JPS6250773B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inspection device for a tubular object, and more particularly to a configuration and control method of an inspection device suitable for remotely and automatically visually inspecting a tubular object surface.

Generally, large-scale plants, such as liquid storage tanks and nuclear reactors, have various types of piping installed inside them. Periodic inspections are carried out to ensure the safety of such plants, and in this case, it is desirable for operators to be able to inspect the various pipings described above automatically and quickly from a safe remote location.

FIG. 1 shows a schematic structure of a nuclear reactor, which is one of the objects of inspection of the present invention. 1 is the reactor, 2 (2
-a to 2-f) are various types of piping installed around the reactor 1. At the time of inspection, after some of the structures inside the furnace are removed, a pedestal 5 is installed on the top of the furnace, and a transport device 6 is attached to this.

The transport device 6 carries an inspection device 10 and moves it to the front of each pipe, after which the inspection device performs a predetermined inspection work. In the case of nuclear reactors, there are several types of inspections, one of which is visual inspection. In this case it was attached to 10
The video signal from the TV camera is transmitted to a TV monitor 8 located at a remote point, and is observed by an operator 9. On the other hand, the transport device 6 and the inspection device 10 are also controlled by a control device 7 located at a remote point.

A problem when visually inspecting such a large plant is that there are many types of piping to be inspected. In other words, there are pipes with different diameters as shown in Figure 2 a and b, and pipes with other structures 3 installed inside the pipe as shown in c, and in the latter case, the structure that becomes an obstacle It is necessary to perform visual inspection under conditions that avoid.

In order to deal with such problems, conventional methods have been to design inspection devices according to the structure to be inspected and replace them as necessary, or to mount multiple types of inspection devices together on a transport device. However, different methods have been devised depending on the inspection target. However, the former method increases inspection work time, while the latter method inevitably increases the size of the device.

The present invention was made to solve these conventional problems, and an object of the present invention is to provide an inspection device that can visually inspect many types of piping with one device.

Another object of the present invention is to provide an apparatus that can perform such visual inspection on many types of piping in a non-contact manner.

Still another important object of the present invention is to provide a device that allows accurate visual inspection even if the setting of the inspection device on the front surface of the pipe by the transportation device deviates from a predetermined position.

Hereinafter, the content of the present invention will be explained with reference to the drawings. First, FIG. 3 shows the mechanical configuration of the inspection device of the present invention, which is suitable for visual inspection of many types of piping. In the figure, 2 is the pipe to be inspected, and 6-a is the end of the conveying means 6 on which the inspection mechanism 10 is mounted and is roughly set at the front position of the pipe, which is outside the scope of the present invention. be. This inspection mechanism has the following five degrees of freedom as shown by the thick arrows, with the purpose of inspecting the inner surfaces of many types of tubes with different diameters. First, the delivery shaft 15 that moves the inspection head along the pipe axis direction, and the swing shaft 1 that changes the inclination angle of the part that includes the shafts 14, 14 and 15 that rotate it.
3. A shaft 12 for expanding and contracting the above parts, and a shaft 11 for rotating the whole above. However, some of these operating axes may be omitted depending on the type of pipe to be processed and work conditions. On the other hand, the inspection head 20 at the tip includes an imaging optical system 21 that illuminates the target surface and inputs the image, and a proximity sensor 22 that detects the relative distance between the inspection head and the target surface.
-a and 22-b are arranged. Input from the video optical system is sent to ITV2 via the image guide.
7, and is further provided as video information to an operator monitoring a TV monitor located at a remote point, that is, 9 in FIG. flexible cable 25
In addition to the image guide for this purpose, there is a light source device 2.
It has a built-in light guide etc. that sends the illumination light from 6 to the inspection head.

The fact that such a configuration is suitable for visual inspection of many types of piping will be explained using FIG. 2 again.

FIG. 2a shows inspection information for the large diameter pipe 2-a. In this case, the scanning of the inspection head 20 in the circumferential direction can be carried out by means of the pivot shaft 11 and the scanning in the axial direction by means of the delivery shaft 15. At this time, if the central axis of the piping indicated by the dashed line Z ₁ ,
If the reference axis of the inspection device shown by the two-dot chain line Z ₂ does not coincide, the relative distance between the inspection head and the target surface can be made constant by controlling the telescopic shaft 12. Further, if the relative angle between the inspection head and the target surface deviates from a predetermined angle due to the above-mentioned mismatch, correction using the rotating shaft 14 is also possible.

