A large fixed-wing unmanned aerial vehicle rear door type air-drop test flight method and system

Abstract

The application discloses a large fixed-wing unmanned aerial vehicle rear door type air-drop test flight method and system, and belongs to the technical field of flight test. The method comprises a test preparation stage, a test implementation stage and a post-flight achievement solidification stage. The test implementation stage is implemented in a progressive logic layering manner according to ground sliding, cabin door opening and closing verification in the air, simulated air-drop, single drop, interval drop, continuous drop, precision parameter adjustment and precision verification, and a test point matrix is designed to cover various working condition combinations. The application also discloses an air-drop test flight system for executing the method, comprising a data acquisition module, a test point matrix generation module, a test flight process control module, a precision adjustment and verification module and a risk early warning module. The application establishes a systematic and standardized air-drop test flight process for a rear door type large fixed-wing unmanned aerial vehicle, fills the industry gap, significantly improves the test flight safety and efficiency, and is suitable for unmanned aerial vehicle air-drop test flight tasks in the fields of emergency rescue and material delivery.

Description

Technical Field

[0001] This invention belongs to the field of flight test technology, specifically relating to a rear-door airdrop test flight method for a large fixed-wing unmanned aerial vehicle and an airdrop test flight system for performing this method. Background Technology

[0002] With the explosive growth of China's low-altitude economy, drone technology is advancing rapidly. Large fixed-wing drones, with their advantages of large payload capacity, long range, and strong flight stability, are increasingly widely used in airdrop applications, especially in emergency rescue and remote area resupply scenarios, enabling them to quickly overcome terrain obstacles and achieve precise delivery of supplies. The rear-opening door structure, due to its advantages of a wide airdrop channel, smooth cargo unloading, and adaptability to large / heavy airdropped items, has become the mainstream structural form for large fixed-wing drone airdrop systems.

[0003] Airdrop test flights are a crucial step before the finalization, mass production, and deployment of large fixed-wing UAV rear-door airdrop systems. Their core purpose is to verify the compatibility of the airdrop system with the UAV fuselage, the reliability of the rear door opening and closing, the smoothness of airdropping, and the stability of the flight attitude. They also aim to identify potential faults during the test flights, optimize airdrop parameters, and ensure the safety and accuracy of actual airdrop missions.

[0004] At present, although the development of large fixed-wing cargo drones in China is rapid, most of them rely on the airdrop experience of small drones or manned aircraft, and have the following technical problems: First, there is a lack of specific flight test designs for the rear-opening door structure of large fixed-wing UAVs. The rear-opening door structure differs significantly from traditional side-opening doors or tail doors (opening downwards) in terms of dynamic characteristics, cargo exit trajectory, and interference risks with the airframe. Directly applying existing experience may lead to safety accidents such as cargo jamming and airframe collisions.

[0005] Second, the flight test process lacks a systematic approach. Existing methods often involve executing individual test items in a fragmented manner, without forming a complete progressive logic from ground to air, from empty to full load, from single-piece to multi-piece, and from functional verification to accuracy verification. This results in low flight test efficiency and insufficient risk control.

[0006] Third, the layered flight test procedures were not designed in conjunction with the autonomous flight of the UAV and the opening and closing characteristics of the rear-opening door structure. The risk assessment of interference between the airdropped goods and the rear-opening door was insufficient, which could easily lead to flight test safety issues.

[0007] Therefore, developing a systematic and standardized test flight method and auxiliary system specifically for large fixed-wing UAV rear-door airdrop systems has become an urgent technical problem to be solved in this field. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and system for test flights of large fixed-wing UAVs with a rear-opening airdrop capability. By establishing a hierarchical and progressive test flight process and a matrix of test points, the airdrop capability of this type of UAV can be systematically verified, thereby improving the safety and efficiency of test flights.

[0009] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a method for test flight of a large fixed-wing UAV with a rear-opening door, including a pre-test preparation stage, a test implementation stage, and a post-flight results consolidation stage. The test implementation phase shall be carried out in the following order: Step S1: Conduct a ground taxiing test of the airdropped cargo; Step S2: Conduct a test flight to verify the in-flight opening and closing function of the cabin door; Step S3: Conduct simulated airdrop test flights; Step S4: Conduct test flights to verify the single-drop airdrop function; Step S5: Conduct test flights to verify the interval airdrop function; Step S6: Conduct test flights to verify the continuous airdrop function; Step S7: Conduct test flights to fine-tune airdrop parameters; Step S8: Conduct a special test flight to verify the accuracy of airdrops; Steps S1 to S8 are implemented in a progressive, layered manner, from ground to air, from empty to full load, from single item to multiple items, and from functional verification to accuracy verification.

