Three-dimensional tangent point-passing route planning method based on hierarchical projection and sliding window geometric analysis
By using a layered projection and sliding window geometric analysis method, a 3D tangent-point route planning method is generated, which solves the path planning problem in complex airspace environments, achieves efficient and smooth route planning, and reduces energy consumption and time costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHENGDU BOOSTOR TECH
- Filing Date
- 2026-02-03
- Publication Date
- 2026-05-01
AI Technical Summary
Existing route planning methods suffer from problems such as disconnect between two-dimensional planning and three-dimensional application, difficulty in tangent calculation, difficulty in ensuring path continuity, lack of a general processing framework, and insufficient coordinate transformation accuracy in complex airspace environments. These problems result in high energy consumption, long flight times, and poor safety for aircraft.
A three-dimensional tangent-point route planning method based on layered projection and sliding window geometric analysis is adopted. The optimal smooth path in two dimensions is generated by the three-element sliding window geometric solution algorithm and transformed into three-dimensional geographic space. The common tangent between the point and the circle is calculated by analytical geometry to construct a smooth connection between the straight line and the arc segment.
It significantly reduces algorithm complexity, generates paths with fewer turns and smoother turns, conforms to aircraft dynamics, shortens flight time, reduces energy consumption, and ensures that the path is continuous and smooth at the tangent point, meeting the needs of real-time or near-real-time planning.
Smart Images
Figure CN121954014A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of route planning technology, and in particular to a three-dimensional tangent passing point route planning method based on layered projection and sliding window geometric analysis. Background Technology
[0002] With the rapid development of the air transport industry and the increasing variety of drone application scenarios, the demand for refined and automated route planning in complex airspace environments is constantly increasing. In actual operation scenarios, aircraft often need to avoid various threatening or restricted areas such as weather thunderstorm areas, temporary no-fly zones, and military exercise areas. In airspace management and planning, such areas are usually abstractly represented as a circular airspace with a certain radius centered on a certain point.
[0003] In existing technologies, route planning often relies on human experience or general path search algorithms based on grids and sampling. When faced with complex channels consisting of point-circle-point or multiple continuous circular areas, the following main problems exist: (1) Disconnect between two-dimensional planning and three-dimensional application: Many path planning methods only plan on a two-dimensional plane, ignoring the fact that actual flight takes place in three-dimensional space. Simply projecting three-dimensional geographic coordinates onto a plane and then performing path search will result in the loss of altitude information or mismatch with actual terrain and airspace altitude restrictions. If fine geometric calculations are performed directly in three-dimensional space, the algorithm complexity will increase significantly, making it difficult to meet the planning requirements of real-time or near-real-time; (2) Difficulty in tangent calculation and geometric optimal path selection: Traditional path search results based on grids or sampling are mostly combinations of broken line segments, lacking strict geometric tangent relationships, and cannot naturally form a smooth path of "straight line-circular arc-straight line". When the aircraft flies along such broken line paths, it needs to frequently change its heading, with many turns and large turning angles, which increases flight time and energy consumption and is not conducive to meeting the dynamic characteristics of the aircraft; (3) Difficulty in ensuring path continuity between multiple circular areas: When When a route needs to continuously traverse the passage between multiple circular avoidance areas, a geometrically matching tangent must be selected for each pair of adjacent elements (points or circles) to keep the entire path smooth and continuous at the tangent point. Existing methods lack an effective mechanism to verify the global consistency of the tangent selected in adjacent windows, which can easily lead to jumps, reversals, or discontinuities at the connection points. (4) Lack of a general and scalable point-circle mixed path processing framework: Actual routes are often composed of route points (forced passage points) and circular avoidance areas mixed in any order, such as complex arrangements like "point-circle-circle-point" and "circle-point-circle". Existing algorithms are mostly designed for single scenarios or specific structures (such as point obstacle avoidance or circular obstacle avoidance only). There is a lack of a general geometric planning framework that can uniformly handle point elements and circle elements and adapt to their arbitrary arrangement order. This results in poor system scalability and requires significant modifications to the core of the algorithm when facing new task configurations. (5) Coordinate transformation accuracy and long-distance planning problems: In large-scale route planning, if the latitude and longitude are simply transformed into plane coordinates without considering the curvature of the earth, significant errors will be generated in long-distance paths, affecting the geometric accuracy of the route and flight safety. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a three-dimensional tangent point-passing route planning method based on layered projection and sliding window geometric analysis.
