Positioning method for underwater robot in reactor pressure vessel

Abstract

The invention discloses a positioning method for an underwater robot in a reactor pressure vessel, positioning is carried out based on a positioning device, and the positioning device comprises a support, a target light source, a shooting module and a laser ranging module; the target light source and the laser ranging module are arranged on the underwater robot through a support, and the shooting module is arranged above a reactor pressure vessel; the positioning method comprises the following steps: shooting a target light source by using a shooting module, and obtaining a course angle of the underwater robot under a first inertial coordinate system of a reactor pressure vessel through image processing; the method comprises the following steps: respectively and horizontally emitting two beams of orthogonal laser with a specific wave band to the inner wall of a reactor pressure vessel by using a laser ranging module to obtain two ranging values; converting the first inertial coordinate system of the reactor pressure vessel into a second inertial coordinate system according to the course angle; and calculating the position coordinates of the underwater robot in the second inertial coordinate system according to a positioning algorithm, and calculating the position coordinates of the underwater robot in the first inertial coordinate system through a corresponding relational expression.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater robot positioning, and particularly relates to a positioning method for an underwater robot in a reactor pressure vessel. Background Art

[0002] A reactor pressure vessel is a pressure vessel used to maintain the pressure required for a nuclear reactor and to confine nuclear reactions within it. Usually, a reactor pressure vessel is composed of large metal forgings, and metal nozzles for the nuclear reaction cycle are welded to the pressure vessel. To ensure the normal progress of nuclear reactions, nuclear power plants need to regularly use underwater robots equipped with ultrasonic detection devices to detect the metal nozzle welds of the reactor pressure vessel.

[0003] Currently, the positioning technology of underwater robots in reactor pressure vessels has the following problems that can lead to positioning failure of underwater robots:

[0004] The geomagnetometer of the inertial navigation system (IMU) used will generate geomagnetic interference due to the container material and thickness, affecting the measurement of the yaw angle;

[0005] In the acoustic wave ranging of the acoustic sensor used, blind spots or distortion phenomena will occur in the acoustic wave reflection on the smooth wall surface of the container arc, and multipath effects and near-field interference of acoustic waves will also occur. Summary of the Invention

[0006] In view of this, the present invention provides a positioning method for an underwater robot in a reactor pressure vessel, which can realize the positioning of the underwater robot in the reactor pressure vessel and also overcome the problem of positioning failure of the existing positioning methods.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A positioning method for an underwater robot in a reactor pressure vessel, which positions the underwater robot in the reactor pressure vessel based on a positioning device. The positioning device includes: a bracket, a target light source, a photographing module, and a laser ranging module; the target light source and the laser ranging module are respectively arranged on the underwater robot through the bracket, and the photographing module is used to be arranged above the reactor pressure vessel;

[0009] The positioning method includes:

[0010] Using the photographing module to photograph the target light source, and obtaining the heading angle of the underwater robot in the first inertial coordinate system of the reactor pressure vessel through image processing heading angle ;

[0011] Use the laser ranging module to horizontally emit two beams of laser with specific wavelengths to the inner wall of the reactor pressure vessel, and obtain the first ranging value and the second ranging value ; wherein, the two beams of laser are orthogonally distributed;

[0012] According to the heading angle transform the first inertial coordinate system of the reactor pressure vessel into a second inertial coordinate system ; wherein, the two axes of the second inertial coordinate system are parallel to the two beams of laser one by one;

[0013] is the position coordinate of the underwater robot in the first inertial coordinate system ;

[0014] is the position coordinate of the underwater robot in the second inertial coordinate system ;

[0015] and The transformation relationship between them satisfies the relational expression , is the coordinate transformation matrix;

[0016]

[0017] Given the radius R of the reactor pressure vessel (2), the first ranging value and the second ranging value , calculate the position coordinate of the underwater robot in the second inertial coordinate system according to the positioning algorithm, and then calculate the position coordinate of the underwater robot in the first inertial coordinate system through .

[0018] Preferably, using the shooting module to shoot the target light source and obtaining the heading angle of the underwater robot in the first inertial coordinate system of the reactor pressure vessel through image processing includes: Use the shooting module to shoot the target light source to obtain a binary image of the captured image; wherein, the target light source is a T-shaped target light source;

[0019] Process the obtained binary image and draw the rectangular contour of the target light source;

[0020] Process the obtained binary image and draw the rectangular contour of the target light source;

[0021] Calculate the pixel coordinates of the feature points on the rectangular contour of the target light source;

[0022] Determine the heading angle of the underwater robot in the first inertial coordinate system of the reactor pressure vessel under .

[0023] Preferably, the step of using the laser ranging module to horizontally emit two beams of laser with specific wavelengths to the inner wall of the reactor pressure vessel includes:

[0024] Using the laser ranging module to horizontally emit two beams of laser with a wavelength of 520 nm to the inner wall of the reactor pressure vessel.

[0025] Preferably, the step of calculating the position coordinates of the underwater robot in the second inertial coordinate system according to the positioning algorithm, and then calculating the position coordinates of the underwater robot in the first inertial coordinate system through includes: The second inertial coordinate system under

[0026] satisfies the following relational expression: under Simplifying the above relational expression to obtain:

[0027]

[0028] Solving the above relational expression to obtain:

[0029]

[0030] Considering inside the reactor pressure vessel, calculating the position coordinates of the underwater robot in the second inertial coordinate system under the condition of satisfying , and then calculating the position coordinates of the underwater robot in the first inertial coordinate system through under , and then through calculate the position coordinates of the underwater robot in the first inertial coordinate system under .

[0031] Preferably, the positioning device further includes an IMU module and an attitude compensation and adjustment device;

[0032] The attitude compensation and adjustment device is arranged on the bracket and is used to adjust the attitude of the laser ranging module so that the laser ranging module is in a horizontal attitude;

[0033] Before using the laser ranging module to horizontally emit two beams of laser with specific wavelengths to the inner wall of the reactor pressure vessel, it further includes:

[0034] The attitude angle of the underwater robot is obtained by using the IMU module. If there is an attitude deviation in the underwater robot, the attitude of the laser ranging module is adjusted by the attitude compensation adjustment device so that the laser ranging module is in a horizontal attitude.