Next, FIG. 2b shows the inspection situation for the small diameter pipe 2-b. In this case, scanning in the circumferential direction is performed by the rotating shaft 14, unlike in case a,
Control to maintain a constant relative distance between the object surface and the inspection head is performed by a combined operation of the rotation axes 11 and 12, which extend and retract.

Further, c in FIG. 2 shows the inspection status of the pipe 2-c in which the cylindrical structure 3 is installed. In this case, the usage conditions for each shaft are basically the same as in case a, but since the delivery shaft 15 is arranged at the most extreme end of the mechanism, it can be avoided from the structural protrusion 3-a. Inspection operations can be performed under specified conditions. Furthermore, by designing the delivery shaft moving part on which the inspection head is attached to be thin, the inspection head can be inserted into the narrow gap formed between the structure 3 and the pipe 2.

On the other hand, in any of the cases shown in Fig. 2, when a relative inclination occurs between the central axis Z ₁ of the piping and the reference axis Z ₂ of the inspection device, the swing axis 13 shown in Fig. 3 is controlled. This can be corrected by doing this.

As described above, the feature of the inspection mechanism according to the present invention is that a linear telescopic shaft 1 is provided next to the rotation shaft 11.
A rotating shaft 14 rotating around an axis perpendicular to the rotating shaft 14 and a delivery shaft 15 linearly moving in a direction parallel to the central axis of the rotating shaft 14 are arranged next to the rotating shaft 14, and an inspection head 20 is placed at the tip of the rotating shaft 14. By arranging it, you can inspect not only many types of pipes with different diameters, but also objects with structures inside the pipes.

FIG. 4 shows an embodiment of a control circuit for scanning the inspection head along the inner surface of a pipe using the visual inspection mechanism described above.

In FIG. 4, 10 is an inspection mechanism section, in which 41 (41-a to 41-e) is indicated by a broken line.
is a part for driving each of the axes, and is composed of, for example, a DC servo motor 42, a reduction gear 43, and a potentiometer 44 as a position detector. Actually, there are five systems of drive units corresponding to the movements of the five types of operating axes shown in FIG. 3, but for the sake of simplicity, the signal connection 41-a is shown as a representative example. In addition to this, the inspection mechanism includes a proximity sensor 22,
A contact sensor 47, a limit switch 48, etc. are arranged. Among these, the contact sensor 47 is, for example, the device protection cover 16-a shown in FIG.
Alternatively, it is attached to the inspection mechanism 16-b, etc., and generates a signal when the inspection mechanism comes into contact with the target surface due to some kind of malfunction. A limit switch 48 also generates a signal when the drive has moved to the limit of its operating range. Although one proximity sensor, contact sensor, or limit switch is shown in the figure for simplicity, in reality, a large number of them may be arranged as required.

In this way, as shown in FIG. 1, the inspection mechanism section 10 is controlled by the control device 7 which is located at a point quite remote from the inspection position. However, if a method is adopted in which the output signals from the large number of potentiometers, limit switches, or sensors mentioned above are directly transmitted to a remote point, the connecting cable will become extremely large. Therefore, it is desirable to parallel-serial convert these outputs and transmit them through a small number of transmission lines. For this purpose, a preprocessing circuit section, shown at 30 in FIG. 3 or 4, is located near the inspection mechanism.

In the case of the embodiment shown in FIG. 4, two transmission circuits are arranged in the preprocessing circuit section 30.
First, in the case of a signal whose output level fluctuates depending on the situation, such as a potentiometer or proximity sensor,
A multiplexer 31, a DA converter 32, and a transmission output circuit 33 are used to serially transmit the signal in the form of a digital signal. In addition, the connected sensor 47 and limit switch 4, which originally generate on/off signal output,
8, serial transmission is performed using the multiplexer 34 and the transmission output circuit 35. In this way,
A large number of signal outputs can be transmitted to the control device using only two transmission lines.

