A ship assembly simulation path planning method based on digital twinning

Abstract

The application discloses a ship assembly simulation path planning method based on digital twinning, and relates to the technical field of intelligent ship manufacturing. The method comprises the following steps: constructing a digital twinning scene in a unified assembly coordinate system, deducing multiple future assembly states according to assembly process requirements and current assembly progress, and forming corresponding assembly space occupation relationships; summarizing the space occupation range boundaries of each future assembly state, uniformly dividing the assembly space used by each future assembly state, determining the occupation time period of the operating equipment, and forming the passable time interval, the connectable time interval and the passing time sequence. The application deduces multiple future assembly states through the digital twinning scene and forms the passable time interval and the passing time sequence, realizes the coordinated constraint of the assembly space occupation change and the path passing time, and reduces the path failure and space-time conflict risk.

Description

Technical Field

[0001] This invention relates to the field of intelligent ship manufacturing technology, and in particular to a ship assembly simulation path planning method based on digital twins. Background Technology

[0002] As ship segment construction, assembly, and loading operations become increasingly digital and intelligent, digital twin technology is gradually being applied to ship assembly simulation. By associating the 3D models, pose information, and process status of hull segments, work equipment, and assembly areas, digital twin scenarios can dynamically map the assembly site. Combined with path search, collision detection, and process simulation, the movement process of work equipment can be planned and verified, thereby improving the visualization and collaborative operation capabilities of the ship assembly process.

[0003] Existing methods have some shortcomings. They mostly rely on the current state or a single predicted state for path search, failing to continuously reflect the changes in space occupancy of hull sections and operating equipment during the process. They also struggle to coordinate the occupancy period with the path passage time, which can easily cause the original path to fail or spatiotemporal conflicts when the assembly progress changes. In addition, when the real-time state in the digital twin scenario deviates from the predicted state, it is usually necessary to replan the entire path. There is a lack of identification of common passable locations under different future assembly states and a path safety connection mechanism, which can easily lead to problems such as discontinuous path switching, unsafe connection positions, and large amounts of redundant calculations. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a digital twin-based ship assembly simulation path planning method to solve the problems of difficulty in accurately representing spatiotemporal traffic relationships and difficulty in safely switching paths in dynamic assembly environments.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] This invention provides a ship assembly simulation path planning method based on digital twins, comprising: constructing a digital twin scene in a unified assembly coordinate system; deducing various future assembly states according to assembly process requirements and current assembly progress to form corresponding assembly space occupancy relationships; summarizing the space occupancy boundaries of each future assembly state; uniformly dividing the assembly space used by each future assembly state; determining the time period occupied by the operating equipment and forming passable time intervals, connectable time intervals, and passable sequence; generating and screening candidate paths for each future assembly state using the passable time intervals and passable sequence; comparing the remaining candidate paths; determining the safe connection position as the location where the operating equipment poses are consistent, there is a common time period, and the preceding and following path segments remain passable; dividing the shared path segment and the state-corresponding path segment according to the safe connection position to form a path branch set; determining the real-time assembly state and selecting matching path branches; when the currently effective path branch is consistent with the selected path branch, intercepting the path from the current position to the target pose; when they are inconsistent, connecting the corresponding path segment at the common safe connection position in the common time period at the expected arrival time; using the obtained path as the path to be verified; and forming a ship assembly simulation planning path after verification by interference simulation.

[0008] As a preferred embodiment of the ship assembly simulation path planning method based on digital twins described in this invention, the specific steps for constructing a digital twin scene in a unified assembly coordinate system are as follows:

[0009] Establish a unified assembly coordinate system by selecting fixed reference points within the assembly area;

[0010] Based on the current pose of the hull sections and working equipment, the local coordinates of the corresponding geometric points are transformed to a unified assembly coordinate system. The hull sections, working equipment, and assembly areas are then arranged according to the transformed geometric point coordinates to form a digital twin scene.

[0011] As a preferred embodiment of the ship assembly simulation path planning method based on digital twins described in this invention, the specific steps for forming the corresponding assembly space occupancy relationship are as follows:

[0012] Based on the assembly process requirements and the current assembly progress, the expected execution time of each process is determined. The start, end, and intermediate times of the expected execution time are determined as state times. The expected pose is determined according to the proportion of the state times in the corresponding expected execution time, thus forming the future assembly state.

[0013] The assembly process requirements refer to the sequential relationship of each process recorded in the assembly process document, as well as the starting position, target position, and expected duration of the corresponding hull sections and working equipment.

[0014] The space occupancy range is determined based on the expected positions of the hull sections and working equipment in each future assembly state. The space occupancy range is then associated with the corresponding objects, processes, and expected execution periods to form the assembly space occupancy relationship for each future assembly state.

[0015] As a preferred embodiment of the ship assembly simulation path planning method based on digital twins described in this invention, the specific steps for forming the passable time interval, the connectable time interval, and the passage sequence are as follows:

[0016] Summarize the spatial occupancy boundaries of each future assembly state, and uniformly divide the assembly space with fixed boundaries and unique numbers, so that each future assembly state uses the same assembly space division result.

[0017] The occupation period is determined based on the changes in the space occupied by the working equipment during the planned period, and the overlapping occupation periods are adjusted according to the sequence of work processes and the expected start time.

[0018] The time intervals in the assembly space not occupied by hull sections and not occupied by working equipment are defined as passable time intervals. When adjacent assembly spaces have a common time interval for their corresponding passable time intervals, the common time interval is defined as a connectable time interval, and a passable time sequence is formed according to the start time of the connectable time interval.

[0019] As a preferred embodiment of the ship assembly simulation path planning method based on digital twins described in this invention, the candidate path is generated through the following steps:

[0020] Starting from the state time corresponding to the future assembly state, the path is extended between the initial assembly space and the target assembly space according to the passage sequence.

