River channel patrol unmanned aerial vehicle dynamic termination area access and termination method based on water level prediction

Abstract

The application discloses a kind of river channel patrol unmanned plane dynamic termination area access and termination method based on water level prediction.Acquire water level prediction sequence, predicted water level is mapped as inundation range according to forecast period, and available emergency termination area set is generated in combination with topography, exclusion boundary and land connectivity;Trajectory point prediction arrival time is determined according to trigger anchor point planned arrival time and each trajectory termination duration, and according to corresponding time, termination area accommodation and trajectory exclusion are judged, and access, rejection, shorten time window or change line instruction is output;Selected target emergency termination area is executed, and the earliest time when the same target emergency termination area is disabled according to predicted water level, the time required to arrive and complete termination disposal and safety margin determine the prospective termination boundary.The application improves the safety termination capability of patrol task under rising water condition.

Description

Technical Field

[0001] This invention relates to the fields of hydrology and water resources engineering, safe operation of unmanned aerial vehicles (UAVs), and low-altitude emergency patrol technology, specifically to a method for dynamic termination zone access and termination of UAVs for river patrol based on water level forecasting. Background Technology

[0002] During periods of torrential rain, floods, and rapidly rising water levels, emergency patrols are frequently conducted in rivers, reservoirs, dikes, and flood detention areas, including water level monitoring, cross-sectional image acquisition, floating debris inspection, and dike hazard investigation. Compared to manual wading patrols, drones can reduce the frequency of personnel entering dangerous areas to some extent; however, emergency patrols typically occur during periods of rainfall, rising water levels, reduced communication quality, and decreased ground accessibility, making mission launches and abnormal terminations more risky.

[0003] Existing unmanned aerial vehicle (UAV) solutions for water conservancy mainly focus on the perception tasks themselves, such as flow measurement, water level identification, image acquisition, shoreline change extraction, or dike patrol. Existing UAV mission planning or emergency landing point selection schemes are usually based on a one-time screening of maps, terrain, buildings, roads, slopes, water bodies, or static restricted areas. Such schemes can determine whether the nominal flight path is reachable, but they usually treat emergency landing areas or emergency termination areas as static areas that do not change with the mission time.

[0004] However, in river wading scenarios, the availability of low-lying areas, floodplains, drawdown zones, and shore platforms that can be used for abnormal drone termination changes with water level fluctuations: low-lying areas may be submerged after the water level exceeds the normal level, and shore platforms may no longer be permitted as termination areas after the water level reaches the guaranteed or safety limit level due to risks of submersion, erosion, or levee protection requirements. If static termination areas are still used for flight determination, situations may arise where the mission is nominally reachable at takeoff, but no safe termination area exists during mission execution or in the event of a malfunction.

[0005] Meanwhile, when a drone experiences events such as satellite positioning failure, communication link interruption, or low battery, its actual movement is affected by the inherent failure response logic of the flight controller. Selecting the termination zone solely based on straight-line distance or nominal return path cannot reflect the controller's termination behavior trajectory and endpoint dispersion range under a specific configuration, which may lead to an overestimation of mission feasibility.

[0006] In addition, existing solutions typically screen termination trajectories based on environmental conditions at the start of the mission or during a fixed forecast period, without aligning the duration of the UAV's arrival at different trajectory points and endpoints with the continuous rise in water levels. Therefore, even if a candidate termination area is available when an anomaly is triggered, it may have already been submerged or lost land connectivity with the safe shoreline area by the time the UAV actually arrives at that termination area.

[0007] Therefore, there is a need for a method for the access and termination of UAV missions for emergency river patrol that combines time-varying available emergency termination zones driven by water level forecasts, time constraints on calibrated controller termination behavior, and forward-looking termination timing, in order to improve the safety and traceability of UAV patrol missions under rising water conditions. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies that treat river emergency termination zones as static areas and rely solely on nominal geometric reachability or fixed-time environmental conditions for mission launch judgment. This invention provides a dynamic termination zone access and termination method for river patrol drones based on water level forecasts. This method can generate a dynamic set of available emergency termination zones for different forecast periods and aligns the arrival times of each trajectory point in the calibrated controller termination behavior trajectory set with the predicted water level time before conducting a capacity determination. This avoids releasing patrol missions even when available termination zones have shrunk, disappeared, or lost connectivity with safe areas on the bank after water levels rise. Technical solution

[0009] To achieve the above objectives, the present invention adopts the following technical solution: It acquires the water level forecast sequence and flood warning level of the target river section, and acquires the flow forecast sequence as auxiliary data for determining the emergency patrol triggering conditions; when the flood warning level, water level change characteristics, or flow forecast characteristics reach the preset emergency patrol triggering conditions, it invokes the digital elevation model, bank slope data, restricted access boundary data, candidate emergency termination areas, and preset shoreline safety areas. The restricted access boundary data includes at least water surface restricted access area boundary data and dike restricted access area boundary data. The task time window is divided into several forecast periods, and the predicted water level within each forecast period is mapped to the inundation range. Areas that are inundated, have excessive slope, are located within water surface or dike restricted access areas, or cannot be connected to the preset shoreline safety area via a land path that does not cross water surface or dike restricted access areas are removed from the candidate emergency termination areas, forming a set of available emergency termination areas for each forecast period.

