JP7549232B2 - Edge detection device, slab length measurement device, edge detection method, and slab length measurement method - Google Patents

Description

The present invention relates to an end detection device, a slab length measurement device, an end detection method, and a slab length measurement method for detecting the end of a slab being transported or calculating the length of the slab from the detected end.

For example, in the steelmaking process in the steel industry, slabs, which are steel materials, are produced by a continuous casting process and temporarily stored in an outdoor yard according to the schedule of the downstream process, and then transported to the downstream process. Slabs stored in the yard have a control number printed on their surface that is linked to the slab's components and dimensions, and are managed based on that control number.
In order to prevent the wrong slab from being sent to the downstream process, the control number is read before the slab is loaded into the heating furnace of the downstream process, and based on the read control number, it is confirmed whether the slab being transported to the downstream process is the correct slab.

However, there are cases where the control number printed on the slab disappears during storage in outdoor yards or during transport, making it impossible to read correctly. Therefore, it is required to measure not only the slab's control number but also its dimensions (width, length, thickness) before the slab is transported to the next process, so that if the control number cannot be read correctly, it is possible to confirm whether the slab being transported to the next process is the correct slab based on the measurement results of the slab's dimensions.

From the standpoint of productivity and equipment, it is desirable to measure the dimensions of the slab (especially the length at which the measured values become larger) while the slab is being transported outdoors on a transport line installed outdoors before it is loaded into the heating furnace. The length of a slab is the length from the front end to the rear end of the slab, so measuring the length of a slab requires a method for accurately detecting the front and rear ends of the slab.

Patent document 1 discloses a device that irradiates a light beam toward an object to be measured and identifies the position of the edge of the object to be measured based on the signal level of the light beam detected by a line sensor.

JP 2019-35605 A

However, the device described in Patent Document 1 uses laser light with wavelengths ranging from visible light to infrared light. Therefore, although the device described in Patent Document 1 can obtain high spatial resolution, when measurements are performed outdoors where slabs are being transported, there is a problem in that the laser light, which is visible light or infrared light, is scattered by raindrops or dust. Therefore, when a laser-based sensor such as the device described in Patent Document 1 is used outdoors, there is a risk that the edge of the slab being transported cannot be detected with high accuracy.

In addition, there are camera-based sensors that detect the ends of objects to be measured, but these have the disadvantage that they are not suitable for measurements at night when it is difficult to ensure sufficient light.

In order to solve the above problems in outdoor measurements, it is conceivable to use electromagnetic waves in the microwave band (microwaves). The use of microwaves has the advantage that the edges of the transported slabs can be detected while suppressing the effects of raindrops, dust, and darkness. However, microwaves generally have poor spatial resolution, which creates the problem of not being able to detect the edges of the slabs with the desired accuracy.

Therefore, the present invention aims to provide, as an example, an end detection device, a slab length measurement device, an end detection method, and a slab length measurement method that can accurately detect the end of a slab being transported, even in an environment that is easily affected by raindrops, dust, or darkness, or that can calculate the length of the slab based on the detected end.

In order to solve the above problems, an end detection device according to an embodiment of the present invention is an end detection device that detects the end of a slab being transported, and includes a microwave transmitting unit that is arranged on the side of the slab and transmits microwaves to the slab, a microwave receiving unit that is arranged alongside the microwave transmitting unit and receives reflected waves of the microwaves from the side of the slab, and a calculation processing unit that detects the end of the slab based on the timing when the end of the slab passes in front of the microwave transmitting unit or the microwave receiving unit, and the calculation processing unit determines that the timing when the end of the slab passes in front of the microwave transmitting unit or the microwave receiving unit is a predetermined timing corresponding to a signal strength that is predetermined between the signal strength of the reflected wave when the slab is present in front of the microwave transmitting unit or the microwave receiving unit and the signal strength of the reflected wave when the slab is not present in front of the microwave transmitting unit or the microwave receiving unit.
In addition, the slab length calculation device according to an embodiment of the present invention calculates the length of the slab from the front end and the rear end of the slab detected using the end detection device.

In order to solve the above problems, an end detection method according to an embodiment of the present invention is an end detection method for detecting the end of a transported slab, the end detection method comprising: a microwave transmitting step of transmitting microwaves to the slab using a microwave transmitting unit arranged on the side of the slab; a microwave transmitting and receiving step of receiving reflected waves of the microwaves from the side of the slab using a microwave receiving unit arranged alongside the microwave transmitting unit; and a calculation processing step of detecting the end of the slab based on the timing at which the end of the slab passed in front of the microwave transmitting unit or the microwave receiving unit, wherein the calculation processing step determines that the timing at which the end of the slab passed in front of the microwave transmitting unit or the microwave receiving unit is a predetermined timing corresponding to a signal strength that is predetermined between the signal strength of the reflected wave when the slab is present in front of the microwave transmitting unit or the microwave receiving unit and the signal strength of the reflected wave when the slab is not present in front of the microwave transmitting unit or the microwave receiving unit.
Moreover, in the slab length calculation method according to the embodiment of the present invention, the length of the slab is calculated from the front end and the rear end of the slab detected using the end detection method.

The present invention provides an edge detection device, a slab length measurement device, an edge detection method, and a slab length measurement method that can accurately detect the edge of a slab being transported, even in an environment susceptible to the effects of raindrops, dust, and darkness, or that can calculate the length of the slab based on the detected edge.

FIG. 2 shows a measurement device and a slab according to an embodiment of the present invention. FIG. 13 is a diagram illustrating the state in which the front end of a slab passes in front of a sensor according to one embodiment of the present invention. FIG. 13 is a diagram illustrating the rear end of a slab passing in front of a sensor according to one embodiment of the present invention. 1 is a graph showing the relationship between the signal strength of a reflected wave obtained when a slab according to an embodiment of the present invention passes in front of a sensor and time during transportation of the slab. FIG. 4 is a diagram showing a process flow in a calculation processing unit according to an embodiment of the present invention. FIG. 2 is a diagram for explaining a model of knife-edge diffraction in a measurement device according to an embodiment of the present invention, showing the state when the front end of a slab passes in front of a sensor. FIG. 2 is a diagram for explaining a model of knife-edge diffraction in a measurement device according to an embodiment of the present invention, showing the state when the rear end of a slab passes in front of a sensor. FIG. 13 is a diagram showing a case in which a slab is transported in a tilted state with respect to the transport direction in a measuring device according to an embodiment of the present invention. 4 is a graph showing the signal intensity of a reflected wave obtained in Example 1. 1 is a graph showing a comparison of signal intensities of reflected waves obtained in Example 1 and Example 2. 1 is a graph showing a comparison of signal intensities of reflected waves obtained in Examples 1 and 3. 1 is a graph showing a comparison of the signal intensities of reflected waves obtained in Example 1 and Example 4.

Embodiments of the present invention propose an edge detection device, a slab length measurement device, an edge detection method, and a slab length measurement method that can accurately detect the front and rear ends of a slab being transported, and thus accurately measure the length of the slab, while using electromagnetic waves (microwaves) in the microwave band that are not easily affected by raindrops, dust, or darkness.

(Explanation of Slab 12)
1 is a diagram showing a measuring device 10 and a slab 12 according to the present invention. The slab 12 is a steel material in the shape of a flat rectangular parallelepiped, which is manufactured by a continuous casting process in the steelmaking process in the steel industry and is a semi-finished product before being processed into a thick plate, a thin plate, or the like. After being manufactured by the continuous casting process, the slab 12 is temporarily stored in an outdoor yard according to the schedule of the subsequent process, and is then transported to the subsequent process. At this time, the slab 12 is transported outdoors by a transport line (not shown) installed outdoors.