On the other hand, the control circuit 50 and microcomputer 70 shown in FIG. 4 constitute a part of the control device 7 described above, and share the control of the inspection mechanism section 10. Of these, the control circuit 50 is divided into a receiving circuit system that divides the serial signals serially transmitted from the preprocessing circuit 30 again in parallel, and a servo circuit system that controls the DC servo motor of the mechanical section. The servo circuit 51 has five systems, 51-a to 51-e, as indicated by broken lines, but for simplicity, only the signal connection for 51-a is shown. Among these, the receiving circuit system includes a circuit 61 for receiving a signal from the transmission output circuit 33 and decoding it into a parallel signal, and a circuit 62 for receiving a signal from the transmission circuit 35 and decoding it into a parallel signal.
There is. Of the outputs of circuit 61, the potentiometer signal is transferred to register 55 in the servo circuit, and the signal from the proximity signal is transferred to register 63. On the other hand, the output of 62, ie, the signal from the contact sensor or limit switch, is transferred to register 64 (only one is shown for simplicity).
Each of these registers is
0 signal bus line 77 and used for various control processing as described later.

By the way, the servo circuit 51-a is configured as follows. First, there is a register 52 that receives a movement command value from the microcomputer 70, which is turned into an analog signal by the DA converter 53 and drives the DC servo motor of the mechanical section via the servo amplifier 54. The output signal of the potentiometer indicating the movement of the motor is transmitted to the register 55 as described above, and this output is fed back to the comparator circuit 57 via the DA converter 56.

The microcomputer 70 includes a processor 71,
In addition to RAM 72, ROM 73, and an arithmetic unit 74, it also includes an interface circuit 75 for enabling connection with a separate control circuit 80 for controlling the transport device 6 and others. As described later, this microcomputer controls the sequence of inspection operations, stores the measurement results of the relative positional relationship between the inspection device and the piping to be inspected, and performs arithmetic processing such as the inspection operation angle based on this. do.

When visually inspecting the inner surface of piping automatically using an inspection device having the mechanism and control circuit as described above, the following points are particularly important.

(1) Be able to accurately know the inspection location.

When visually inspecting piping in a large plant, it is not enough to simply find dirt or damage on the target surface; it is also necessary to know its location accurately. Because after inspection,
This is because there are cases where the location where stains, etc. are found is repaired using other equipment, and there are also cases where it is necessary to grasp the progress status of stains, etc. during inspection after a certain period of time. For example, consider the case where the visual inspection head 20 has a rectangular field of constant dimensions. When scanning the inspection head along the inner surface of a cylindrical object under these conditions, as shown by the broken line in Figure 5, a mesh-shaped position (hereinafter referred to as an address) corresponding to the size of the field of view is created. It is necessary for the inspection head to move sequentially while responding to the Such a mesh must be formed using the cylindrical pipe itself as a reference, and conversely, if a predetermined address is specified, the inspection head must be positioned at the center of the mesh corresponding to this address. No.

(2) The inspection operation must be performed while the facing distance and facing angle between the inspection target and the inspection head are kept approximately constant.

If the distance between the inspection head and the target surface changes, the dimensions of the target stain etc. will naturally appear different on the TV monitor being monitored by the operator.
It is also clear that a change in the opposing angle causes similar image distortion.

The important conditions required for accurate visual inspection have been described above, but it is extremely difficult to satisfy these conditions when inspecting a large plant or the like. Firstly, the position of the piping itself is inaccurate, and secondly, since the conveying means 6 for setting this mechanical device on the front surface of the pipe body is extremely large, there is a limit to its positioning ability. Therefore, the visual inspection mechanism requires a function to correct relative setting errors caused by these.

In order to realize such a correction function, the apparatus of the present invention uses the proximity sensor 22 attached to the inspection head, but in the present invention, a small number of proximity sensors can be used by using the target surface measurement calculation process as described below. It achieves position correction and has extremely high practical value. The contents will be explained below.

First, the method of arranging the proximity sensor will be described.
If the inspection head 20 is connected to a pipe and scans the target surface at regular intervals, two proximity sensors are basically required. That is, when the inspection head 20 is in the state shown in FIG. 6, there is a sensor that measures the distance on the wall surface around the pipe in the direction of the dashed line arrow, and when the inspection head 20 is in the state shown in FIG. 6, there is a sensor that measures the distance in the direction of the dashed line. However, if a diagonal proximity sensor is placed at the tip of the inspection head as shown by the broken line in Fig. 7, it becomes possible to measure distances in the two directions mentioned above with one sensor. As shown in Fig. 7, it is also possible to measure the distance to a corner section moving from the wall surface to the inner surface. In the configuration shown in FIG. 3, in addition to the proximity sensor 22-a having such a function, a proximity sensor 22-b for detecting the inner surface of the pipe is arranged. Detection of relative tilt is now possible.