[0010] Furthermore, based on the failure event type, the current UAV's aircraft model, flight control firmware version, parameter configuration, and the flight and battery status corresponding to the trigger anchor point to be determined, a matching set of termination behavior trajectories is retrieved from a pre-calibrated controller termination behavior trajectory library. This set of termination behavior trajectories is then translated and rotated along the survey route's trigger anchor points to the mission coordinate system. Based on the planned arrival time of the trigger anchor points and the termination duration of each trajectory point relative to the failure event trigger time, the predicted arrival time of each trajectory point is determined. The flooding range and available emergency termination zone set corresponding to the predicted arrival time are then called to determine whether all mapped trajectory endpoints fall into the available emergency termination zone set at the actual predicted arrival time, and whether all mapped trajectory points avoid the water surface and embankment restricted areas at that time. Only when all trigger anchor points and termination trajectories covered by the mission time window meet the aforementioned conditions is a mission access command generated; otherwise, a takeoff rejection, mission time window shortening, or route rerouting command is output.

[0011] Furthermore, during mission execution, a target emergency termination zone is selected from the currently available emergency termination zones. Based on the earliest predicted moment when the water level will reach the critical elevation that would render the target emergency termination zone ineffective, and considering the time required for the UAV to reach the same target emergency termination zone from its current position and complete the termination process, as well as the safety margin, the forward termination boundary corresponding to the target emergency termination zone is calculated. When the forward termination boundary is reached at the current moment, the UAV is controlled to perform an emergency termination and an audit log is recorded.

[0012] In a preferred embodiment of the present invention, the critical elevation includes at least one of the normal water level, the warning water level, and the guaranteed water level; the safety limit water level corresponds to the candidate emergency termination zone. The forecast period is defined by the moment when the predicted water level crosses the critical elevation, or by the moment when the conservatively predicted water level reaches the safety limit water level. The safety limit water level can be determined by the candidate emergency termination zone elevation and the net height margin, for example, the safety limit water level 24 for the shore platform; the critical elevation that causes the set of available emergency termination zones to shrink can be either the legally defined characteristic water level or the safety limit water level. Candidate emergency termination zones include low-lying shoal candidate emergency termination zones and shore-side platform candidate emergency termination zones. Low-lying shoal candidate emergency termination zones are eliminated when the predicted water level exceeds the normal water level. The elimination of shore-side platform candidate emergency termination zones is controlled by the shore-side platform safety limit water level 24: when the conservative predicted water level H_safe(t) for the forecast period is not lower than the shore-side platform safety limit water level 24, the shore-side platform candidate emergency termination zone 142 is eliminated. The shore-side platform safety limit water level 24 is the elevation of the shore-side platform candidate emergency termination zone 142 minus a preset net height margin. The net height margin can be determined based on the platform's flood risk and wave run-up conditions, for example, 0.3m. Because the conservative predicted water level incorporates forecast error margins and elevation error margins, the shore-side platform candidate emergency termination zone 142 may be eliminated before the predicted water level crosses the guaranteed water level 23.

[0013] In a preferred embodiment of the present invention, the flooding mapping of the predicted water level is determined based on the grid elevation of the digital elevation model and the connectivity of the water body. For a forecast period, a conservative predicted water level H_safe(t) is taken for that forecast period, where H_safe(t) = H_pred(t) + ΔH_forecast + ΔH_DEM; H_pred(t) is the predicted water level, ΔH_forecast is the forecast error margin, and ΔH_DEM is the elevation error margin of the digital elevation model. Grids with elevations lower than the conservative predicted water level and connected to the river surface are defined as the flooding range. Candidate emergency termination zones should also meet the requirements of minimum effective area, maximum slope, safe distance from water surface, embankment, road, or obstacle, and be connected to a preset safe area on the bank via a land route that does not cross the restricted water surface area or the restricted embankment area.