[0010] As a further technical solution of the present invention: the pre-experiment preparation stage includes the following steps: a) Conduct laboratory tests and bench tests of the UAV airdrop system and software control logic functions: check the unlocking function under different working conditions of expected airdrop attitude and cargo weight, and check the control logic of the airdrop system on the bench. b) Conduct ground power-on and testing of the UAV airdrop system: Focus on checking whether the motion performance of the door mechanism and the unlocking function of the limit lock are normal, and ensure that the working logic of the airdrop system is normal under the data link communication state; c) Conduct test flight site selection and environmental condition confirmation: Select an open test flight site with no obstacles and good airspace conditions, delineate the test flight area and airdrop area (such as a circular area with a radius of 1km), and prohibit the presence of buildings, houses and personnel within the airdrop landing area; formulate airdrop wind speed limits before test flights to ensure that the wind speed is ≤6m / s. d) Prepare test items for airdrop test flights: Prepare testing instruments such as theodolites and crosswind radars to measure the layer wind at the airdrop site, and support the airdrop software in correcting the airdrop composite wind. e) Preparation of test items for airdrop test flights: Prepare airdrop cargo boxes, cargo platforms, parachute components and scales. The weight of the cargo must be weighed before loading the cargo onto the aircraft. f) Conduct hazard identification for each test flight subject during the flight implementation phase and formulate risk control measures.

[0011] The post-flight results consolidation phase includes the following steps: g) Based on the flight test data during the test implementation phase, iterate and solidify the airdrop software and flight control software; h) Complete the solidification of test flight methods and hazard sources to form a standardized airdrop test flight method.

[0012] As a further technical solution of the present invention: In step S2, the test flight to verify the air-to-air opening and closing function of the hatch needs to complete the opening and closing operations of the hatch at at least three different speed points (e.g., 170km / h, 200km / h, 240km / h) within the speed envelope of the UAV, so as to verify the working reliability of the hatch under different dynamic pressure conditions.

[0013] In step S3, the simulated airdrop test flight is used to verify the normality of the airdrop logic, including: the normality of the aircraft's control during the entry into the airdrop segment, within the airdrop segment, and after the airdrop; the flight altitude and speed control meeting expectations; the cabin door being able to open and close autonomously; the limit lock being able to unlock automatically according to preset logic; and the simulated airdrop being completed safely.

[0014] As a further technical solution of the present invention: the single-drop airdrop function verification test flight in step S4 adopts a test point matrix design, which includes multiple combinations of the following factors: cargo weight, cargo loading position, airdrop altitude, airdrop speed, and parachute opening method; The cargo weight includes at least two levels: light weight (e.g., 200-400 kg) and heavy weight (e.g., 500-800 kg); the cargo loading position includes at least the front, middle, and rear positions (in the direction of flight); the airdrop altitude includes at least the normal altitude (300-400 m) and the low altitude (200-300 m, 150-200 m); the airdrop speed includes at least the low speed (e.g., 150 km / h), medium speed (e.g., 200 km / h), and high speed (e.g., 240 km / h); and the parachute deployment method includes at least the first-stage deployment and the second-stage deployment.

[0015] Before conducting test flights for airdropping cargo from the front and rear cargo positions, it is necessary to assess the impact of changes in the front and rear center of gravity on takeoff and landing characteristics to prevent the center of gravity from exceeding limits and causing aircraft control problems. If necessary, additional test flights of takeoff and landing performance under the front and rear center of gravity of the aircraft should be conducted.

[0016] As a further technical solution of the present invention: the interval airdrop function verification test flight in step S5 and the continuous airdrop function verification test flight in step S6 both adopt a multi-item cargo (such as 3 heavy-weight cargoes) loading configuration and are verified according to the test point matrix design. The term "interval airdrop" refers to the sequential delivery of multiple goods with adjustable intervals, while "continuous delivery" refers to the continuous delivery of multiple goods without any intervals. Before conducting interval or consecutive airdrop verification, it is necessary to conduct assessments of the interrupted takeoff distance, takeoff distance, and landing distance under the corresponding total weight before the aircraft can be launched. If necessary, takeoff and landing performance tests under the appropriate weight should be conducted.

[0017] As a further technical solution of the present invention: the airdrop accuracy parameter adjustment test flight in step S7 is based on the requirements of cargo airdrop landing point index (the landing accuracy of cargo in interval airdrop is ≤100 meters, and the dispersion distance of consecutive airdrop is ≤500 meters) for two airdrop modes, and the airdrop algorithm parameters are adjusted. The specific number of test flights is determined according to the algorithm parameter adjustment requirements.

[0018] The airdrop accuracy verification test flight in step S8 involves conducting accuracy verification test flights under two modes: interval airdrop and continuous airdrop, after completing step S7 and freezing the software configuration. At least 4 to 6 tests need to be completed under each airdrop mode, and the test flight results are expressed as the average value or circular probability error (CEP) value.

[0019] Secondly, the present invention provides an airdrop test flight system for performing the rear-door airdrop test flight method for any of the above-described large fixed-wing UAVs, characterized in that it comprises: The data acquisition module is used to collect aircraft status parameters, airdrop system status parameters, environmental parameters, and cargo landing point parameters during the test flight. The test point matrix generation module is used to automatically generate a test point matrix containing different combinations of cargo weight, loading position, airdrop altitude, airdrop speed, and parachute deployment method based on the input aircraft configuration parameters and mission requirements. The test flight process control module is used to control the execution of each test flight subject in the order of steps S1 to S8 above, and to determine whether the conditions for entering the next subject are met based on the data fed back by the data acquisition module after each subject is completed. The accuracy tuning and verification module is used to adjust the parameters of the airdrop algorithm based on the accuracy requirements of the airdrop landing point, and to perform accuracy verification test flights after the software configuration is frozen, and output the accuracy assessment results. The risk warning module is used to issue risk warnings during flight tests based on pre-set hazard identification rules and real-time collected data.