In Figure 1, the slab 12 and the sensor 14, which will be described later, are shown in a plan view viewed from the vertical direction. The arrow T indicates the conveying direction, which is determined by the operating direction of the conveying line when the slab 12 is conveyed on the conveying line. The slab 12 may be conveyed parallel to the conveying direction or at an angle to the conveying direction.

When the slab 12 is transported parallel to the transport direction, this refers to the case where the longitudinal direction of the slab 12 is parallel to the transport direction in a planar view, and when the slab 12 is transported tilted relative to the transport direction, this refers to the case where the slab 12 is transported tilted relative to the transport direction in a planar view. Figure 1 shows, as an example, the case where the slab 12 is transported parallel to the transport direction.

In the following description, regardless of whether there is an inclination between the longitudinal direction of the slab 12 and the transport direction, the end portion (front end portion) that is the front side when the slab 12 is transported is referred to as the front end portion 12A of the slab 12, and the end portion (rear end portion) that is the rear side when the slab 12 is transported is referred to as the rear end portion 12B of the slab 12. The front end portion 12A and rear end portion 12B of the slab 12 are each an example of the "end portion of the slab." The length of the slab 12 corresponds to the length between the front end portion 12A and rear end portion 12B along the longitudinal direction of the slab 12.

(Description of Measuring Device 10)
The measuring device 10 detects the ends (at least one of the front end and rear end) of the slab 12 being transported while the slab 12 is being transported outdoors, and if necessary, detects the front end and rear end of the slab 12 being transported, and calculates the length of the slab 12 from the passing timing of the detected front end and rear end of the slab 12. The measuring device 10 has a sensor 14, a transmitting/receiving circuit 16, and an arithmetic processing unit 18.

The sensor 14 is directed toward the slab 12 being transported outdoors, and is positioned on the horizontal side of the slab 12. The sensor 14 has a microwave transmitting unit 20 and a microwave receiving unit 22. The microwave transmitting unit 20 provided in the sensor 14 is positioned on the side of the slab 12 being transported, and transmits microwaves to the slab 12, while the microwave receiving unit 22 provided in the sensor 14 is positioned alongside the microwave transmitting unit 20, and receives the microwave waves reflected from the side of the slab 12.

In FIG. 1, the microwave transmitter 20 and the microwave receiver 22 are illustrated as being aligned along the transport direction of the slab 12, but the microwave transmitter 20 and the microwave receiver 22 may be aligned in any direction. Also, in FIG. 1, the microwave transmitter 20 and the microwave receiver 22 are provided in one sensor, but they may be provided in separate sensors.

The transmission/reception circuit 16 is electrically connected to the microwave transmission unit 20 and the microwave reception unit 22. The transmission/reception circuit 16 causes the microwave transmission unit 20 to transmit microwaves. The transmission/reception circuit 16 also outputs data corresponding to the signal strength of the reflected wave received by the microwave reception unit 22 to the calculation processing unit 18.

The calculation processing unit 18 is configured by a computer. This calculation processing unit 18 has a processor 24 and a memory 26 as a hardware configuration. The processor 24 is configured by, for example, a CPU (Central Processing Unit) and the like. The memory 26 is configured by, for example, a ROM (Read Only Memory), a RAM (Random Access Memory), and storage and the like.

The ROM stores various programs and data. The RAM temporarily stores programs or data as a working area. The storage is composed of a HDD (Hard Disk Drive) or SSD (Solid State Drive), etc., and stores various programs including the operating system and various data.

The ROM or storage stores a program 28 for detecting the front end 12A and rear end 12B of the slab 12, as described below, and calculating the length of the slab 12 based on the detection results. The processor 24 reads the program 28 and executes the program 28 using the RAM as a working area.

The calculation processing unit 18 detects the end of the slab 12 based on the timing when the end of the slab 12 passes in front of the microwave transmitting unit 20 or the microwave receiving unit 22. That is, the calculation processing unit 18 detects the front end (front end 12A) of the slab 12 based on the timing when the front end (front end 12A) of the slab 12 passes in front of the microwave transmitting unit 20 or the microwave receiving unit 22, and detects the rear end (rear end 12B) of the slab 12 based on the timing when the rear end (rear end 12B) of the slab 12 passes in front of the microwave transmitting unit 20 or the microwave receiving unit 22.
The calculation processing unit 18 has, as functional components, a transmission/reception control unit 30, a slab end detection unit 32, and a slab length calculation unit 34. The transmission/reception control unit 30, the slab end detection unit 32, and the slab length calculation unit 34 are realized by the processor 24 reading a program 28 from the memory 26 and executing the program 28.

As described below, the transmission/reception control unit 30 has a function of controlling the transmission/reception circuit 16 so that microwaves are transmitted from the microwave transmission unit 20. The transmission/reception control unit 30 also has a function of controlling the transmission/reception circuit 16 so that data corresponding to the signal strength of the reflected wave received by the microwave reception unit 22 is output to the calculation processing unit 18. The slab end detection unit 32 has a function of detecting the front end 12A and the rear end 12B of the slab 12, and the slab length calculation unit 34 has a function of calculating the length of the slab 12.

(Description of how the slab 12 passes in front of the sensor 14)
2 is a diagram illustrating the state in which the front end 12A of the slab 12 according to the present invention passes in front of the sensor 14. State A is a state before the front end 12A of the slab 12 passes in front of the sensor 14, and the slab 12 is not present in front of the sensor 14. State B is a state in which the front end 12A of the slab 12 is passing in front of the sensor 14, and state C is a state after the front end 12A of the slab 12 has passed in front of the sensor 14, and the slab 12 is present in front of the sensor 14.

Figure 3 is a diagram illustrating the state in which the rear end 12B of the slab 12 according to the present invention passes in front of the sensor 14. State D is the state before the rear end 12B of the slab 12 passes in front of the sensor 14, and the slab 12 is present in front of the sensor 14, and state E is the state in which the rear end 12B of the slab 12 is passing in front of the sensor 14. State F is the state after the rear end 12B of the slab 12 has passed in front of the sensor 14, and the slab 12 is not present in front of the sensor 14.

The front end 12A of the slab 12 passing in front of the sensor 14 is equivalent to the front end 12A of the slab 12 passing in front of the microwave transmitting unit 20 or the microwave receiving unit 22. The rear end 12B of the slab 12 passing in front of the sensor 14 is equivalent to the rear end 12B of the slab 12 passing in front of the microwave transmitting unit 20 or the microwave receiving unit 22.

Furthermore, the presence of the slab 12 in front of the sensor 14 corresponds to the slab 12 being in front of the microwave transmitting unit 20 or the microwave receiving unit 22, and the absence of the slab 12 in front of the sensor 14 corresponds to the slab 12 not being in front of the microwave transmitting unit 20 or the microwave receiving unit 22.

(Explanation of reflected signal strength)
Fig. 4 is a graph showing the relationship between the signal strength of the reflected wave obtained when the slab 12 according to the present invention passes in front of the sensor 14 and the time during transportation of the slab 12. The vertical axis of Fig. 4 shows the signal strength of the reflected wave, and the horizontal axis of Fig. 4 shows the time during transportation of the slab 12. The time during transportation of the slab 12 may be the time when the slab 12 is transported, or may be the elapsed time from a reference time. The times at which the signal strengths indicated by the arrows A to F in Fig. 4 are obtained correspond to states A to F in Figs. 2 and 3, respectively.

