Fuel assembly deformation measurement and automatic compensation loading and unloading system and method

Abstract

The application discloses a fuel assembly deformation measurement and automatic compensation loading and unloading system, which comprises a pool wall positioning platform fixedly installed on the wall of a fuel pool and provided with a positioning matching part; a measurement module detachably installed on the positioning matching part and comprising at least two laser line scanning units for projecting laser lines to fuel assemblies and collecting laser line images; a synchronous triggering module for synchronously triggering the laser line scanning units to collect images and record corresponding height positions according to a preset triggering condition of an encoder position signal; a deformation identification module for reconstructing a three-dimensional appearance point cloud of the fuel assembly and identifying a deformation amount; a compensation amount calculation module for calculating a pose compensation amount according to the deformation amount; an automatic compensation control interface for outputting the pose compensation amount to a refueling machine control system to drive the refueling machine to perform pose fine adjustment; and a safety interlocking module for triggering a safety response when detecting an abnormal state. The application realizes automatic measurement of fuel assembly deformation and automatic compensation of loading and unloading poses.

Description

Technical Field

[0001] This invention relates to the field of nuclear power plant fuel handling and storage equipment technology, and in particular to a fuel assembly deformation measurement and automatic compensation loading and unloading system and method. Background Technology

[0002] During nuclear power plant refueling overhauls, the refueling machine is a crucial piece of equipment for transferring fuel assemblies between the reactor core and the fuel transfer device. Traditional refueling machines typically rely on semi-automatic or manual operation by operators via control consoles, video surveillance, and position encoders. For regularly shaped fuel assemblies, loading and unloading can be completed using preset core coordinates and encoder feedback. However, under long-term irradiation and thermal-hydraulic loads, fuel assemblies may deform, such as bending, tilting, or twisting, causing the actual grab centerline, insertion channel centerline, or outer safety envelope of the fuel assembly to deviate from the theoretical coordinates. If loading and unloading are still performed according to the standard coordinates, friction may occur between the assembly and the core structure, leading to descent jamming, underload, or overload alarms. Operators need to make repeated adjustments, resulting in a significant reduction in refueling efficiency and, in severe cases, damage to the fuel assembly.

[0003] To address the aforementioned issues, existing technologies have provided automated control solutions for refueling machines. These include methods such as generating operating paths by reading the refueling sequence, using cameras to identify scales and combining them with rangefinder data to locate the refueling machine's position, and using sensors to monitor the refueling machine's operating status for fault diagnosis. However, none of these solutions detect the actual geometric state of the fuel assembly when it bends, tilts, or twists underwater, nor do they disclose closed-loop control methods for automatically calculating the refueling machine's pose compensation based on the fuel assembly's deformation. When there is a deviation between the actual centerline of the fuel assembly and its theoretical coordinates, alignment errors may still occur, or manual intervention may be required. Summary of the Invention

[0004] This invention provides a fuel assembly deformation measurement and automatic compensation loading and unloading system and method, which can detect the actual deformation state of the fuel assembly underwater and convert the detected deformation amount into the pose compensation amount of the refueling machine in real time, thereby realizing automatic centering, automatic fine adjustment and automatic loading and unloading of deformed fuel assemblies, effectively improving the success rate of automatic loading and unloading and the safety of operation under deformed fuel assembly conditions.

[0005] This invention provides a fuel assembly deformation measurement and automatic compensation loading and unloading system, comprising: A pool wall positioning platform is fixedly installed on the wall of a fuel water pool. The pool wall positioning platform is provided with a positioning mating part for detachable engagement with a measurement module. The measurement module is detachably mounted on the positioning mating part of the pool wall positioning platform during refueling. The measurement module includes at least two laser line scanning units, each of which is used to project a laser line onto the surface of the fuel assembly and acquire laser line images. The synchronous triggering module is connected to the encoder signal of the lifting mechanism used to drive the fuel assembly to rise and fall. It is used to synchronously trigger each laser line scanning unit to acquire images according to the position signal of the encoder and preset triggering conditions, and to record the height position corresponding to each frame image. The deformation recognition module is used to reconstruct the three-dimensional shape point cloud of the fuel assembly based on the laser line image and to identify the amount of deformation of the fuel assembly. The compensation calculation module is used to calculate the pose compensation amount of the fuel assembly relative to the target loading / unloading position based on the deformation amount; An automatic compensation control interface is used to output the pose compensation amount to the material changer control system, driving the material changer to perform pose fine-tuning; And a safety interlock module, used to trigger a safety response when an abnormal state is detected.

[0006] In one embodiment of the present invention, the measurement module further includes an underwater sealed housing, and each of the laser line scanning units is encapsulated within the underwater sealed housing; Each of the laser line scanning units includes a laser projector and an image acquisition unit. The laser projector is used to project laser lines onto the surface of the fuel assembly, and the image acquisition unit is used to acquire laser line images of the surface of the fuel assembly.

[0007] In one embodiment of the present invention, the preset triggering condition is any one of a preset height interval, a preset time interval, or an encoder pulse signal; The synchronous triggering module also records the timestamp, measurement module status, laser channel number and image frame number each time it is triggered, and binds each frame image with the corresponding height value and timestamp.

[0008] In one embodiment of the present invention, the deformation recognition module identifies the deformation amount in the following ways: Fit the centerline of the fuel assembly; Based on the centerline, extract the lateral offset of each height section, and calculate the maximum lateral offset of the centerline relative to the ideal straight line or the centerline of the standard model based on the lateral offset of each height section. And based on the centerline, calculate the top center offset, bottom center offset, bending direction, overall tilt angle, torsion angle, and local outward convex position of the fuel assembly; The matching residual between the three-dimensional shape point cloud and the pre-established centerline of the standard model is calculated as a measurement reliability index. Furthermore, the oscillating component and the true bending component are distinguished based on the variation characteristics of the lateral offset of the centerline and each height section in the time and space dimensions; if the lateral offset of each height section is a translation in the same direction as a whole and changes periodically with time, it is determined to be an oscillating component; if different height sections have a stable spatial curvature relative to the standard centerline, it is determined to be a true bending component.

[0009] In one embodiment of the present invention, the deformation recognition module further outputs an insertion feasibility index; The insertion feasibility index is used to evaluate the feasibility of automatically inserting the fuel assembly into the target loading / unloading position and serves as input to the safety interlock module.

[0010] In one embodiment of the present invention, when the fuel assembly is not picked up by the refueling machine, the pose compensation amount is the position compensation amount of the refueling trolley; When the fuel assembly has been grabbed and suspended by the fuel changer, the position compensation amount is at least one of the micro-motion compensation amount of the fuel changer trolley, the fuel changer carriage, or the lifting mechanism.

[0011] In one embodiment of the present invention, the pose compensation amount includes at least one of horizontal displacement compensation amount, rotation compensation amount about the vertical axis, or insertion angle compensation amount. The automatic compensation control interface also outputs a speed limit signal and a command signal that allows automatic insertion.

[0012] In one embodiment of the present invention, the abnormal state is at least one of the following: abnormal insertion force, abnormal lateral force, abnormal torque, excessive position deviation, excessive laser measurement residual, excessive fuel assembly swing amplitude, or abnormal communication state. The safety response is at least one of the following: stopping the current action, retracting the fuel assembly to a safe altitude, re-performing the deformation measurement, or switching to manual control mode.

[0013] In one embodiment of the present invention, the security response is executed in stages according to the severity of the anomaly: Level 1: Stop the current action and enter self-diagnosis mode; The second stage involves retracting the fuel assembly to a safe altitude. Level 3: Re-perform full-height deformation measurement; Level 4: Switch to manual control mode.

[0014] In one embodiment of the present invention, the system has three selectable working modes: manual confirmation mode, semi-automatic execution mode, and fully automatic closed-loop mode.

[0015] In one embodiment of the present invention, the pool wall positioning platform is further provided with fixed calibration targets, and the number of fixed calibration targets is at least three. After the measurement module is installed in place, it performs external parameter self-calibration by scanning the fixed calibration target to correct the installation attitude deviation of the measurement module relative to the pool wall reference coordinate system established based on the pool wall positioning platform.

[0016] In one embodiment of the present invention, the measurement module is further provided with a narrowband filter and a polarizing filter on the light-collecting path of each of the image acquisition devices; The passband wavelength of the narrowband filter is matched with the laser wavelength of the laser projector; each of the image acquisition devices acquires images by means of synchronous exposure with the laser projector.

[0017] In one embodiment of the present invention, the deformation recognition module reconstructs the three-dimensional shape point cloud in the following manner: A pool wall reference coordinate system is established based on the pool wall positioning platform; The laser line images in each frame are subjected to denoising, brightness normalization, and laser line enhancement processing. Extract the center of the laser line from each frame of the processed laser line image; Based on the triangulation model, the center of the laser line is converted into cross-sectional contour points at various height positions, and then unified to the reference coordinate system of the pool wall through extrinsic parameter transformation; The cross-sectional contour points at each height position, which are unified to the reference coordinate system of the pool wall, are spliced ​​together according to the height position to generate the three-dimensional shape point cloud of the fuel assembly. Outlier removal and voxel downsampling are performed on the three-dimensional shape point cloud.