[0014] In a preferred embodiment of the present invention, the controller termination behavior trajectory library is obtained through failure event injection calibration under a fixed flight control firmware version, fixed aircraft model, fixed parameter configuration, and fixed simulation environment. The trajectory interception range is from the failure event trigger time to the moment when the landing judgment condition is first met, and a timestamp or termination duration relative to the failure event trigger time is recorded for each trajectory point. The calibration results represent the controller termination response characteristics under a fixed configuration and are used as a conservative constraint for mission admission, rather than as a direct prediction of the actual river flight landing point.

[0015] In this specification, emergency termination refers to the UAV ceasing its original survey mission after a failure event or prospective termination condition is triggered, flying to the selected target emergency termination zone, and completing a controlled descent and landing within that zone; completion of termination refers to the UAV meeting the preset landing judgment conditions for the first time. The landing judgment conditions are jointly determined by at least two of the following: flight control landing status flag, grounding detection status, relative ground altitude, vertical speed, and motor status. The judgment items and thresholds used are fixed before the target is located in the corresponding trajectory library.

[0016] Beneficial effects: 1. Compared to schemes that treat emergency landing zones as static areas, this invention performs conservative flooding mapping and candidate termination zone elimination based on water level forecast periods, resulting in a set of available emergency termination zones that shrinks with water level changes. It also excludes isolated candidate zones that have lost land connectivity to the pre-set shoreline safety area, reducing the overestimation of available land termination zones during flooding. 2. Compared to schemes that only screen based on nominal flight paths, straight-line distances, or fixed-time environmental conditions, this invention uses a calibrated set of controller termination behavior trajectories and endpoint envelopes as admission constraints. It aligns the termination duration of each trajectory point and endpoint with the water level forecast time, enabling the identification of missions where the termination zone is still visible when an anomaly occurs, but which have failed by the time the UAV actually arrives. 3. This invention targets the same emergency termination zone and couples the earliest time when the predicted water level will cause the emergency termination zone to fail with the time required for the UAV to arrive at the zone and complete the termination process, forming a forward-looking termination boundary. This can trigger emergency termination before the target emergency termination zone is flooded or before safety rules fail. At the same time, by recording conservatively predicted water level parameters, reasons for area removal, predicted arrival time of trajectory points, trajectory database identifiers, judgment results, and termination trigger records, it is convenient to conduct mission audits and post-event reviews. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the overall process of the method of the present invention.

[0018] Figure 2 A system structure block diagram for implementing the method of the present invention.

[0019] Figure 3 This is a schematic diagram of the river channel cross-section and water level classification.

[0020] Figure 4 This is a schematic diagram of the task's planar layout and the envelope mapping of the termination behavior trajectory.

[0021] Figure 5 This is a schematic diagram showing the division of forecast periods and the forward termination boundary.

[0022] Figure 6 This is a simplified schematic diagram illustrating the main technical features of the present invention.

[0023] Figure Labeling Explanation: 11. No-entry zone on water surface; 12. Floodplain extension zone; 13. No-entry zone on dike; 141. Candidate emergency termination zone for low-lying beach; 142. Candidate emergency termination zone for shore platform; 21. Normal water level; 22. Warning water level; 23. Guaranteed water level; 24. Safety limit water level for shore platform; 31. Survey route; 32. Trigger anchor point; 33. Set of termination behavior trajectories and endpoint envelope; 41. Forecasted water level process line; 42. Time t21 for crossing normal water level; 43. Time tc for reaching the safety limit water level for shore platform; 44. Time required to reach the target termination zone and safety margin; 45. Forward termination boundary t_stop; 46. Conservatively predicted water level process line; 1. Hydrological forecast access module; 2. Geographic data module; 3. Inundation mapping and dynamic emergency termination zone generation module; 4. Controller termination behavior trajectory library; 5. Task access judgment module; 6. Execution monitoring and forward termination module. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings. It should be understood that the following embodiments are for illustrative purposes only and not for limiting the present invention; any equivalent substitutions made to the order of steps, parameter values, data sources, and scene objects without departing from the concept of the present invention shall fall within the protection scope of the present invention.

[0025] like Figure 1 and Figure 2 As shown, the system in this embodiment includes a hydrological forecast access module 1, a geographic data module 2, an inundation mapping and dynamic emergency termination zone generation module 3, a controller termination behavior trajectory library 4, a task access determination module 5, and an execution monitoring and forward-looking termination module 6. Each module can be implemented by a processor and memory located in a ground control station, an edge computing terminal, an UAV onboard computing unit, or a combination thereof, and the modules exchange data via wired or wireless means.