[0035] Preferably, the attitude compensation adjustment device includes two three-axis attitude compensation adjustment devices;

[0036] The two three-axis attitude compensation adjustment devices are symmetrically arranged on the left and right on the bracket, and their movable ends can rotate around three mutually perpendicular axes respectively;

[0037] The laser ranging module includes two laser rangefinders;

[0038] The two laser rangefinders are respectively arranged on the movable ends of the two three-axis attitude compensation adjustment devices; wherein, the movable ends of the two three-axis attitude compensation adjustment devices can respectively adjust the attitudes of the two laser rangefinders so that the two laser rangefinders are both in a horizontal attitude.

[0039] Preferably, the three-axis attitude compensation adjustment device includes: a fixed frame, a connecting rod, a U-shaped frame, an annular frame, a first rotating component, a second rotating component and a third rotating component;

[0040] The fixed frame is arranged on the bracket;

[0041] The first rotating component is arranged downward on the fixed frame, and its rotating shaft is along the vertical direction;

[0042] The upper end of the connecting rod is arranged on the movable end of the first rotating component;

[0043] The second rotating component is arranged at the lower end of the connecting rod frame, and its rotating shaft is along the first horizontal direction;

[0044] The middle part of the U-shaped frame is arranged on the movable end of the second rotating component;

[0045] The two third rotating components are respectively arranged at both ends of the U-shaped frame, and their rotating shafts are both along the second horizontal direction and perpendicular to the first horizontal direction;

[0046] The annular frame is sleeved on the laser rangefinder, and its two opposite outer side walls are respectively arranged on the movable ends of the two third rotating components.

[0047] Preferably, the target light source is a T-shaped target light source;

[0048] The T-shaped target light source is arranged horizontally on the top of the bracket;

[0049] The laser ranging module is arranged in the middle of the bracket, and the two laser beams are symmetrically distributed left and right with respect to the middle part of the T-shaped target light source.

[0050] Preferably, the positioning device further includes: a vision recognition module, a sealed cabin, and an acrylic hemisphere cover;

[0051] The sealed cabin is arranged on the bracket, and its first end is an open structure;

[0052] The acrylic hemisphere cover is hermetically arranged at the first end of the sealed cabin;

[0053] The vision recognition module is arranged in the sealed cabin and is used to recognize the target pipe orifice of the reactor pressure vessel through the acrylic hemisphere cover.

[0054] Preferably, the positioning device further includes a plurality of compensation light sources;

[0055] The plurality of compensation light sources are arranged on the bracket and are distributed around the acrylic hemisphere cover.

[0056] As can be seen from the above technical solutions, the positioning method for an underwater robot in a reactor pressure vessel provided by the present invention solves the problem of measuring the yaw angle of the underwater robot by using visual image processing, and avoids the problems existing in the existing acoustic ranging by using laser ranging in a specific wavelength band. Moreover, according to the course angle the original inertial coordinate system of the reactor pressure vessel is transformed into another inertial coordinate system, and then the position coordinates of the underwater robot in the transformed inertial coordinate system are calculated according to the positioning algorithm. Finally, the position coordinates of the underwater robot in the original inertial coordinate system are calculated through the relationship formula of these two inertial coordinate systems, so as to realize the positioning of the underwater robot in the reactor pressure vessel. Of course, the problem of positioning failure of the existing positioning method is also overcome. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to these drawings.

[0058] Figure 1 It is a flowchart of the positioning method for an underwater robot in a reactor pressure vessel provided by an embodiment of the present invention;

[0059] Figure 2 It is a top view of the positioning device for an underwater robot in a reactor pressure vessel working in the pressure vessel provided by an embodiment of the present invention;

[0060] Figure 3 Schematic structural diagram of the reactor pressure vessel provided by the embodiment of the present invention;

[0061] Figure 4 Cross-sectional view of the positioning device provided by the embodiment of the present invention working in the reactor pressure vessel;

[0062] Figure 5 Schematic structural diagram of the positioning device provided by the embodiment of the present invention;

[0063] Figure 6 Schematic diagram of the distribution of the compensation light source of the positioning device provided by the embodiment of the present invention;

[0064] Figure 7 Schematic diagram of the back structure of the positioning device provided by the embodiment of the present invention;

[0065] Figure 8 Rear view of the structure of the positioning device provided by the embodiment of the present invention;

[0066] Figure 9 Cross-sectional view of the structure of the positioning device provided by the embodiment of the present invention;

[0067] Figure 10 Front view of the assembly of the laser rangefinder and the three-axis attitude compensation adjustment device provided by the embodiment of the present invention;

[0068] Figure 11 Side view of the assembly of the laser rangefinder and the three-axis attitude compensation adjustment device provided by the embodiment of the present invention;

[0069] Figure 12 Top view of the assembly of the laser rangefinder and the three-axis attitude compensation adjustment device provided by the embodiment of the present invention.

[0070] Wherein, 1 is the positioning device, 11 is the bracket, 11.1 is the first mounting plate, 11.2 is the second mounting plate, 12 is the target light source, 13 is the three-axis attitude compensation adjustment device, 13.1 is the fixing frame, 13.2 is the connecting rod, 13.3 is the U-shaped frame, 13.4 is the annular frame, 13.5 is the first driving motor assembly, 13.6 is the second driving motor assembly, 13.7 is the third driving motor assembly, 14 is the laser rangefinder, 15 is the sealed cabin, 16 is the acrylic hemisphere cover, 17 is the compensation light source, 18 is the fixed flange, 19 is the acrylic hemisphere cover pressing plate, 110 is the joint flange, 111 is the global camera, 112 is the monocular camera, 113 is the fish-eye lens, 114 is the M10 bolt, 115 is the end-face sealing fluororubber ring, 116 is the inner-wall sealing fluororubber ring, 117 is the monocular camera fixing bracket, 118 is the air pressure sensor;

[0071] 2 is the reactor pressure vessel, and 21 is the pressure vessel nozzle. Detailed implementation mode

[0072] Most of the current positioning methods for underwater robots rely on GNSS and sonar systems for positioning. However, in an indoor underwater environment, their signals may be affected. Common lidar and millimeter-wave radar on the ground are also affected by the water medium and cannot work properly in the underwater environment. Among them, GNSS and sonar systems are for the positioning of underwater robots in open large waters. The reactor pressure vessel mentioned in this solution is a circular structure water area of an indoor metal material tank. GNSS cannot locate indoor targets, and the sonar system is distorted because the inner wall of the circular structure water area of the reactor pressure vessel is smooth. To solve the above problems, this solution uses vision combined with laser in a special band for joint positioning to achieve the positioning of the underwater robot in the indoor structured water area of the reactor pressure vessel.