[0021] The estimated arrival time of the transition position is determined based on the length of the path segment and the moving speed of the working equipment. When the path segment's moving period is covered by the corresponding passable time interval and the estimated arrival time is within the corresponding connectable time interval, the path extension is retained.

[0022] The path is repeatedly extended until the target assembly space is entered. The resulting complete path is associated with the transition poses passed in sequence and the expected arrival time to form a candidate path.

[0023] As a preferred embodiment of the ship assembly simulation path planning method based on digital twins described in this invention, the candidate path selection steps are as follows:

[0024] The estimated times for the work equipment to enter and leave each assembly space are determined based on the estimated arrival times at each transition position;

[0025] Verify whether the time period from the entry time to the exit time is completely covered by the corresponding passable time interval, and verify whether the elapsed time between adjacent assembly spaces is within the corresponding connectable time interval.

[0026] Candidate paths that fail any validation or do not meet assembly process requirements are eliminated, resulting in the remaining candidate paths.

[0027] As a preferred embodiment of the ship assembly simulation path planning method based on digital twins described in this invention, the steps for determining the safe connection position are as follows:

[0028] Compare the remaining candidate paths corresponding to different future assembly states, determine the transition poses with consistent 3D coordinates and expected attitudes as poses to be confirmed, and determine the common time of the passable time intervals corresponding to the poses to be confirmed as common time periods.

[0029] When the estimated elapsed time of the pose to be confirmed in each future assembly state is within the corresponding passable time interval, and the movement time of the path segment before and after the pose to be confirmed is covered by the corresponding passable time interval, and the estimated elapsed time between adjacent assembly spaces is within the corresponding connectable time interval, the position corresponding to the pose to be confirmed is determined as the safe connection position.

[0030] As a preferred embodiment of the ship assembly simulation path planning method based on digital twins described in this invention, the steps of dividing the shared path segment and the state-corresponding path segment according to the safe connection position are as follows:

[0031] Arrange safe connection positions along the travel direction of the remaining candidate paths, and use the current pose, the pose of the working equipment corresponding to the safe connection position, and the target pose as the segmentation pose to divide the remaining candidate paths into continuous path segments;

[0032] By comparing the path segments defined by adjacent segment poses under different future assembly states, the path segments with the same start pose, end pose, assembly space traversal order, and transition pose are identified as shared path segments, while the remaining path segments are identified as state-corresponding path segments.

[0033] As a preferred embodiment of the ship assembly simulation path planning method based on digital twins described in this invention, the step of forming a path branch set is as follows:

[0034] Connect the shared path segment and the path segment corresponding to the status in the order of the remaining candidate paths, and establish the connection when the connection pose of adjacent path segments is consistent and the corresponding expected time is in a safe connection position during the common time period.

[0035] The path segments that continuously reach the target pose from the current pose are determined as path branches. The path branches are associated with the corresponding future assembly states. The shared path segments that are reused by each path branch are merged and the association between the path segments corresponding to the state and the future assembly states is retained to form a path branch set.

[0036] As a preferred embodiment of the ship assembly simulation path planning method based on digital twins described in this invention, the steps for forming the ship assembly simulation planning path are as follows:

[0037] Based on the actual position and orientation of the hull sections and working equipment and the execution status of the process, a real-time assembly status is formed, and a future assembly status association path branch is selected where the process execution status is consistent and the position and attitude deviations are within the corresponding allowable range.

[0038] When the currently active path branch is consistent with the selected path branch, the path from the current position of the working equipment to the target pose is extracted to form the path to be verified;

[0039] When the currently effective path branch is inconsistent with the selected path branch, determine the safe connection position that is common to both path branches and is located after the current position of the working equipment. Retain the safe connection position whose expected arrival time is within the corresponding common time period. Determine the safe connection position that is reached first along the currently effective path branch as the nearest safe connection position and connect the corresponding path segments to form the path to be verified.

[0040] Interference simulation is performed on the path to be verified to generate a ship assembly simulation planning path that passes the verification.

[0041] The beneficial effects of this invention are as follows: by extrapolating various future assembly states through digital twin scenarios and forming passable time intervals and passage sequences, the invention achieves coordinated constraints between changes in assembly space occupancy and path passage times, reducing the risk of path failure and spatiotemporal conflicts; by relying on digital twin scenarios to determine safe connection positions and organize path branch sets, the invention enables continuous path switching and interference verification under real-time state changes, thereby improving the safety, adaptability, and execution efficiency of path planning. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a flowchart of a ship assembly simulation path planning method based on digital twins.

[0044] Figure 2A flowchart was created to illustrate the relationship between digital twin scenarios and assembly space occupancy.

[0045] Figure 3 A flowchart for generating assembly space timing constraints and candidate paths is provided.

[0046] Figure 4 A flowchart was created to plan the safe connection points and ship assembly simulation paths. Detailed Implementation

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0048] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0049] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0050] Reference Figures 1-4 As one embodiment of the present invention, this embodiment provides a ship assembly simulation path planning method based on digital twins, including the following steps:

[0051] S1. Construct a digital twin scenario in a unified assembly coordinate system, and deduce various future assembly states according to assembly process requirements and current assembly progress to form corresponding assembly space occupancy relationships.

[0052] S1.1 Acquire the three-dimensional geometric data and current pose data of the hull sections, working equipment and assembly area, transform the local coordinates corresponding to the three-dimensional geometric data to the unified assembly coordinate system, arrange the hull sections and working equipment according to the current pose, determine the position of the assembly area in the unified assembly coordinate system, and construct a digital twin scene.