[0026] Step S1: The hydrological forecasting access module 1 acquires the water level forecast sequence and flood warning level for the target river section, and acquires the flow forecast sequence as auxiliary data for determining the emergency monitoring trigger conditions. The water level forecast sequence can be provided by a hydrological forecasting model, water level telemetry station, dispatching system, or a fused rainfall-water level relationship model; the flow forecast sequence can be provided by hydrological stations, dam dispatching information, or a hydrological model. The emergency monitoring trigger conditions can be set as follows: receiving a flood warning of a preset level or above, and / or the predicted water level rise exceeding a preset threshold within a preset time period, and / or the predicted flow exceeding a preset flow threshold. If the trigger conditions are not met, the system can maintain ground or fixed station monitoring.

[0027] Step S2: Geographic data module 2 acquires the river channel digital elevation model, levee elevation, bank slope, river centerline, restricted access boundary, candidate emergency termination zone boundary, and preset bankside safety zone boundary. The digital elevation model can be a raster digital elevation model, a triangulation model, or an elevation model obtained by interpolation of measurement points; the restricted access boundary can at least include the water surface restricted access zone 11, the levee restricted access zone 13, and buffer boundaries of roads, buildings, power transmission facilities, or other obstacles set according to project safety requirements; the preset bankside safety zone can be a pre-delineated land area connected to ground support personnel, roads, fixed recovery points, or safe evacuation routes.

[0028] Step S3: Divide the task time window into several forecast periods, and let m represent the forecast period number. In this embodiment, the time when the predicted water level crosses the normal water level 21, the warning water level 22 and the guaranteed water level 23, and the time when the conservatively predicted water level reaches the safety limit water level 24 of the shore platform are used as the segment points. Alternatively, segments can be made according to a fixed step size. For the m-th forecast period, the highest predicted water level H_pred,max within that period is taken, and the conservative predicted water level is determined according to H_safe,max=H_pred,max+ΔH_forecast+ΔH_DEM. The set of grids in the digital elevation model whose elevation is less than H_safe,max and which are connected to the river surface through four-neighbor or eight-neighbor searches are determined as the inundation range, and this inundation range is merged with the preset water surface restricted area as the water surface restricted area for that period. Then, areas located within the inundation range, areas with a slope exceeding the slope threshold, areas located within the water surface restricted area or the dike restricted area, and areas that cannot be connected to the preset shore safety area through a land path that does not cross the water surface restricted area or the dike restricted area are removed from the candidate emergency termination areas, so as to obtain the set of available emergency termination areas A_m for the m-th forecast period.

[0029] To avoid candidate areas being geometrically visible but unsuitable for termination, candidate emergency termination areas should simultaneously meet the conditions of effective area, slope, surface continuity, land connectivity, and safe distance. Optionally, the effective area of ​​the candidate area should not be less than the maximum planar projection area of ​​the UAV plus the area required for the safe outer boundary; the maximum slope of the candidate area should not exceed the preset slope threshold; the minimum distance between the candidate area and the boundaries of the water surface restricted area 11, the embankment restricted area 13, and other obstacles should not be less than the corresponding safe distance; after removing the water surface restricted area 11 and the embankment restricted area 13, the candidate area should belong to the same land connectivity component as the preset shoreline safe area.

[0030] like Figure 3As shown, candidate emergency termination area 141 for low-lying shoals can be exposed under low water conditions and included in the available set; when the predicted water level exceeds the normal water level 21, 141 is considered to be submerged or no longer meets the safety rules, and is therefore removed from the set A_m for the corresponding forecast period. Candidate emergency termination area 142 for shore platforms has a platform elevation higher than the guaranteed water level 23; its availability is controlled by the shore platform safety limit water level 24: 142 is removed when the conservative predicted water level H_safe(t) is not lower than the safety limit water level 24.

[0031] Step S4: The controller termination behavior trajectory library 4 stores a set of termination behavior trajectories corresponding to different failure event types and different flight state combinations. Each standard trajectory is recorded in the local coordinate system with the failure trigger point as the origin. Each trajectory point also records the timestamp or termination duration from the failure trigger point to that trajectory point, and is associated with metadata such as the aircraft model, flight control firmware version, parameter configuration, failure event type, initial heading, initial speed range, and battery status. Failure events may include satellite positioning failure, communication link interruption, low battery, or a combination thereof.

[0032] Step S5: As Figure 4 As shown, one or more trigger anchor points 32 are selected on the survey route 31, and k represents the trigger anchor point number, i represents the termination behavior trajectory number, and j represents the trajectory point number in a termination behavior trajectory. For any trigger anchor point P_k, each trajectory point q_ij in the standard termination trajectory set is translated and rotated according to P_ij = P_k + R(θ_k)q_ij, where R(θ_k) is the rotation matrix determined by the survey heading θ_k at the trigger anchor point, and P_ij is the mapped trajectory point in the mission coordinate system. Let the planned arrival time of the trigger anchor point be T_k, and the termination duration of trajectory point q_ij relative to the failure trigger be τ_ij, then the predicted arrival time of the mapped trajectory point is T_ij = T_k + τ_ij. The endpoints of the mapped trajectories form the termination behavior trajectory set and endpoint envelope 33.