[0073] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0074] The positioning method for the underwater robot in the reactor pressure vessel provided by the embodiment of the present invention positions the underwater robot in the reactor pressure vessel 2 based on the positioning device 1, as Figure 5 shown. The positioning device 1 includes: a bracket 11, a target light source 12, a shooting module, and a laser ranging module. The target light source 12 and the laser ranging module are respectively arranged on the underwater robot (not shown in the figure) through the bracket 11, as Figure 4 shown. The shooting module is used to be arranged above the reactor pressure vessel 2.

[0075] The positioning method includes:

[0076] Use the shooting module to shoot the target light source 12, and obtain the heading angle of the underwater robot in the first inertial coordinate system of the reactor pressure vessel 2 through image processing ; ;

[0077] Use the laser ranging module to horizontally emit two beams of laser in a specific band to the inner wall of the reactor pressure vessel 2, and obtain the first ranging value and the second ranging value ; Among them, as Figure 2 shown, the two beams of laser are orthogonally distributed.

[0078] According to the heading angle Transform the first inertial coordinate system of the reactor pressure vessel 2 into a second inertial coordinate system ; wherein, the two axes of the second inertial coordinate system are parallel to the two laser beams one by one;

[0079] is the position coordinate of the underwater robot in the first inertial coordinate system ;

[0080] is the position coordinate of the underwater robot in the second inertial coordinate system ;

[0081] and The transformation relationship between them satisfies the relational expression , is the coordinate transformation matrix;

[0082]

[0083] Given the radius R of the reactor pressure vessel 2, the first ranging value and the second ranging value , calculate the position coordinate of the underwater robot in the second inertial coordinate system according to the positioning algorithm, and then calculate the position coordinate of the underwater robot in the first inertial coordinate system through .

[0084] It should be noted that the bracket 11 is used to be arranged on the underwater robot (not shown in the figure), as Figure 5 shown, the target light source 12 can be arranged at the top of the bracket 11, and the laser ranging module can be arranged in the middle of the bracket 11; as Figure 4 shown, the photographing module can be the global camera 111, and can be arranged above the water area of the reactor pressure vessel 2, so as to take pictures of the target light source 12 located in the reactor pressure vessel 2;

[0085] In the first step of the above positioning method, take a picture of the target light source 12 located on the underwater robot through the photographing module to obtain the target light source image, and obtain the heading angle of the underwater robot in the first inertial coordinate system of the reactor pressure vessel 2 through image processing, that is, obtain the heading angle of the positioning device relative to the first inertial coordinate system of the reactor pressure vessel 2, and further solve the problem of measuring the yaw angle through the method of visual image processing;

[0086] In the second step of the above positioning method, two orthogonal laser beams of a specific wavelength band are respectively emitted along the horizontal direction towards the inner wall of the reactor pressure vessel 2 by the laser ranging module to obtain the first ranging value and the second ranging value , that is, the laser ranging module has two laser emission ends, and the emitted laser beams are orthogonally distributed; among them, the laser beam of a specific wavelength band (blue-green laser pulse) emitted by the laser ranging module, after being reflected by the inner wall of the reactor pressure vessel 2, the laser echo signal will be received by the laser receiver of the laser ranging module. According to the time difference between the laser emission and return, combined with the propagation speed of light in the medium, the distance between the laser ranging module and the inner wall of the reactor pressure vessel can be obtained :

[0087]

[0088] Among them, represents the distance to the target, represents the speed of light in water, represents the time difference between the light pulse transmission and reception;

[0089] That is, the first ranging value and the second ranging value can be calculated in the above manner; that is to say, in the positioning method provided by this solution, the method of using a laser of a specific wavelength band for ranging avoids the problems existing in the existing acoustic ranging;

[0090] In the third step of the above positioning method, in order to find the geometric relationship between the laser ranging value and the inertial coordinate system, it is necessary to transform the inertial coordinate system of the reactor pressure vessel 2. Since the included angle between the two laser beams is 90°, it is necessary to transform the inertial coordinate system to a position where the two axes of the coordinate system are parallel to the two laser beams of the laser, as Figure 2 shown, that is, it is necessary to transform the first inertial coordinate system of the reactor pressure vessel 2 into the second inertial coordinate system , only in this way can the geometric relationship between the laser ranging value and the inertial coordinate system be found;

[0091] In the fourth step of the above positioning method, according to the positioning algorithm, first calculate the coordinate values (x”y”) of the underwater robot in the transformed inertial coordinate system, and then through transform back to the coordinate values (x, y) in the original inertial coordinate system, so as to obtain the coordinate values (x, y) of the underwater robot in the original inertial coordinate system.

[0092] The positioning method for the underwater robot in the reactor pressure vessel provided by this solution solves the problem of measuring the yaw angle of the underwater robot by means of visual image processing, and uses a laser in a specific band for ranging to avoid the problems existing in the existing acoustic ranging. Moreover, according to the heading angle transforms the original inertial coordinate system of the reactor pressure vessel 2 into another inertial coordinate system, and then calculates the position coordinates of the underwater robot in the transformed inertial coordinate system according to the positioning algorithm. Finally, the position coordinates of the underwater robot in the original inertial coordinate system are calculated through the relational expression of these two inertial coordinate systems, so as to realize the positioning of the underwater robot in the reactor pressure vessel. Of course, it also overcomes the problem of positioning failure of the existing positioning method; that is to say, this solution realizes the precise positioning of the underwater robot in the indoor structured water area of the reactor pressure vessel through the combination of vision and laser in a special band.

[0093] In this solution, the shooting module is used to shoot the target light source 12, and the heading angle of the underwater robot in the first inertial coordinate system of the reactor pressure vessel 2 is obtained through image processing as follows: including:

[0094] Use the shooting module to shoot the target light source 12 to obtain a binary image of the captured image; among them, the target light source 12 is a T-shaped target light source;

[0095] Process the obtained binary image and draw the rectangular contour of the target light source 12;

[0096] Calculate the pixel coordinates of the feature points on the rectangular contour of the target light source 12;

[0097] Determine the heading angle of the underwater robot in the first inertial coordinate system of the reactor pressure vessel 2 as follows: .