[0005] The objective of this invention is achieved through the following technical solution: a three-dimensional tangent-point route planning method based on layered projection and sliding window geometric analysis, comprising the following steps:
[0006] S1: Unify and initialize the coordinate system;
[0007] S2: A two-dimensional optimal smooth path consisting of line segments and circular arc segments is generated using a three-element sliding window geometric solution algorithm;
[0008] S3: Convert the optimal two-dimensional smooth path to a three-dimensional geographic space;
[0009] S4: Output the 3D coordinate information of all path points to the external visualization module.
[0010] Preferably, step S1 further includes the following step:
[0011] S11: Receives the input sequence of route elements, each element being defined as three-dimensional geographic coordinates in the form of longitude, latitude, and altitude;
[0012] S12: Calculate the average latitude and longitude of all input elements as the projection reference center point to obtain the projection coordinates and height value of each element in the local two-dimensional plane.
[0013] Preferably, in step S11, the route element sequence includes at least one starting point, one ending point, and at least one circular avoidance area or intermediate waypoint located between the starting point and the ending point.
[0014] Preferably, step S2 further includes the following step:
[0015] S21: Arrange the route element sequence according to the input order, select three adjacent consecutive elements in turn to form a processing window, and denot them as the first element A, the middle element B and the third element C respectively;
[0016] S22: Construct a geometric calculation model based on the type of intermediate element B;
[0017] S23: Calculate the external and internal common tangents using analytical geometry to obtain all candidate tangent combinations;
[0018] S24: Perform geometric screening on candidate tangent combinations;
[0019] S25: Calculate and verify the path intersections;
[0020] S26: Match and correct elements and tangents shared between sliding windows.
[0021] Preferably, in step S22, when the intermediate element B is a circle, all geometrically defined tangent combinations between the first element A and the intermediate element B, as well as all geometrically defined tangent combinations between the third element C and the intermediate element B, are calculated.
[0022] When the intermediate element B is a point, the intermediate element B serves as a path constraint point. The path configuration includes a straight line segment connecting to the point, and a geometric tangent or transition straight line segment passing through the point is constructed based on the relative positional relationship between the first element A and the third element C.
[0023] Preferably, step S24 further includes the following step:
[0024] S24.1: Using the line AC connecting points A and C, find the foot H of the perpendicular from the center O_B of the circle to the line AC, and construct a reference vector v_HB = H→O_B;
[0025] S24.2: Construct a vector v_BPAB = O_B→P_AB from the center O_B to the point of tangency P_AB from the first element A; construct a vector v_BPCB = O_B→P_CB from the center O_B to the point of tangency P_CB from the third element C. Calculate the dot product between the reference vector v_HB and the above two vectors.
[0026] d_1 = v_HB·v_BPAB;
[0027] d_2 = v_HB·v_BPCB;
[0028] When d_1 > 0 and d_2 > 0, the combination is retained as a candidate; if any dot product is less than or equal to zero, it is eliminated.
[0029] Preferably, step S25 further includes the following step:
[0030] S25.1: Find the analytical expression of the two tangents of the retained tangent combination in the plane, and calculate the intersection point Q of their extensions;
[0031] S25.2: Determine the planar positional relationship between the intersection point Q and the center O_B and radius R_B of the intermediate element B, and verify whether Q meets the preset logical conditions. If it does not meet the conditions, discard the corresponding tangent combination; if it does meet the conditions, mark the intersection point Q and the corresponding tangent point position as local path nodes within the window.
[0032] Preferably, step S26 further includes the following step:
[0033] S26.1: Traverse the route elements in order and process all adjacent sliding windows in turn. Perform steps S21 to S25 for each window to obtain one or more legal candidate tangent combinations and intersection information corresponding to the window.
[0034] S26.2: By comparing the tangent parameters associated with the shared element in adjacent windows, verify whether they are consistent. If they are not consistent, backtrack or reselect the tangent combination.