[0033] For each mapped trajectory, the task admission judgment module 5 queries the conservative flooding range and the set of available emergency termination zones for the corresponding m-th forecast period according to the predicted arrival time T_ij of each trajectory point: First, it determines whether the trajectory endpoints of the termination behavior trajectory fall into the corresponding set of available emergency termination zones A_m at their predicted arrival time; Second, it determines whether each trajectory point of the termination behavior trajectory falls into the water surface restricted zone 11 or the embankment restricted zone 13 at its respective predicted arrival time. If both conditions are met, the trigger anchor point, the failure event type, and the termination behavior trajectory are determined to be robust and feasible; if some trajectory endpoints cannot fall into the restricted zone, it is determined to be limited feasible and a shortened task window or rerouting suggestion is generated; if any trajectory point falls into the restricted zone or all trajectory endpoints cannot fall into the restricted zone, it is determined to be infeasible.

[0034] Step S6: The mission admission judgment module 5 summarizes all predicted time periods, all trigger anchor points that need to be covered, and their corresponding termination behavior trajectories within the mission time window. A mission admission instruction is generated only when each trajectory point and trajectory endpoint is robustly feasible after alignment with its predicted arrival time. When limited feasibility exists, instructions to shorten the mission time window, adjust the survey order, shorten flight segments, or change routes can be generated according to preset strategies. When infeasibility exists, a takeoff rejection instruction is output.

[0035] Step S7: During mission execution, the monitoring and forward-looking termination module 6 receives the rolling updated water level forecast sequence and regenerates the set of available emergency termination zones based on the updated conservative water level forecast. The system selects a target emergency termination zone from the currently available emergency termination zones; the target emergency termination zone can be selected according to the forward-looking availability duration, arrival time, and preset priority. For the same target emergency termination zone, the earliest time t_cross at which the conservative water level causes the zone to be removed is taken, and the forward-looking termination boundary is calculated: t_stop = t_cross − t_reach − Δt. Wherein, t_reach includes the flight time from the current position to the target emergency termination zone, the attitude adjustment time, and the termination descent time; Δt is a safety margin used to mitigate forecast errors, communication delays, and control execution deviations. When the current time reaches t_stop, the system stops the survey, controls the UAV to fly to the target emergency termination zone, completes the controlled descent and landing, and records the audit log.

[0036] This embodiment uses Figures 3 to 5 Using the parameterized river channel shown as an example, the construction of the time-varying termination zone and the prospective termination process of this invention are explained. This example is used to illustrate the algorithm steps and data organization method, and does not limit the river segment size, threshold, or forecast model in actual engineering. The target river segment adopts a digital elevation model with a 1m grid resolution. The normal water level 21 is set to 100.0m, the warning water level 22 is set to 101.0m, and the guaranteed water level 23 is set to 102.2m. The candidate emergency termination zone 141 for the low-shoal is available when the predicted water level is lower than 100.0m. The platform elevation of the candidate emergency termination zone 142 for the bank platform is 102.35m. Taking a net height margin of 0.3m, the safe limit water level 24 for the bank platform is 102.05m. 142 is eliminated when the conservative predicted water level H_safe(t) is not lower than 102.05m. The maximum allowable slope can be set to 8°, and the minimum effective termination area can be pre-configured according to the UAV's external dimensions and safe buffer distance. The forecast error margin ΔH_forecast can be set to 0.15m, the digital elevation model elevation error margin ΔH_DEM can be set to 0.10m, and the inundation mapping is conservatively determined using H_safe=H_pred+0.25m.

[0037] Assume the predicted water level process line 41 gradually rises from 99.7m, and the predicted water level crosses the normal water level 21 at 50 minutes, denoted as t21; the conservative predicted water level process line 46 (i.e., the total error margin of the predicted water level is 0.25m) reaches the safety limit water level 24 of the shore platform at 113 minutes (equivalent to the predicted water level H_pred reaching 101.8m), denoted as tc; the guaranteed water level 23 (102.2m) is higher than the safety limit water level 24, and the time when the predicted water level crosses the guaranteed water level 23 is later than tc, which does not affect the removal time of the shore platform 142. This forms three forecast periods: when t < t21, both 141 and 142 are usable; when t21 ≤ t < tc, 141 is removed, and only 142 is usable; when t ≥ tc, both 141 and 142 are removed, and the available emergency termination zone set is empty. The specific time-segment relationships are as follows: Figure 5 As shown.