In general, microwaves have the characteristic that they propagate through space while spreading at a constant angle proportional to the wavelength, and while most of them are reflected by objects on the transmission path, some of them go around objects on the transmission path. Due to the influence of this characteristic, as shown in FIG. 4, in state A where the slab 12 is not present in front of the sensor 14, the signal strength of the reflected wave is almost zero, and in state B where the front end 12A of the slab 12 is passing in front of the sensor 14, the signal strength of the reflected wave increases rapidly. In states C and D where the slab 12 is present in front of the sensor 14, the signal strength of the reflected wave increases and remains almost constant. In state E where the rear end 12B of the slab 12 is passing in front of the sensor 14, the signal strength of the reflected wave decreases rapidly, and in state F where the slab 12 is not present in front of the sensor 14, the signal strength of the reflected wave becomes almost zero.

(Explanation of the process flow of the measuring device 10)
The process flow of the measurement device 10 according to the first embodiment of the present invention will be described.
5 is a diagram showing a process flow in the measuring device 10. The measuring device 10 starts the process from step S001, and executes the processes of steps S001 to S006.

(Step S001)
In step S001, the calculation processing unit 18 (transmission/reception control unit 30) in the measuring device 10 controls the transmission/reception circuit 16 so that microwaves are transmitted from the microwave transmission unit 20. As a result, the measuring device 10 transmits microwaves to the slab 12 using the microwave transmission unit 20 arranged to the side of the slab 12 being transported.
It is assumed that prior to step S001, the front end 12A of the slab 12 has not reached (i.e., has not passed in front of) the sensor 14 (i.e., the microwave transmitting unit 20 and the microwave receiving unit 22).
Then, proceed to step S002.

(Step S002)
In step S002, the calculation processing unit 18 (transmission/reception control unit 30) controls the transmission/reception circuit 16 so that data corresponding to the signal strength of the reflected wave received by the microwave receiving unit 22 is output to the calculation processing unit 18. As a result, the measurement device 10 receives the microwave reflected from the side surface of the microwave slab 12 using the microwave receiving unit 22 arranged alongside the microwave transmitting unit 20. As a result, data corresponding to the signal strength of the reflected wave received by the microwave receiving unit 22 is output from the transmission/reception circuit 16 to the calculation processing unit 18.
Then, proceed to step S003.

(Step S003)
In step S003, it is determined whether the rear end 12B of the slab 12 has passed in front of the sensor 14 (i.e., in front of the microwave transmitting unit 20 and the microwave receiving unit 22), i.e., whether the slab 12 is no longer in front of the microwave transmitting unit 20 or the microwave receiving unit 22. The method for making this determination is not particularly limited, but for example, it is possible to determine that the rear end 12B has "at least passed" by adding a margin of time to the time when the rear end 12B would pass in front of the sensor 14 based on the conveying speed of the conveying line and the approximate length of the slab 12.
Then, if it is determined that the rear end 12B has not passed in front of the sensor 14, the process returns to step S001; if it is determined that the rear end 12B has passed in front of the sensor 14, the process controls the transmission/reception circuit 16 using the transmission/reception control unit 30 to stop the transmission and reception of microwaves, and then proceeds to step S004.
That is, the calculation processing unit 18 (transmission/reception control unit 30) continues to control the transmission/reception circuit 16 while the slab 12 passes in front of the sensor 14, and continues to acquire data according to the signal strength of the reflected wave.
4, the signal strength value does not change much. Therefore, as long as it is possible to acquire the upper value S1 and the lower value S2 of the signal strength of the reflected wave described later, or to acquire data sufficient to perform fitting, it is also possible to temporarily halt the processing of steps S001 to S002 and not acquire data between states C and D.

(Step S004)
In step S004, the processes in steps S001 to S003 are executed, thereby obtaining data on the signal intensity of the reflected wave, which changes with time during transportation of the slab 12 (see FIG. 4).

The calculation processing unit 18 has a clock function that measures the time when the slab 12 is transported, and links the signal strength of the reflected wave to the time when the slab 12 is transported, obtained by the clock function. The calculation processing unit 18 then stores the data linking the signal strength of the reflected wave to the time when the slab 12 is transported in the memory 26 as detection data.

As a result, the memory 26 stores detection data obtained while the slab 12 passes in front of the sensor 14, i.e., detection data obtained from before the front end 12A of the slab 12 passes in front of the sensor 14 to after the rear end 12B of the slab 12 passes in front of the sensor 14. This detection data includes data obtained from before the front end 12A of the slab 12 passes in front of the sensor 14 to after it has passed, and data obtained from before the rear end 12B of the slab 12 passes in front of the sensor 14 to after it has passed.
Then, proceed to step S005.

(Step S005)
In step S005, the calculation processing unit 18 (slab end detection unit 32) executes a process to detect the front end 12A of the slab 12 based on the timing when the front end 12A of the slab 12 passes in front of the sensor 14, as described below. Also, in step S005, the calculation processing unit 18 (slab end detection unit 32) executes a process to detect the rear end 12B of the slab 12 based on the timing when the rear end 12B of the slab 12 passes in front of the sensor 14, as described below.

Here, the timing when the front end 12A of the slab 12 passes in front of the sensor 14 and the timing when the rear end 12B of the slab 12 passes in front of the sensor 14 are conceptually considered to be the timings at which a signal strength is obtained that is half the signal strength of the reflected wave when the slab 12 is in front of the sensor 14 and the signal strength of the reflected wave when the slab 12 is not in front of the sensor 14. These can also be considered to be the timings at which the absolute value of the slope of the signal strength of the reflected wave with respect to the time change (which can also be called the position change since the conveying speed of the slab 12 is known) becomes maximum.
However, since the front end 12A of the slab 12 passing in front of the sensor 14 and the rear end 12B of the slab 12 passing in front of the sensor 14 are actions that occur in an extremely short time, it is not necessary to judge strictly based on the timing when half the signal strength is obtained or the timing when the absolute value of the inclination is maximum, and a certain degree of flexibility can be tolerated.
Therefore, in this embodiment, an arbitrary signal strength corresponding to the signal strength at which the absolute value of the above-mentioned 1/2 signal strength or slope is maximum is predetermined from among the signal strengths between the signal strength of the reflected wave when the slab 12 is present in front of the microwave transmitting unit 20 or the microwave receiving unit 22 and the signal strength of the reflected wave when the slab 12 is not present in front of the microwave transmitting unit 20 or the microwave receiving unit 22, and the "predetermined timing" corresponding to the predetermined signal strength is determined as the timing at which the end of the slab 12 passes in front of the microwave transmitting unit 20 or the microwave receiving unit 22.
In addition, in this embodiment, the slope near the rising or falling edge of the signal strength is obtained, and the timing at which the obtained slope becomes a predetermined slope corresponding to the maximum absolute value of the slope is regarded as a ``predetermined timing'' corresponding to a predetermined signal strength, and this can be determined as the timing at which the end of the slab 12 passes in front of the microwave transmitting unit 20 or the microwave receiving unit 22.
In addition, when evaluating the inclination, the time change (or position change) of the signal strength is divided into small intervals and the inclination is calculated for each interval, but the signal strength of the reflected microwave is affected not only by the positional relationship between the slab 12 and the sensor 14 but also by microwave diffraction (for example, in FIG. 9, peaks due to vibrations caused by diffraction are visible near -0.04 and -0.07), so if the intervals are taken too narrow, it may be impossible to distinguish the inclination from the peak due to diffraction. Therefore, when evaluating the inclination, it is preferable to sample and evaluate the inclination in an interval wide enough to exclude the effects of microwave diffraction (specifically, 50 mm or more is preferable).