[0018] In one embodiment of the present invention, the pool wall positioning platform is a passive mechanical structure, without electronic components, optical components and seals; the pool wall positioning platform is also provided with a locking fit structure for locking the fit between the measuring module and the pool wall positioning platform.

[0019] In one embodiment of the present invention, the positioning mating part is a three-point kinematic positioning pair, which is any one of a ball-groove-plane three-point positioning structure, a tapered pin and V-groove mating structure, or a ball-and-socket positioning structure.

[0020] In one embodiment of the present invention, the fixed calibration target is at least one of a stainless steel ball, a ceramic circular hole target, a cross target, a reflective target, or a calibration block.

[0021] In one embodiment of the present invention, in each of the laser line scanning units, the laser projector and the image acquisition unit form a fixed triangulation baseline, which is used to determine the three-dimensional position of the laser line on the surface of the fuel assembly based on the triangulation model.

[0022] In one embodiment of the present invention, the automatic compensation control interface communicates with the material changer control system via any one of industrial Ethernet, fieldbus, hard contact, or safety PLC interface.

[0023] In one embodiment of the present invention, the material of the pool wall positioning platform is any one of 316L stainless steel, duplex stainless steel or titanium alloy.

[0024] In one embodiment of the present invention, the at least two laser line scanning units are four laser line scanning units, and the four laser line scanning units are respectively arranged facing the four sides of the fuel assembly.

[0025] The present invention provides a method for measuring and automatically compensating for deformation of fuel assemblies during loading and unloading, comprising the following steps: The measuring module is installed on a positioning platform fixed to the wall of the fuel water tank; During the movement of the fuel assembly along the height direction, laser line images of the surface of the fuel assembly are acquired by at least two laser line scanning units in the measurement module; The three-dimensional shape point cloud of the fuel assembly is reconstructed based on the laser line image, and the deformation of the fuel assembly is identified. The pose compensation amount of the fuel assembly relative to the target loading / unloading position is calculated based on the deformation amount; The material changer is driven to perform fine-tuning of its posture based on the posture compensation amount. In addition, during the loading and unloading process, abnormal conditions are monitored and a safety response is triggered when an abnormal condition is detected.

[0026] In one embodiment of the present invention, when acquiring the laser line image, each laser line scanning unit is synchronously triggered to acquire images according to the encoder signal of the lifting mechanism and a preset trigger condition, and the height position corresponding to each frame image is recorded; the preset trigger condition is any one of a preset height interval, a preset time interval, or an encoder pulse signal.

[0027] In one embodiment of the present invention, the measurement module includes an underwater sealed housing, and each of the laser line scanning units is encapsulated within the underwater sealed housing; each of the laser line scanning units includes a laser projector and an image acquisition unit, wherein the laser projector is used to project laser lines onto the surface of the fuel assembly, and the image acquisition unit is used to acquire laser line images of the surface of the fuel assembly.

[0028] In one embodiment of the present invention, the step of identifying the amount of deformation includes: Fit the centerline of the fuel assembly; Based on the centerline, calculate the maximum lateral offset of the centerline relative to the ideal straight line or the centerline of the standard model; Based on the centerline, calculate the top center offset, bottom center offset, bending direction, overall tilt angle, torsion angle, and local outward convex position of the fuel assembly, and extract the lateral offset of each height section. Calculate the matching residual between the three-dimensional shape point cloud and the centerline of the standard model, and use it as a measurement reliability index; Furthermore, the oscillating component and the true bending component are distinguished based on the variation characteristics of the lateral offset of the centerline and each height section in the time and space dimensions; if the lateral offset of each height section is a translation in the same direction as a whole and changes periodically with time, it is determined to be an oscillating component; if different height sections have a stable spatial curvature relative to the standard centerline, it is determined to be a true bending component.

[0029] In one embodiment of the present invention, the invention further includes an insertion feasibility index, which is used to evaluate the feasibility of automatically inserting the fuel assembly into the target loading / unloading position.

[0030] In one embodiment of the present invention, when the fuel assembly is not grabbed by the refueling machine, the position compensation amount is the position compensation amount of the refueling trolley; when the fuel assembly has been grabbed and suspended by the refueling machine, the position compensation amount is at least one of the micro-motion compensation amount of the refueling machine trolley, the refueling trolley, or the lifting mechanism.

[0031] In one embodiment of the present invention, the pose compensation amount includes at least one of horizontal displacement compensation amount, rotation compensation amount about the vertical axis, or insertion angle compensation amount; and a lifting speed limit signal and an instruction signal to allow automatic insertion.

[0032] In one embodiment of the present invention, the security response is executed in stages according to the severity of the anomaly: Level 1: Stop the current action and enter self-diagnosis mode; The second stage involves retracting the fuel assembly to a safe altitude. Level 3: Re-perform full-height deformation measurement; Level 4: Switch to manual control mode.

[0033] In one embodiment of the present invention, the method is implemented in three stages: In the first stage, offline measurements are performed and deformation reports are output without intervening in the material changer control. In the second stage, the pose compensation amount is automatically calculated and fine-tuned after manual confirmation. The third stage involves fully automated measurement, compensation, and loading / unloading operations.

[0034] In one embodiment of the present invention, after the measurement module is installed on the pool wall positioning platform, the method further includes performing external parameter self-calibration by scanning a fixed calibration target set on the pool wall positioning platform.

[0035] In one embodiment of the present invention, the step of reconstructing a three-dimensional shape point cloud includes: A pool wall reference coordinate system is established based on the pool wall positioning platform; The laser line images in each frame are subjected to denoising, brightness normalization, and laser line enhancement processing. Extract the center of the laser line from each frame of the processed laser line image; Based on the triangulation model, the center of the laser line is converted into cross-sectional contour points at various height positions, and then unified to the reference coordinate system of the pool wall through extrinsic parameter transformation; The cross-sectional contour points at each height position, which are unified to the reference coordinate system of the pool wall, are spliced ​​together according to the height position to generate the three-dimensional shape point cloud of the fuel assembly. Outlier removal and voxel downsampling are performed on the three-dimensional shape point cloud.

[0036] The present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the method described herein.

[0037] The beneficial effects of this invention: The fuel assembly deformation measurement and automatic compensation loading and unloading system provided by this invention, through the coordinated operation of the pool wall positioning platform, measurement module, synchronous triggering module, deformation identification module, compensation calculation module, automatic compensation control interface, and safety interlock module, achieves the following beneficial effects: The system utilizes a fixed positioning platform mounted on the fuel tank wall, onto which the measurement module is detachably mounted during refueling. This ensures that the measurement module can be used for measurements with the same fixed reference point after each installation, eliminating positioning errors caused by variations in the measurement device's placement and guaranteeing the consistency and repeatability of the measurement data. Furthermore, the measurement module is temporarily installed during refueling and removed afterward, preventing prolonged immersion in the underwater environment and improving the system's maintainability.

[0038] The system connects to the encoder of the lifting mechanism via a synchronous trigger module. As the fuel assembly moves along its height, it synchronously triggers each laser line scanning unit to acquire laser line images according to preset trigger conditions, recording the height position corresponding to each frame. This achieves precise synchronization between the laser line scanning units and the actual movement of the fuel assembly, ensuring that each acquired cross-sectional image accurately corresponds to the actual height position of the fuel assembly, providing a precise data foundation for subsequent 3D reconstruction. The synchronous triggering method utilizes the fuel assembly's own lifting and lowering motion to complete the scanning of cross-sections at different heights, eliminating the need for an additional underwater scanning motion mechanism and simplifying the system structure.

[0039] The system reconstructs the three-dimensional shape point cloud of the fuel assembly through the deformation recognition module and identifies its deformation amount, realizing the quantitative detection of the deformation of the fuel assembly underwater. This allows the actual deformation state of the fuel assembly to be quantified, providing input parameters for subsequent compensation control.

[0040] The system calculates the pose compensation amount based on the deformation amount through the compensation calculation module, and outputs it to the refueling machine control system via the automatic compensation control interface to drive the refueling machine to perform pose fine-tuning. This establishes a closed-loop control link from deformation measurement to pose compensation, enabling the system to automatically adjust the refueling machine's pose according to the actual deformation state of the fuel assembly. When the fuel assembly deforms due to irradiation and thermal-hydraulic loads, the system can automatically compensate for the deviation between the actual centerline and the theoretical coordinates, avoiding descent jamming, underload, or overload alarms caused by operating according to the theoretical coordinates, and reducing manual intervention.

[0041] The system triggers a safety response when an abnormal state is detected through a safety interlock module, providing a safety protection mechanism independent of the normal control process during automatic loading and unloading. When an abnormal state is detected, a safety response can be triggered in a timely manner, reducing the risk of equipment damage or fuel component damage due to abnormal conditions during loading and unloading. Attached Figure Description

[0042] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0043] In the attached diagram: Figure 1 This is a block diagram of the overall structure of a fuel assembly deformation measurement and automatic compensation loading and unloading system provided in an embodiment of the present invention; Figure 2 This is a flowchart of a fuel assembly deformation measurement and automatic compensation loading and unloading method provided in one embodiment of the present invention; Figure 3 A detailed flowchart of a fuel assembly deformation measurement and automatic compensation loading and unloading method provided in an embodiment of the present invention; Detailed Implementation The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. In the absence of conflict, the features in the various embodiments can be combined with each other.