[0038] In a mission instance, assuming the current time is 70 minutes, the candidate emergency termination zone 142 on the shore-side platform upon which the current mission depends remains available before time c; the conservative time required for the UAV to reach 142 from its current position and complete termination is 25 minutes, with a safety margin Δt of 10 minutes. Therefore, the look-ahead termination boundary is t_stop = 113 − 25 − 10 = 78 minutes. If the mission continues to execute until 78 minutes without completion, the execution monitoring and look-ahead termination module 6 issues an emergency termination command, causing the UAV to complete termination according to the termination strategy on shore-side platform 142, thus avoiding the UAV remaining in a survey state when the available termination zone set is empty after 113 minutes.

[0039] In another proposed access mission, assuming the planned arrival time of a certain trigger anchor point is 112.0 min, and the termination durations of the three termination behavior trajectories corresponding to the same failure event are 40 s, 90 s, and 130 s, respectively, then the predicted arrival times of their trajectory endpoints are 112.67 min, 113.50 min, and 114.17 min, respectively. Since the conservatively predicted water level reaches the shore platform safety limit water level 24 at 113 min (tc), the available emergency termination zone set will be empty when the endpoints of the latter two trajectories arrive. Therefore, even if the shore platform 142 is still visible during the abnormal triggering, this proposed access mission should be determined as infeasible or its mission window should be shortened.

[0040] First period If t < t21, the predicted water level is 21 seconds lower than the normal water level. Available Available {141，142} Second period t21≤t<tc, the predicted water level is not lower than the normal water level 21, and the conservatively predicted water level is lower than the safety limit water level 24 for the shore platform. Eliminate Available {142} Third period t≥tc, conservatively predicted water level will not be lower than the safety limit water level of the shore platform (24). Eliminate Eliminate empty set

[0041] The controller termination behavior trajectory library 4 can be obtained through calibration in a software-in-the-loop simulation environment with a fixed configuration. In one alternative implementation, using a fixed version of the flight control firmware, a fixed quadcopter model, a fixed parameter file, and a fixed initial simulation environment, satellite positioning failure, communication link interruption, or low battery events are injected for different combinations of relative states of trigger anchor points, flight heading, cruise speed range, and battery status. Each simulation starts from the time the failure event is injected, recording the aircraft position, speed, navigation status, and landing status at a uniform sampling period, and assigning a timestamp to the relative failure trigger time for each trajectory point, until the landing judgment condition is first met, at which point recording stops.

[0042] For the same failure event type, trajectories obtained from multiple simulations are aggregated to form a set of termination behavior trajectories. The endpoint distribution envelope can be constructed by using a minimum bounding ellipse, convex hull, α-shaped envelope, or by applying a preset buffer distance around the endpoint set. Different trajectory library entries should be established for different controller versions, aircraft models, parameter configurations, or failure injection conditions, and the results of one entry should not be directly used for another configuration.

[0043] It should be noted that the trajectory library represents the termination response characteristics of the controller under preset simulation or calibration conditions in a fixed configuration, and its purpose is to provide conservative constraints for mission admission. This trajectory library is not used as a deterministic prediction of the actual landing point in real river flight; actual flight can still be affected by factors such as wind, rainfall, positioning error, communication quality, load changes, and terrain obstruction.

[0044] During mission execution, the hydrological forecast access module 1 can update the water level forecast sequence according to a preset cycle or after receiving new hydrological forecast products. The execution monitoring and forward-looking termination module 6 inputs the updated forecast sequence and conservatively predicted water level parameters into the inundation mapping and dynamic emergency termination zone generation module 3, recalculates the set of available emergency termination zones for each forecast period, and calls the mission admission judgment module 5 to verify the remaining time window of the current mission according to the planned arrival time of each trigger anchor point and the termination duration of each trajectory point in the remaining mission.

[0045] When the updated predicted water level exceeds the normal water level 21 ahead of schedule, or the conservative predicted water level reaches the safety limit water level 24 for the shore platform ahead of schedule, or when the updated inundation area expands, land connectivity fails, or the predicted arrival time of the trajectory points changes, causing the current termination area to no longer meet the accommodation conditions, the system can perform downgraded handling according to preset priorities: prioritize shortening the remaining survey segments; if this cannot be met, adjust the route to an area still covered by available termination areas; if this still cannot be met, trigger emergency termination in advance. The handling process and the forecast version on which it is based are all written to the audit log.