[0098] It should be noted that in the above first step, the shooting module can adopt the global camera 111 (water camera). As Figure 4 shown, the global camera 111 is set directly above the pool, and the global camera 111 is used to directly shoot the target light source 12 at the top of the positioning device. The high-brightness target area is separated from the image through threshold segmentation to obtain a binary image; among them, as Figure 6 shown, the target light source 12 is a T-shaped target light source;

[0099] In the above second step, the target area is marked by the connected component labeling method, and then the two rectangular frames of the target area are drawn through the OpenCV image contour detection, and the pixel coordinates of the center position of the rectangular frame, as well as the width W and height H of the rectangular frame, will be directly obtained;

[0100] In the above third step, the two rectangular frames are a vertical rectangular frame and a horizontal rectangular frame respectively. By calculating the central pixel coordinates, width W, and height H of each rectangular frame, the pixel coordinates of the top and bottom sides of each rectangular frame can be obtained;

[0101] In the above fourth step, two pixel coordinates can determine a vector. The starting point of the vector can be determined by the position of the horizontal rectangular frame. Of course, once the starting point is determined, the ending point is defaultly confirmed. According to the above method, the heading angle in the first inertial coordinate system can be determined under .

[0102] Specifically, the use of the laser ranging module to horizontally emit two beams of laser with specific wavelengths to the inner wall of the reactor pressure vessel 2 includes:

[0103] Using the laser ranging module to horizontally emit two beams of laser with a wavelength of 520 nm to the inner wall of the reactor pressure vessel 2. Among them, the laser with a wavelength of 520 nm belongs to the green spectral range, and the absorption of the green spectrum in the nuclear reactor pressure vessel is weak. Therefore, the laser ranging module with a wavelength of 520 nm can be used to obtain the distance between it and the measured wall surface.

[0104] Further, the calculation of the position coordinates of the underwater robot in the second inertial coordinate system under, and then through calculating the position coordinates of the underwater robot in the first inertial coordinate system under includes:

[0105] The second inertial coordinate system under satisfies the following relational expression:

[0106]

[0107] Solving the above relational expression gives:

[0108]

[0109] This binary quadratic equation system has two sets of solutions. Considering that inside the reactor pressure vessel 2, under the condition of satisfying calculate the position coordinates of the underwater robot in the second inertial coordinate system under , and then through calculate the position coordinates of the underwater robot in the said first inertial coordinate system under .

[0110] For a better understanding of this solution, the following gives the calculation of the underwater robot in the said first inertial coordinate system Position coordinates below Example of:

[0111] Obtain parameters = 700 mm, = 700 mm, = 1300 mm, the first inertial coordinate system below = 57.296°;

[0112] Step 1: Calculate the square terms ,

[0113]

[0114] Step 2: Calculate the quadratic equation coefficients

[0115]

[0116]

[0117]

[0118] Step 3: Calculate the discriminant and solve the quadratic equation to obtain and solve the quadratic equation to get

[0119]

[0120] At this time, there are two corresponding :

[0121]

[0122]

[0123] Step 4: Calculate the corresponding :

[0124]

[0125] When at this time ;

[0126] When at this time ;

[0127] Step 5: Verify the legality of the solution according to the geometric constraint conditions and obtain the coordinates in the second inertial coordinate system ;

[0128] Among them, the geometric constraint (inside the circle) needs to be satisfied , the physical constraints (distance range) need to be satisfied and ;

[0129] Finally, it can be calculated that the unique true solution in the second inertial coordinate system ;

[0130] Step 6: According to the heading angle in the first inertial coordinate system Transform the solved coordinates to the first inertial coordinate system ;

[0131] Substitute the heading angle into the rotation transformation matrix ;

[0132]

[0133] Furthermore, the positioning device 1 further includes an IMU module and an attitude compensation and adjustment device;

[0134] The attitude compensation and adjustment device is arranged on the bracket 11 and is used to adjust the attitude of the laser ranging module so that the laser ranging module is in a horizontal attitude;

[0135] Before using the laser ranging module to horizontally emit two beams of laser with specific wavelengths to the inner wall of the reactor pressure vessel 2, it further includes:

[0136] Use the IMU module to obtain the attitude angle of the underwater robot. If there is an attitude deviation in the underwater robot, adjust the attitude of the laser ranging module through the attitude compensation and adjustment device so that the laser ranging module is in a horizontal attitude.

[0137] It should be noted that the IMU module can be arranged on the bracket 11 or replaced by the IMU module of the underwater robot; among them, the IMU module is used to measure the attitude angle of the underwater robot , where is represented by the following formula, where is the roll angle, is the pitch angle, is the heading angle;

[0138]

[0139] Under ideal measurement conditions, and the angles should be 0 degrees, but under actual measurement conditions, due to the uneven mass of the underwater robot body and the unstable attitude during movement, and The angle is not 0 degrees, which causes the attitude change of the underwater robot to interfere with the emission angle of the laser beam of the laser ranging module. When the IMU module measures the attitude angle of the underwater robot, the attitude of the laser ranging module is adjusted through the attitude compensation adjustment device, so that the laser ranging module is in a horizontal state relative to the horizontal plane, and the two 520nm lasers of the laser ranging module are respectively emitted along the orthogonal horizontal directions.

[0140] That is to say, the IMU module of the visual laser joint positioning device is used to obtain the attitude angle of the underwater robot body, and the obtained attitude angle is compensated to the attitude compensation adjustment device. Then, the attitude of the laser ranging module is adjusted through the attitude compensation adjustment device, so that the laser ranging module is in a horizontal state, thereby eliminating the laser measurement error caused by the attitude error of the underwater robot itself and improving the accuracy of laser measurement.

[0141] In this solution, as Figure 7 shown, the attitude compensation adjustment device includes two three-axis attitude compensation adjustment devices 13;

[0142] The two three-axis attitude compensation adjustment devices 13 are symmetrically arranged on the left and right on the bracket 11, and their movable ends can respectively rotate around three mutually perpendicular axes;

[0143] The laser ranging module includes two laser rangefinders 14;

[0144] The two laser rangefinders 14 are respectively arranged on the movable ends of the two three-axis attitude compensation adjustment devices 13; among them, the movable ends of the two three-axis attitude compensation adjustment devices 13 can respectively adjust the attitudes of the two laser rangefinders 14, so that the two laser rangefinders 14 are both in a horizontal attitude.