[0044] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0045] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0046] During refueling overhauls at nuclear power plants, fuel assemblies are transferred between the reactor core, fuel transfer unit, spent fuel pool, dumping zone, and related storage areas. The refueling machine is a key piece of equipment for loading, unloading, lifting, transferring, lowering, and positioning fuel assemblies. Its operational reliability, positioning accuracy, and level of automation directly affect the refueling schedule, personnel radiation exposure, fuel assembly safety, and nuclear power unit availability.

[0047] Traditional refueling machines typically rely on operators for semi-automatic or manual operation via control consoles, video surveillance, position encoders, load displays, limit signals, and procedural steps. For regularly shaped fuel assemblies, refueling can be completed using preset core coordinates, encoder feedback, and manual monitoring. However, under long-term irradiation, thermal-hydraulic loads, manufacturing deviations, core operating environments, mechanical stress, or abnormal operating conditions, fuel assemblies may deform, tilt, twist, or shift in the grid, causing the actual grab centerline, insertion channel centerline, or outer safety envelope of the fuel assembly to deviate from the theoretical coordinates. If refueling is still performed according to the standard coordinates, friction may occur between the assembly and the core structure, leading to descent jamming, underload, or overload alarms. Operators must make repeated adjustments, reducing refueling efficiency and potentially damaging the fuel assembly in severe cases.

[0048] To address the aforementioned issues, existing technologies have provided automated control solutions for refueling machines. These include methods such as generating operating paths by reading the refueling sequence, using cameras to identify scales and combining them with rangefinder data to locate the refueling machine's position, and using sensors to monitor the refueling machine's operating status for fault diagnosis. However, none of these solutions detect the actual geometric state of the fuel assemblies when they bend, tilt, or twist underwater, nor do they establish a closed-loop control link from the fuel assembly deformation to the refueling machine's pose compensation. These solutions primarily focus on refueling machine equipment status monitoring, fault diagnosis, or interlocking data recording, without prioritizing underwater deformed fuel assemblies as the main detection target. They do not disclose the use of underwater laser and visual fusion data to create an actual three-dimensional shape model of the fuel assemblies; they do not disclose real-time feedback of fuel assembly deformation to the refueling machine's motion control system for refueling trolley position compensation; and they do not disclose automatic centering, automatic fine-tuning, and automatic refueling closed-loop control for deformed fuel assemblies. When there is a deviation between the actual centerline of the fuel assembly and the theoretical coordinates, the above solution cannot directly solve the problems of gripper centering deviation and insertion / removal path deviation caused by the deformed fuel assembly, and centering deviation may still occur or manual intervention may be required.

[0049] To this end, this application provides a fuel assembly deformation measurement and automatic compensation loading and unloading system and method, which can detect the actual deformation state of the fuel assembly underwater and convert the detected deformation amount into the pose compensation amount of the refueling machine in real time, thereby realizing automatic centering, automatic fine adjustment and automatic refueling of deformed fuel assemblies.

[0050] like Figure 1 As shown in Example 1: The fuel assembly deformation measurement and automatic compensation loading and unloading system provided by the present invention includes a pool wall positioning platform, a measurement module, a synchronous triggering module, a deformation identification module, a compensation amount calculation module, an automatic compensation control interface, and a safety interlocking module.

[0051] The pool wall positioning platform is fixedly installed on the fuel water pool wall. This platform is equipped with a positioning mating part for the detachable installation of the measuring module. During refueling operations, the measuring module is installed on the pool wall positioning platform via this positioning mating part; after the operation is completed, the measuring module is removed, and the pool wall positioning platform remains on the pool wall as a fixed reference.

[0052] The measurement module includes at least two laser line scanning units. Each laser line scanning unit can project a laser line onto the surface of the fuel assembly and acquire laser line images of the fuel assembly surface. As the fuel assembly moves along the height direction, each laser line scanning unit in the measurement module scans the surface of the fuel assembly from different orientations to obtain the cross-sectional profile of the fuel assembly at different height positions.

[0053] The synchronous triggering module is connected to the encoder signal of the lifting mechanism used to drive the fuel assembly's lifting and lowering. As the lifting mechanism moves the fuel assembly vertically, the encoder outputs a position signal reflecting the fuel assembly's current position in real time. Based on the position signal output by the encoder, the synchronous triggering module synchronously triggers each laser line scanning unit to acquire images according to preset triggering conditions. During each acquisition trigger, the synchronous triggering module also records the height position corresponding to each frame of image, thus ensuring a one-to-one correspondence between each frame of image and the actual height position of the fuel assembly.

[0054] The deformation recognition module receives laser line images acquired by each laser line scanning unit and reconstructs the three-dimensional shape point cloud of the fuel assembly based on these images. During the reconstruction process, the cross-sectional contours acquired at different height positions are stitched together according to their corresponding height positions to restore the complete three-dimensional shape of the fuel assembly. Based on the reconstructed three-dimensional shape point cloud, the deformation recognition module further identifies whether the fuel assembly has deformations such as bending, tilting, or torsion, and outputs the corresponding deformation amount.

[0055] The compensation calculation module obtains the deformation of the fuel assembly from the deformation identification module, and calculates the pose compensation amount of the fuel assembly relative to the target loading / unloading position based on this deformation amount. The target loading / unloading position is the core hole where the fuel assembly is to be loaded or the designated position to which it is to be transferred. The compensation calculation module calculates the pose compensation amount to be output based on the deviation between the actual end position of the fuel assembly and the target loading / unloading position.

[0056] The automatic compensation control interface outputs the pose compensation amount calculated by the compensation amount calculation module to the refueling machine control system. Based on this pose compensation amount, the refueling machine control system drives the refueling machine to perform pose fine-tuning, thereby aligning the actual pose of the fuel assembly with the target loading / unloading position.

[0057] The safety interlock module continuously monitors abnormal conditions throughout the loading and unloading process and triggers corresponding safety responses when an abnormal condition is detected to prevent equipment damage or fuel component damage caused by abnormal situations during loading and unloading.

[0058] The pool wall positioning platform is fixedly installed on the fuel water pool wall. During refueling, the measurement module is detachably installed on the pool wall positioning platform via a positioning mating part; the two are physically connected in a detachable manner. The positioning mating part enables high repeatability of positioning between the measurement module and the pool wall positioning platform. A locking mechanism, independent of the positioning mating part, locks the connection between the measurement module and the pool wall positioning platform after the measurement module is in place, preventing displacement of the measurement module due to water flow impact or vibration during measurement. Each laser line scanning unit in the measurement module is connected to the synchronous triggering module via a signal line, and the synchronous triggering module sends synchronous trigger signals to each laser line scanning unit. The synchronous triggering module is also connected to the encoder of the lifting mechanism via a signal line, receiving the position signal output by the encoder. Each image acquisition unit in the measurement module is connected to the deformation recognition module via a data line, transmitting the acquired laser line images to the deformation recognition module. The synchronous triggering module is also connected to the deformation recognition module via a signal line, transmitting the height position corresponding to each frame of the image to the deformation recognition module. The deformation recognition module and the compensation calculation module are connected via a data cable, transmitting the recognized deformation to the compensation calculation module. The deformation recognition module is also connected to the safety interlock module via a signal cable, transmitting the insertion feasibility index to the safety interlock module. The compensation calculation module is connected to the automatic compensation control interface via a data cable, transmitting the calculated pose compensation to the automatic compensation control interface. The automatic compensation control interface is connected to the material changer control system via a communication interface, transmitting the pose compensation, lifting speed limit signal, and automatic insertion permission command signal to the material changer control system. The material changer control system is connected to the material changer via a control cable, driving the material changer to perform pose fine-tuning. The material changer is connected to the safety interlock module via a signal cable, feeding back force and position signals to the safety interlock module. The safety interlock module is connected to the automatic compensation control interface via a signal cable, transmitting a safety response signal to the automatic compensation control interface when an abnormal state is detected.

[0059] In actual operation, the above system first installs the measurement module on the positioning platform on the pool wall. The lifting mechanism drives the fuel assembly to move along the height direction, and the synchronous triggering module triggers the laser line scanning unit according to the encoder signal and preset triggering conditions to acquire laser line images at various height positions. The deformation recognition module reconstructs the three-dimensional shape of the fuel assembly based on the acquired laser line images and identifies the amount of deformation. The compensation calculation module calculates the pose compensation amount based on the deformation amount and outputs it to the refueling machine control system via the automatic compensation control interface. The refueling machine control system then drives the refueling machine to perform fine adjustments. The safety interlock module continuously monitors the entire process and triggers a safety response when an anomaly is detected. Thus, the system can achieve automatic alignment and safe loading and unloading even when the fuel assembly is deformed.

[0060] Example 2: The measurement module needs to operate in an underwater environment, and its sealing performance and the reliability of its optical components directly affect the measurement accuracy and service life.