Then, the calculation processing unit 18 (slab end detection unit 32) determines the above-mentioned specified timing to be the timing when the front end 12A of the slab 12 passes in front of the sensor 14 and the timing when the rear end 12B of the slab 12 passes in front of the sensor 14.

The above-mentioned method for determining the predetermined timing includes first to fourth examples, which will be described later.
In the first to fourth examples described below, for the sake of simplicity, the above-mentioned predetermined timing is set to a timing at which a signal strength that is half the signal strength of the reflected wave when the slab 12 is in front of the sensor 14 and the signal strength of the reflected wave when the slab 12 is not in front of the sensor 14 (i.e., the absolute value of the slope of the signal strength of the reflected wave with respect to the time change is maximum), but the present invention is not limited to this. In other words, as the above-mentioned predetermined timing, it is possible to use a timing corresponding to any signal strength between the signal strength of the reflected wave when the slab 12 is in front of the microwave transmitting unit 20 or the microwave receiving unit 22 and the signal strength of the reflected wave when the slab 12 is not in front of the microwave transmitting unit 20 or the microwave receiving unit 22.

In addition, the calculation processing unit 18 (slab end detection unit 32) detects the times corresponding to the above-mentioned specified timings, i.e., the first time corresponding to the timing when the front end 12A of the slab 12 passes in front of the sensor 14 and the second time corresponding to the timing when the rear end 12B of the slab 12 passes in front of the sensor 14, based on the detection data stored in the memory 26 (data linking the signal strength of the reflected wave with the time when the slab 12 was transported), and stores the times in the memory 26.
Then, proceed to step S006.

(Step S006)
In step S006, the calculation processing unit 18 (slab length calculation unit 34) calculates the length of the slab 12 based on the timing when the front end 12A of the slab 12 passes in front of the sensor 14 and the timing when the rear end 12B of the slab 12 passes in front of the sensor 14.

Specifically, the calculation processing unit 18 (slab length calculation unit 34) reads the first time and the second time stored in the memory 26, and calculates the length of the slab 12 by multiplying the difference between the first time corresponding to the timing when the front end 12A of the slab 12 passes in front of the sensor 14 and the second time corresponding to the timing when the rear end 12B of the slab 12 passes in front of the sensor 14 by the conveying speed of the slab 12.

The conveying speed of the slab 12 may be a preset value or may be a measured value measured using a measuring device. When the conveying speed of the slab 12 changes, the length of the slab 12 is calculated by integrating the speed history v(t) measured using a measuring device between the first time t1 and the second time t2 as shown in formula (A).

The measuring device 10 according to an embodiment of the present invention functions as a slab length measuring device, and in the manner described above, the front end 12A and rear end 12B of the slab 12 being transported are detected, and the length of the slab 12 is calculated based on the detection results.
Here, the length of the slab 12 is calculated using the times (first and second times) corresponding to the timing when the end of the slab 12 passes in front of the sensor 14, but the present invention is not limited to this method. For example, an encoder may be attached to the conveying line to grasp the position of the slab 12 from the movement of the conveying line, and the length of the slab 12 may be calculated by expressing the timing when the end of the slab 12 passes in front of the sensor 14 using the position of the slab 12 (e.g., the movement distance from the reference position). That is, the length of the slab 12 can be calculated from the difference between the first position corresponding to the timing when the front end 12A of the slab 12 passes in front of the sensor 14 and the second position corresponding to the timing when the rear end 12B of the slab 12 passes in front of the sensor 14.
In the above description, the measuring device 10 according to the embodiment of the present invention has been described as a slab length measuring device having a function of calculating the length of the slab 12, but the measuring device 10 according to the embodiment of the present invention can also function as an end detection device that detects the front end 12A or the rear end 12B of the slab 12, rather than as a slab length measuring device. In that case, this can be achieved by omitting the above-mentioned step S006.

(Example of a method for determining the above-mentioned predetermined timing)
Next, the method of determining the above-mentioned specified timing will be explained as first to fourth examples, taking as an example a method of determining the timing at which a signal strength that is half the signal strength of the reflected wave when the slab 12 is present in front of the sensor 14 and the signal strength of the reflected wave when the slab 12 is not present in front of the sensor 14 is obtained (i.e., the timing at which the absolute value of the slope of the signal strength of the reflected wave with respect to the change in time is maximum).

(First Example)
In the first example, the calculation processing unit 18 (slab end detection unit 32) determines the timing at which the above-mentioned 1/2 signal strength is obtained in the following manner.
First, the calculation processing unit 18 (slab end detection unit 32) reads out the detection data (data linking the signal strength of the reflected wave with the time during which the slab 12 was transported) stored in the memory 26.

Then, the calculation processing unit 18 (slab end detection unit 32) calculates the upper value S1 and the lower value S2 of the signal strength of the reflected wave based on the read detection data. The upper value S1 of the signal strength of the reflected wave is the signal strength when the signal strength of the reflected wave increases and becomes almost constant in response to the presence of the slab 12 in front of the sensor 14 (i.e., in front of the microwave transmission unit 20 or the microwave reception unit 22), and may be the average value of the signal strength in a predetermined period, or may be the maximum value of the signal strength of the reflected wave. Similarly, the lower value S2 of the signal strength of the reflected wave is the signal strength when the signal strength of the reflected wave becomes almost zero in response to the absence of the slab 12 in front of the sensor 14 (i.e., in front of the microwave transmission unit 20 or the microwave reception unit 22), and may be the average value of the signal strength in a predetermined period, or may be the minimum value or zero of the signal strength of the reflected wave.

Next, the calculation processing unit 18 (slab end detection unit 32) calculates an intermediate value ΔS _1/2 where the signal strength is half the value between the upper value S1 and the lower value S2 of the signal strength of the reflected wave. Then, the calculation processing unit 18 (slab end detection unit 32) determines the timing when the intermediate value ΔS 1/2 is obtained at the rising edge of the signal strength of the reflected wave (state B in FIG. 4) and the timing when the intermediate value ΔS _1/2 is obtained at the falling edge of the signal strength of the reflected wave (state E in FIG. 4) _.

The timing when the intermediate value ΔS _1/2 is obtained at the rising edge of the signal strength of the reflected wave corresponds to the timing when, when the front end 12A of the slab 12 passes in front of the sensor 14, a signal strength that is 1/2 between the signal strength of the reflected wave when the slab 12 is present in front of the microwave transmitting unit 20 or the microwave receiving unit 22 and the signal strength of the reflected wave when the slab 12 is not present in front of the microwave transmitting unit 20 or the microwave receiving unit 22 is obtained (the timing when the slope of the time change in the signal strength of the reflected wave is maximum), and corresponds to the timing when the front end 12A of the slab 12 passes in front of the microwave transmitting unit 20 or the microwave receiving unit 22.
Furthermore, the timing when the intermediate value ΔS1/2 is obtained at the falling edge of the signal strength of the reflected wave corresponds to the timing when, when the rear end 12B of the slab 12 passes in front of the sensor 14, a signal strength that is 1/2 between the signal strength of the reflected wave when the slab 12 is present in front of the microwave transmitting unit 20 or the microwave receiving unit 22 and the signal strength of the reflected wave when the slab 12 is not present in front of the microwave transmitting unit 20 or the microwave receiving unit 22 is obtained (the timing when the slope of the time change in the signal strength of the reflected wave is minimum), and corresponds to the timing when the rear end 12B of the slab 12 passes in front of the microwave transmitting unit 20 or the microwave receiving unit 22.