[0035] S26.3: Based on the retained tangent combinations, connect the starting point, straight tangent segments, circular arc segments, and ending point in sequence according to the route elements to construct a two-dimensional path.
[0036] Preferably, step S3 further includes the following step:
[0037] S31: For all straight segments in the path, find the corresponding original route elements according to the inflection points and connection relationships on the two-dimensional plane, and obtain the height information at each inflection point;
[0038] S32: For each arc segment in the path, the height of all points on the arc is uniformly set to the height of the center point of the associated circular avoidance area, forming a horizontal arc in three-dimensional space;
[0039] S33: Combine the two-dimensional plane coordinates with the height coordinates to obtain a three-dimensional path point sequence.
[0040] The present invention has the following advantages:
[0041] 1. This invention adopts a hierarchical strategy of first solving two-dimensional problems and then three-dimensional problems, decomposing complex three-dimensional problems into low-dimensional two-dimensional geometric solutions and height mappings. It also uses a three-element sliding window to iteratively analyze local elements, avoiding large-scale global optimization solutions, significantly reducing algorithm complexity, and making the planning process more computationally efficient, which can meet the needs of real-time or near-real-time route planning.
[0042] 2. This invention is based on analytical geometry, directly calculates the common tangent between a point and a circle, and between circles, and uses standard circular arcs to construct the flight path. The generated path is composed of straight lines and circular arcs that are smoothly connected, strictly satisfying geometric tangent and circular arc constraints. Compared with the polyline path generated based on grids or sampling, it has fewer turns and smoother turns, which is more in line with the dynamic characteristics of the aircraft and helps to shorten flight time and reduce energy consumption.
[0043] 3. This invention ensures that each straight line is a precise tangent to the target circular area by filtering the directionality of tangent combination, verifying the intersection position, and verifying the consistency of tangents in adjacent windows. Adjacent path segments are continuous and smooth at the tangent point, effectively eliminating path jumps, discontinuities, or geometrically infeasible situations. Attached Figure Description
[0044] Figure 1 This is a schematic diagram of a 3D tangent-through-point route planning method based on layered projection and sliding window geometric analysis.
[0045] Figure 2 A schematic diagram for screening and verifying the tangents of the first element A, the middle element B, and the third element C;
[0046] Figure 3This is a schematic diagram of the final path of element A→B→C→D→E. Detailed Implementation
[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0048] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.
[0049] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.
[0050] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.
[0051] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0052] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0053] In this embodiment, as Figures 1-3 As shown, a 3D tangent-through-point route planning method based on layered projection and sliding window geometric analysis includes the following steps:
[0054] S1: Unify and initialize the coordinate system;
[0055] S2: A two-dimensional optimal smooth path consisting of line segments and circular arc segments is generated using a three-element sliding window geometric solution algorithm;
[0056] S3: Convert the optimal two-dimensional smooth path to a three-dimensional geographic space;
[0057] S4: Outputs the 3D coordinate information of all path points to the external visualization module. Specifically, it outputs structured data including the 3D coordinates (longitude, latitude, altitude) of all path points, as well as the type label (straight line or circular arc), segment length, and turning direction of each path segment. It also provides the 2D projected path and 3D path data to the external visualization module to generate 2D projection maps and 3D stereoscopic display maps, facilitating path review, fine-tuning, and confirmation by task planners. By adopting a hierarchical strategy of first solving the 2D problem and then the 3D problem, the complex 3D problem is decomposed into low-dimensional 2D geometric solutions and height mapping. It uses a three-element sliding window to iteratively analyze local elements, avoiding large-scale global optimization, significantly reducing algorithm complexity, and making the planning process computationally efficient, meeting the needs of real-time or near-real-time route planning.
[0058] Furthermore, step S1 also includes the following steps:
[0059] S11: Receive the input sequence of route elements, each element defining three-dimensional geographic coordinates in the form of longitude, latitude, and altitude; preferably, the sequence of route elements includes at least one origin, one destination, and at least one circular avoidance area or intermediate waypoint located between the origin and the destination. Specifically, each element is given three-dimensional geographic coordinates in the form of longitude, latitude, and altitude (altitude or relative altitude).