Next, a control procedure for a visual inspection operation using a target surface measurement using the proximity sensor arranged in this manner and calculation results based thereon will be described.

FIG. 8 shows the basic contents of the inspection operation control. First, the inspection device 10 is set at the front position of the pipe to be inspected by the transport device (block a1).
At this time, the inspection head 20 in FIG. 1 is in a retracted state inside the protective cover 16-a.

Next, we move on to the measurement operation of the target position, the contents of which are as follows. First, move the delivery shaft 15 of the mechanism forward to bring the inspection head closer to the wall surrounding the pipe.
Checking the wall position using a proximity sensor (Blog a2)
This is the state shown in FIG. 6 or 7, and means that the origin position of the piping in the Z direction has been measured. As a result, in the mesh shown in FIG. 5, the positions of the delivery shafts corresponding to the addresses 101-a, 102-a, etc. in the Z direction can be defined.

In such a measurement operation, if the target wall surface position is abnormally far away, it is determined that inspection is impossible, but if it is almost normal, a pipe inner surface position measurement operation is performed next (block a3). That is, as shown in Fig. 7, the delivery shaft is further advanced along the corner or by moving the inspection head close to the axis of the target piping using the telescopic shaft 12 of the mechanical section.
Insert the inspection head into the pipe. Thereafter, in the state shown in FIG. 6 or 7, the inspection head is brought close to a certain distance from the inner surface of the cylinder, and the inspection head is moved circumferentially while maintaining this distance. At this time, the central axis position Z ₁ of the pipe can be determined from the rotation angle of the pivot shaft 11 and the movement position of the telescopic shaft 12. In other words, the origin of the pipe in the x and y directions has been measured. As a result, the fifth
In the mesh shown in the figure, address 10 in the θ direction
The angular position of the rotation axis corresponding to 0-a, 100-b, etc. and the position of the telescopic axis required for inspection of each address can be defined. If the circumference measurement reveals that the relative positional deviation of the piping is abnormally large, it is determined that inspection is impossible and a correction of the position of the transport device is requested.

If it is determined that inspection is possible, indexing is performed by calculation of the operating position necessary for accurate automatic inspection of the mesh-like address shown in Figure 5 (block a).
4) Based on this, accurately inspect the target surface divided into mesh shapes (block a5) Here, the contents of the indexing of the operating position performed in block a4 will be further explained with reference to FIG. do. In FIG. 9, 2 indicates the inner surface position of the pipe to be inspected, and 90 indicates the movement position of the inspection head 20 during circumferential inspection. For simplicity, let's consider a case where the mesh is divided into 8 addresses in the circumferential direction. At this time, the center of the rotation axis of the inspection device is the center of the pipe.
If it matches P ₀ , when moving the inspection head from M ₁ → M ₂ → M ₃ corresponding to 8 addresses, the rotation axis 1
1 is a constant angle θ ₀ (45° in this case), and the telescopic shaft 12 only needs to move while maintaining a constant position r ₀ . However, if the center of the rotation axis is set to the position P ₁ due to a shift in the stop position of the transport device, the changes from M ₁ to M ₂ and M ₃
For the transition to , the rotation axes must be changed to θ ₂ and θ ₃ , and the expansion and contraction axes must be changed to r ₂ and r ₃ . According to the device of the present invention, the operating position of the rotation axis or the telescopic axis corresponding to each address can be calculated based on the positional deviations a and b of P ₁ with respect to P ₀ . and the size of b is
It can be calculated from the circumference measurement results mentioned above. Note that it is not always necessary to measure the circumference over the entire circumference of the cylindrical cross section. In addition, when a structure is installed inside the pipe and the positional relationship between this and the pipe is determined, measuring the surrounding position of this structure may be used as a substitute for circumference measurement. . Further, such a circumference measurement operation does not necessarily need to be performed under the condition that the proximity sensor is at a constant distance from the target surface. That is, a method may be used in which the rotation axis is rotated while the telescopic axis is kept constant, and the relationship between this rotation angle and the distance information of the proximity sensor is determined.