In the first example, the timing at which the signal strength of 1/2 as described above is obtained is determined in the above manner.

(Second Example)
In the second example, the calculation processing unit 18 (slab end detection unit 32) determines the timing at which the above-mentioned 1/2 signal strength is obtained in the following manner.
First, the calculation processing unit 18 (slab end detection unit 32) reads out the detection data (data linking the signal strength of the reflected wave with the time during which the slab 12 was transported) stored in the memory 26.

Then, the calculation processing unit 18 (slab end detection unit 32) approximates the rising edge (state B in FIG. 4) of the signal strength of the reflected wave obtained from before the front end 12A of the slab 12 passes in front of the sensor 14 to after the rear end 12B of the slab 12 passes in front of the sensor 14, including the upper value S1 and the lower value S2 of the signal strength, with the sigmoid function f(α) shown in formula (1) based on the read detection data. In addition, near the falling edge (state E in FIG. 4), the signal strength decreases with increasing time or position, so the falling edge (state E in FIG. 4) of the signal strength of the reflected wave, including the upper value S1 and the lower value S2 of the signal strength, is approximated with f(-α), which is the sigmoid function with the sign of α inverted, shown in formula (1).

Here, α is the time taken for the slab 12 to be transported (from an arbitrarily determined reference time) or the position x of the slab 12 in the transport direction (from an arbitrarily determined reference position), and a, b, and c are fitting coefficients.

Assuming the sigmoid function f(α) shown in the above formula (1) and fitting using the least squares method, the signal strength of the reflected wave is approximated by the sigmoid functions f(α) and f(-α) shown in the above formula (1) for each of the rising edge (state B in Figure 4) and falling edge (state E in Figure 4) of the signal strength of the reflected wave, and the fitting coefficients a, b, and c are obtained.
Here, based on the characteristics of the sigmoid functions f(α) and f(-α) themselves, the fitting coefficient c of the sigmoid functions f(α) and f(-α) obtained as a result of fitting can be regarded as a value of α corresponding to the intermediate value ΔS _1/2 , which is 1/2 of the value between the upper value S1 and the lower value S2 of the signal strength of the reflected wave.
Therefore, when α is the time taken to transport the slab 12, the value of c obtained by fitting is the value of the time during transportation, so by knowing the value of c, the timing at which the intermediate value ΔS _1/2 , which is half the value between the upper value S1 and the lower value S2 of the signal strength of the reflected wave, occurs can be known from the time information.
Furthermore, when α is the position x in the transport direction of the slab 12, the value of c obtained by fitting is a value indicating the position in the transport direction, so by knowing the value of c, the timing at which the intermediate value ΔS _1/2 , which is 1/2 the value between the upper value S1 and the lower value S2 of the signal strength of the reflected wave, occurs can be known from the position information.

In addition, the timing based on the value of c at the rising edge of the signal strength of the reflected wave corresponds to the timing when the front end 12A of the slab 12 passes in front of the sensor 14, at which a signal strength that is half the signal strength of the reflected wave when the slab 12 is present in front of the microwave transmitting unit 20 or the microwave receiving unit 22 and the signal strength of the reflected wave when the slab 12 is not present in front of the microwave transmitting unit 20 or the microwave receiving unit 22 is obtained (the timing at which the slope of the time change in the signal strength of the reflected wave is maximum), and corresponds to the timing when the front end 12A of the slab 12 passes in front of the microwave transmitting unit 20 or the microwave receiving unit 22.
Furthermore, the timing based on the value of c at the falling edge of the signal strength of the reflected wave corresponds to the timing when the rear end 12B of the slab 12 passes in front of the sensor 14, at which a signal strength that is 1/2 of the signal strength of the reflected wave when the slab 12 is present in front of the microwave transmitting unit 20 or the microwave receiving unit 22 and the signal strength of the reflected wave when the slab 12 is not present in front of the microwave transmitting unit 20 or the microwave receiving unit 22 is obtained (the timing at which the slope of the time change in the signal strength of the reflected wave is minimum), and corresponds to the timing when the rear end 12B of the slab 12 passes in front of the microwave transmitting unit 20 or the microwave receiving unit 22.

In the second example, the timing at which the signal strength of 1/2 as described above is obtained is determined in the above manner.

(Third Example)
In the third example, the calculation processing unit 18 (slab end detection unit 32) determines the timing at which the above-mentioned 1/2 signal strength is obtained in the following manner.
First, the calculation processing unit 18 (slab end detection unit 32) reads out the detection data (data linking the signal strength of the reflected wave with the time during which the slab 12 was transported) stored in the memory 26.

Then, the calculation processing unit 18 (slab end detection unit 32) approximates the rising edge (state B in FIG. 4) of the signal strength of the reflected wave obtained from before the front end 12A of the slab 12 passes in front of the sensor 14 to after the rear end 12B of the slab 12 passes in front of the sensor 14, including the upper value S1 and the lower value S2 of the signal strength, with the knife-edge diffraction model g(α) shown in formulas (2) to (4) based on the read detection data. In addition, near the falling edge (state E in FIG. 4), the signal strength decreases with increasing time or position, so the falling edge (state E in FIG. 4) of the signal strength of the reflected wave, including the upper value S1 and the lower value S2 of the signal strength, is approximated with the knife-edge diffraction model g(-α) shown in formulas (2) to (4).

Here, α is the time taken for the slab 12 to be transported (from an arbitrarily determined reference time) or the position x of the slab 12 in the transport direction (from an arbitrarily determined reference position), a and b are fitting coefficients, C(ν) is the Fresnel cosine integral function, and S(ν) is the Fresnel sine integral function.

The reason for approximating the signal strength of the reflected wave with the knife-edge diffraction models g(α) and g(-α) in this way is based on the idea that, if we assume that the slab 12 is a mirror that totally reflects microwaves, then the signal of the reflected wave reflected by the slab 12 is equivalent to the signal received by a receiver located on the opposite side of the slab 12 from the transmitter.

Figures 6 and 7 are diagrams explaining a model of knife-edge diffraction in the measurement device 10. Figure 6 is a diagram showing the state when the front end 12A of the slab 12 passes in front of the sensor 14, and Figure 7 is a diagram showing the state when the rear end 12B of the slab 12 passes in front of the sensor 14.

As shown in state A of FIG. 6, the state in which the slab 12 is not present in front of the sensor 14 before the front end 12A of the slab 12 passes in front of the sensor 14 is equivalent to the presence of a partition 42 between the transmitter 50 and the receiver 52 in the knife-edge diffraction model. As shown in state B of FIG. 6, the state in which the front end 12A of the slab 12 is passing in front of the sensor 14 is equivalent to the presence of an end 42A of the partition 42 between the transmitter 50 and the receiver 52 in the knife-edge diffraction model. As shown in state C of FIG. 6, the state in which the slab 12 is present in front of the sensor 14 after the front end 12A of the slab 12 has passed in front of the sensor 14 is equivalent to the absence of a partition 42 between the transmitter 50 and the receiver 52 in the knife-edge diffraction model.

Similarly, as shown in state D of FIG. 7, the state before the rear end 12B of the slab 12 passes in front of the sensor 14, and the state in which the slab 12 is in front of the sensor 14, is the same as the state in which there is no partition 42 between the transmitter 50 and the receiver 52 in the knife-edge diffraction model. As shown in state E of FIG. 7, the state in which the rear end 12B of the slab 12 is passing in front of the sensor 14 is the same as the end 42B of the partition 42 being between the transmitter 50 and the receiver 52 in the knife-edge diffraction model. As shown in state F of FIG. 7, the state after the rear end 12B of the slab 12 has passed in front of the sensor 14, and the state in which the slab 12 is not in front of the sensor 14 is the same as the state in which there is a partition 42 between the transmitter 50 and the receiver 52 in the knife-edge diffraction model.