[0020] As a further technical solution of the present invention: the data acquisition module includes: a crosswind radar and a theodolite for measuring the layer wind at the airdrop site, a flight control data interface for acquiring aircraft attitude and position information, and an airborne camera device for recording the cargo unloading process.

[0021] As a further technical solution of the present invention: the test point matrix generation module supports the generation of three test matrices: single drop mode, interval air drop mode, and continuous drop mode, and allows users to configure the number of repetitions for each test point; the test point matrix generation module also has a built-in center of gravity envelope verification unit, which is used to automatically verify whether the aircraft's center of gravity is within the safety envelope when generating test points containing different cargo loading positions, and to issue an alarm if it exceeds the safety envelope.

[0022] As a further technical solution of the present invention: in the accuracy adjustment and verification module, the landing accuracy requirement for interval airdrop is ≤100 meters, and the dispersion distance requirement for consecutive airdrop is ≤500 meters; the accuracy verification test flight needs to be executed after the software configuration is frozen, and the number of verification flights for each airdrop mode is not less than 4, and the accuracy evaluation results are output in the form of average value or circular probability error (CEP).

[0023] As a further technical solution of the present invention: the pre-stored hazards in the risk warning module include: cargo jamming, accidental unlocking of the limit lock, loss of aircraft control, collision between cargo and aircraft body after cargo leaves the cabin, and collision between aircraft and obstacles; the risk warning module issues a warning when it detects any of the following situations: wind speed in the airdrop area exceeds 6m / s, aircraft attitude exceeds the preset safety threshold, inconsistent door opening / closing command and status feedback, and abnormal cargo exit sequence.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention establishes a systematic flight test method specifically for the rear-opening airdrop system of large fixed-wing UAVs, filling the gap in the standardized flight test process in this field, and can be used as a reference for the entire industry.

[0025] 2. This invention adopts a layered and progressive design of "ground taxiing verification → cabin door in-flight function verification → simulated airdrop → single drop → interval drop → continuous drop → accuracy parameter adjustment → accuracy verification" to verify the performance of the airdrop system step by step, ensuring the orderliness and reliability of the flight test process and significantly reducing the flight test risk.

[0026] 3. This invention designs a detailed test point matrix that covers multiple combinations of factors such as different cargo weights, loading positions, airdrop altitudes, airdrop speeds, and parachute deployment methods. This allows for comprehensive verification of the airdrop system's performance under various operating conditions, improving the coverage and efficiency of flight tests.

[0027] 4. This invention, through a phased design of precision tuning and precision verification, independently verifies precision after the software configuration is frozen, thus ensuring the reliability of the final airdrop precision.

[0028] 5. The airdrop flight test system provided by this invention can automatically generate test matrices, control flight test processes, and provide real-time risk warnings, which greatly improves the automation and intelligence level of flight test operations and reduces human error.

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0030] Figure 1 This diagram illustrates the steps involved in determining the test flight method for the large fixed-wing UAV with a rear-opening door according to the present invention. It shows the logical relationship between the three major stages—preparation before the test, test implementation, and post-flight result consolidation—and their internal steps.

[0031] Figure 2 This is a schematic diagram illustrating the hierarchical flight test design logic of the flight test implementation phase of this invention; it shows the progressive relationship of four levels: ground taxiing, airdrop function flight test, airdrop accuracy parameter adjustment flight test, and airdrop accuracy verification special flight test. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some embodiments of this invention, but not all embodiments.

[0033] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0034] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0035] The following is in conjunction with the appendix Figure 1-2 The embodiments of the present invention will be described in detail below.

[0036] Example 1: Complete Implementation Process of Flight Test Method This embodiment provides a method for test-dropping a large fixed-wing UAV with a rear-opening cargo bay, applied to a certain type of twin-engine large fixed-wing cargo UAV (maximum takeoff weight 5 tons, rear-opening cargo bay, capable of carrying 3 standard cargo boxes). The method follows... Figure 1 Perform the steps shown.

[0037] I. Pre-experiment preparation stage Laboratory and bench tests: On the airdrop system bench, simulate different aircraft pitch attitudes (-5° to +10°) and different cargo weights (200kg, 500kg, 800kg), and conduct no less than 50 tests on the limit lock unlocking function to ensure 100% unlocking reliability. At the same time, verify the control logic of the airdrop software on the flight control simulation bench, including the condition judgment for entering the airdrop segment, the door opening / closing sequence, and the limit lock automatic unlocking trigger logic.