[0053] It should be noted that a fixed and repeatable reference point within the assembly area is selected as the unified assembly coordinate system. The origin is defined by the direction from the stern to the bow, the direction from the port side to the starboard side, and the direction from the hull baseline vertically upwards, respectively. axis, shaft and The axes are obtained from the three-dimensional data files corresponding to the hull sections, working equipment and assembly areas to obtain the local coordinates of geometric points representing the external shape and the connection relationship of geometric points. The current pose data of the hull sections and working equipment are obtained from the field measurement results. The current pose data includes the position vector of the origin of the local coordinate system in the unified assembly coordinate system and the attitude angles around the three coordinate axes.

[0054] by The serial number of the hull section or working equipment is indicated by a column vector representing the coordinates, and is arranged according to the order of rotation. Axis, then winding Axis, final winding The order of axes is based on attitude angles. , and Find the first The rotation matrix for each object is as follows:

[0055] ;

[0056] in, , and The first An object around axis, shaft and The attitude angle of the axis; , and These are the corresponding coordinate rotation matrices, specifically:

[0057] ;

[0058] ;

[0059] ;

[0060] by Indicates the first The geometric point index of each object is used to apply a rotation matrix to the local coordinates of the corresponding geometric point, and the sum of the rotated coordinates and the position vector is calculated to obtain the coordinates of this geometric point in the unified assembly coordinate system. Specifically:

[0061] ;

[0062] in, For the first The first object The coordinates of a geometric point in the local coordinate system, with superscript... Indicates a local coordinate system; For the first The coordinates of a geometric point in the unified assembly coordinate system, with superscript... Indicates a unified assembly coordinate system; The first in the current pose data The position vector of the origin of the local coordinate system of an object in the unified assembly coordinate system.

[0063] Arrange hull sections and work equipment according to the converted geometric point coordinates and the original geometric point connection relationships; determine the coordinates of the geometric points of the assembly area boundary according to the origin and coordinate axis direction of the unified assembly coordinate system, and determine the position and range of the assembly area by the space enclosed by the boundary geometric points; save the geometric point coordinates, geometric point connection relationships and current pose of each object, and construct a digital twin scene for subsequent pose updates and spatial occupancy range determination.

[0064] A digital twin scenario refers to a virtual assembly environment formed by arranging hull sections, operating equipment, and assembly areas in a unified assembly coordinate system according to their actual positions and attitudes, and saving their three-dimensional shape, position, and attitude data.

[0065] S1.2 Analyze the process sequence, starting pose, target pose and expected duration in the assembly process requirements, determine the completed process, the process being executed and the process to be executed in combination with the current assembly progress, determine the expected execution time of the process being executed and the process to be executed, and update the hull sections and working equipment in the digital twin scenario in sequence according to the process sequence and the expected execution time to form multiple future assembly states.

[0066] It should be noted that the assembly process requirements refer to the sequential relationship of each process recorded in the assembly process document, the starting and target positions of the corresponding hull sections and working equipment, and the expected duration; the current assembly progress includes the execution status and completion ratio of each process; processes with the execution status of "completed" are defined as completed processes, processes that have started but not yet ended are defined as processes in progress, and processes that have not yet started are defined as processes to be executed.

[0067] For a process currently in execution, the current time is taken as the estimated start time of the remaining execution period. The product of the unfinished percentage and the estimated duration is calculated, and then summed with the current time to obtain the estimated end time. Specifically:

[0068] ;

[0069] in, The current assembly progress is in the first stage. The completion rate of each process step; The expected end time is indicated by a superscript. This indicates "end," meaning the end. Indicates the current time; Indicates the process sequence number; Indicates the expected duration.

[0070] The end times of each preceding process in the process to be executed are compared. Completed processes use their actual end times, while processes currently being executed and those to be executed use their estimated end times. The later of the latest end time and the current time is taken as the estimated start time, and then summed with the estimated duration to obtain the estimated end time. Specifically:

[0071] , ;

[0072] in, Superscript indicates the expected start time. It means "start," or "begin." For the first The set of sequence numbers of the preceding processes in the current process; This is the sequence number of the preceding process; if there is no preceding process, the current time is used as the expected start time. This indicates that the maximum value among the time points being compared is taken.

[0073] The expected start time, expected end time, and intermediate times divided according to the digital twin scenario update interval are merged and arranged chronologically as state times. For each process within its expected execution period, the proportion of state times within that expected execution period is calculated, specifically:

[0074] ;

[0075] in, This refers to the state at a given moment; For the first The execution ratio of each process at this state moment.

[0076] For ongoing processes, the current pose of the corresponding hull section and working equipment is used as the starting pose for the remaining execution time period; for processes to be executed, the starting pose in the assembly process requirements is used as the starting pose for the expected execution time period; the coordinate difference between the target position and the starting position is calculated, and the product of the coordinate difference and the execution ratio is summed with the starting position to obtain the expected position; the difference between each target attitude angle and the corresponding starting attitude angle is converted to negative values. to Within the range, the product of each parameter with the execution ratio is summed with the corresponding initial attitude angle to obtain the expected attitude.

[0077] The hull sections and operating equipment in the digital twin scenario are updated sequentially according to the expected position, expected attitude and process execution status corresponding to each state moment, and the updated scenarios are saved respectively, forming multiple future assembly states arranged in chronological order.

[0078] The future assembly state refers to the combination of the expected position, expected attitude, and corresponding process execution state of each hull section and operating equipment in the digital twin scenario at any given moment; different moments correspond to different future assembly states.

[0079] S1.3 Determine the spatial occupancy range of hull sections and working equipment in a unified assembly coordinate system for each future assembly state, establish the correspondence between each spatial occupancy range and hull sections, working equipment, corresponding processes and expected execution periods, and form the assembly spatial occupancy relationship for each future assembly state.