[0061] The measurement module also includes an underwater sealed housing, within which each laser line scanning unit is encapsulated. The underwater sealed housing is made of a corrosion-resistant metal material, such as 316L stainless steel, forming a sealed cavity in which each laser line scanning unit is installed. A light-transmitting window is located at the front of the underwater sealed housing, fitted with a sapphire or quartz viewing window to ensure unobstructed optical paths for laser projection and image acquisition, while also withstanding underwater pressure. The seams of the underwater sealed housing are watertight using O-rings to prevent boron-containing water from the spent fuel pool from seeping into the housing and damaging the optical components. The underwater sealed housing also has a cable interface for leading the control and signal lines of the laser line scanning units to the surface control equipment; this interface is also sealed with a watertight connector. Each laser line scanning unit includes a laser projector and an image acquisition unit. The laser projector projects laser lines onto the surface of the fuel assembly, and the image acquisition unit acquires images of the laser lines on the surface of the fuel assembly. When a line laser emitted by a laser projector illuminates the surface of a fuel assembly, it forms a light stripe on the assembly surface. The shape of this light stripe reflects the cross-sectional profile of the fuel assembly at that height. An image acquisition device captures this light stripe from another angle, obtaining a laser line image containing the light stripe. Because there is a fixed angle between the projection direction of the laser projector and the optical axis of the image acquisition device, there is a definite geometric correspondence between the pixel position of the light stripe in the laser line image and the spatial position of that point on the fuel assembly surface. Subsequently, the pixel position can be converted into three-dimensional spatial coordinates using the principle of triangulation. This structure provides protection for each laser line scanning unit through an underwater sealed shell, enabling it to operate normally in an underwater environment. Simultaneously, the collaborative work of the laser projector and the image acquisition device acquires the cross-sectional profile information of the fuel assembly surface, providing raw data for subsequent 3D reconstruction.

[0062] Example 3: In order to ensure that the cross-sectional data collected by each laser line scanning unit corresponds precisely with the actual height position of the fuel assembly, a reliable synchronous triggering mechanism and data binding method are required.

[0063] The preset trigger condition can be any one of a preset height interval, a preset time interval, or an encoder pulse signal. A preset height interval means that a data acquisition is triggered every fixed distance the fuel assembly moves along the height direction; a preset time interval means that a data acquisition is triggered every fixed time period; an encoder pulse signal means that the encoder output pulse signal is used directly as the trigger source, with each encoder pulse triggering a data acquisition. The frequency of the encoder pulse signal corresponds to the rotation angle of the lifting mechanism, and thus to the displacement of the fuel assembly. The synchronous trigger module also records a timestamp, measurement module status, laser channel number, and image frame number at each trigger, and binds each image frame to its corresponding height value and timestamp. The timestamp records the time of image acquisition for subsequent analysis of the fuel assembly's motion state at different times. For example, when the fuel assembly oscillates underwater, the timetamp can be used to analyze the oscillation period and amplitude. The measurement module status records the working status of each component of the measurement module at the trigger time for subsequent data quality traceability. The laser channel number identifies which laser line scanning unit the image frame comes from, for subsequent multi-channel data classification processing. The image frame number is the sequence number of that frame within the entire acquisition sequence, used for subsequent data sorting and integrity verification. The synchronization trigger module binds the above data with the corresponding height value and timestamp, storing or transmitting them as associated data groups. This ensures that each subsequent image frame can be traced back to its acquisition time, height position, time information, and various status parameters. This method synchronizes the trigger acquisition with the actual height position of the fuel assembly through encoder position signals, and by recording and binding multiple data points, it provides a data foundation for subsequent 3D reconstruction.

[0064] Example 4: In order to extract deformation information of fuel assembly from acquired laser line images, a data processing flow that can convert image data into quantitative deformation parameters is needed.

[0065] The centerline of the fuel assembly is fitted. The deformation recognition module first extracts the cross-sectional profile point cloud of the fuel assembly at each height position from each frame of laser line image. Then, for the cross-sectional profile point cloud at each height position, the geometric center of the cross-section is calculated, for example, by calculating the centroid of the cross-sectional profile or taking the center of the rectangle after fitting the circumscribed rectangle of the cross-sectional profile. The calculated cross-sectional geometric centers at each height position are arranged in order of height to obtain the centerline of the fuel assembly. In the undeformed state, the centerline of the fuel assembly is a straight line parallel to the height direction; after bending deformation, the centerline will deviate from this straight line at different height positions. Based on the centerline, the lateral offset of each height section is extracted. The lateral offset of each height section refers to the horizontal offset vector of the cross-sectional geometric center at each height position relative to the ideal straight line, including the offset direction and offset magnitude. Based on the lateral offset of each height section, the maximum lateral offset of the centerline relative to the ideal straight line or the standard model centerline is calculated. The ideal straight line is a theoretical straight line in the completely undeformed state where the centerline of the fuel assembly completely coincides with the height direction; the standard model centerline is the centerline of the standard fuel assembly in its theoretical undeformed state stored in the database. The maximum lateral offset is the maximum horizontal distance between the actual centerline and the ideal straight line or the centerline of the standard model across the entire height range. Based on the centerline, the top center offset, bottom center offset, bending direction, overall tilt angle, torsion angle, and local convexity position of the fuel assembly are calculated. The top and bottom center offsets refer to the horizontal offsets of the geometric centers of the top and bottom sections of the fuel assembly relative to the corresponding positions of the ideal straight line or the centerline of the standard model, respectively. The bending direction refers to the main direction of the fuel assembly's bending deformation, determined by the direction in which the centerline deviates from the ideal straight line. The overall tilt angle refers to the angle of inclination of the fuel assembly relative to the vertical direction, determined by the angle between the line connecting the centers of the bottom and top sections and the vertical direction. The torsion angle refers to the rotation angle of the fuel assembly around its own centerline, determined by analyzing the azimuth changes of the profile at various heights. The local convexity position refers to the outward protrusion of a local area on the surface of the fuel assembly, determined by analyzing points in the cross-sectional profile point cloud where the distance from the centerline increases abnormally. The matching residual between the 3D shape point cloud and the centerline of the standard model is calculated as a measurement reliability index. Matching residuals refer to the statistical value of the portion that fails to match when the reconstructed 3D shape point cloud is registered with the 3D model of a standard fuel assembly. This residual value reflects the reliability of the measurement results; a smaller residual value indicates a more reliable measurement result, while a larger residual value indicates a potentially large error in the measurement process or that the fuel assembly deformation exceeds the normal range. The swaying component and the true bending component are distinguished based on the variation characteristics of the lateral offset of the centerline and each height section in both time and space dimensions.During the movement of the fuel assembly, the assembly may experience overall oscillation due to water flow impact or vibration of the lifting mechanism. This oscillation causes a uniform lateral displacement across all height sections, and this displacement varies periodically over time. True bending deformation, on the other hand, manifests as a stable, non-periodic deviation of different height sections from the standard centerline. If the lateral displacement of each height section is a uniform translational movement that varies periodically over time, it is identified as an oscillation component; if different height sections exhibit a stable spatial curvature relative to the standard centerline, it is identified as a true bending component. This distinction method separates the true bending deformation of the fuel assembly from the oscillation during movement, improving the accuracy of deformation identification.

[0066] The aforementioned deformation recognition method, through the system's data processing flow, gradually converts the original image data into quantitative deformation parameters, enabling the deformation state of the fuel assembly to be accurately described and quantified, providing input data for subsequent pose compensation.

[0067] Example 5: After identifying the deformation of the fuel assembly, it is also necessary to quantitatively evaluate whether the deformation affects the automatic insertion operation, so as to provide a basis for decision-making for the safety interlock module.

[0068] The deformation identification module also outputs an insertion feasibility index. This index is used to evaluate the feasibility of automatically inserting the fuel assembly into the target loading / unloading position and serves as input to the safety interlock module. The deformation identification module comprehensively judges whether the current fuel assembly can be safely and automatically inserted into the target loading / unloading position based on calculated deformation parameters. When the maximum bending amount exceeds a preset threshold, or the overall tilt angle exceeds a preset threshold, or the torsion angle exceeds a preset threshold, it indicates that the fuel assembly has undergone significant deformation, and automatic insertion may cause jamming with the core hole wall. In this case, the insertion feasibility index determines it to be infeasible. Conversely, when all deformation parameters are within the preset threshold range, it is determined to be feasible. This index is output to the safety interlock module in the form of a quantified value or level, serving as one of the criteria for determining whether automatic insertion is permitted. If determined to be infeasible, the safety interlock module triggers a safety response, switching to manual control mode or stopping the current action to avoid damage to the fuel assembly caused by forced insertion.

[0069] Example 6: Fuel assemblies exist in two different physical states during loading and unloading: the state before being grabbed by the refueling machine and the state after being grabbed and suspended by the refueling machine. The constraints on the fuel assemblies are different in these two states, and the required compensation methods are also different. Therefore, it is necessary to differentiate the output of the pose compensation amount.