[0038] Ground power-on test: After the aircraft is fully assembled, a ground power-on test is conducted on the rear door mechanism. The smoothness of the door opening and closing motion is tested under different voltages (26V~30V), the locking / unlocking function of the limit lock is checked, and the normal operation logic of the airdrop system is verified under the data link communication state.

[0039] Site and Environment Confirmation: A general aviation airport was selected as the test flight site. The airport has good surrounding airspace with an open airspace radius of more than 2km. A circular airdrop landing zone with a radius of 1km was demarcated, with no buildings or personnel within the area. Weather conditions on the day of the test flight: Ground wind speed ≤4m / s, meeting the requirement of ≤6m / s.

[0040] Preparation of test items: Two theodolites (for intersection measurement of the landing point) and one crosswind radar (for measuring the layer wind profile at heights of 0-300m) are set up around the airdrop landing area for the purpose of correcting the synthetic wind in the airdrop software.

[0041] Test sample preparation: Prepare 3 standard airdrop cargo boxes (each including cargo platform and umbrella), load the counterweights to the target weight (300kg for small weight and 600kg for large weight), weigh them using a calibrated electronic scale with an error ≤0.5%.

[0042] Hazard identification and control measures: Identified hazards include: cargo jamming, accidental unlocking of limit locks, loss of aircraft control, collision between cargo and the aircraft after cargo exits the cargo hold, and collision between the aircraft and obstacles. Control measures: Select an open area to avoid obstacles; conduct sufficient bench tests; conduct test flights according to a step-by-step logic; ensure that all subsystems of the airdrop system are functioning normally; maintain the aircraft in a level flight attitude (pitch angle ≤ 5°) during airdrop.

[0043] II. Trial Implementation Phase Step S1: Cargo Ground Taxiing Test. Load and secure three cargo items (total weight approximately 1800 kg) in the cargo hold. The aircraft taxis at low speed (20 km / h) and medium speed (40 km / h) on the runway to check that the cargo is securely fastened and that there are no abnormal noises when the rear cargo door is closed. Then, open the rear cargo door on the tarmac and taxi slowly (10 km / h) to verify that there is no interference when the door is open.

[0044] Step S2: Verification of the cabin door's in-flight opening and closing function. After takeoff, at a safe altitude (≥500m), the cabin door was opened → held for 5 seconds → closed at speeds of 170km / h, 200km / h, and 240km / h (all within the speed limit envelope). Each speed point was repeated twice, and the cabin door movement time, limit lock status, and aircraft attitude changes were recorded. The test results showed that the cabin door moved smoothly under all operating conditions, with no abnormal vibration, and the limit lock feedback was normal.

[0045] Step S3: Simulated Airdrop Test Flight. The aircraft is loaded with a simulated load (of equal weight and center of gravity to a real cargo container) and enters the airdrop route. At an altitude of 300m and a speed of 200km / h, the simulated airdrop procedure is executed: open the hatch → unlock the limit lock → simulated load is not actually dropped → close the hatch. Verify that the aircraft's control is normal in the three phases: entering the airdrop phase (stable altitude and speed), the airdrop phase (hat opening and unlocking), and post-airdrop (hat closing and resumption of cruise), with altitude deviation ≤10m and speed deviation ≤5km / h, meeting expectations.

[0046] Step S4: Single-item airdrop function verification test flight. Perform a single-item airdrop according to the test point matrix in Table 1 (partial example). Typical test points are selected below: Serial Number | Airdrop Altitude (m) | Airdrop Speed ​​(km / h) | Cargo Weight (kg) | Cargo Location | Parachute Deployment Method 1350150300 Medium cargo space, level two, open umbrella 2350200300 Medium cargo space, level two, open umbrella 3350240600 Medium cargo space, level 2 opening umbrella 4250200600 rear cargo space secondary opening umbrella 5250200600 Front cargo position, level one umbrella opening Each test point was run twice. Key monitoring parameters included: aircraft pitch / roll changes (Δpitch ≤ 3°, Δroll ≤ 2°) at the moment of cargo ejection, parachute deployment timing, and landing point distribution. Results showed that cargo ejection was smooth under all conditions, without interference with the rear-opening door structure, and aircraft attitude changes remained within safe limits.

[0047] Step S5: Interval airdrop function verification test flight. Load 3 heavy cargo items (600kg each), totaling 1800kg. Before takeoff, assess the takeoff distance (approximately 800m) and landing distance (approximately 700m) to ensure they meet the airport runway length (2400m) requirements. According to the test point matrix in Table 2, at an altitude of 300m and a speed of 200km / h, sequentially drop cargo into the front, middle, and rear cargo positions with a 5-second interval. Verify that the airdrop system can unlock the limit locks of each cargo position sequentially, and that the aircraft's center of gravity changes within a controllable range.

[0048] Step S6: Verification test flight of the continuous airdrop function. With three heavy cargo items loaded, at an altitude of 200m and a speed of 200km / h, a continuous, uninterrupted airdrop was performed (i.e., all limit locks were unlocked, and the cargo slid out sequentially). The test verified that during the continuous airdrop mode, the aircraft's attitude changed (maximum pitch change ≤ 5°), and no collisions occurred during cargo exit.