[0080] It should be noted that for each future assembly state, the coordinates of the corresponding geometric points are updated according to the expected poses of the hull sections and working equipment. The coordinates of all geometric points of each object in the three coordinate axes of the unified assembly coordinate system are compared to determine the minimum and maximum coordinates in each direction. The cuboid range that can enclose the current object is formed by the six extreme coordinates and is used as the space occupied by the current object in the current future assembly state, so as to conservatively represent the actual space occupied by the object.

[0081] Summarize the space occupancy ranges of each current and future assembly state, as well as the correspondence between the space occupancy ranges and the corresponding objects, corresponding processes, and expected execution periods, to form the assembly space occupancy relationships of the current and future assembly states; process the remaining future assembly states in the same way to form the assembly space occupancy relationships of each future assembly state.

[0082] S2. Summarize the spatial occupancy boundaries of each future assembly state, uniformly divide the assembly space used by each future assembly state, determine the time period occupied by the working equipment, and form the passable time interval, the connectable time interval, and the passable sequence.

[0083] S2.1 Divide the assembly spaces into non-overlapping ones according to the space occupied by the hull sections and working equipment in each future assembly state, determine the adjacency relationship between the assembly spaces, and establish the correspondence between each assembly space and working equipment, corresponding process and expected execution time.

[0084] It should be noted that the spatial occupancy boundaries of all future assembly states are summarized, and assembly spaces with fixed boundaries and unique numbers are uniformly divided. Each future assembly state uses the same assembly space division result; the assembly area is located within... axis, shaft and The minimum and maximum coordinates along the axis are used to define the outer boundary. The coordinates of the assembly area boundary and the minimum and maximum coordinates of each space's occupied range along the same axis are deduplicated and arranged in ascending order of value. The coordinate intervals along the three axes are divided by adjacent coordinate values. The coordinate intervals along the three axes are combined one by one to form a cuboid assembly space located within the assembly area that does not overlap with each other.

[0085] Compare each assembly space with the occupied area of ​​each space one by one; when the common interval length of the space occupied by the assembly space and the hull section is greater than zero in all three coordinate axes, record the corresponding hull section and mark the assembly space as occupied by the hull section; when the common interval length of the space occupied by the assembly space and the working equipment is greater than zero in all three coordinate axes, record the corresponding working equipment and associate it with the corresponding process and the expected execution time; when multiple objects are involved, save all the corresponding relationships separately.

[0086] The boundaries of any two assembly spaces are compared sequentially. When two assembly spaces share a boundary surface with an area greater than zero, they are recorded as adjacency. When only the edges, vertices, or boundaries do not touch, the adjacency relationship is not recorded. The assembly spaces, adjacency relationships, and the correspondence between the assembly spaces and the hull sections, working equipment, corresponding processes, and expected execution periods are summarized to form the assembly space division results for each future assembly state.

[0087] S2.2 Compare the space occupied by the working equipment in the continuous future assembly state with the overlap relationship of each assembly space, determine the time period occupied by the working equipment in each assembly space, and adjust the overlapping time periods according to the sequence of processes and the expected start time, so that the time periods occupied in the same assembly space are staggered.

[0088] It should be noted that the space occupancy range is continuously updated according to the chronological order of the state moments and the positional changes of the working equipment between adjacent state moments. When the common interval length of the space occupancy range of the working equipment and the assembly space in the three coordinate axes is greater than zero, the time period between the corresponding state moments is determined as the time period of the working equipment's occupation of the assembly space. When the same working equipment occupies the same assembly space continuously, the continuous time periods are merged, and the start time of the first time period and the end time of the last time period are used as the start and end times of the occupation time period.

[0089] The occupancy periods corresponding to the same assembly space are arranged according to the expected start time; if two occupancy periods have a common time with a length greater than zero, it is determined that the occupancy periods overlap; if the corresponding processes have a sequential relationship, the occupancy period of the preceding process remains unchanged, and the occupancy period of the subsequent process is postponed until after the occupancy period of the preceding process ends; if the corresponding processes do not have a sequential relationship, the occupancy period with the earlier expected start time remains unchanged, and the occupancy period with the later expected start time is postponed; if the expected start times are the same, the sequence is determined according to the process arrangement order recorded in the assembly process requirements.

[0090] When extending the occupation period, the occupation duration remains unchanged. Simultaneously extend the expected start time, expected end time of the corresponding process, and the occupation period subsequently formed by the same work equipment. Update the expected pose in the affected future assembly state according to the adjusted expected execution period. After the occupation period is extended, redetermine the state time, expected pose, space occupation range, and occupation period of the affected process. Repeatedly compare and adjust overlapping occupation periods until the occupation periods in the same assembly space are staggered.

[0091] S2.3 Determine the time periods when each assembly space is not occupied by the operating equipment to form a passable time interval. According to the adjacency relationship between the assembly spaces, associate the passable time intervals that can be continuously connected to form the passable time intervals and passable sequence corresponding to each future assembly state.

[0092] It should be noted that the period from the state time corresponding to any future assembly state to the end time of the assembly simulation is defined as the planning period. The occupied period and the passable time interval within the planning period are determined according to the changes in space occupancy at the corresponding state time and subsequent state times. The latest expected end time among all unfinished processes is defined as the end time of the assembly simulation. The end state corresponding to the end time of the assembly simulation is not divided into a separate planning period. The assembly space occupied by the hull sections does not form a passable time interval.

[0093] For assembly spaces not occupied by hull sections, the time periods occupied by the working equipment within the planned time period are arranged according to their start times. The time intervals from the start time of the planned time period to the start time of the first occupied time period, the time intervals between adjacent occupied time periods, and the time interval from the end time of the last occupied time period to the end time of the planned time period are respectively determined as passable time intervals. When there are no time periods occupied by working equipment, the entire planned time period is determined as a passable time interval. Non-occupied time periods with a duration of zero are not retained. Each passable time interval is associated with and saved with the corresponding assembly space.

