 and f b 下 The two equations are used to determine the target distance and the travel speed of the billet to be measured.

6. The method for measuring billet speed and head warpage according to claim 5, characterized in that, After mixing the local oscillator signal and the echo signal to obtain the difference frequency signal, and before performing spectrum analysis processing on the difference frequency signal, the method further includes: The difference frequency signal obtained from mixing is filtered, amplified, and sampled by an analog-to-digital converter (AD).

7. A measuring device for billet speed and head warpage, characterized in that, include: The local oscillator signal transmitting module is configured to transmit a symmetrical triangular linear frequency modulated continuous wave signal to the billet under test. The symmetrical triangular linear frequency modulated continuous wave signal is a linear frequency modulated continuous wave that changes in time in a triangular pattern and has a symmetrical slope. The symmetrical triangular linear frequency modulated continuous wave, as the local oscillator signal, is generated by a detection device installed at a preset position at the mill exit. The difference frequency signal determination module is configured to generate an echo signal after the linear frequency modulated continuous wave is emitted to the steel billet to be tested, and to mix the local oscillator signal and the echo signal to obtain the difference frequency signal. The distance and speed measurement module is configured to perform spectrum analysis processing on the difference frequency signal to measure the target distance and travel speed of the steel billet to be measured. The first warping determination module is configured to calculate the difference between two target distances measured in the direction of travel of the billet to be tested, and determine whether the difference is within a first preset threshold range. If the difference is within the first preset threshold range, the billet to be tested is determined to be warped.

8. The billet speed and head warpage measuring device according to claim 7, characterized in that, Also includes: The second warping determination module is configured to determine whether the steel billet under test has warped or buckled if the difference is not within the range of the first preset threshold.

9. The billet speed and head warpage measuring device according to claim 8, characterized in that, Also includes: Third warp determination module; The third warping determination module is configured to determine whether the target distance is less than a first preset distance. If the target distance is less than the first preset distance, it is determined that the steel billet under test has warped.

10. The billet speed and head warpage measuring device according to claim 9, characterized in that, Also includes: Fourth warp determination module; The fourth warping determination module is configured to determine whether the target distance is greater than the second preset distance. If the target distance is less than the second preset distance, it is determined that the steel billet under test has warped.

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