[0049] Step S7: Airdrop Accuracy Parameter Adjustment Test Flight. Based on preliminary data from interval airdrops and consecutive airdrops, it was found that the landing point dispersion for interval airdrops was approximately 120 meters (target ≤ 100 meters), and the dispersion for consecutive airdrops was approximately 550 meters (target ≤ 500 meters). By adjusting the wind correction algorithm and parachute deployment timing parameters in the airdrop software, five parameter adjustment test flights were conducted to gradually optimize the process. Ultimately, the average landing point deviation for interval airdrops was reduced to 85 meters, and the dispersion for consecutive airdrops was reduced to 420 meters.

[0050] Step S8: Airdrop Accuracy Verification Test Flight. After the software configuration was frozen, accuracy verification was performed on four sorties in interval airdrop mode and four sorties in consecutive airdrop mode. The results are as follows: the landing point deviations for the four interval airdrops were 78m, 92m, 83m, and 88m, with an average of 85.25m and a CEP of 82m; the dispersion for consecutive airdrops were 410m, 435m, 445m, and 420m, with an average of 427.5m. All results meet the performance requirements.

[0051] III. Post-flight results consolidation stage Based on the test data, the final optimized airdrop software parameters (wind correction coefficient, parachute opening delay time, etc.) will be solidified into the flight control software version.

[0052] The "Standard Procedure for Test Flight of Large Fixed-Wing UAVs with Rear-Opening Door" was compiled, which solidifies the test flight process, test point matrix, and risk control measures of this embodiment into an enterprise standard for subsequent test flights of the same model of aircraft.

[0053] Example 2: Application of the airdrop test flight system This embodiment provides an airdrop flight test system for performing the above-described flight test method. The system uses a ground control station as a carrier and includes hardware (data link ground terminal, computing server, display terminal) and software modules.

[0054] During a test flight mission, the operator first input the aircraft parameters (maximum takeoff weight 5 tons, center of gravity range 28%–35% MAC), cargo parameters (3 pieces, each weighing 200–800 kg), and mission requirements (interval drop accuracy ≤100m, continuous drop dispersion ≤500m) into the test point matrix generation module. The system automatically generates a single drop matrix containing 15 test points, an interval drop matrix containing 12 test points, and a continuous drop matrix containing 8 test points, and marks the test points that may cause the center of gravity to exceed the limit (such as when only the front cargo position is loaded with a large weight), issuing an alarm prompting that additional counterweights should be added or the loading sequence adjusted.

[0055] The flight test process control module guides the test pilot and commander step-by-step through S1 to S8. After each maneuver is completed, the data acquisition module automatically analyzes aircraft status data (such as door opening time, limit lock feedback, and attitude changes upon exiting the aircraft) to determine if the safety threshold for proceeding to the next maneuver is met. For example, in a simulated airdrop test flight, if the limit lock does not respond with "unlocked" within 2 seconds after the unlock command is issued, the system will pause the process and prompt for a check.

[0056] The accuracy adjustment and verification module calculates the landing point deviation for each flight in real time during the parameter adjustment phase and provides suggested parameter adjustment directions (such as "increase the wind correction factor by 0.05"). During the verification phase, an accuracy report is automatically generated, including the average value, standard deviation, and CEP value.

[0057] The risk warning module continuously monitored the entire flight test process. During one interval airdrop test flight, when the crosswind radar measured a wind speed of 7.5 m / s at an altitude of 500m in the airdrop area (exceeding the set threshold of 6 m / s), the system immediately issued a voice warning: "Wind speed in the airdrop area exceeds the limit, it is recommended to postpone the airdrop." The flight test commander then terminated the sortie and waited for the wind speed to decrease before proceeding, thus avoiding a landing point deviation due to strong winds.

[0058] Through the application of this system, the airdrop test flight cycle of this model of UAV was shortened from the original 45 days to 28 days, and the number of test flights was reduced from 42 to 31, without any safety accidents.

[0059] Example 3 Referring to the attached diagram, the steps of this application for a rear-opening door-type airdrop test flight method for a large fixed-wing UAV are as follows: Figure 1 It includes three stages: the pre-test preparation stage, the test implementation stage, and the post-flight results consolidation stage.

[0060] The aforementioned pre-experiment preparation stage is characterized by including the following steps: a) Conduct laboratory tests and bench tests of the UAV airdrop system and software control logic functions: check the unlocking function under different working conditions of expected airdrop attitude and cargo weight, and check the control logic of the airdrop system on the bench. b) Conduct ground power-on and testing of the UAV airdrop system: Focus on checking whether the motion performance of the door mechanism and the unlocking function of the limit lock are normal, and ensure that the working logic of the airdrop system is normal under the data link communication state; c) Select test flight sites and confirm environmental conditions: Select open, unobstructed test flight sites with good airspace clearance, and delineate the test flight area and airdrop area (e.g., a circular area with a radius of 1km). Buildings, houses, and personnel are prohibited within the airdrop landing area. Establish airdrop wind speed limits before the test flight to ensure wind speed ≤ 6m / s; d) Prepare test items for airdrop test flights: Prepare testing instruments such as theodolites and crosswind radars to measure the layer wind at the airdrop site, and support the airdrop software in correcting the airdrop composite wind. e) Preparation of test items for airdrop test flights: Prepare airdrop cargo boxes, cargo platforms, parachutes, and scales (Note: The weight of the cargo must be weighed before loading the cargo onto the aircraft). f) Conduct hazard identification for each test flight subject during the flight implementation phase and formulate risk control measures.