[0094] The permissible time intervals corresponding to adjacent assembly spaces are compared sequentially. When two permissible time intervals share a common time with a length greater than zero, a passage association is established between the corresponding assembly spaces, and the common time is determined as a connectable time interval. If there is no common time, no passage association is established. The passage associations are arranged according to the start time of the connectable time interval associated with each assembly space, and the corresponding adjacent assembly spaces and connectable time intervals are recorded to form the permissible time intervals and passage sequence for each future assembly state. The passage sequence refers to the permissible connection relationship formed between each assembly space and its adjacent assembly spaces according to the order of time, and does not represent a fixed passage route.

[0095] S3. Generate and filter candidate paths for each future assembly state using the passable time interval and passable sequence. Compare the remaining candidate paths and determine the safe connection positions as the positions where the working equipment has the same posture, there is a common time period, and the preceding and following path segments remain passable. Divide the shared path segments and the path segments corresponding to the state according to the safe connection positions to form a path branch set.

[0096] S3.1 Determine the current pose and target pose of the working equipment in each future assembly state, associate the passable time interval and passable timing with the corresponding assembly space, expand the path according to the adjacency relationship between the assembly spaces, and use the passable time interval and passable timing to restrict the path expansion, and generate candidate paths corresponding to each future assembly state.

[0097] It should be noted that the expected pose at the start of the future assembly state planning period is determined as the current pose, and the target pose specified by the corresponding process is determined as the target pose; the assembly space containing the origin of the local coordinate system of the working equipment in the current pose and the target pose is determined as the starting assembly space and the target assembly space, respectively; when the path is extended, the occupancy period formed by the working equipment to be planned is not used as a passage restriction.

[0098] Starting from the initial assembly space, record the assembly spaces already traversed, the end position of the path, and the estimated arrival time of the end position. Select adjacent assembly spaces that have not yet been traversed according to their adjacency relationship, and determine the center of the shared boundary surface of the two assembly spaces as the transition position. Connect the end position of the path and the transition position to form a new path segment. Calculate the ratio of the length of the new path segment to the moving speed in the technical parameters of the working equipment to obtain the new moving time, and sum it with the estimated arrival time of the end position of the path to obtain the estimated arrival time of the transition position.

[0099] If the movement time corresponding to the newly added path segment is completely covered by the passable time interval of the current assembly space, and the expected arrival time of the transition position is within the connectable time interval between the current assembly space and the adjacent assembly space, the path extension will be retained. If the expected arrival time of the transition position is earlier than the start time of the connectable time interval, the working equipment is allowed to wait in the current assembly space, but the waiting time should be completely covered by the passable time interval of the current assembly space. If the time conditions are not met, the path extension will be discarded.

[0100] For each retained incomplete path, it is repeatedly expanded until it enters the target assembly space; connect the last transition position with the position in the target pose, and calculate the movement time of the last path segment and the expected arrival time of the target pose; if the movement time of the last path segment is completely covered by the passable time interval of the target assembly space, the complete path is retained; otherwise, the complete path is discarded; according to the proportion of the expected arrival time of each transition position in the expected execution time of the corresponding process, the expected pose is determined between the starting pose and the target pose of the corresponding process according to the shortest turning angle, and the transition position and the expected pose are combined into a transition pose; the verified complete path, as well as the assembly spaces, transition poses and expected arrival times passed through in sequence, are associated and saved to form candidate paths corresponding to each future assembly state.

[0101] S3.2 Determine the estimated times when the working equipment enters and leaves the assembly space along each candidate path, and eliminate candidate paths whose entry time to exit time is not completely covered by the corresponding passable time interval, whose passing order does not conform to the passable timing, and whose movement process does not conform to the assembly process requirements, to form the remaining candidate paths.

[0102] It should be noted that each candidate path records the assembly spaces traversed sequentially, the transition positions between adjacent assembly spaces, and the estimated times when the working equipment arrives at each transition position and the target pose. For the initial assembly space, the start time of the candidate path is determined as the entry time, and the estimated time of reaching the first transition position is determined as the exit time. For the intermediate assembly space, the estimated time of reaching the previous transition position is determined as the entry time, and the estimated time of reaching the next transition position is determined as the exit time. For the target assembly space, the estimated time of reaching the last transition position is determined as the entry time, and the estimated time of reaching the target pose is determined as the exit time. When the working equipment is waiting in the assembly space, the waiting period is included in the time period between the entry time and the exit time.

[0103] The entry time and exit time of each assembly space are compared with the corresponding passable time interval. If there is a passable time interval that completely covers the entry time to the exit time, the current assembly space passes the verification. If there is no complete coverage relationship, the entire candidate path is eliminated.

[0104] The access relationships are checked according to the order in which candidate paths pass through assembly spaces; if there is no access relationship between adjacent assembly spaces, or if the expected time of reaching the transition position on the shared boundary surface is not within the corresponding connectable time interval, the entire candidate path is eliminated.

[0105] Verify the candidate paths against the assembly process requirements: The start time of a candidate path must not be earlier than the end time of the preceding process. If the preceding process has been completed, the actual end time shall be used; if the preceding process has not been completed, the expected end time shall be used. The starting pose and ending pose of the path should be consistent with the current pose and the target pose, respectively. The expected time to reach the target pose must not be later than the expected end time of the corresponding process. All candidate paths that pass the verification shall be determined as the remaining candidate paths.

[0106] S3.3 Compare the remaining candidate paths corresponding to different future assembly states, determine the positions where the working equipment has the same posture and the passing time is within the corresponding passable time interval, confirm that the path segments before and after the corresponding position remain passable in different future assembly states, and determine the confirmed passable position as the safe connection position.