As such, since a knife-edge diffraction model that represents the signal strength received by the receiver 52 when a partition 42 is between the transmitter 50 and the receiver 52 is publicly known, it is possible to use such a knife-edge diffraction model to approximate the signal strength of the reflected wave when the slab 12 passes in front of the sensor 14 with the knife-edge diffraction models g(α) and g(-α).

In other words, by assuming the knife-edge diffraction models g(α) and g(-α) shown in the above equations (2) to (4) and fitting using the least squares method, the signal intensity of the reflected wave is approximated by the knife-edge diffraction models g(α) and g(-α) shown in the above equations (2) to (4) for each of the rising edge (state B in Figure 4) and falling edge (state E in Figure 4) of the signal intensity of the reflected wave, and the fitting coefficients a and b are obtained.
Here, based on the characteristics of the knife-edge diffraction models g(α) and g(-α) themselves, the fitting coefficient b of the knife-edge diffraction models g(α) and g(-α) obtained as a result of fitting can be regarded as a value of α corresponding to the intermediate value ΔS _1/2 , which is 1/2 the value between the upper value S1 and the lower value S2 of the signal strength of the reflected wave.
Therefore, when α is the time taken to transport the slab 12, the value of b obtained by fitting is the value of the time during transportation, so by knowing the value of b, the timing at which the intermediate value ΔS _1/2 , which is 1/2 of the value between the upper value S1 and the lower value S2 of the signal strength of the reflected wave, occurs can be known from the time information.
Furthermore, when α is the position x in the transport direction of the slab 12, the value of b obtained by fitting is a value indicating the position in the transport direction, so by knowing the value of b, the timing at which the intermediate value ΔS _1/2 , which is 1/2 the value between the upper value S1 and the lower value S2 of the signal strength of the reflected wave, occurs can be known from the position information.

In addition, the timing based on the value of b at the rising edge of the signal strength of the reflected wave corresponds to the timing when the front end 12A of the slab 12 passes in front of the sensor 14, at which a signal strength that is half the signal strength of the reflected wave when the slab 12 is present in front of the microwave transmitting unit 20 or the microwave receiving unit 22 and the signal strength of the reflected wave when the slab 12 is not present in front of the microwave transmitting unit 20 or the microwave receiving unit 22 is obtained (the timing at which the slope of the time change in the signal strength of the reflected wave is maximum), and corresponds to the timing when the front end 12A of the slab 12 passes in front of the microwave transmitting unit 20 or the microwave receiving unit 22.
Furthermore, the timing based on the value of b at the falling edge of the signal intensity of the reflected wave corresponds to the timing when the rear end 12B of the slab 12 passes in front of the sensor 14, at which a signal intensity is obtained that is 1/2 the signal intensity of the reflected wave when the slab 12 is present in front of the microwave transmitting unit 20 or the microwave receiving unit 22, and the signal intensity of the reflected wave when the slab 12 is not present in front of the microwave transmitting unit 20 or the microwave receiving unit 22 (the timing at which the slope of the time change in the signal intensity of the reflected wave is minimum), and corresponds to the timing when the rear end 12B of the slab 12 passes in front of the microwave transmitting unit 20 or the microwave receiving unit 22.

In the third example, the timing at which the signal strength of 1/2 as described above is obtained is determined in the above manner.

(Fourth Example)
The fourth example is an example assuming a case where the slab 12 is transported in a tilted state with respect to the transport direction. Fig. 8 is a diagram showing a case where the slab 12 is transported in a tilted state with respect to the transport direction in the measuring device 10. The tilt angle θ is the tilt angle of the slab 12 with respect to the transport direction.
In this way, when the slab 12 is transported in a tilted state with respect to the transport direction, the distance from the microwave transmitter 20 and the microwave receiver 22 to the side surface 12C of the slab 12 changes from moment to moment, so it is not easy to obtain the upper value S1 and the lower value S2 of the signal strength of the reflected wave, and it is not easy to simply approximate it using the sigmoid functions f(α) and f(-α) or the knife-edge diffraction models g(α) and g(-α). Therefore, it is desirable to use a knife-edge diffraction model in which the change in the signal strength of the reflected wave is corrected according to the change in the distance.

Therefore, in the fourth example, the calculation processing unit 18 (slab end detection unit 32) determines the timing at which the above-mentioned 1/2 signal strength is obtained in the following manner.
First, the calculation processing unit 18 (slab end detection unit 32) reads out the detection data (data linking the signal strength of the reflected wave with the time during which the slab 12 was transported) stored in the memory 26.

Then, the calculation processing unit 18 (slab end detection unit 32) approximates the rising edge of the signal strength of the reflected wave (state B in FIG. 4), which includes the upper value S1 and the lower value S2 of the signal strength, with the knife-edge diffraction model h(α) shown in formulas (5) to (7) that takes into account the inclination of the slab 12 with respect to the conveying direction, for the signal strength of the reflected wave obtained from before the front end 12A of the slab 12 passes in front of the sensor 14 to after the rear end 12B of the slab 12 passes in front of the sensor 14, based on the read detection data. In addition, near the falling edge (state E in FIG. 4), the signal strength decreases with increasing time or position, so the falling edge of the signal strength of the reflected wave (state E in FIG. 4), which includes the upper value S1 and the lower value S2 of the signal strength, is approximated with h(-α), which is the inverted sign of α of the knife-edge diffraction model shown in formulas (5) to (7).

Here, α is the time taken for the slab 12 to be transported (from an arbitrarily determined reference time) or the position x of the slab 12 in the transport direction (from an arbitrarily determined reference position), r is the distance from the microwave transmitting unit 20 and the microwave receiving unit 22 to the side surface 12C of the slab 12 when the slab 12 is located in front of the sensor 14, a and b are fitting coefficients, C(ν) is the Fresnel cosine integral function, and S(ν) is the Fresnel sine integral function.

Assuming the knife-edge diffraction models h(α) and h(-α) shown in the above equations (5) to (7) and fitting by the least squares method, the signal intensity of the reflected wave is approximated by the knife-edge diffraction model h(α) shown in the above equations (5) to (7) for each of the rising edge (state B in Figure 4) and falling edge (state E in Figure 4) of the signal intensity of the reflected wave, and the fitting coefficients a and b are obtained.
Here, based on the characteristics of the knife-edge diffraction models h(α) and h(-α) that take into account the inclination of the slab 12 with respect to the conveying direction, the fitting coefficient b of the knife-edge diffraction models h(α) and h(-α) that take into account the inclination of the slab 12 with respect to the conveying direction obtained as a result of fitting can be deemed to be a value of α corresponding to the intermediate value ΔS _1/2 , which is 1/2 the value between the upper value S1 and the lower value S2 of the signal strength of the reflected wave.
Therefore, when α is the time taken to transport the slab 12, the value of b obtained by fitting is the value of the time during transportation, so by knowing the value of b, the timing at which the intermediate value ΔS _1/2 , which is 1/2 of the value between the upper value S1 and the lower value S2 of the signal strength of the reflected wave, occurs can be known from the time information.
Furthermore, when α is the position x in the transport direction of the slab 12, the value of b obtained by fitting is a value indicating the position in the transport direction, so by knowing the value of b, the timing at which the intermediate value ΔS _1/2 , which is 1/2 the value between the upper value S1 and the lower value S2 of the signal strength of the reflected wave, occurs can be known from the position information.
In addition, the timing based on the value of b at the rising edge of the signal strength of the reflected wave corresponds to the timing when the front end 12A of the slab 12 passes in front of the sensor 14, at which a signal strength that is half the signal strength of the reflected wave when the slab 12 is present in front of the microwave transmitting unit 20 or the microwave receiving unit 22 and the signal strength of the reflected wave when the slab 12 is not present in front of the microwave transmitting unit 20 or the microwave receiving unit 22 is obtained (the timing at which the slope of the time change in the signal strength of the reflected wave is maximum), and corresponds to the timing when the front end 12A of the slab 12 passes in front of the microwave transmitting unit 20 or the microwave receiving unit 22.
Furthermore, the timing based on the value of b at the falling edge of the signal intensity of the reflected wave corresponds to the timing when the rear end 12B of the slab 12 passes in front of the sensor 14, at which a signal intensity is obtained that is 1/2 the signal intensity of the reflected wave when the slab 12 is present in front of the microwave transmitting unit 20 or the microwave receiving unit 22, and the signal intensity of the reflected wave when the slab 12 is not present in front of the microwave transmitting unit 20 or the microwave receiving unit 22 (the timing at which the slope of the time change in the signal intensity of the reflected wave is minimum), and corresponds to the timing when the rear end 12B of the slab 12 passes in front of the microwave transmitting unit 20 or the microwave receiving unit 22.