[0061] The aforementioned test implementation phase is characterized by including the following steps: a) Conduct airdrop cargo ground taxiing tests: verify the reliability of airdrop cargo fixing and verify the aircraft's ground taxiing characteristics with the hatch open and closed; b) Conduct test flights to verify the in-flight opening and closing function of the cabin doors: verify whether the in-flight opening function of the cabin doors is normal. In order to ensure the reliability of the in-flight cabin door opening, the opening and closing of the cabin doors need to be completed at different flight speeds (within the speed limit envelope, such as 150 to 240 km / h). c) Conduct simulated airdrop test flights: verify whether the airdrop logic is normal, whether the aircraft control is normal during the airdrop phase, airdrop phase and post-airdrop phase, whether the flight altitude and speed control are as expected, whether the cabin door can open and close autonomously, whether the limit lock can be automatically unlocked according to the preset unlocking function, and whether the simulated airdrop can be completed safely. d) Conduct single-item airdrop capability verification test flights: Verify the single-item airdrop capability for cargo of different weights (e.g., small, medium, large), loading positions (e.g., front, middle, rear), airdrop altitudes (e.g., normal, low altitude), airdrop speeds (e.g., small, medium, large), and different parachute types (e.g., level 1 and level 2 parachutes). Examples are shown in Table 1 below. Before verifying the airdrop test flights at the front and rear cargo positions, the takeoff and landing characteristics of the front and rear center of gravity must be assessed to prevent exceeding limits.

[0062] e) Conduct interval airdrop capability verification test flights: Verify the interval airdrop capability under different airdrop altitudes (e.g., normal, low altitude), airdrop speeds (e.g., small, medium, large), and different parachute deployment methods (e.g., first-stage and second-stage deployment) when carrying 3 cargoes, as shown in Table 2 below. Before conducting interval airdrops of 3 cargoes, it is necessary to conduct assessments of the interrupted takeoff distance, takeoff distance, and landing distance under the relevant weights before the aircraft can be launched. f) Conduct test flights to verify the continuous airdrop function: Verify the continuous airdrop function with 3 cargoes loaded at different airdrop altitudes (e.g., normal, low altitude), airdrop speeds (e.g., small, medium, large), and different parachute types (e.g., level 1 and level 2 parachutes). Examples are shown in Table 3 below. g) Conduct test flights to adjust airdrop accuracy parameters: For the two airdrop modes of interval airdrop and consecutive airdrop, based on the requirements of cargo airdrop landing point indicators (e.g., cargo landing accuracy of interval airdrop ≤ 100 meters, dispersion distance of consecutive airdrop ≤ 500 meters), conduct airdrop algorithm parameter adjustment. The specific number of flights for this test flight subject shall be given according to the airdrop algorithm parameter adjustment requirements. h) Conduct special test flights to verify airdrop accuracy: After completing the software configuration freeze in section g), conduct accuracy verification test flights under two airdrop modes: interval airdrop and continuous airdrop. At least 4 to 6 tests should be completed under each airdrop mode. The test flight results can be expressed as average value or CEP value.

[0063] The post-flight results consolidation stage is characterized by including the following steps: a) Based on the test flight data of interval airdrops and consecutive airdrops during the flight implementation phase, iterate and solidify the airdrop software and flight control software; b) Complete the solidification of the test flight method and hazard sources, and form a large fixed-wing UAV rear-door airdrop test flight method.

[0064] The aforementioned hazards and risk control measures are characterized by the following: For airdrop test flights, the most specific hazards are cargo jamming, accidental unlocking of limit locks, loss of aircraft control, cargo collision with the aircraft body after exiting the cargo hold, and collision between the aircraft and obstacles. Regarding risk control measures, firstly, an open area should be selected according to the airdrop mission profile to avoid collisions with obstacles during the airdrop entry, execution, and recovery phases; secondly, sufficient bench tests should be conducted, and test flights should be carried out according to a progressive logic to ensure the aircraft remains controllable under different weight and center of gravity conditions; finally, the normal functioning of each subsystem of the airdrop system should be ensured, enabling unlocking according to preset logic to prevent cargo jamming and accidental unlocking; and during the airdrop, the correct airdrop attitude should be ensured to prevent the possibility of cargo colliding with the aircraft body after exiting the cargo hold.