[0107] It should be noted that each remaining candidate path records the initial pose, the expected pose corresponding to each transition position, the target pose, and the expected time when the working equipment arrives at each position. When comparing the remaining candidate paths corresponding to different future assembly states, if the three-dimensional coordinates and three attitude angle values ​​of the two transition poses are consistent, the two transition poses are merged into a pose to be confirmed.

[0108] Check the estimated time when the working equipment passes through the position corresponding to the pose to be confirmed and the passable time interval of the assembly space where the position corresponding to the pose to be confirmed is located. If each estimated time is within the corresponding passable time interval, and there is a common time period with a length greater than zero for the passable time intervals corresponding to different future assembly states, retain the pose to be confirmed. If neither condition is met, discard the pose to be confirmed.

[0109] Each remaining candidate path is verified by checking the preceding and following path segments that are directly connected to the position corresponding to the pose to be confirmed. The movement time of each path segment is completely covered by the passable time interval of the corresponding assembly space, and when the expected time of the shared boundary surface of adjacent assembly spaces is within the corresponding connectable time interval, it is confirmed that the path segments before and after the position corresponding to the pose to be confirmed remain passable in the relevant future assembly state.

[0110] The location corresponding to the confirmed pose to be confirmed is determined as the safe connection position. The pose of the working equipment, common time period, future assembly status, remaining candidate paths and expected arrival time corresponding to the safe connection position are recorded. When the same safe connection position corresponds to multiple remaining candidate paths, the correspondence between the safe connection position and each remaining candidate path is saved separately.

[0111] S3.4. Divide the remaining candidate paths corresponding to each future assembly state according to the safe connection position, take the same path segments as the common path segments, associate different path segments with the corresponding future assembly states respectively, and connect the common path segments and different path segments according to the safe connection position to form a path branch set.

[0112] It should be noted that safe connection positions are arranged along the travel direction of each remaining candidate path. The remaining candidate paths are divided into continuous path segments using the current pose, each safe connection position, and the target pose as dividing points. The starting pose, ending pose, assembly space passage sequence, transition pose, and expected passage time of each path segment are recorded.

[0113] Compare the path segments corresponding to different future assembly states; when the starting pose, ending pose, assembly space traversal order and transition pose are consistent, merge the corresponding path segments into a common path segment and retain the expected traversal time of the common path segment in each future assembly state; when any inconsistency exists, retain the corresponding path segment as a different path segment and associate it with the corresponding future assembly state and the remaining candidate paths.

[0114] Connect path segments in the order of the remaining candidate paths; when the end pose of the previous path segment is the same as the start pose of the next path segment, the estimated end time of the previous path segment is not later than the estimated start time of the next path segment, and both estimated times are within the common time period corresponding to the safe connection position, establish a connection at the safe connection position; the remaining candidate paths without a safe connection position form separate path branches.

[0115] The path branches are determined by the combination of path segments that continuously reach the target pose from the current pose. The future assembly state, path segment order, safe connection position and expected transit time of the path branch are recorded. The common path segments used repeatedly by each path branch are merged, and the association between different path segments and future assembly states is retained to form a path branch set.

[0116] S4. Determine the real-time assembly status and select a matching path branch. If the currently effective path branch is consistent with the selected path branch, extract the path from the current position to the target pose. If they are inconsistent, connect the corresponding path segment at the common safe connection position in the same time period when the expected arrival time is different. Use the obtained path as the path to be verified. After verification by interference simulation, the ship assembly simulation planning path is formed.

[0117] S4.1 Determine the real-time assembly state in the digital twin scenario, match the real-time assembly state with the future assembly state in the path branch set, and select the path branch corresponding to the real-time assembly state as the selected path branch.

[0118] It should be noted that the real-time position and attitude of the hull sections and working equipment, as well as the process execution records that record the start and end of the process, are collected to update the digital twin scene. Based on the process execution records, processes that have been completed are marked as completed, processes that have started but have not yet ended are marked as being executed, and processes that have not yet started are marked as pending execution. The real-time assembly status is composed of the actual position, actual attitude, and process execution status of each hull section and working equipment at the current moment.

[0119] The real-time assembly state is compared with the future assembly state in the path branch set in turn. First, the future assembly state with the same execution state of each process is retained. Then, the spatial distance between the actual position and the expected position of the same hull section and the working equipment, as well as the shortest turning angle difference between the actual attitude angle and the expected attitude angle are calculated respectively. When all spatial distances do not exceed the allowable position deviation specified by the corresponding process, and all shortest turning angle differences do not exceed the allowable attitude deviation, the real-time assembly state is determined to match the future assembly state.

[0120] When there are multiple matching future assembly states, calculate the ratio of each spatial distance to the allowable position deviation and the ratio of each shortest rotation angle difference to the allowable attitude deviation, and sum all the ratios. The future assembly state with the smallest sum is determined as the matching result. Select the path branch associated with the matching result as the selected path branch. When the same matching result is associated with multiple path branches, select the path branch that is expected to reach the target pose earliest.

[0121] S4.2. Compare the currently effective path branch with the selected path branch. If the currently effective path branch is consistent with the selected path branch, the path segment from the current position of the working equipment to the target pose in the currently effective path branch is determined as the path to be verified. If the currently effective path branch is inconsistent with the selected path branch, determine the common nearest safe connection position, and connect the path segment from the current position of the working equipment to the nearest safe connection position in the currently effective path branch and the path segment from the nearest safe connection position to the target pose in the selected path branch to form the path to be verified.