[0070] When the fuel assembly is not gripped by the refueling machine, the pose compensation is the position compensation of the refueling trolley. At this time, the fuel assembly is still on the refueling trolley, its bottom supported by the trolley, and the assembly's posture is mainly determined by the trolley's position. The compensation calculation module calculates the horizontal position compensation of the refueling trolley based on the deviation between the bottom end position of the fuel assembly output by the deformation recognition module and the target loading / unloading position, and outputs it to the refueling machine control system through the automatic compensation control interface. The refueling machine control system adjusts the trolley position accordingly, moving the bottom center of the fuel assembly directly below the center of the gripper, ensuring that the gripper can accurately grip the fuel assembly. When the fuel assembly has been gripped and suspended by the refueling machine, the pose compensation is at least one of the micro-motion compensation of the refueling machine's main trolley, the refueling trolley, or the lifting mechanism. At this time, the top of the fuel assembly is constrained by the gripper, and the entire assembly moves with the refueling machine's main trolley, trolley, and lifting mechanism. To align the fuel assembly's axis with the target loading / unloading position, the poses of the main trolley, trolley, and lifting mechanism must be adjusted simultaneously. The compensation calculation module calculates the micro-motion compensation amounts for the main trolley, auxiliary trolley, and lifting mechanism based on the overall tilt angle, torsion angle, and bottom end offset, and outputs the results through the automatic compensation control interface. The material changer control system performs coordinated fine-tuning based on these micro-motion compensation amounts to align the component axes with the target position.

[0071] Example 7: In order to achieve precise alignment between the fuel assembly and the target loading / unloading position, the pose compensation amount needs to cover the adjustment of multiple degrees of freedom. At the same time, the insertion speed and insertion permission state also need to be controlled during the insertion process.

[0072] The positional compensation includes at least one of horizontal displacement compensation, rotational compensation around the vertical axis, or insertion angle compensation. Horizontal displacement compensation is the adjustment of the refueling machine's displacement in two orthogonal directions within the horizontal plane, used to correct positional deviations of the fuel assembly in the horizontal plane. Rotational compensation around the vertical axis is the adjustment of the refueling machine's rotation around the vertical axis, used to correct torsional angular deviations of the fuel assembly. Insertion angle compensation is the adjustment of the refueling machine's angle in the insertion direction, used to correct overall tilt angular deviations of the fuel assembly, ensuring the assembly's axial direction aligns with the centerline of the target loading / unloading position. The automatic compensation control interface also outputs a lifting speed limit signal and a command signal to allow automatic insertion. The lifting speed limit signal limits the lowering speed of the lifting mechanism during insertion; when the fuel assembly has significant deformation or low insertion feasibility indicators, the lifting mechanism is limited to a lower speed to reduce impact risks during insertion. The command signal to allow automatic insertion is a logic signal used to indicate whether the refueling machine control system can execute the automatic insertion action. When the signal is true, the material changer control system performs automatic insertion; when it is false, the system stops automatic insertion and waits for manual confirmation or switches to manual mode.

[0073] Example 8: Various abnormal situations may occur during the automatic loading and unloading process, which need to be monitored and the corresponding safety response should be triggered when detected.

[0074] An abnormal state is defined as at least one of the following: abnormal insertion force, abnormal lateral force, abnormal torque, excessive position deviation, excessive laser measurement residual, excessive fuel assembly sway amplitude, or abnormal communication status. An abnormal insertion force is defined as the axial insertion force exceeding the preset normal range detected during insertion, indicating jamming between the fuel assembly and the core hole wall. An abnormal lateral force is defined as the lateral force perpendicular to the insertion direction exceeding the preset normal range detected during insertion, indicating tilting or displacement of the fuel assembly. An abnormal torque is defined as the torque around the vertical axis exceeding the preset normal range detected during insertion, indicating torsion of the fuel assembly. An excessive position deviation is defined as the deviation between the fuel assembly position and the target position monitored in real time during insertion exceeding the preset allowable range. An excessive laser measurement residual is defined as the laser measurement residual exceeding the preset allowable range calculated by the deformation recognition module during 3D reconstruction, indicating insufficient measurement data quality or interference during measurement. An excessive fuel assembly sway amplitude is defined as the sway amplitude exceeding the preset allowable range caused by water flow or mechanical vibration underwater. A communication anomaly occurs when communication between the synchronization trigger module, deformation identification module, compensation calculation module, automatic compensation control interface, or safety interlock module is interrupted or contains data errors. The safety response includes at least one of the following: stopping the current action, retracting the fuel assembly to a safe height, re-executing deformation measurement, or switching to manual control mode. Stopping the current action means immediately halting all ongoing movements, keeping the refueling machine in its current position. Retracting the fuel assembly to a safe height means raising the fuel assembly to a preset safe height away from the core apertures to prevent it from remaining in a dangerous position under abnormal conditions. Re-executing deformation measurement means triggering the deformation identification module to re-acquire the laser line image and recalculate the deformation to confirm the accuracy of the previous measurement results. Switching to manual control mode means exiting automatic control mode and transferring control of the refueling machine to the operator, who will then manually complete subsequent operations.

[0075] Example 9: During the automatic loading and unloading process, different abnormal situations have different degrees of severity. Using a uniform response method may lead to overreaction or underreaction. Therefore, it is necessary to set up a graded safety response strategy according to the severity of the abnormality.

[0076] Safety responses are executed in tiers according to the severity of the anomaly. Tier 1: Stop current action and enter self-diagnostic mode. When a minor anomaly is detected, the system first executes a Tier 1 response, pausing all ongoing movements, keeping the refueling machine in its current position, and simultaneously initiating a self-diagnostic program to check the operational status of each system module to determine if the anomaly is caused by a temporary factor. Tier 2: Return fuel assemblies to a safe height. If the self-diagnostic process cannot eliminate the anomaly or the anomaly persists, the system executes a Tier 2 response, returning the fuel assemblies along the lifting direction to a preset safe height position away from the core apertures, preventing the assemblies from remaining in a dangerous position under abnormal conditions. Tier 3: Re-execute full-height deformation measurement. After the fuel assemblies return to a safe height, the system automatically triggers the deformation recognition module to re-acquire laser line images and re-executes deformation measurements across the entire height range to confirm whether the deformation state of the fuel assemblies has changed or whether there were errors in the previous measurement results. Tier 4: Switch to manual control mode. If the anomaly persists after remeasurement, or if the system detects a serious fault, the system executes a Level 4 response, exiting automatic control mode and transferring control of the material changer to the operator, who then manually performs subsequent operations based on the actual situation. This four-level response constitutes a progressive strategy from automatic recovery to manual takeover. Each level escalates if the previous level fails to resolve the issue, avoiding premature manual intervention for minor anomalies and promptly transferring control in cases of serious anomalies.

[0077] Example 10: During the retrofitting of nuclear power plant equipment, the introduction of new systems requires gradual verification before they can be put into fully automated operation. Therefore, the system needs to provide different levels of automation to adapt to the needs of gradual deployment.

[0078] The system offers three selectable operating modes: manual confirmation, semi-automatic execution, and fully automatic closed-loop. In manual confirmation mode, the system measures and calculates the deformation of the fuel assembly, outputting the results to the operator. After operator confirmation, the system manually controls the refueling machine to perform posture adjustment; the system does not automatically perform compensation or loading / unloading operations. In semi-automatic execution mode, the system automatically measures deformation, calculates deformation, and calculates posture compensation, displaying the calculated compensation amount to the operator. After operator confirmation, the system automatically performs posture fine-tuning and loading / unloading operations. In fully automatic closed-loop mode, the system automatically executes the entire process from deformation measurement, deformation calculation, posture compensation calculation to posture fine-tuning and loading / unloading operations without manual intervention. It only triggers a safety response and alerts the operator when an anomaly is detected. These three modes provide a gradual progression from manual control to fully automatic control, allowing operators to select the appropriate operating mode based on actual site conditions and system verification progress.

[0079] Example 11: The position of the measurement module may have slight deviations after each installation. In order to eliminate the impact of these deviations on the measurement accuracy, it is necessary to calibrate the external parameters of the measurement module by fixing a calibration target.

[0080] The pool wall positioning platform is equipped with at least three fixed calibration targets. After the measurement module is installed, external parameters are self-calibrated by scanning the fixed calibration targets to correct the installation attitude deviation of the measurement module relative to the pool wall reference coordinate system established based on the pool wall positioning platform. The fixed calibration targets are located near the pool wall positioning platform, and their three-dimensional spatial coordinates relative to the pool wall reference coordinate system are pre-calibrated by precision measurement and stored in the system. After the measurement module is installed, the laser line scanning unit scans each fixed calibration target to obtain the coordinates of each target in the measurement coordinate system of the measurement module itself. Since the coordinates of each target in the pool wall reference coordinate system are known, the system establishes the transformation relationship between the measurement coordinate system and the pool wall reference coordinate system through spatial coordinate transformation, using at least three sets of corresponding coordinate points, and solves for the rotation matrix and translation vector of the measurement module relative to the pool wall reference coordinate system, i.e., the installation attitude deviation. Based on this deviation, the external parameters are corrected so that all data obtained from subsequent measurements can be accurately converted to the pool wall reference coordinate system, ensuring the accuracy and repeatability of the measurement results. This method achieves automatic external parameter calibration of the measurement module after each installation by using a fixed calibration target, thus eliminating the impact of installation deviation on measurement accuracy.