[0145] It should be noted that the movable end of the three-axis attitude compensation adjustment device 13 can rotate around the X-axis, Y-axis and Z-axis respectively, and is used to drive the laser rangefinder 14 to realize the adjustment of the roll angle, pitch angle and yaw angle, that is, to drive the laser rangefinder 14 to realize the adjustment of the attitude angle, so that the laser rangefinder 14 is in a horizontal attitude. Among them, the two three-axis attitude compensation adjustment devices 13 can be a left three-axis attitude compensation adjustment device and a right three-axis attitude compensation adjustment device. Correspondingly, the two laser rangefinders 14 can be a left laser rangefinder and a right laser rangefinder, and are respectively arranged on the movable ends of the left three-axis attitude compensation adjustment device and the right three-axis attitude compensation adjustment device.

[0146] Specifically, as Figure 8 shown, the three-axis attitude compensation adjustment device 13 includes: a fixed frame 13.1, a connecting rod 13.2, a U-shaped frame 13.3, a ring frame 13.4, a first rotating assembly, a second rotating assembly and a third rotating assembly;

[0147] The fixing frame 13.1 is arranged on the bracket 11;

[0148] The first rotating assembly is disposed downward on the fixed frame 13.1, and its rotating axis is along the vertical direction;

[0149] The upper end of the connecting rod 13.2 is arranged at the movable end of the first rotating assembly;

[0150] The second rotating assembly is disposed at the lower end of the connecting rod frame 13.2, and its rotating axis is along the first horizontal direction;

[0151] The middle part of the U-shaped frame 13.3 is arranged at the movable end of the second rotating assembly;

[0152] Two third rotating components are respectively arranged at two ends of the U-shaped frame 13.3, and their rotating axes are along the second horizontal direction and perpendicular to the first horizontal direction;

[0153] The annular frame 13.4 is sleeved on the laser rangefinder 14, and two opposite outer side walls thereof are respectively arranged at the movable ends of the two third rotating components.

[0154] It should be noted that if Figure 8 As shown, the fixing frame 13.1 may be an L-shaped fixing frame, and its vertical plate is fixed to the back of the bracket 11 by a bolt assembly; Figure 12 As shown, the first rotating assembly can adopt the first driving motor assembly 13.5, and can be arranged downward at the bottom of the horizontal plate of the L-shaped fixed frame, and the output end of the first driving motor assembly 13.5 is also distributed downward accordingly to realize the rotation around the Z axis; the connecting rod 13.2 can be a bending connecting rod, and its upper end is transmission-connected with the output end of the first driving motor assembly 13.5; the second rotating assembly can be the second driving motor assembly 13.6, and is arranged at the lower end of the bending connecting rod along the first horizontal direction, and the output end of the second driving motor assembly 13.6 is correspondingly distributed along the first horizontal direction and away from the lower end of the bending connecting rod to realize the rotation around the X axis or the Y axis; the outer wall of the middle part of the U-shaped frame 13.3 is connected to the second driving motor assembly The output end of the component 13.6 is transmission connected; the third rotating component can be a third driving motor component 13.7, and the two third driving motor components 13.7 can be respectively arranged at the two ends of the U-shaped frame 13.3 along the second horizontal direction, and the output ends thereof are both located on the inner sides of the two ends of the U-shaped frame 13.3 to realize rotation around the X-axis or the Y-axis; the annular frame 13.4 can be a circular frame, and is sleeved on the outer peripheral wall of the laser rangefinder 14, and the two opposite outer side walls of the circular frame are transmission connected one by one with the output ends of the two third driving motor components 13.7, thereby driving the laser rangefinder 14 to rotate around the X-axis, the Y-axis and the Z-axis respectively; wherein, the three-axis posture compensation adjustment device 13 is designed in this way, and the structure is simple and the adjustment is convenient.

[0155] Furthermore, if Figure 5 As shown, the target light source 12 is a T-shaped target light source;

[0156] The T-shaped target light source is horizontally arranged on the top of the bracket 11;

[0157] The laser ranging module is arranged in the middle of the bracket 11, and the two laser beams are symmetrically distributed left and right with respect to the middle part of the T-shaped target light source.

[0158] It should be noted that, as Figure 5 shown, the bracket 11 includes: a first mounting plate 11.1 and a second mounting plate 11.2. The first mounting plate 11.1 is a vertical mounting plate and is used to be arranged on the underwater robot. The second mounting plate 11.2 is an L-shaped mounting plate. The vertical part of the L-shaped mounting plate is fixedly attached to the back of the top of the vertical mounting plate through a bolt assembly. The T-shaped target light source is horizontally arranged on the top of the horizontal part of the L-shaped mounting plate. Two three-axis attitude compensation adjustment devices 13 are arranged on the left and right sides of the back of the middle part of the vertical mounting plate and are symmetrically distributed left and right with respect to the middle part of the T-shaped target light source. Two laser rangefinders 14 are respectively arranged on the movable ends of the two three-axis attitude compensation adjustment devices 13; wherein, the target light source 12 is designed as a T-shaped target light source, which is convenient to obtain the heading angle of the underwater robot in the first inertial coordinate system of the reactor pressure vessel 2 according to the graphic processing method under ; Of course, the target light source 12 can also adopt other axisymmetric graphics, such as a cross.

[0159] Furthermore, as Figure 9 shown, the positioning device 1 further includes: a visual recognition module, a sealed cabin 15 and an acrylic hemisphere 16;

[0160] The sealed cabin 15 is arranged on the bracket 11, and its first end is an open structure;

[0161] The acrylic hemisphere 16 is hermetically arranged at the first end of the sealed cabin 15;

[0162] The visual recognition module is arranged in the sealed cabin 15 and is used to identify the target pipe orifice 21 of the reactor pressure vessel 2 through the acrylic hemisphere 16 (as Figure 3 shown).