[0122] It should be noted that the currently effective path branch is the path branch being executed by the operating equipment in the digital twin scenario; the unexecuted parts of the currently effective path branch are divided according to the start and end positions of each path segment; the projection ratio of the current position in the extension direction of each path segment is calculated, and the projection ratio is limited to between zero and one to obtain the nearest position and the shortest distance within each path segment, specifically:

[0123] ;

[0124] ;

[0125] , ;

[0126] in, This is the projection scale; This is the restricted projection scale; For the first The location of the nearest path to the current location within each path segment; Shortest distance; superscript Transpose of a vector; The length of the vector; This refers to the path segment number; and The first The starting and ending points of each path segment; This indicates the current position of the operating equipment.

[0127] The nearest position corresponding to the minimum shortest distance is determined as the starting point of the path interception; when there are multiple identical minimum distances, the nearest position reached first along the current effective path branch is selected.

[0128] When the path segments and their order are consistent with those of the currently active path branch and the selected path branch, the current position of the working equipment is connected to the starting point of the path capture, and the path segments from the starting point of the path capture to the target pose are connected to form the path to be verified.

[0129] When two path branches are inconsistent, arrange the safe connection positions that belong to both path branches and are located after the path interception point along the current effective path branch's travel direction; calculate the sum of the lengths of the continuous path segments from the path interception point to each safe connection position, then calculate the ratio of the sum of lengths to the movement speed to obtain the estimated movement time, and sum it with the current time to obtain the estimated arrival time; retain the safe connection positions whose estimated arrival time is within the corresponding common time period, and determine the safe connection position that is reached first along the current effective path branch as the nearest safe connection position.

[0130] The path to be verified is formed by sequentially connecting the current position of the working equipment, the starting point of the path interception, the path segment from the starting point of the path interception in the currently effective path branch to the nearest safe connection position, and the path segment from the nearest safe connection position in the selected path branch to the target pose. The estimated time of reaching the nearest safe connection position is used as the start time of the next part of the path, while keeping the estimated travel time of each path segment unchanged. The estimated time of reaching the subsequent transition position and the target pose is updated sequentially.

[0131] S4.3. In the digital twin scenario, perform interference simulation verification on the path to be verified. After the verification is passed, the ship assembly simulation planning path is formed.

[0132] It should be noted that the safety distance is the minimum allowable distance between the planned work equipment and the hull section and other work equipment as specified by the assembly process requirements; the path to be verified includes the current pose of the work equipment, each transition pose, the target pose, and the corresponding estimated time.

[0133] The path to be verified is divided into initial path segments according to the adjacent path positions; the starting and ending poses of the equipment to be planned and the hull sections and other equipment that undergo pose changes at the same time are determined according to the start and end times of each initial path segment, the coordinates of the geometric points with the same number are transformed, and the maximum spatial distance between the corresponding geometric points of each object and the two poses is calculated.

[0134] When any maximum spatial distance exceeds half of the safety clearance, the midpoint between the start and end times of the path segment is taken as the segmentation time, the midpoint between the start and end positions is taken as the position, and the attitude is determined according to the shortest turning angle of each attitude angle. The original path segment is then divided into two equal parts. The distance comparison and bisection are repeated until the maximum spatial distance between the corresponding geometric points of each object in each sub-path segment does not exceed half of the safety clearance. The pose and time corresponding to the endpoints of each sub-path segment are then determined as the verification pose and verification time.

[0135] According to the verification time, update the equipment to be planned to the corresponding verification pose, and update the hull sections and other equipment to the expected poses of the corresponding future assembly state; when the equipment to be planned intersects with any hull section or other equipment, the geometric point enters the interior of another object, or the minimum distance between object surfaces is less than the safety distance, record the interfering object, verification pose, and verification time, and save the recorded information in association with the corresponding path to be verified to identify the path position where the interference occurred, and determine that the path to be verified has failed; when no interference occurs in all verification poses, determine the path to be verified and the expected time corresponding to each position as the ship assembly simulation planning path.

[0136] Half of the safety distance is taken as the subdivision threshold to limit the object displacement between adjacent verification poses, thereby reducing the risk that the object will cross the interference region between two verification poses without being detected.

[0137] In summary, this invention achieves coordinated constraints between changes in assembly space occupancy and path passage time by: using digital twin scenarios to extrapolate various future assembly states and form passable time intervals and passage sequences, thereby reducing the risk of path failure and spatiotemporal conflicts; and by relying on digital twin scenarios to determine safe connection positions and organize path branch sets, thereby achieving continuous path switching and interference verification under real-time state changes, improving the safety, adaptability, and execution efficiency of path planning.

[0138] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for ship assembly simulation path planning based on digital twins, characterized in that, include: In a unified assembly coordinate system, a digital twin scenario is constructed, and various future assembly states are deduced based on assembly process requirements and current assembly progress, forming corresponding assembly space occupancy relationships. Summarize the spatial occupancy boundaries of each future assembly state, uniformly divide the assembly space used by each future assembly state, determine the time periods occupied by the working equipment, and form the passable time intervals, connectable time intervals, and passable sequence. Candidate paths for each future assembly state are generated and screened using passable time intervals and passable time sequences. The remaining candidate paths are compared, and the positions of the working equipment with the same posture, a common time period, and passable path segments before and after are determined as safe connection positions. Shared path segments and path segments corresponding to the state are divided according to the safe connection positions to form a set of path branches. The real-time assembly status is determined and a matching path branch is selected. When the currently effective path branch is consistent with the selected path branch, the path from the current position to the target pose is intercepted. When they are inconsistent, the corresponding path segment is connected at the common safe connection position in the same time period when the expected arrival time is. The obtained path is used as the path to be verified. After verification by interference simulation, the ship assembly simulation planning path is formed.

2. The ship assembly simulation path planning method based on digital twins as described in claim 1, characterized in that, The specific steps for constructing a digital twin scene in a unified assembly coordinate system are as follows: Establish a unified assembly coordinate system by selecting fixed reference points within the assembly area; Based on the current pose of the hull sections and working equipment, the local coordinates of the corresponding geometric points are transformed to a unified assembly coordinate system. The hull sections, working equipment, and assembly areas are then arranged according to the transformed geometric point coordinates to form a digital twin scene.