[0060] S12: Calculate the average latitude and longitude of all input elements as the projection reference center point to obtain the projected coordinates and altitude of each element in the local two-dimensional plane. Specifically, calculate the average latitude and longitude of all input elements as the projection reference center point. Using this center point as a reference, convert the longitude and latitude differences into eastward and northward distances in the local "East-North-Sky" rectangular coordinate system using the Earth's average radius, thereby obtaining the projected coordinates and corresponding altitude of each element in the local two-dimensional plane. Under a unified coordinate system, record the two-dimensional plane coordinates and altitude of waypoint elements, and record the two-dimensional plane coordinates, radius, and center altitude of the circular avoidance area elements, while maintaining their circular geometric properties, to prepare data for subsequent two-dimensional geometric calculations.
[0061] In this embodiment, step S2 further includes the following step:
[0062] S21: Arrange the route element sequence according to the input order, and select three adjacent consecutive elements in sequence to form a processing window, and denot them as the first element A, the middle element B and the third element C respectively; Specifically, the elements can be waypoints or circular avoidance areas, and the window types include but are not limited to "point-circle-point", "circle-point-circle", "point-circle-circle", "circle-circle-point" and "circle-circle-circle", etc.
[0063] S22: Construct a geometric calculation model based on the type of the intermediate element B; specifically, when the intermediate element B is a circle, calculate all geometrically defined tangent combinations between the first element A and the intermediate element B, as well as all geometrically defined tangent combinations between the third element C and the intermediate element B.
[0064] When the intermediate element B is a point, the intermediate element B serves as a path constraint point. The path configuration includes a straight line segment connecting to the point, and a geometric tangent or transition straight line segment passing through the point is constructed based on the relative positional relationship between the first element A and the third element C.
[0065] S23: By calculating the external and internal common tangents through analytical geometry, all candidate tangent combinations are obtained. Specifically, based on analytical geometry, the common tangents between points and circles, and between circles, are directly calculated, and standard circular arcs are used to construct the flight path. The generated path consists of straight lines and circular arcs that are smoothly connected, strictly satisfying the geometric tangent and circular arc constraints. Compared with the polyline path generated based on mesh or sampling, it has fewer turns, smoother turns, and is more in line with the dynamic characteristics of the aircraft, which is conducive to shortening flight time and reducing energy consumption.
[0066] S24: Perform geometric screening on candidate tangent combinations, including at least directional and distance constraints; specifically, its main function is to avoid path reversals, detours, and unreasonable geometric configurations. Furthermore, step S24 also includes the following steps:
[0067] S24.1: Using the line AC connecting points A and C, find the foot H of the perpendicular from the center O_B of the circle to the line AC, and construct a reference vector v_HB = H→O_B;
[0068] S24.2: Construct a vector v_BPAB = O_B→P_AB from the center O_B to the point of tangency P_AB from the first element A; construct a vector v_BPCB = O_B→P_CB from the center O_B to the point of tangency P_CB from the third element C. Calculate the dot product between the reference vector v_HB and the above two vectors.
[0069] d_1 = v_HB·v_BPAB;
[0070] d_2 = v_HB·v_BPCB;
[0071] When d_1 > 0 and d_2 > 0, the combination is retained as a candidate; if either dot product is less than or equal to zero, it is discarded. Specifically, only when d_1 > 0 and d_2 > 0 is the combination considered to have both tangents located on one side of the reference vector, with the tangent directions pointing towards the same side away from the reference line AC, satisfying the reasonable directional constraint, thus retaining the combination as a candidate; if either dot product is less than or equal to zero, the combination is determined to be geometrically likely to cause path reversal or non-intuitive detour, and is discarded. Based on directional screening, further rules such as intersection point extension distance constraints, minimum turning radius constraints, and deflection selection can be used to refine the remaining candidate combinations, retaining several tangent combinations with the optimal geometric length and best directional continuity within the local window.