[0163] It should be noted that, as Figure 9As shown in the figure, the first end (front end) of the sealed cabin 15 penetrates the first mounting plate 11.1 in the horizontal direction, and the first end of the sealed cabin 15 is fixed to the first mounting plate 11.1 through the fixed flange 18; the acrylic hemispherical cover 16 is hermetically arranged at the first end of the sealed cabin 15, and the acrylic hemispherical cover 16 is pressed against the first end of the sealed cabin 15 through the acrylic hemispherical cover pressing plate 19; the visual recognition module is arranged in the sealed cabin 15 and includes: a monocular camera 112 and a fish-eye lens 113. The monocular camera 112 is fixed in the sealed cabin 15 through the monocular camera fixing bracket 117. The fish-eye lens 113 is arranged on the front side of the monocular camera 112, and the central axis of the fish-eye lens 113 coincides with the central axis of the sealed cabin 15; wherein, the combination of the monocular camera 112 and the fish-eye lens 113 is used to identify the target pipe orifice 21 of the reactor pressure vessel 2, which is equivalent to the underwater robot identifying the target pipe orifice 21 of the reactor pressure vessel 2 and obtaining the position information of the target pipe orifice.

[0164] In this solution, as Figure 5 shown, the positioning device 1 further includes a plurality of compensation light sources 17;

[0165] The plurality of compensation light sources 17 are arranged on the bracket 11 and distributed around the acrylic hemispherical cover 16. Among them, as Figure 5 shown, the first mounting plate 11.1 is respectively provided with four light source through holes, which are evenly distributed around the acrylic hemispherical cover 16. There may be four compensation light sources 17. The four compensation light sources 17 are respectively arranged in the four light source through holes of the first mounting plate 11.1 and are all located on the back of the first mounting plate 11.1. The compensation light source 17 can adopt a high-lumen waterproof lamp; that is to say, a plurality of compensation light sources 17 are evenly arranged around the acrylic hemispherical cover 16 to supplement light for the visual recognition module, and improve the problems of dark visual imaging pictures, unclear pipe orifice features, and low recognition rate caused by insufficient brightness when the visual recognition module identifies the target pipe orifice in the overly dark nuclear reactor pressure vessel, thereby helping to improve the recognition stability of the visual recognition module.

[0166] In addition, it should be noted that, on the one hand, this solution provides an underwater robot positioning system (i.e., the positioning device) in a reactor pressure vessel, and includes: a visual measurement system, a laser measurement system (i.e., the laser ranging module), a laser measurement error compensation system (i.e., the attitude compensation adjustment device), a light source system (i.e., the compensation light source), and an IMU module;

[0167] The visual measurement system includes: a monocular camera, a fish-eye lens, and a global camera (i.e., the shooting module); the combination of the monocular camera and the fish-eye lens is used to identify the target pipe orifice and obtain the relative pose of the visual laser joint positioning system with respect to the target pipe orifice in the inertial coordinate system of the reactor pressure vessel.

[0168] The laser measurement system includes: a left laser rangefinder with a wavelength of 520 nm and a right laser rangefinder with a wavelength of 520 nm; the laser wavelength of the 520-nm laser rangefinder belongs to the green spectral range, and the absorption of the green spectrum in the nuclear reactor pressure vessel is weak. Therefore, this laser measurement system is used to obtain the distance from the measured wall surface.

[0169] The laser measurement error compensation system is used to eliminate the laser measurement error caused by the attitude error of the underwater robot itself, and improve the measurement accuracy.

[0170] The light source system is used to compensate for the problems of the visual measurement system, such as the dark visual imaging picture, unclear pipe orifice features, and low recognition rate caused by insufficient brightness when identifying the pipe orifice in the too-dark nuclear reactor pressure vessel, and improve the stability of the visual measurement system.

[0171] The IMU module is used to measure the attitude angle of the underwater robot , where is represented by the following formula, where is the roll angle, is the pitch angle, is the heading angle;

[0172]

[0173] Under ideal measurement conditions and the angles should be 0 degrees. However, under actual measurement conditions, due to the uneven mass of the robot body and the unstable attitude during movement, and the angles are not 0 degrees. This causes the attitude change of the underwater robot to interfere with the emission angle of the laser beam of the laser measurement system, and the attitude angle data measured by the IMU module is compensated to the laser measurement error compensation system.

[0174] Such as Figure 9As shown in the figure, the sealed cabin 15 of the monocular camera 112 is installed on the support plate (i.e., the bracket 11) by using M10 bolts for fixing the waterproof sealed cabin. Among them, the cabin body of the waterproof sealed cabin is a cylindrical structure with a through hole in the middle, and there are 6 fixed screw holes at the front and rear ends of the cabin body. When the fixed flange of the waterproof sealed cabin (i.e., the fixed flange 18) and the joint flange of the waterproof sealed cabin (i.e., the joint flange 110) are correctly installed at the front and rear ends of the cabin body, and the fixed bolts are inserted at both ends, the front and rear flanges can be firmly fixed on the cabin body to improve the pressure resistance of the cabin body. Among them, there are sealing fluororubber ring installation grooves on the fixed flange of the waterproof sealed cabin and the joint flange of the waterproof sealed cabin. When the front and rear flanges are installed on the cabin body, the sealing fluororubber ring will be tightly pressed against the inner wall of the cabin body to ensure its sealing effect. Among them, the camera fixing bracket (i.e., the monocular camera fixing bracket 117) is installed on the wall surface of the waterproof sealed cabin body, the monocular camera is installed on the camera fixing bracket, and the fish-eye lens is installed on the monocular camera through a threaded interface. When the camera and the lens are installed, the installation position of the camera fixing bracket just makes the central axis of the lens coincide with the central axis of the cabin body. A precise air pressure sensor is installed on the back of the camera fixing bracket to detect whether the air pressure in the cabin changes and to judge whether there is a seal leakage. Among them, the acrylic hemisphere cover is pressed on the end face sealing fluororubber ring, the hemisphere cover pressing plate (i.e., the acrylic hemisphere cover pressing plate 19) is pressed on the acrylic hemisphere cover, and there are 6 installation holes on the hemisphere cover pressing plate. When the screws are screwed into the installation holes and the 6 screws are tightened, the pressing plate is tightly pressed on the end face sealing fluororubber ring.

[0175] As Figure 7 shown in the figure, the left and right lasers in the laser measurement system are installed on the three-axis laser attitude compensation device (i.e., the three-axis attitude compensation adjustment device 13) for fixing the positions of the left and right lasers in the positioning system. Among them, the three-axis laser attitude compensation device is installed on the support plate by bolt connection for fixing the position of the entire laser measurement system in the positioning system.