[0081] Example 12: In an underwater environment, light is attenuated and distorted after being scattered and absorbed by water. At the same time, specular reflection may occur on the metal surface of the fuel assembly. These factors will affect the image acquisition quality. Therefore, it is necessary to take corresponding optical measures to optimize image acquisition.

[0082] The measurement module also incorporates narrowband and polarizing filters along the light-collecting paths of each image acquisition unit. The passband wavelength of the narrowband filter matches the laser wavelength of the laser projector. The narrowband filter allows only narrow-band light with wavelengths matching or close to the laser wavelength to pass through, while blocking stray light of other wavelengths from entering the image acquisition unit. In underwater environments, ambient light is typically broadband; most of this ambient light is filtered out by the narrowband filter, while the line laser emitted by the laser projector can pass through smoothly because its wavelength falls within the passband of the narrowband filter, thus improving the signal-to-noise ratio of the laser line image. The polarizing filter suppresses specular reflections from the metal surface of the fuel assembly. The reflection of laser light from the metal surface includes diffuse and specular components; specular reflections are polarized, while diffuse reflections are unpolarized. By blocking light with specific polarization directions, the polarizing filter effectively suppresses specular reflections from entering the image acquisition unit while retaining diffuse reflections, resulting in clearer and more uniform light stripes in the laser line image. Each image acquisition unit uses a synchronous exposure method with the laser projector to acquire images. Synchronous exposure means that the exposure time of the image acquisition unit is consistent with the light emission time of the laser projector, acquiring images only during the laser projector's light emission period to avoid acquiring invalid image data during the laser's off-state. This method, through the synergistic effect of narrowband filters, polarization filters, and synchronous exposure, optimizes image acquisition from three dimensions: spectral, polarization, and temporal, improving the quality of laser line images and the accuracy of subsequent laser line extraction.

[0083] Example 13: The conversion from each frame of laser line image to a complete 3D shape point cloud involves multiple data processing steps, and the processing quality of each step will affect the accuracy of the final reconstruction result.

[0084] The deformation recognition module reconstructs the 3D shape point cloud as follows: A pool wall reference coordinate system is established based on the pool wall positioning platform; denoising and brightness normalization are performed on each frame of laser line images, followed by laser line enhancement; the laser line center is extracted from each frame of processed laser line images; the laser line center is converted into cross-sectional contour points at various height positions based on a triangulation model, and then unified to the pool wall reference coordinate system through extrinsic parameter transformation; the cross-sectional contour points at various height positions unified to the pool wall reference coordinate system are stitched together according to their height positions to generate the 3D shape point cloud of the fuel assembly; outlier removal and voxel downsampling are performed on the 3D shape point cloud. The pool wall reference coordinate system is the reference system for all subsequent data transformations, and its origin is defined at a specific reference point on the pool wall positioning platform. Denoising is used to eliminate scattering noise and sensor noise in the underwater environment; brightness normalization is used to eliminate the influence of ambient light changes at different acquisition times; and laser line enhancement is used to improve the contrast between the laser stripes and the background. The laser line center can be extracted using the gray-scale centroid method or the Steger algorithm. The triangulation model utilizes a fixed baseline between the laser projector and the image acquisition unit to convert the two-dimensional coordinates of each pixel at the center of the laser line in the image into three-dimensional coordinates in the measurement coordinate system. Extrinsic parameter transformation unifies the cross-sectional contour points in the measurement coordinate system to the pool wall reference coordinate system through rotation and translation transformations. This step uses the coordinate transformation parameters obtained from the extrinsic parameter self-calibration in Example 11. After the transformation, the cross-sectional contour points at different heights are stitched together according to the height values ​​recorded by the encoder to form a complete three-dimensional shape point cloud of the fuel assembly. Outlier removal is used to eliminate isolated noise points caused by scattering or reflection anomalies. Voxel downsampling divides the point cloud space into a regular three-dimensional grid, retaining only the centroid of all points within each grid, thereby reducing the data volume while maintaining the overall shape characteristics and improving subsequent processing efficiency.

[0085] Example 14: The pool wall positioning platform is fixed in the underwater environment of the fuel water pool wall for a long time. Its structural design needs to take into account both long-term service reliability and the accuracy of cooperation with the measurement module.

[0086] The pool wall positioning platform is a passive mechanical structure, containing no electronic components, optical components, or seals. It also features a locking mechanism to secure the measurement module to the platform. The passive mechanical structure means the platform does not rely on power supplies, signal lines, or sealed cavities to maintain its function; its functionality is entirely determined by mechanical geometry. The absence of electronic components, optical components, and seals avoids the risk of aging and failure of these parts in long-term underwater irradiation, improving the platform's long-term reliability. The locking mechanism locks the measurement module to the platform after installation, preventing displacement during measurement due to water flow impact or vibration.

[0087] Example 15: The positioning and mating parts need to ensure that the measuring module has a consistent position during multiple hoisting and installation processes in order to reduce positioning errors caused by repeated installations.

[0088] The positioning mating part is a three-point kinematic positioning pair, which can be any one of the following: a ball-groove-plane three-point positioning structure, a tapered pin and V-groove mating structure, or a ball-and-socket positioning structure. The three-point kinematic positioning pair uses three contact points to define the six degrees of freedom of a rigid body in space. In the ball-groove-plane structure, the fit between the ball and the groove constrains two translational degrees of freedom, and the fit between the ball and the plane constrains one translational degree of freedom and one rotational degree of freedom; the three contact points together constitute a defined geometric constraint. In the tapered pin and V-groove mating structure, the fit between the tapered pin and the V-groove provides precise positioning constraints. In the ball-and-socket positioning structure, the fit between the ball and the socket provides point contact constraints. All three structures can provide defined geometric constraints during each repeated installation of the measurement module, reducing installation stress and repetitive positioning errors caused by over-constraint.

[0089] Example 16: The type of fixed calibration target used as a reference for external parameter self-calibration affects the calibration accuracy and ease of operation.

[0090] The fixed calibration target is at least one of the following: a stainless steel sphere, a ceramic circular hole target, a cross-shaped target, a reflective target, or a calibration block. A stainless steel sphere, with its spherical geometry, provides isotropic detection characteristics, suitable for scanning from any angle. A ceramic circular hole target provides a circular feature, allowing for high-precision feature point extraction through center positioning; the corrosion resistance and dimensional stability of the ceramic material make it suitable for long-term underwater use. A cross-shaped target provides a cross-shaped feature, facilitating rapid feature point positioning. A reflective target uses its highly reflective surface to generate a strong reflection signal from the laser, improving the signal-to-noise ratio of the detection. A calibration block is a block-shaped target with known three-dimensional geometric features, providing multiple spatial reference points through its geometric characteristics. The above target types can be selected according to the on-site environmental conditions and measurement accuracy requirements.

[0091] Example 17: The laser line scanning unit achieves the measurement of cross-sectional contours through the coordinated work of the laser projector and the image acquisition unit. The geometric configuration between the two determines the calibration parameters and measurement accuracy of the measurement system.

[0092] In each laser line scanning unit, a fixed triangulation baseline is formed between the laser projector and the image acquisition unit. This baseline is used to determine the three-dimensional position of the laser line on the fuel assembly surface based on a triangulation model. The triangulation baseline is the line connecting the emission point of the laser projector and the optical center of the image acquisition unit. The length and direction of this line are determined and fixed through calibration after the measurement module is manufactured. During the measurement process, the laser projector projects a line laser beam onto the surface of the fuel assembly, forming a light stripe on the surface. Each point on the light stripe, together with the emission point of the laser projector and the optical center of the image acquisition unit, forms a triangle. The image acquisition unit captures the light stripe from another angle. There is a definite mathematical relationship between the position of the light stripe in the image and the geometry of the triangle. Based on this relationship and the pre-calibrated baseline parameters, the three-dimensional spatial coordinates of each point on the light stripe are calculated using the principle of triangulation.

[0093] Example 18: The automatic compensation control interface needs to interact with the refueling machine control system. The refueling machine control systems at different nuclear power sites may use different communication protocols and interface standards.

[0094] The automatic compensation control interface communicates with the refueling machine control system via any of the following: Industrial Ethernet, Fieldbus, hard contacts, or a safety PLC interface. Industrial Ethernet is an industrial communication network based on the standard Ethernet protocol, offering high bandwidth and real-time performance, suitable for transmitting large amounts of compensation data. Fieldbus is a digital communication bus specifically designed for industrial automation, offering excellent real-time performance and reliability. Hard contacts are an interface that directly transmits signals via physical electrical signal lines, using switch or analog signals to transmit compensation commands. They feature fast response and high reliability, making them suitable for transmitting critical safety control signals. The safety PLC interface communicates through a dedicated interface for programmable logic controllers that conforms to nuclear safety standards, meeting the special safety requirements of nuclear power plants for instrumentation and control systems. The interface type can be selected based on the existing communication architecture of the refueling machine control system.

[0095] Example 19: The positioning platform on the pool wall is immersed in boron-containing water in the fuel water pool for a long time. The material selection needs to take into account both corrosion resistance and the impact on water quality.