[0065] See the schematic diagram of the hierarchical flight test subject design logic during the flight test implementation phase. Figure 2 The airdrop test flights were conducted using a tiered design: ground taxiing verification, airdrop function test flights, airdrop accuracy parameter tuning test flights, and airdrop accuracy verification-specific test flights. The first tier was ground taxiing verification, with test flights involving ground taxiing (cargo-loaded). The second tier was airdrop function test flights, including verification of the cabin door's in-flight opening and closing function, simulated airdrop test flights, single-drop airdrop function verification test flights, interval airdrop function verification test flights, and continuous airdrop function verification test flights. The third tier was airdrop accuracy parameter tuning test flights, with test flights involving airdrop accuracy parameter tuning test flights. The fourth tier was dedicated airdrop accuracy verification test flights, with test flights involving dedicated airdrop accuracy verification-specific test flights.

[0066] Example 4 This invention discloses a method for test flight of a large fixed-wing UAV with a rear-opening door, which includes a pre-test preparation stage, a test implementation stage, and a post-flight results consolidation stage.

[0067] The aforementioned pre-experiment preparation phase includes the following steps: a) Conduct laboratory tests and bench tests of the UAV airdrop system and software control logic functions: check the unlocking function under different working conditions of expected airdrop attitude and cargo weight, and check the control logic of the airdrop system on the bench. b) Conduct ground power-on and testing of the UAV airdrop system: Focus on checking whether the motion performance of the door mechanism and the unlocking function of the limit lock are normal, and ensure that the working logic of the airdrop system is normal under the data link communication state; c) Select test flight sites and confirm environmental conditions: Select open, unobstructed test flight sites with good airspace clearance, and delineate the test flight area and airdrop area (e.g., a circular area with a radius of 1km). Buildings, houses, and personnel are prohibited within the airdrop landing area. Establish airdrop wind speed limits before the test flight to ensure wind speed ≤ 6m / s; d) Prepare test items for airdrop test flights: Prepare testing instruments such as theodolites and crosswind radars to measure the layer wind at the airdrop site, and support the airdrop software in correcting the airdrop composite wind. e) Preparation of test items for airdrop test flights: Prepare airdrop cargo boxes, cargo platforms, parachutes, and scales (Note: The weight of the cargo must be weighed before loading the cargo onto the aircraft). f) Conduct hazard identification for each test flight subject during the flight implementation phase and formulate risk control measures.

[0068] The aforementioned trial implementation phase includes the following steps: a) Conduct airdrop cargo ground taxiing tests: verify the reliability of airdrop cargo fixing and verify the aircraft's ground taxiing characteristics with the hatch open and closed; b) Conduct test flights to verify the in-flight opening and closing function of the cabin doors: verify whether the in-flight opening function of the cabin doors is normal. In order to ensure the reliability of the in-flight cabin door opening, the opening and closing of the cabin doors need to be completed at different flight speeds (within the speed limit envelope, such as 150 to 240 km / h). c) Conduct simulated airdrop test flights: verify whether the airdrop logic is normal, whether the aircraft control is normal during the airdrop phase, airdrop phase and post-airdrop phase, whether the flight altitude and speed control are as expected, whether the cabin door can open and close autonomously, whether the limit lock can be automatically unlocked according to the preset unlocking function, and whether the simulated airdrop can be completed safely. d) Conduct single-item airdrop capability verification test flights: Verify the single-item airdrop capability of cargo with different weights (e.g., small, medium, large), loading positions (e.g., front, middle, rear), airdrop altitudes (e.g., normal, low altitude), airdrop speeds (e.g., small, medium, large), and different parachute deployment methods (e.g., first-stage and second-stage deployment). Examples are shown in Table 1 below. It is crucial to assess the impact of the front and rear center of gravity on takeoff and landing characteristics before verifying airdrop test flights at the front and rear cargo positions. This is to prevent exceeding limits and causing aircraft control problems. If necessary, additional takeoff and landing performance test flights with the front and rear center of gravity of the aircraft should be conducted. Table 1. Example of the state point matrix for single-drop airdrop function verification flight test.

[0069] e) Conduct interval airdrop capability verification test flights: Verify the interval airdrop capability under different airdrop altitudes (e.g., normal, low altitude), airdrop speeds (e.g., small, medium, large), and different parachute deployment methods (e.g., first-stage and second-stage deployment) when carrying 3 cargoes, as shown in Table 2 below. Before conducting interval airdrops of 3 cargoes, it is necessary to conduct assessments of the interrupted takeoff distance, takeoff distance, and landing distance under relevant weights before the aircraft can be launched. If necessary, takeoff and landing performance tests under appropriate weights should be conducted. Table 2 Example of the state point matrix for interval airdrop function verification flight test

[0070] f) Conduct test flights to verify the continuous airdrop function: Verify the continuous airdrop function with 3 cargoes loaded at different airdrop altitudes (e.g., normal, low altitude), airdrop speeds (e.g., small, medium, large), and different parachute opening methods (e.g., first-stage and second-stage parachute opening), as shown in Table 3 below; Table 3 Example of the state point matrix for continuous launch function verification flight test