[0176] Among them, as Figures 10 to 12 shown in the figure, the three-axis laser attitude compensation device consists of an inner ring (i.e., the annular frame 13.4), an inner ring drive motor (i.e., the third drive motor assembly 13.7), a middle ring (i.e., the U-shaped frame 13.3), a middle ring drive motor (i.e., the second drive motor assembly 13.6), an outer ring (i.e., the connecting rod 13.2), and an outer ring drive motor (i.e., the first drive motor assembly 13.5). Among them, the outer ring is fixed on the installation bracket (i.e., the fixed frame 13.1).

[0177] As Figure 6 shown in the figure, the light source system consists of four high-lumen waterproof lights for front light source compensation (i.e., the compensation light source 17) and a target light source lamp for top visual recognition (i.e., the target light source 12).

[0178] In a second aspect, this solution also provides a positioning method for an underwater robot in a nuclear reactor pressure vessel implemented based on the above positioning system.

[0179] For reference, Figure 1 As shown, a specific process of a positioning method for an underwater robot in a nuclear reactor pressure vessel is as follows:

[0180] Step 1: According to the attitude angle of the underwater robot measured by the IMU module, adjust the attitude of the laser measurement system through the laser ranging module so that the 520-nm laser of the laser measurement system is emitted horizontally.

[0181] Step 2: The laser measurement system emits a laser pulse. After being reflected by the wall of the nuclear reactor pressure vessel, the pulse echo signal will be received by the laser receiver (equipped with a laser rangefinder). According to the time difference between the emission of the signal and the return of the echo signal, combined with the propagation speed of light in the medium, the distance between the laser measurement system and the wall of the nuclear reactor pressure vessel can be obtained. :

[0182]

[0183] Among them, represents the distance to the target, represents the speed of light in water, represents the time difference from the emission to the reception of the light pulse;

[0184] Step 3: The global camera fixed at the top captures the long strip of light emitted by the target light source, uses the long strip of light as the target for measuring the yaw angle, and calculates the yaw angle of the underwater robot in the first inertial coordinate system of the nuclear reactor pressure vessel.

[0185] Step 4: Transform the first inertial coordinate system to the second inertial coordinate system , where is the position coordinate of the underwater robot in the coordinate system, is the position coordinate of the underwater robot in the coordinate system. Therefore, and The transformation relationship between them satisfies the relational expression ;

[0186] Step 5: Calculate the position coordinate of the underwater robot in the first inertial coordinate system according to the positioning algorithm of the underwater robot in the reactor pressure vessel.

[0187] More specifically, a positioning method for an underwater robot in a pressure vessel in a closed pressure vessel, the method includes the following steps:

[0188] Use the global camera 111 at the top of the pressure vessel to capture the target light source 12 at the top of the positioning device. After image processing, obtain the heading angle of the positioning device relative to the first inertial coordinate of the nuclear reactor pressure vessel. ;

[0189] Use the IMU module of the vision-laser combined positioning device (i.e., the positioning device) to obtain the pitch angle of the underwater robot body. and roll angle , and compensate the obtained attitude angles to the three-axis laser attitude compensation device of the fixed laser, so that the laser is in a horizontal state relative to the horizontal plane. The angle compensation relationship between the pitch angle and roll angle of the underwater robot body and the three rings in the three-axis laser attitude compensation device is shown in the following formula:

[0190]

[0191] Among them, are the three rotation angles of the three-axis laser attitude compensation device, is the angle of the outer ring relative to the central axis of the positioning device, and the preset angle is 45°;

[0192] Use the blue-green laser pulse emitted by the laser of the vision-laser combined positioning device. When the laser pulse hits the inner wall of the pressure vessel, a part of the scattered light will be captured by the laser receiver. According to the time difference between the emission of light and its return to the laser after being reflected by the object, combined with the propagation speed of light in the medium, the distance between the laser and the measured surface can be obtained. ;

[0193]

[0194] Among them, represents the distance to the target, represents the speed of light in water, represents the time difference between the transmission and reception of the light pulse;

[0195] According to the yaw angle of the underwater robot, transform the first inertial coordinate system to the second inertial coordinate system , where is the position coordinate of the underwater robot in coordinate system, is the position coordinate of the underwater robot in coordinate system. Therefore, and The transformation relationship between them satisfies the relationship formula , is the coordinate transformation matrix:

[0196]

[0197] Calculate the position coordinates of the underwater robot in the second inertial coordinate system according to the underwater robot positioning algorithm in the reactor pressure vessel Given that the radius of the pressure vessel is R and the left and right laser measurement values 、 In coordinate system Satisfy the following relationship:

[0198]

[0199] Further solve the above relationship to obtain:

[0200]

[0201] This binary quadratic equation has two sets of solutions. Because Inside the pressure vessel, under the condition of satisfying A unique true solution can be obtained, and then through Find out at The position coordinates in the coordinate system.

[0202] In summary, the present invention uses a visual measurement system, a laser measurement system, and a laser measurement error compensation system to achieve the underwater positioning of the robot in the nuclear reactor pressure vessel; uses the proposed underwater robot positioning method in the nuclear reactor pressure vessel to fuse the data of the visual measurement system and the laser measurement system, achieving a high-precision underwater positioning effect; compared with the existing positioning technologies, the present invention particularly solves the problems of geomagnetic meter failure due to the container material in the nuclear reactor pressure vessel and acoustic sensor failure due to the arc-shaped and smooth wall of the nuclear reactor pressure vessel, that is, solves the problem of yaw angle measurement by using the visual measurement system, and solves the ranging problem of smooth walls and small volume inside the container in the sealed pressure vessel by using the laser measurement system, overcoming the problem of positioning failure of the existing positioning technologies in the nuclear reactor pressure vessel.

[0203] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same and similar parts among the embodiments, reference can be made to each other.