In the fourth example, the timing at which the above-mentioned 1/2 signal strength is obtained is determined in the above manner.
When the slab 12 is transported at an angle to the transport direction, the signal strength of the reflected wave changes as the distance between the slab 12 and the sensor 14 changes over time, making it difficult to determine the upper value S1 and the lower value S2. However, by using the fourth example, it is possible to know the timing at which 1/2 of the signal strength is obtained, even if the signal strength value is inclined relative to the position.

(Explanation of the Effects of the Invention)
Next, the operation and effects of the embodiment of the present invention will be described.

As described above in detail, in an embodiment of the present invention, microwaves are used to detect the front end 12A and rear end 12B of the slab 12 being transported. Therefore, the front end 12A and rear end 12B of the slab 12 being transported can be detected while suppressing the effects of raindrops, dust, and darkness. Furthermore, even if the area around the slab 12 is dark and unlit, the front end 12A and rear end 12B of the slab 12 being transported can be detected.

Moreover, the timing when the front end 12A of the slab 12 passes in front of the sensor 14 and the timing when the rear end 12B of the slab 12 passes in front of the sensor 14 are determined to correspond to a predetermined signal strength between the signal strength of the reflected wave when the slab 12 is in front of the sensor 14 and the signal strength of the reflected wave when the slab 12 is not in front of the sensor 14, respectively. Therefore, even when microwaves are used, the front end 12A and rear end 12B of the slab 12 being transported can be detected with high accuracy.

In addition, since the front end 12A and rear end 12B of the slab 12 being transported can be detected with high accuracy, the length of the slab 12 can be measured with high accuracy based on the detection results of the front end 12A and rear end 12B of the slab 12.

According to the first example described above, the upper value S1 and the lower value S2 of the signal strength of the reflected wave are calculated, and the predetermined timing is determined based on the timing at which the intermediate value ΔS _1/2 is obtained at the rising edge of the signal strength of the reflected wave and the timing at which the intermediate value ΔS _1/2 is obtained at the falling edge of the signal strength of the reflected wave. Therefore, the predetermined timing can be detected with high accuracy.

Furthermore, according to the second example described above, the signal strength of the reflected wave is approximated by the sigmoid functions f(α) and f(-α) shown in formula (1), and the above-mentioned predetermined timing is determined based on the value of c in these sigmoid functions f(α) and f(-α). Therefore, the above-mentioned predetermined timing can be detected with high accuracy.

Furthermore, according to the third example described above, the signal strength of the reflected wave is approximated by the knife-edge diffraction models g(α) and g(-α) shown in equations (2) to (4), and the above-mentioned predetermined timing is determined based on the value of b in these knife-edge diffraction models g(α) and g(-α). Therefore, the above-mentioned predetermined timing can be detected with high accuracy.

Furthermore, according to the fourth example described above, the signal strength of the reflected wave is approximated by the knife-edge diffraction models h(α) and h(-α) shown in equations (5) to (7), which take into account the inclination of the slab 12 with respect to the conveying direction, and the above-mentioned predetermined timing is determined based on the value of b in these knife-edge diffraction models h(α) and h(-α). Therefore, even if the slab 12 is conveyed in a state where it is inclined with respect to the conveying direction, the above-mentioned predetermined timing can be detected with high accuracy.

Next, we will explain some variations of the embodiment of the present invention.

In the above embodiment, the front end 12A and rear end 12B of the slab 12 are detected for the purpose of calculating the length of the slab 12, but the front end 12A and rear end 12B of the slab 12 may also be detected for purposes other than calculating the length of the slab 12.

In addition, in the above embodiment, both the front end 12A and the rear end 12B of the slab 12 are detected, but only one of the front end 12A and the rear end 12B of the slab 12 may be detected.

(Example)
Next, an embodiment will be described.

In Examples 1 to 4 described below, a sensor was placed on the side of a metal rectangular parallelepiped that was treated as a slab. The sensor used was capable of transmitting and receiving microwaves with a frequency of 79 GHz. The metal rectangular parallelepiped was then transported with its longitudinal direction parallel to the transport direction in a plan view, and microwaves were transmitted along a direction perpendicular to the transport direction of the metal rectangular parallelepiped in a plan view, while the signal strength of the reflected waves received by the sensor was measured.

Figures 9 to 12 are graphs showing the signal strength of the reflected wave obtained in Examples 1 to 4. In Figures 9 to 12, the vertical axis shows the signal strength of the reflected wave, and the horizontal axis shows the position of the front end of the metal rectangular parallelepiped. The dimension of the vertical axis in Figures 9 to 12 is the electric field strength of the reflected wave, and its magnitude is expressed in arbitrary units (au) proportional to the electric field strength.
The position of the front end of the metal rectangular parallelepiped is based on the central axis of the sensor. In other words, the position of the front end of the metal rectangular parallelepiped when it is located in front of the sensor (on the central axis of the sensor) is set to 0 m.

Example 1
Example 1 corresponds to a first example of the method for determining the predetermined timing described above. Fig. 9 is a graph showing the signal strength of the reflected wave obtained in Example 1. Graph G1 in Fig. 9 shows the signal strength of the reflected wave measured in Example 1.

In this Example 1, when the front end of the metal rectangular parallelepiped is located at -0.2 m, the metal rectangular parallelepiped is located in front of the sensor, and the signal strength of the reflected wave is 831.8 a.u. On the other hand, when the front end of the metal rectangular parallelepiped is located at +0.2 mm, the metal rectangular parallelepiped is not located in front of the sensor, and the signal strength of the reflected wave is 18.2 a.u.

If the upper value S1 of the signal strength of the reflected wave is set to 831.8 a.u. and the lower value S2 of the signal strength of the reflected wave is set to 18.2 a.u., and the intermediate value ΔS _1/2 , which is half the value between the upper value S1 and the lower value S2 of the signal strength of the reflected wave, is calculated, the intermediate value ΔS _1/2 is 406.8 a.u. The position of the front end of the metal rectangular parallelepiped when the intermediate value ΔS _1/2 is 406.8 a.u. In this way, in Example 1, the position of the front end of the metal rectangular parallelepiped could be detected with an accuracy of several mm.