[0046] This invention is not limited to natural river channel surveys. For reservoir banks, dike patrols, flood storage areas, waters adjacent to bridges across rivers, and other water-related areas, the corresponding reservoir bank elevations, water level control curves, dike protection boundaries, no-entry boundaries, or telemetry water level data can be replaced with the input data in this invention. Forecast periods can be divided according to fixed time intervals or according to events that cross water level, flow, or rainfall thresholds. Candidate emergency termination areas can be low-lying beaches, shore platforms, safety platforms on the outer side of the dike top, or certified fixed recovery points, but their availability in each forecast period must be reassessed based on water level forecasts, topographic constraints, and no-entry constraints.

[0047] This invention also provides a river emergency patrol drone mission access and termination system, including a hydrological forecast access module 1, a geographic data module 2, an inundation mapping and dynamic emergency termination zone generation module 3, a controller termination behavior trajectory library 4, a mission access determination module 5, and an execution monitoring and forward-looking termination module 6. The functional division of each module is as follows: Figure 2 As shown, the system is configured to perform the methods described in any of the above embodiments. Each module can be implemented by software, hardware, or a combination thereof, and can be integrated and deployed on the same computing device, or distributed across ground stations, cloud servers, and airborne computing units.

[0048] The present invention also provides an electronic device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the method described in any of the above embodiments. This electronic device may be a ground station computer, a server, a portable terminal, or an airborne computing unit.

[0049] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described in any of the above embodiments. The computer-readable storage medium includes, but is not limited to, magnetic storage, optical disks, flash memory, and other non-volatile memories.

Claims

1. A method for dynamic termination zone access and termination of unmanned aerial vehicles (UAVs) for river channel surveying based on water level forecasting, characterized in that, Includes the following steps: S1. Obtain the water level forecast sequence and water situation warning level of the target river section, and obtain the flow forecast sequence as auxiliary judgment data for emergency patrol triggering conditions; when the water situation warning level, water level change characteristics or flow forecast characteristics reach the preset emergency patrol triggering conditions, initiate the task access judgment. S2. Obtain the digital elevation model of the target river section, bank slope data, restricted access boundary data, preset candidate emergency termination area and preset bankside safety area. The restricted access boundary data includes at least water surface restricted access area boundary data and dike restricted access area boundary data. S3. Divide the task time window into several forecast periods. For each forecast period, map the predicted water level of the forecast period to the flood range. Remove areas located within the flood range, areas with a slope exceeding a preset slope threshold, areas located within the water surface restricted area or the dike restricted area, and areas that cannot be connected to the preset shore safety area by a land path that does not cross the water surface restricted area or the dike restricted area from the candidate emergency termination area. This will result in a set of available emergency termination areas for the forecast period. S4. Based on the preset failure event type and the current UAV's aircraft model, flight control firmware version, parameter configuration, and the flight status and power status corresponding to the trigger anchor point to be determined, retrieve the matching set of termination behavior trajectories from the pre-calibrated controller termination behavior trajectory library. S5. Map the set of termination behavior trajectories to the task coordinate system along the trigger anchor points on the survey route; For each termination behavior trajectory in the set of termination behavior trajectories, the predicted arrival time of each trajectory point is determined based on the planned arrival time of the trigger anchor point and the termination duration of each trajectory point from the triggering of the failure event to the corresponding trajectory point. According to the predicted arrival time of each trajectory point, the flood range and available emergency termination zone set for the corresponding forecast period are called to determine whether the trajectory endpoint of the termination behavior trajectory falls into the available emergency termination zone set for the corresponding forecast period, and whether each trajectory point of the termination behavior trajectory does not fall into the water surface restricted area and the embankment restricted area for the corresponding forecast period. S6. When all termination behavior trajectories corresponding to each trigger anchor point covered by the mission time window meet the judgment conditions of step S5, generate a mission admission instruction; otherwise, output a takeoff rejection instruction, a mission time window shortening instruction, or a route change instruction. S7. During mission execution, a target emergency termination zone is selected from the currently available emergency termination zones. Based on the earliest time when the predicted water level reaches the critical elevation that would render the target emergency termination zone ineffective, the time required for the UAV to arrive at the target emergency termination zone from its current position and complete the termination process, and a preset safety margin, the forward termination boundary corresponding to the target emergency termination zone is determined. When the forward termination boundary is reached at the current time, the UAV is controlled to perform an emergency termination and an audit log is recorded. The emergency termination includes stopping the survey, flying to the target emergency termination zone, and completing a controlled descent and landing within the target emergency termination zone.

2. The method according to claim 1, characterized in that, The key elevation includes at least one of the normal water level, warning water level, and guaranteed water level; the forecast period is divided by the moment when the predicted water level crosses the key elevation, or by the moment when the conservatively predicted water level reaches the safety limit water level of the shore platform.

3. The method according to claim 1, characterized in that, In step S3, mapping the predicted water level to the inundation range includes: for a forecast period, taking the highest predicted water level within the forecast period, comparing the highest predicted water level with the elevation of each grid cell in the digital elevation model, and determining the set of grid cells whose elevation is lower than the highest predicted water level and which are connected to the river surface as the inundation range for the forecast period.