3. The ship assembly simulation path planning method based on digital twins as described in claim 1, characterized in that, The specific steps for establishing the corresponding assembly space occupancy relationship are as follows: Based on the assembly process requirements and the current assembly progress, the expected execution time of each process is determined. The start, end, and intermediate times of the expected execution time are determined as state times. The expected pose is determined according to the proportion of the state times in the corresponding expected execution time, thus forming the future assembly state. The assembly process requirements refer to the sequential relationship of each process recorded in the assembly process document, as well as the starting position, target position, and expected duration of the corresponding hull sections and working equipment. The space occupancy range is determined based on the expected positions of the hull sections and working equipment in each future assembly state. The space occupancy range is then associated with the corresponding objects, processes, and expected execution periods to form the assembly space occupancy relationship for each future assembly state.

4. The ship assembly simulation path planning method based on digital twins as described in claim 3, characterized in that, The specific steps for forming the passable time intervals, the connectable time intervals, and the passable time sequence are as follows: Summarize the spatial occupancy boundaries of each future assembly state, and uniformly divide the assembly space with fixed boundaries and unique numbers, so that each future assembly state uses the same assembly space division result. The occupation period is determined based on the changes in the space occupied by the working equipment during the planned period, and the overlapping occupation periods are adjusted according to the sequence of work processes and the expected start time. The time intervals in the assembly space not occupied by hull sections and not occupied by working equipment are defined as passable time intervals. When adjacent assembly spaces have a common time interval for their corresponding passable time intervals, the common time interval is defined as a connectable time interval, and a passable time sequence is formed according to the start time of the connectable time interval.

5. The ship assembly simulation path planning method based on digital twins as described in claim 4, characterized in that, The candidate path is generated through the following steps: Starting from the state time corresponding to the future assembly state, the path is extended between the initial assembly space and the target assembly space according to the passage sequence. The estimated arrival time of the transition position is determined based on the length of the path segment and the moving speed of the working equipment. When the path segment's moving period is covered by the corresponding passable time interval and the estimated arrival time is within the corresponding connectable time interval, the path extension is retained. The path is repeatedly extended until the target assembly space is entered. The resulting complete path is associated with the transition poses passed in sequence and the expected arrival time to form a candidate path.

6. The ship assembly simulation path planning method based on digital twins as described in claim 5, characterized in that, The candidate path selection process is as follows: The estimated times for the work equipment to enter and leave each assembly space are determined based on the estimated arrival times at each transition position; Verify whether the time period from the entry time to the exit time is completely covered by the corresponding passable time interval, and verify whether the elapsed time between adjacent assembly spaces is within the corresponding connectable time interval. Candidate paths that fail any validation or do not meet assembly process requirements are eliminated, resulting in the remaining candidate paths.

7. The ship assembly simulation path planning method based on digital twin as described in claim 6, characterized in that, The steps for determining the safe connection position are as follows: Compare the remaining candidate paths corresponding to different future assembly states, determine the transition poses with consistent 3D coordinates and expected attitudes as poses to be confirmed, and determine the common time of the passable time intervals corresponding to the poses to be confirmed as common time periods. When the estimated elapsed time of the pose to be confirmed in each future assembly state is within the corresponding passable time interval, and the movement time of the path segment before and after the pose to be confirmed is covered by the corresponding passable time interval, and the estimated elapsed time between adjacent assembly spaces is within the corresponding connectable time interval, the position corresponding to the pose to be confirmed is determined as the safe connection position.

8. The ship assembly simulation path planning method based on digital twin as described in claim 7, characterized in that, The steps for dividing the shared path segment and the status-corresponding path segment according to the safe connection location are as follows: Arrange safe connection positions along the travel direction of the remaining candidate paths, and use the current pose, the pose of the working equipment corresponding to the safe connection position, and the target pose as the segmentation pose to divide the remaining candidate paths into continuous path segments; By comparing the path segments defined by adjacent segment poses under different future assembly states, the path segments with the same start pose, end pose, assembly space traversal order, and transition pose are identified as shared path segments, while the remaining path segments are identified as state-corresponding path segments.

9. The ship assembly simulation path planning method based on digital twin as described in claim 8, characterized in that, The steps for forming the path branch set are as follows: Connect the shared path segment and the path segment corresponding to the status in the order of the remaining candidate paths, and establish the connection when the connection pose of adjacent path segments is consistent and the corresponding expected time is in a safe connection position during the common time period. The path segments that continuously reach the target pose from the current pose are determined as path branches. The path branches are associated with the corresponding future assembly states. The shared path segments that are reused by each path branch are merged and the association between the path segments corresponding to the state and the future assembly states is retained to form a path branch set.

10. The ship assembly simulation path planning method based on digital twins as described in claim 9, characterized in that, The steps for forming the ship assembly simulation planning path are as follows: Based on the actual position and orientation of the hull sections and working equipment and the execution status of the process, a real-time assembly status is formed, and a future assembly status association path branch is selected where the process execution status is consistent and the position and attitude deviations are within the corresponding allowable range. When the currently active path branch is consistent with the selected path branch, the path from the current position of the working equipment to the target pose is extracted to form the path to be verified; When the currently effective path branch is inconsistent with the selected path branch, determine the safe connection position that is common to both path branches and is located after the current position of the working equipment. Retain the safe connection position whose expected arrival time is within the corresponding common time period. Determine the safe connection position that is reached first along the currently effective path branch as the nearest safe connection position and connect the corresponding path segments to form the path to be verified. Interference simulation is performed on the path to be verified to generate a ship assembly simulation planning path that passes the verification.

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