[0096] The positioning platform for the pool wall can be made of any one of 316L stainless steel, duplex stainless steel, or titanium alloy. 316L stainless steel is a low-carbon austenitic stainless steel with excellent resistance to uniform corrosion and pitting corrosion, producing very few corrosion products, making it a commonly used material for nuclear-grade subsea equipment. Duplex stainless steel has an austenitic and ferritic dual-phase microstructure, exhibiting superior resistance to stress corrosion compared to ordinary austenitic stainless steel. Titanium alloy possesses excellent corrosion resistance and specific strength, demonstrating good corrosion resistance in chloride-containing environments. All of the above materials can maintain stable corrosion resistance in the boron-containing water environment of the fuel pool for extended periods, preventing corrosion products from entering the pool water and affecting water quality or adhering to the surface of fuel assemblies.

[0097] Example 20: In order to obtain the complete cross-sectional profile of the four sides of the fuel assembly, it is necessary to scan the fuel assembly simultaneously from multiple directions, and the selection of the laser wavelength needs to be adapted to the underwater transmission conditions.

[0098] The system comprises at least two laser line scanning units, making it a four-channel laser line scanning unit. These four units are arranged facing the four sides of the fuel assembly. The laser projector emits laser light with a wavelength ranging from 450 nm to 532 nm. The four laser line scanning units are evenly distributed circumferentially around the fuel assembly, facing the four sides, and are simultaneously exposed under the control of a synchronous trigger module. A single acquisition can obtain the complete cross-sectional profile of the fuel assembly at that height. This wavelength belongs to the blue-green light band, has a low attenuation coefficient in water, and strong penetration ability, enabling good underwater transmission performance in the boron-containing water environment of the fuel pool.

[0099] like Figure 2 and Figure 3 As shown, this invention also provides a method for measuring and automatically compensating for fuel assembly deformation during loading and unloading. This method can be implemented progressively in three stages according to actual needs: the first stage performs offline measurement and outputs a deformation report without intervening in the refueling machine control; the second stage automatically calculates the pose compensation amount, and performs fine-tuning after manual confirmation; the third stage fully automatically performs measurement, compensation, and loading / unloading operations. The degree of automation in the three stages increases progressively, and any stage can be selected for operation based on the system verification progress and actual site conditions.

[0100] S1. Install the measurement module on the pool wall positioning platform and perform external parameter self-calibration.

[0101] S11. The measurement module is hoisted onto a positioning platform fixed to the wall of the fuel tank. A detachable connection between the measurement module and the positioning platform is achieved through a positioning mating part. The measurement module includes an underwater sealed housing, and each laser line scanning unit is encapsulated within the underwater sealed housing. Each laser line scanning unit includes a laser projector and an image acquisition unit. The laser projector projects laser lines onto the surface of the fuel assembly, and the image acquisition unit acquires images of the laser lines on the surface of the fuel assembly.

[0102] S12. After installing the measurement module on the pool wall positioning platform, extrinsic parameter self-calibration is performed by scanning the fixed calibration targets set on the platform. The fixed calibration targets are located near the pool wall positioning platform, and their three-dimensional spatial coordinates relative to the pool wall reference coordinate system are pre-calibrated through precise measurement and stored in the system. After the measurement module is installed, the laser line scanning unit scans each fixed calibration target to obtain the coordinates of each target in the measurement module's own measurement coordinate system. Since the coordinates of each target in the pool wall reference coordinate system are known, the system uses spatial coordinate transformation to establish a transformation relationship between the measurement coordinate system and the pool wall reference coordinate system using at least three sets of corresponding coordinate points. This allows the system to solve for the rotation matrix and translation vector of the measurement module relative to the pool wall reference coordinate system, i.e., the installation attitude deviation. Based on this deviation, the extrinsic parameters are corrected so that all data obtained from subsequent measurements can be accurately converted to the pool wall reference coordinate system.

[0103] S2. During the movement of the fuel assembly along the height direction, acquire the laser line image collected by the laser line scanning unit in the measurement module.

[0104] S21. The lifting mechanism drives the fuel assembly to move along the height direction, and the encoder outputs a position signal that reflects the current position of the fuel assembly in real time.

[0105] S22. Based on the encoder signal of the lifting mechanism, synchronously trigger each laser line scanning unit to acquire images according to preset trigger conditions. The preset trigger conditions are any one of preset height interval, preset time interval, or encoder pulse signal.

[0106] S23. Each time acquisition is triggered, the height position corresponding to each frame image is recorded, as well as the timestamp, measurement module status, laser channel number and image frame number, and each frame image is bound to the corresponding height value and timestamp.

[0107] S3. Reconstruct the three-dimensional shape point cloud of the fuel assembly based on the laser line image.

[0108] S31. Establish a reference coordinate system for the pool wall based on the pool wall positioning platform.

[0109] S32. Perform noise reduction, brightness normalization, and laser line enhancement processing on each frame of laser line image.

[0110] S33. Extract the laser line center from each processed laser line image frame. The laser line center can be extracted using the gray-scale centroid method or the Steger algorithm.

[0111] S34. Based on the triangulation model, the center of the laser line is converted into cross-sectional contour points at various height positions. The triangulation model utilizes a fixed baseline between the laser projector and the image acquisition device to convert the two-dimensional image coordinates of each pixel at the center of the laser line in the image into three-dimensional coordinates in the measurement coordinate system.

[0112] S35. Unify the cross-sectional profile points to the pool wall reference coordinate system through extrinsic parameter transformation. Extrinsic parameter transformation unifies the cross-sectional profile points in the measurement coordinate system to the pool wall reference coordinate system through rotation and translation transformation. This step uses the coordinate transformation parameters obtained from the extrinsic parameter self-calibration in S12.

[0113] S36. The cross-sectional contour points at each height position, which are unified to the pool wall reference coordinate system, are spliced ​​together according to their height positions to generate a three-dimensional shape point cloud of the fuel assembly.

[0114] S37. Perform outlier removal and voxel downsampling on the 3D shape point cloud. Outlier removal is used to remove isolated noise points caused by scattering or reflection anomalies. Voxel downsampling divides the point cloud space into a regular 3D grid, retaining only the centroids of all points within each grid, thereby reducing the amount of data while maintaining the overall shape characteristics and improving the efficiency of subsequent processing.

[0115] S4. Identify the deformation of the fuel assembly based on the laser line image.

[0116] S41, Fit the centerline of the fuel assembly.

[0117] S42. Based on the centerline, calculate the maximum lateral offset of the centerline relative to the ideal straight line or the centerline of the standard model.

[0118] S43. Based on the centerline, calculate the top center offset, bottom center offset, bending direction, overall tilt angle, torsion angle, and local outward convex position of the fuel assembly, and extract the lateral offset of each height section.

[0119] S44. Calculate the matching residual between the 3D shape point cloud and the center line of the standard model, and use it as a measurement reliability index.

[0120] S45. Differentiate between oscillating components and true bending components based on the characteristics of the lateral offset of the centerline and each height section in the time and spatial dimensions. If the lateral offset of each height section shows an overall translation in the same direction and changes periodically with time, it is determined to be an oscillating component; if different height sections have a stable spatial curvature relative to the standard centerline, it is determined to be a true bending component.

[0121] S46, Output insertion feasibility index.

[0122] The deformation recognition module also outputs an insertion feasibility index, which is used to evaluate the feasibility of automatically inserting the fuel assembly into the target loading / unloading position. If the maximum bending amount exceeds a preset threshold, or the overall tilt angle exceeds a preset threshold, or the torsional angle exceeds a preset threshold, the insertion feasibility index determines it to be infeasible. Conversely, if all deformation parameters are within the preset threshold range, it is determined to be feasible.

[0123] S5. Calculate the pose compensation of the fuel assembly relative to the target loading / unloading position based on the deformation amount.

[0124] S51. When the fuel assembly is not picked up by the refueling machine, the position compensation amount is the position compensation amount of the refueling trolley. The compensation amount calculation module calculates the position compensation amount of the refueling trolley in the horizontal direction based on the deviation between the bottom end position of the fuel assembly and the target loading / unloading position.

[0125] S52. When the fuel assembly has been grabbed and suspended by the refueling machine, the positional compensation amount is at least one of the micro-motion compensation amounts of the refueling machine's main trolley, refueling trolley, or lifting mechanism. The compensation amount calculation module calculates the micro-motion compensation amounts for the main trolley, trolley, and lifting mechanism respectively based on the overall tilt angle, torsion angle, and bottom end offset of the fuel assembly. The positional compensation amount includes at least one of the following: horizontal displacement compensation amount, rotation compensation amount around the vertical axis, or insertion angle compensation amount.

[0126] S6. Drive the material changer to perform fine-tuning of its posture based on the posture compensation amount.

[0127] Before performing pose fine-tuning, the insertion feasibility index output by S5 is used to make a judgment: if the insertion feasibility index is determined to be infeasible, automatic insertion is refused and a safety response is triggered; if it is determined to be feasible, the subsequent steps are continued.