[0072] S25: Calculate and verify the path intersections; furthermore, step S25 also includes the following steps:
[0073] S25.1: Find the analytical expression of the two tangents of the retained tangent combination on the plane, and calculate the intersection point Q of their extensions as the transition point between potential polyline connection points or arc tangent points within the sliding window;
[0074] S25.2: Determine the planar positional relationship between the intersection point Q and the center O_B and radius R_B of the intermediate element B. Verify whether Q meets the preset logical conditions. If not, discard the corresponding tangent combination; if it does, mark the intersection point Q and the corresponding tangent point as local path nodes within the window for subsequent overall path splicing and optimization. Specifically, the preset logical conditions are: when the intersection point is outside the intermediate circle or precisely at the tangent point, it does not enter the circular no-fly zone; when the intersection point is in the forward direction of the window path, it satisfies the monotonic forward logic from A through B to C; the distance between the intersection point and the corresponding tangent point does not exceed the preset upper limit to avoid excessive path detours.
[0075] S26: Match and correct the elements and tangents shared between the sliding windows. Specifically, step S26 also includes the following steps:
[0076] S26.1: Traverse the route elements in order and process all adjacent sliding windows in turn. Perform steps S21 to S25 for each window to obtain one or more legal candidate tangent combinations and intersection information corresponding to the window.
[0077] S26.2: By comparing the tangent parameters associated with the shared element in adjacent windows, verify whether they are consistent. If they are not consistent, backtrack or reselect the tangent combination. Specifically, if the candidate tangents in adjacent windows cannot achieve consistency, backtrack or reselect the local suboptimal tangent combination to adjust the tangent selection of the previous or next window, so that the tangents at the shared element are geometrically connected smoothly and the direction is continuous, thereby eliminating the phenomena of path jumps, discontinuities or acute angle reversals.
[0078] S26.3: Based on the retained tangent combinations, connect the starting point, straight tangent segments, circular arc segments, and ending point sequentially according to the flight path elements to construct a two-dimensional path. This path consists of several straight line segments and standard circular arc segments, possessing first-order geometric continuity and satisfying the geometric constraints and flight smoothness requirements of the circular flight area. Through tangent combination directionality filtering, intersection point verification, and adjacent window tangent consistency verification, it is ensured that each straight line is a precise tangent to the target circular area, and adjacent path segments are continuous and smooth at the tangent points, effectively eliminating path jumps, discontinuities, or geometrically infeasible situations.
[0079] In this embodiment, step S3 further includes the following step:
[0080] S31: For all straight segments in the path, find the corresponding original route elements according to the inflection points and connection relationships on the two-dimensional plane, and obtain the altitude information at each inflection point; specifically, the node altitude passing through the waypoint can be set as the original altitude of the corresponding waypoint, and for intermediate inflection points or tangent points inserted between two waypoints, a smoothly changing altitude value can be assigned through linear interpolation or other altitude planning rules.
[0081] S32: For each arc segment in the path, keep its arc geometry unchanged on the horizontal two-dimensional plane, and set the height of all points on the arc to the height of the center point of the associated circular avoidance area to form a horizontal arc in three-dimensional space, thereby satisfying the planar flight avoidance constraint, maintaining height continuity and facilitating flight control.
[0082] S33: Combine two-dimensional plane coordinates with altitude coordinates to obtain a three-dimensional path point sequence, and then convert the three-dimensional path back to latitude, longitude and altitude representation as needed for loading and execution by navigation systems or flight control systems.
[0083] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A three-dimensional tangent-point route planning method based on layered projection and sliding window geometric analysis, characterized in that: Includes the following steps: S1: Unify and initialize the coordinate system; S2: A two-dimensional optimal smooth path consisting of line segments and circular arc segments is generated using a three-element sliding window geometric solution algorithm; S3: Convert the optimal two-dimensional smooth path to a three-dimensional geographic space; S4: Output the 3D coordinate information of all path points to the external visualization module.
2. The three-dimensional tangent-point route planning method based on layered projection and sliding window geometric analysis according to claim 1, characterized in that: Step S1 further includes the following steps: S11: Receives the input sequence of route elements, each element being defined as three-dimensional geographic coordinates in the form of longitude, latitude, and altitude; S12: Calculate the average latitude and longitude of all input elements as the projection reference center point to obtain the projection coordinates and height value of each element in the local two-dimensional plane.