4. The method according to claim 2, characterized in that, The candidate emergency termination areas include low-lying shoal candidate emergency termination areas and shore-side platform candidate emergency termination areas; when the predicted water level exceeds the normal water level, the low-lying shoal candidate emergency termination area is removed from the set of available emergency termination areas; when the conservative predicted water level for the forecast period is not lower than the shore-side platform safety limit water level, the shore-side platform candidate emergency termination area is removed from the set of available emergency termination areas; the shore-side platform safety limit water level is the elevation obtained by subtracting the preset net height margin from the platform elevation of the shore-side platform candidate emergency termination area.

5. The method according to claim 1, characterized in that, In step S3, the predicted water level used to map the flooding range is a conservative predicted water level H_safe(t), which satisfies: H_safe(t) = H_pred(t) + ΔH_forecast + ΔH_DEM; where H_pred(t) is the predicted water level at time t, ΔH_forecast is the forecast error margin, and ΔH_DEM is the elevation error margin of the digital elevation model.

6. The method according to claim 1, characterized in that, The controller termination behavior trajectory library is calibrated in the following way: under a fixed flight control firmware version, fixed aircraft model, fixed parameter configuration and fixed simulation environment, a failure event is injected under a preset combination of flight state and power state, and the trajectory from the triggering of the failure event to the first satisfaction of the landing judgment condition is recorded to form a set of termination behavior trajectories and its endpoint distribution envelope corresponding to the failure event type. The failure event types include at least one of satellite positioning failure, communication link interruption, and low battery.

7. The method according to claim 1, characterized in that, The controller termination behavior trajectory library stores the timestamp or termination duration of each trajectory point relative to the trigger time of the failure event for each termination behavior trajectory. The predicted arrival time is determined by adding the planned arrival time of the trigger anchor point to the timestamp or termination duration of the corresponding trajectory point. The determination in step S5 includes: when all trajectory endpoints of the termination behavior trajectory set fall into the available emergency termination zone set for the corresponding forecast period at their respective predicted arrival times, and all trajectory points do not fall into the water surface restricted zone or the embankment restricted zone for the corresponding forecast period, it is determined to be robust and feasible; when some trajectory endpoints do not fall into the available emergency termination zone set for the corresponding forecast period, it is determined to be restricted and feasible, and a shortened task window instruction or a rerouting instruction is output; when all trajectory endpoints do not fall into the available emergency termination zone set for the corresponding forecast period, or when any trajectory point falls into the water surface restricted zone or the embankment restricted zone for the corresponding forecast period, it is determined to be infeasible.

8. The method according to claim 1, characterized in that, The forward termination boundary corresponding to the target emergency termination zone is determined by the following formula: t_stop = t_cross − t_reach − Δt; where t_stop is the forward termination boundary, t_cross is the earliest time determined based on the predicted water level that causes the target emergency termination zone to be removed from the set of available emergency termination zones, t_reach is the time required for the UAV to arrive at the target emergency termination zone from its current position and complete the termination process, and Δt is a preset safety margin; t_reach includes the flight time, attitude adjustment time, and termination descent time of the UAV from its current position to the target emergency termination zone, and the flight time is determined based on the reachable distance from the current position to the target emergency termination zone and the conservative cruise speed of the UAV.

9. The method according to claim 1, characterized in that, The candidate areas in the set of available emergency termination areas also meet the following conditions: the effective area of ​​the candidate area is not less than the preset minimum termination area; the distance between the candidate area and the water surface restricted area, the embankment restricted area, the road boundary, or the preset obstacle boundary is not less than the corresponding safety distance; and the candidate area is connected to the preset shoreline safety area through a land path that does not cross the water surface restricted area and the embankment restricted area. When the candidate area loses the land path connection with the preset shoreline safety area, the candidate area is removed from the set of available emergency termination areas.

10. The method according to claim 1, characterized in that, Also includes: Receive the continuously updated water level forecast sequence and re-execute steps S3 to S5; when the updated set of available emergency termination zones shrinks, or the flooding range corresponding to the predicted arrival time of the updated trajectory points changes, causing the current task time window to no longer meet the judgment conditions of step S5, output a downgrade disposal instruction or trigger emergency termination in advance; the audit log includes: water level forecast sequence and its release time, forecast period division results, reasons for removing candidate emergency termination zones, conservatively predicted water level parameters, identifier of the terminated behavior trajectory set, predicted arrival time of each trajectory point, trajectory-by-trajectory judgment conclusion, and emergency termination trigger record.

Images