[0128] S61, the automatic compensation control interface outputs the pose compensation amount to the material changer control system, driving the material changer to perform pose fine adjustment.

[0129] S62, the automatic compensation control interface also outputs a lifting speed limit signal and a command signal to allow automatic insertion. The lifting speed limit signal is used to limit the lowering speed of the lifting mechanism during insertion. The command signal to allow automatic insertion is a logic signal used to indicate whether the material changer control system can perform the automatic insertion action. This signal is linked to the insertion feasibility index; when the insertion feasibility index determines that it is feasible, this signal is true, and when it determines that it is not feasible, this signal is false.

[0130] S7. During the loading and unloading process, monitor for abnormal conditions and trigger a safety response when an abnormal condition is detected.

[0131] S71. Monitor multiple abnormal states, including at least one of the following: abnormal insertion force, abnormal lateral force, abnormal torque, excessive position deviation, excessive laser measurement residual, excessive fuel assembly swing amplitude, or abnormal communication status.

[0132] S72. Safety response is executed in stages according to the severity of the anomaly: Level 1, stop the current action and enter self-diagnosis mode; Level 2, return the fuel assembly to a safe height; Level 3, re-execute the full-height deformation measurement; Level 4, switch to manual control mode.

[0133] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A fuel assembly deformation measurement and automatic compensation loading and unloading system, characterized in that, include: A pool wall positioning platform is fixedly installed on the wall of a fuel water pool. The pool wall positioning platform is provided with a positioning mating part for detachable engagement with a measurement module. The measurement module is detachably mounted on the positioning mating part of the pool wall positioning platform during refueling. The measurement module includes at least two laser line scanning units, each of which is used to project a laser line onto the surface of the fuel assembly and acquire laser line images. The synchronous triggering module is connected to the encoder signal of the lifting mechanism used to drive the fuel assembly to rise and fall. It is used to synchronously trigger each laser line scanning unit to acquire images according to the position signal of the encoder and preset triggering conditions, and to record the height position corresponding to each frame image. The deformation recognition module is used to reconstruct the three-dimensional shape point cloud of the fuel assembly based on the laser line image and to identify the amount of deformation of the fuel assembly. The compensation calculation module is used to calculate the pose compensation amount of the fuel assembly relative to the target loading / unloading position based on the deformation amount; An automatic compensation control interface is used to output the pose compensation amount to the material changer control system, driving the material changer to perform pose fine-tuning; And a safety interlock module, used to trigger a safety response when an abnormal state is detected.

2. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 1, characterized in that, The measurement module also includes an underwater sealed housing, and each of the laser line scanning units is encapsulated within the underwater sealed housing; Each of the laser line scanning units includes a laser projector and an image acquisition unit. The laser projector is used to project laser lines onto the surface of the fuel assembly, and the image acquisition unit is used to acquire laser line images of the surface of the fuel assembly.

3. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 1, characterized in that, The preset triggering condition is any one of the preset height interval, preset time interval, or encoder pulse signal; The synchronous triggering module also records the timestamp, measurement module status, laser channel number and image frame number each time it is triggered, and binds each frame image with the corresponding height value and timestamp.

4. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 1, characterized in that, The deformation recognition module identifies the deformation amount in the following ways: Fit the centerline of the fuel assembly; Based on the centerline, extract the lateral offset of each height section, and calculate the maximum lateral offset of the centerline relative to the ideal straight line or the centerline of the standard model based on the lateral offset of each height section. And based on the centerline, calculate the top center offset, bottom center offset, bending direction, overall tilt angle, torsion angle, and local outward convex position of the fuel assembly; The matching residual between the three-dimensional shape point cloud and the pre-established centerline of the standard model is calculated as a measurement reliability index. Furthermore, the oscillating component and the true bending component are distinguished based on the variation characteristics of the lateral offset of the centerline and each height section in the time and space dimensions; if the lateral offset of each height section is a translation in the same direction as a whole and changes periodically with time, it is determined to be an oscillating component; if different height sections have a stable spatial curvature relative to the standard centerline, it is determined to be a true bending component.

5. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 1, characterized in that, The deformation recognition module also outputs an insertion feasibility index; The insertion feasibility index is used to evaluate the feasibility of automatically inserting the fuel assembly into the target loading / unloading position and serves as input to the safety interlock module.

6. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 1, characterized in that, When the fuel assembly is not picked up by the refueling machine, the pose compensation amount is the position compensation amount of the refueling trolley; When the fuel assembly has been grabbed and suspended by the fuel changer, the position compensation amount is at least one of the micro-motion compensation amount of the fuel changer trolley, the fuel changer carriage, or the lifting mechanism.

7. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 1, characterized in that, The pose compensation amount includes at least one of horizontal displacement compensation amount, rotation compensation amount around the vertical axis, or insertion angle compensation amount.

8. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 1, characterized in that, The abnormal state is at least one of the following: abnormal insertion force, abnormal lateral force, abnormal torque, excessive position deviation, excessive laser measurement residual, excessive fuel assembly swing amplitude, or abnormal communication status. The safety response is at least one of the following: stopping the current action, retracting the fuel assembly to a safe altitude, re-performing the deformation measurement, or switching to manual control mode.

9. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 8, characterized in that, The security response is executed in tiers according to the severity of the anomaly: Level 1: Stop the current action and enter self-diagnosis mode; The second stage involves retracting the fuel assembly to a safe altitude. Level 3: Re-perform full-height deformation measurement; Level 4: Switch to manual control mode.

10. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 1, characterized in that, The system has three selectable working modes: manual confirmation mode, semi-automatic execution mode, and fully automatic closed-loop mode.

11. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 1, characterized in that, The pool wall positioning platform is also equipped with fixed calibration targets, and the number of fixed calibration targets is at least three. After the measurement module is installed in place, it performs external parameter self-calibration by scanning the fixed calibration target to correct the installation attitude deviation of the measurement module relative to the pool wall reference coordinate system established based on the pool wall positioning platform.

12. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 1, characterized in that, The measurement module is also equipped with narrowband filters and polarizing filters on the light-collecting paths of each of the image acquisition devices; The passband wavelength of the narrowband filter is matched with the laser wavelength of the laser projector; each of the image acquisition devices acquires images by means of synchronous exposure with the laser projector.

13. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 1, characterized in that, The deformation recognition module reconstructs the three-dimensional shape point cloud in the following ways: A pool wall reference coordinate system is established based on the pool wall positioning platform; The laser line images in each frame are subjected to denoising, brightness normalization, and laser line enhancement processing. Extract the center of the laser line from each frame of the processed laser line image; Based on the triangulation model, the center of the laser line is converted into cross-sectional contour points at various height positions, and then unified to the reference coordinate system of the pool wall through extrinsic parameter transformation; The cross-sectional contour points at each height position, which are unified to the reference coordinate system of the pool wall, are spliced ​​together according to the height position to generate the three-dimensional shape point cloud of the fuel assembly. Outlier removal and voxel downsampling are performed on the three-dimensional shape point cloud.

14. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 1, characterized in that, The pool wall positioning platform is a passive mechanical structure, without electronic components, optical components, or seals; the pool wall positioning platform is also equipped with a locking fit structure for locking the fit between the measurement module and the pool wall positioning platform.

15. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 1, characterized in that, The positioning mating part is a three-point kinematic positioning pair, which can be any one of the following: a ball-groove-plane three-point positioning structure, a tapered pin and V-groove mating structure, or a ball-and-socket positioning structure.

16. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 1, characterized in that, In each of the laser line scanning units, the laser projector and the image acquisition unit form a fixed triangulation baseline, which is used to determine the three-dimensional position of the laser line on the surface of the fuel assembly based on the triangulation model.

17. The fuel assembly deformation measurement and automatic compensation loading and unloading system according to claim 1, characterized in that, The at least two laser line scanning units are four laser line scanning units, and the four laser line scanning units are respectively arranged facing the four sides of the fuel assembly.

18. A method for measuring and automatically compensating for deformation of fuel assemblies during loading and unloading, characterized in that, Includes the following steps: The measuring module is installed on a positioning platform fixed to the wall of the fuel water tank; During the movement of the fuel assembly along the height direction, the encoder signal for the lifting mechanism used to drive the fuel assembly to rise and fall is received. According to the encoder signal and preset triggering conditions, each of the laser line scanning units is synchronously triggered to acquire laser line images of the surface of the fuel assembly. The three-dimensional shape point cloud of the fuel assembly is reconstructed based on the laser line image, and the deformation of the fuel assembly is identified. The pose compensation amount of the fuel assembly relative to the target loading / unloading position is calculated based on the deformation amount; The material changer is driven to perform fine-tuning of its posture based on the posture compensation amount. In addition, during the loading and unloading process, abnormal conditions are monitored and a safety response is triggered when an abnormal condition is detected.

19. The method for measuring and automatically compensating for fuel assembly deformation during loading and unloading according to claim 18, characterized in that, The method is implemented in three stages: In the first stage, offline measurements are performed and deformation reports are output without intervening in the material changer control. In the second stage, the pose compensation amount is automatically calculated and fine-tuned after manual confirmation. The third stage involves fully automated measurement, compensation, and loading / unloading operations.

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