3. The three-dimensional tangent-point route planning method based on layered projection and sliding window geometric analysis according to claim 2, characterized in that: In step S11, the route element sequence includes at least one starting point, one ending point, and at least one circular avoidance area or intermediate waypoint located between the starting point and the ending point.
4. The three-dimensional tangent-point route planning method based on layered projection and sliding window geometric analysis according to claim 3, characterized in that: Step S2 further includes the following steps: S21: Arrange the route element sequence according to the input order, select three adjacent consecutive elements in turn to form a processing window, and denot them as the first element A, the middle element B and the third element C respectively; S22: Construct a geometric calculation model based on the type of intermediate element B; S23: Calculate the external and internal common tangents using analytical geometry to obtain all candidate tangent combinations; S24: Perform geometric screening on candidate tangent combinations; S25: Calculate and verify the path intersections; S26: Match and correct elements and tangents shared between sliding windows.
5. The three-dimensional tangent-point route planning method based on layered projection and sliding window geometric analysis according to claim 4, characterized in that: In step S22, when the intermediate element B is a circle, calculate all geometrically defined tangent combinations between the first element A and the intermediate element B, and all geometrically defined tangent combinations between the third element C and the intermediate element B. When the intermediate element B is a point, the intermediate element B serves as a path constraint point. The path configuration includes a straight line segment connecting to the point, and a geometric tangent or transition straight line segment passing through the point is constructed based on the relative positional relationship between the first element A and the third element C.
6. The three-dimensional tangent-point route planning method based on layered projection and sliding window geometric analysis according to claim 5, characterized in that: Step S24 further includes the following steps: S24.1: Using the line AC connecting points A and C, find the foot H of the perpendicular from the center O_B of the circle to the line AC, and construct a reference vector v_HB = H→O_B; S24.2: Construct a vector v_BPAB = O_B→P_AB from the center O_B to the point of tangency P_AB from the first element A; construct a vector v_BPCB = O_B→P_CB from the center O_B to the point of tangency P_CB from the third element C. Calculate the dot product between the reference vector v_HB and the above two vectors. d_1 = v_HB·v_BPAB; d_2 = v_HB·v_BPCB; When d_1 > 0 and d_2 > 0, the combination is retained as a candidate; if any dot product is less than or equal to zero, it is eliminated.
7. The three-dimensional tangent-point route planning method based on layered projection and sliding window geometric analysis according to claim 6, characterized in that: Step S25 further includes the following steps: S25.1: Find the analytical expression of the two tangents of the retained tangent combination in the plane, and calculate the intersection point Q of their extensions; S25.2: Determine the planar positional relationship between the intersection point Q and the center O_B and radius R_B of the intermediate element B, and verify whether Q meets the preset logical conditions. If it does not meet the conditions, discard the corresponding tangent combination; if it does meet the conditions, mark the intersection point Q and the corresponding tangent point position as local path nodes within the window.
8. The three-dimensional tangent-point route planning method based on layered projection and sliding window geometric analysis according to claim 7, characterized in that: Step S26 further includes the following steps: S26.1: Traverse the route elements in order and process all adjacent sliding windows in turn. Perform steps S21 to S25 for each window to obtain one or more legal candidate tangent combinations and intersection information corresponding to the window. S26.2: By comparing the tangent parameters associated with the shared element in adjacent windows, verify whether they are consistent. If they are not consistent, backtrack or reselect the tangent combination. S26.3: Based on the retained tangent combinations, connect the starting point, straight tangent segments, circular arc segments, and ending point in sequence according to the route elements to construct a two-dimensional path.
9. The three-dimensional tangent-point route planning method based on layered projection and sliding window geometric analysis according to claim 8, characterized in that: Step S3 further includes the following steps: S31: For all straight segments in the path, find the corresponding original route elements according to the inflection points and connection relationships on the two-dimensional plane, and obtain the height information at each inflection point; S32: For each arc segment in the path, the height of all points on the arc is uniformly set to the height of the center point of the associated circular avoidance area, forming a horizontal arc in three-dimensional space; S33: Combine the two-dimensional plane coordinates with the height coordinates to obtain a three-dimensional path point sequence.