Example 2
Example 2 corresponds to a second example of the method for determining the above-mentioned predetermined timing. FIG. 10 is a graph showing a comparison of the signal strength of the reflected wave obtained in Example 1 and Example 2. In FIG. 10, graph G1 shows the signal strength of the reflected wave measured in Example 1, and graph G2 shows the value of the signal strength of the reflected wave measured in Example 1 approximated by the formula f(-α) in which the sign of α of the sigmoid function f(α) shown in the above formula (1) is determined. That is, the sigmoid function f(-α) shown in the above formula (1) was assumed, and the coefficients a, b, and c were fitted by the least squares method to approximate the signal strength of the reflected wave measured in Example 1 by the sigmoid function f(-α) shown in the above formula (1). For α, the position x (mm) in the conveying direction of the slab 12 was used.

When the value of the fitting coefficient c was calculated for the sigmoid function f(-α) shown in the above formula (1), it was found to be 1.57 mm. Thus, in Example 2, the position of the front end of the metal rectangular parallelepiped could be detected with an accuracy of a few mm.

Example 3
Example 3 corresponds to a third example of the method for determining the above-mentioned predetermined timing. FIG. 11 is a graph showing a comparison of the signal strength of the reflected wave obtained in Example 1 and Example 3. In FIG. 11, graph G1 shows the signal strength of the reflected wave measured in Example 1, and graph G3 shows the value of approximating the signal strength of the reflected wave measured in Example 1 with the equation g(-α) in which the sign of α in the knife-edge diffraction model g(α) shown in the above equations (2) to (4) was determined. That is, the knife-edge diffraction model g(-α) shown in the above equations (2) to (4) was assumed, and the coefficients a and b were fitted by the least squares method to approximate the signal strength of the reflected wave measured in Example 1 with the knife-edge diffraction model g(-α) shown in the above equations (2) to (4). For α, the position x (mm) in the conveying direction of the slab 12 was used.

When the fitting coefficient b was calculated for the knife-edge diffraction model g (-α) shown in the above formulas (2) to (4), it was found to be -0.97 mm. Thus, in Example 3, the position of the front end of the metal rectangular parallelepiped could be detected with an accuracy of a few mm.

Example 4
Example 4 corresponds to a fourth example of the method for determining the above-mentioned predetermined timing. FIG. 12 is a graph showing a comparison of the signal strength of the reflected wave obtained in Example 1 and Example 4. In FIG. 12, graph G1 shows the signal strength of the reflected wave measured in Example 1, and graph G4 shows the value of the signal strength of the reflected wave measured in Example 1 approximated by the equation h(-α) in which the sign of α in the knife-edge diffraction model h(α) shown in the above equations (5) to (7) was determined. That is, the knife-edge diffraction model h(-α) shown in the above equations (5) to (7) was assumed, and the coefficients a and b were fitted by the least squares method to approximate the signal strength of the reflected wave measured in Example 1 to the knife-edge diffraction model h(-α) shown in the above equations (5) to (7). For α, the position x (mm) in the conveying direction of the slab 12 was used.

In the knife-edge diffraction model h(-α) shown in the above formulas (5) to (7), the value of coefficient b indicates the position where half the maximum value of the signal strength of the reflected wave is obtained, and this position was calculated to be 0.52 mm. The inclination angle of the metal rectangular parallelepiped with respect to the conveying direction was calculated to be 4.5°. Thus, in Example 4, even when the metal rectangular parallelepiped was conveyed in a tilted state with respect to the conveying direction, the position of the front end of the metal rectangular parallelepiped could be detected with an accuracy of a few mm.

The above describes one example of the present invention, but the present invention is not limited to the above, and can of course be modified in various ways without departing from the spirit of the invention.

10 Measuring device 12 Slab 12A Front end (an example of an end of a slab)
12B Rear end (an example of the end of a slab)
12C Side surface 14 Sensor 16 Transmitter/receiver circuit 18 Arithmetic processing unit 20 Microwave transmitter 22 Microwave receiver 24 Processor 26 Memory 28 Program 30 Transmitter/receiver control unit 32 Slab end detector 34 Slab length calculator

Claims (7)

In an edge detection device for detecting the edge of a conveyed slab,
a microwave transmitting unit disposed on a side of the slab and transmitting microwaves to the slab;
a microwave receiving unit arranged next to the microwave transmitting unit and receiving the microwave reflected from a side surface of the slab;
a calculation processing unit that detects an end of the slab based on a timing when the end of the slab passes in front of the microwave transmitting unit or the microwave receiving unit;
having
The arithmetic processing unit is
An end detection device that determines a predetermined timing corresponding to a predetermined signal strength between the signal strength of the reflected wave when the slab is present in front of the microwave transmitting unit or the microwave receiving unit and the signal strength of the reflected wave when the slab is not present in front of the microwave transmitting unit or the microwave receiving unit as the timing when the end of the slab passes in front of the microwave transmitting unit or the microwave receiving unit. A slab length measuring device that calculates the length of the slab from the front end and rear end of the slab detected using the end detection device described in claim 1. An edge detection method for detecting an edge of a transported slab, comprising:
a microwave transmitting step of transmitting microwaves to the slab using a microwave transmitting unit arranged on a side of the slab;
a microwave transmitting/receiving step of receiving the microwave reflected from a side surface of the slab using a microwave receiving unit arranged alongside the microwave transmitting unit;
a calculation processing step of detecting the end of the slab based on the timing when the end of the slab passes in front of the microwave transmitting unit or the microwave receiving unit;
having
The arithmetic processing step includes:
An end detection method in which a predetermined timing corresponding to a predetermined signal strength between the signal strength of the reflected wave when the slab is present in front of the microwave transmitting unit or the microwave receiving unit and the signal strength of the reflected wave when the slab is not present in front of the microwave transmitting unit or the microwave receiving unit is determined to be the timing when the end of the slab passes in front of the microwave transmitting unit or the microwave receiving unit. The arithmetic processing step includes:
The signal strength of the reflected wave is approximated by a sigmoid function f(α) shown in Equation (1),
4. The edge detection method according to claim 3, wherein the predetermined timing is determined based on a value of c in the approximated sigmoid function f(α).
Here, α is the time t taken for the slab to be transported or the position x of the slab in the transport direction, and a, b, and c are fitting coefficients.
The arithmetic processing step includes:
The signal intensity of the reflected wave is approximated by a knife-edge diffraction model g(α) shown in Equations (2) to (4),
4. The edge detection method according to claim 3, further comprising determining the predetermined timing based on a value of b in the approximated knife-edge diffraction model g(α).
Here, α is the time t taken to transport the slab or the position x of the slab in the transport direction, a and b are fitting coefficients, C(ν) is the Fresnel cosine integral function, and S(ν) is the Fresnel sine integral function.
The arithmetic processing step includes:
The signal intensity of the reflected wave is approximated by a knife-edge diffraction model h(α) shown in Equations (5) to (7), taking into account the inclination of the slab with respect to the conveying direction,
The edge detection method according to claim 3 , further comprising determining the predetermined timing based on a value of b in the approximated knife-edge diffraction model h(α).
Here, α is the time t taken to transport the slab or the position x of the slab in the transport direction, r is the distance from the microwave transmitting unit and the microwave receiving unit to the side of the slab when the slab is located in front of the microwave transmitting unit or the microwave receiving unit, a and b are fitting coefficients, C(ν) is the Fresnel cosine integral function, and S(ν) is the Fresnel sine integral function.
A slab length measurement method that calculates the length of the slab from the front end and rear end of the slab detected using the end detection method described in any one of claims 3 to 6.