By the way, when the positional deviation of P ₁ with respect to P ₀ is large, the rotation axis 11 and the telescopic axis 1 explained in FIG.
Accurate visual inspection cannot be performed only by the correction operation according to 2. That is, as shown in FIG. 10, the viewing direction angle of the inspection head is φ with respect to the target mesh.
₂ , _φ3 . Therefore, in order to calculate this deviation angle and direct the viewing direction angle to the center position of the mesh, the device of the present invention uses a third
A rotating shaft 14 shown in the mechanism section of the figure is used.

As described above, in the inspection device according to the present invention, prior to the automatic inspection operation, the position of the pipe to be inspected is measured in advance by the proximity sensor, and based on this, it is determined whether or not to perform the inspection operation. If practicable, the operating position of each operating axis can be calculated to enable accurate automatic inspection along a mesh-like address with piping as a reference. As a result, automatic post-inspection can be carried out quickly, and even if a manual operation by an operator temporarily intervenes during automatic inspection, it is possible to accurately return the inspection head to the required address. Of course, it is also possible to feed back the output of the proximity sensor during the automatic inspection process to compensate for the lack of calculation accuracy, or to correct the index position of each axis that has already been calculated and stored, as necessary. be.

On the other hand, as mentioned in the explanation using Figure 2,
Under conditions where the relative inclination between the axis Z ₁ of the piping and the reference axis Z ₂ (for example, the rotation axis) of the inspection mechanism cannot be ignored, it is sufficient to perform a correction operation using the swing axis 13.
The correction angle required for this is the difference in the output of two proximity sensors that measure the inner surface of the pipe during circumference measurement, or if only one proximity sensor is used, two circumference measurements with different positions of the delivery axis. can be derived from the results.

In the above explanation, the content of the present invention was mainly explained for inspection of the inner surface of piping with a circular cross section. The principles of the present invention can also be applied to.

As described above, according to the present invention, it is possible to perform a fast and accurate visual inspection operation using a relatively small number of proximity sensors, and the industrial value of the present invention is extremely high.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of a plant to be inspected by the device of the present invention, Fig. 2 is a diagram showing examples of various piping structures in the plant and their inspection operation states, and Fig.
The figure shows an embodiment of the inspection device according to the present invention.
FIG. 4 is a diagram showing an example of a control circuit for controlling the inspection device, and FIG. 5 is a diagram showing an example of mesh-like address settings set on the cylindrical surface of the pipe to be inspected. , FIGS. 6 and 7 are diagrams showing examples of the arrangement of proximity sensors necessary for controlling inspection operations,
FIG. 8 is a diagram showing the basic procedure of the inspection operation according to the present invention, and FIGS. 9 and 10 respectively,
FIG. 3 illustrates a method of motion modification necessary to perform positionally accurate visual inspection. In FIG. 1, 1 is a nuclear reactor, 6 is a transport device, 10 is an operating mechanism of an inspection device according to the present invention,
7 is a control device, 8 is a monitor TV, 2-a to 2-f
indicates a tubular object to be inspected.

Claims (1)

[Scope of Claims] 1. An inspection head section for inputting an image of a predetermined area of the inner surface of a tubular object to be inspected; at least one provided in the head part
a positioning mechanism for moving the inspection head, an elongated first operating axis movable and rotatable in the direction of the central axis of the tubular object; a second operating axis that moves in a direction perpendicular to the central axis; and a third operating axis that is orthogonal to the second operating axis and rotates the second operating axis, the first operating axis In an inspection device for a tubular object, the inspection head portion is located at the tip of a tubular object, and a control device that controls the positioning mechanism, the control device controlling the relative distance obtained by the proximity sensor, and the respective operations. The amount of relative positional deviation between the central axis of the tubular object and the central axis of the third motion axis is calculated based on the position of the axis, and based on the calculated relative positional deviation amount, the position of the tubular object is A motion amount for moving the inspection head part to a position a predetermined distance away from the inner surface of the tubular object is determined so as to input images of arbitrarily different predetermined areas on the inner surface of the object, and the positioning mechanism is determined based on the determined motion amount. An inspection device for a tubular object, characterized in that it controls. 2. The apparatus for inspecting a tubular object according to claim 1, wherein at least one of the proximity sensors is oriented obliquely forward and is provided to detect a relative distance to the object in this direction.