[0204] The foregoing description of the disclosed embodiments enables those skilled in the art to practice or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A positioning method for an underwater robot in a reactor pressure vessel, which positions the underwater robot in the reactor pressure vessel (2) based on a positioning device (1), characterized in that, The positioning device (1) includes: a bracket (11), a target light source (12), a shooting module, and a laser ranging module; the target light source (12) and the laser ranging module are respectively arranged on the underwater robot through the bracket (11), and the shooting module is used to be arranged above the reactor pressure vessel (2); The positioning method includes: The shooting module is used to shoot the target light source (12), and the heading angle of the underwater robot in the first inertial coordinate system of the reactor pressure vessel (2) is obtained through image processing under ; Use the laser ranging module to horizontally emit two beams of laser with specific wavelengths to the inner wall of the reactor pressure vessel (2) to obtain a first ranging value and a second ranging value ; wherein, the two beams of laser are orthogonally distributed; According to the heading angle transform the first inertial coordinate system of the reactor pressure vessel (2) into a second inertial coordinate system ; wherein, two axes of the second inertial coordinate system are parallel to the two beams of the laser respectively; is the position coordinate of the underwater robot in the first inertial coordinate system ; is the position coordinate of the underwater robot in the second inertial coordinate system ; and The transformation relationship between them satisfies the relational expression , where [[0000025]] is the coordinate transformation matrix; Given the radius R of the reactor pressure vessel (2), the first ranging value and the second ranging value , the position coordinates of the underwater robot in the second inertial coordinate system are calculated according to the positioning algorithm, and then the position coordinates of the underwater robot in the first inertial coordinate system are calculated through .

2. The positioning method for the underwater robot in the reactor pressure vessel according to claim 1, characterized in that, The shooting module is used to shoot the target light source (12), and the heading angle of the underwater robot in the first inertial coordinate system of the reactor pressure vessel (2) is obtained through image processing under the heading angle including: Using the shooting module to shoot the target light source (12) to obtain a binary image of the shooting image; wherein, the target light source (12) is a T-shaped target light source; Processing the obtained binary image and drawing the rectangular contour of the target light source (12); Calculating the pixel coordinates of the feature points on the rectangular contour of the target light source (12); Determine the heading angle of the underwater robot in the first inertial coordinate system of the reactor pressure vessel (2) .​ 3. The positioning method for the underwater robot in the reactor pressure vessel according to claim 1, wherein The using the laser ranging module to horizontally emit two beams of laser with a specific wavelength band to the inner wall of the reactor pressure vessel (2) includes: Using the laser ranging module to horizontally emit two beams of laser with a wavelength of 520 nm to the inner wall of the reactor pressure vessel (2).

4. The positioning method for the underwater robot in the reactor pressure vessel according to claim 1, characterized in that, The position coordinates of the underwater robot in the second inertial coordinate system are calculated according to the positioning algorithm, and then through the position coordinates of the underwater robot in the first inertial coordinate system are calculated, including: ​ The second inertial coordinate system below satisfies the following relational expressions: Solving the above relational expression to obtain: Considering that inside the reactor pressure vessel (2), under the condition of satisfying the position coordinates of the underwater robot in the second inertial coordinate system are calculated, and then through the position coordinates of the underwater robot in the first inertial coordinate system are calculated under the condition of satisfying .

5. The positioning method for the underwater robot in the reactor pressure vessel according to claim 1, characterized in that, The positioning device (1) further includes an IMU module and an attitude compensation and adjustment device; The attitude compensation and adjustment device is arranged on the bracket (11) and is used to adjust the attitude of the laser ranging module so that the laser ranging module is in a horizontal attitude; Before using the laser ranging module to horizontally emit two beams of laser with a specific wavelength band to the inner wall of the reactor pressure vessel (2), it further includes: Using the IMU module to obtain the attitude angle of the underwater robot. If there is an attitude deviation of the underwater robot, the attitude of the laser ranging module is adjusted through the attitude compensation and adjustment device so that the laser ranging module is in a horizontal attitude.

6. The positioning method for the underwater robot in the reactor pressure vessel according to claim 5, characterized in that, The attitude compensation and adjustment device includes two three-axis attitude compensation and adjustment devices (13); The two three-axis attitude compensation and adjustment devices (13) are arranged symmetrically left and right on the bracket (11), and their movable ends can respectively rotate around three mutually perpendicular axes; The laser ranging module includes two laser rangefinders (14); The two laser rangefinders (14) are respectively arranged on the movable ends of the two three-axis attitude compensation and adjustment devices (13); wherein, the movable ends of the two three-axis attitude compensation and adjustment devices (13) can respectively adjust the attitudes of the two laser rangefinders (14) so that the two laser rangefinders (14) are both in a horizontal attitude.

7. The positioning method for the underwater robot in the reactor pressure vessel according to claim 6, wherein, The three-axis attitude compensation and adjustment device (13) includes: a fixed frame (13.1), a connecting rod (13.2), a U-shaped frame (13.3), a circular frame (13.4), a first rotation component, a second rotation component, and a third rotation component; The fixed frame (13.1) is arranged on the bracket (11); The first rotation component is arranged downward on the fixed frame (13.1), and its rotation axis is along the vertical direction; The upper end of the connecting rod (13.2) is arranged at the movable end of the first rotation component; The second rotation component is arranged at the lower end of the connecting rod frame (13.2), and its rotation axis is along the first horizontal direction; The middle part of the U-shaped frame (13.3) is arranged at the movable end of the second rotating assembly; The two third rotating assemblies are respectively arranged at both ends of the U-shaped frame (13.3), and their rotating shafts are all along the second horizontal direction and perpendicular to the first horizontal direction; The annular frame (13.4) is sleeved on the laser rangefinder (14), and its two opposite outer side walls are respectively arranged at the movable ends of the two third rotating assemblies.

8. The positioning method for the underwater robot in the reactor pressure vessel according to claim 1, characterized in that, The target light source (12) is a T-shaped target light source; The T-shaped target light source is arranged horizontally at the top of the bracket (11); The laser ranging module is arranged in the middle of the bracket (11), and the two beams of laser are symmetrically distributed about the middle part of the T-shaped target light source.

9. The positioning method for the underwater robot in the reactor pressure vessel according to claim 1, wherein The positioning device (1) further includes: a visual recognition module, a sealed cabin (15) and an acrylic hemispherical cover (16); The sealed cabin (15) is arranged on the bracket (11), and its first end is an open structure; The acrylic hemispherical cover (16) is hermetically arranged at the first end of the sealed cabin (15); The visual recognition module is arranged in the sealed cabin (15) and is used to recognize the target pipe orifice (21) of the reactor pressure vessel (2) through the acrylic hemispherical cover (16).

10. The positioning method for the underwater robot in the reactor pressure vessel according to claim 9, wherein The positioning device (1) further includes a plurality of compensation light sources (17); The plurality of compensation light sources (17) are arranged on the bracket (11) and are distributed around the acrylic hemispherical cover (16).

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