[0071] g) Conduct test flights to adjust airdrop accuracy parameters: For the two airdrop modes of interval airdrop and consecutive airdrop, based on the requirements of cargo airdrop landing point indicators (e.g., cargo landing accuracy of interval airdrop ≤ 100 meters, dispersion distance of consecutive airdrop ≤ 500 meters), conduct airdrop algorithm parameter adjustment. The specific number of flights for this test flight subject shall be given according to the airdrop algorithm parameter adjustment requirements. h) Conduct dedicated test flights to verify airdrop accuracy: After completing the software configuration freeze in section g), conduct accuracy verification test flights under two airdrop modes: interval airdrop and continuous airdrop. At least 4 to 6 tests should be completed under each airdrop mode. The test flight results can be expressed as average values ​​or CEP values. The post-flight results consolidation stage includes the following steps: a) Based on the test flight data of interval airdrops and consecutive airdrops during the flight implementation phase, iterate and solidify the airdrop software and flight control software; b) Complete the solidification of the test flight method and hazard sources, and form a large fixed-wing UAV rear-door airdrop test flight method.

[0072] The aforementioned hazards and risk control measures specifically address the following hazards in airdrop test flights: cargo jamming, accidental unlocking of limit locks, loss of aircraft control, collision between cargo and the aircraft body after cargo exits the cargo hold, and collision between the aircraft and obstacles. Regarding risk control measures, firstly, an open area should be selected according to the airdrop mission profile to avoid collisions with obstacles during the airdrop entry, execution, and recovery phases. Secondly, sufficient bench testing should be conducted, and test flights should be carried out according to a progressive logic to ensure the aircraft remains controllable under different weight and center of gravity conditions. Finally, it should be ensured that all subsystems of the airdrop system function normally and can unlock according to preset logic to prevent cargo jamming and accidental unlocking. During the airdrop, the correct airdrop attitude should be ensured to prevent the possibility of cargo colliding with the aircraft body after exiting the cargo hold. The beneficial effects of this application are as follows: 1) This invention establishes a test flight method for a large fixed-wing UAV with a rear-opening door, which can be used as a reference for the entire industry; 2) The test flight process is highly systematic, adopting a layered design of "ground taxiing verification - airdrop function test flight - airdrop accuracy parameter adjustment test flight - airdrop accuracy verification special test flight". Combining the opening and closing characteristics of the rear-opening door structure, the interference risk between the airdropped object and the rear-opening door, and the load and buffer requirements of the rear-opening door, the performance of the airdrop system is verified step by step, ensuring the orderliness and reliability of the test flight process; the layered test flight from empty to fully loaded can gradually verify the performance of the airdrop system under different loads, reducing the test flight risk; 3) High safety, improving the risk analysis and control measures in the early preparation of the test flight and during the test flight process, which can quickly respond to sudden failures during the test flight process and avoid the occurrence of safety accidents.

[0073] Thus, the objective of this invention has been achieved.

[0074] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. 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 method for test-dropping a large fixed-wing unmanned aerial vehicle (UAV) with a rear-opening door, characterized in that, This includes the pre-test preparation phase, the test implementation phase, and the post-flight results consolidation phase. The test implementation phase shall be carried out in the following order: Step S1: Conduct a ground taxiing test of the airdropped cargo; Step S2: Conduct a test flight to verify the in-flight opening and closing function of the cabin door; Step S3: Conduct simulated airdrop test flights; Step S4: Conduct test flights to verify the single-drop airdrop function; Step S5: Conduct test flights to verify the interval airdrop function; Step S6: Conduct test flights to verify the continuous airdrop function; Step S7: Conduct test flights to fine-tune airdrop parameters; Step S8: Conduct a special test flight to verify the accuracy of airdrops; Steps S1 to S8 are implemented in a progressive, layered manner, from ground to air, from empty to full load, from single item to multiple items, and from functional verification to accuracy verification.

2. The method according to claim 1, characterized in that, The pre-experiment preparation phase includes the following steps: a) Conduct laboratory tests and bench tests of the unmanned aerial vehicle (UAV) airdrop system and its software control logic function. b) Conduct ground power-on and testing of the UAV airdrop system; c) Conduct test flight site selection and environmental condition confirmation; d) Prepare for the airdrop of test flight supplies; e) Prepare for the airdrop of test samples; f) Conduct hazard identification for each test flight subject during the flight implementation phase and formulate risk control measures; The post-flight results consolidation phase includes the following steps: g) Based on the flight test data during the test implementation phase, iterate and solidify the airdrop software and flight control software; h) Complete the solidification of flight test methods and hazard sources.

3. The method according to claim 1, characterized in that, In step S2, the test flight to verify the in-flight opening and closing function of the hatch needs to complete the opening and closing operations of the hatch at at least three different speed points within the speed envelope of the UAV. In step S3, the simulated airdrop test flight is used to verify the normality of the airdrop logic, including: the normality of the aircraft's control during the airdrop phase, within the airdrop phase, and after the airdrop phase; the flight altitude and speed control meeting expectations; the cabin door being able to open and close autonomously; and the limit lock being able to unlock automatically according to preset logic.

4. The method according to claim 1, characterized in that, The single-drop airdrop function verification test flight in step S4 adopts a test point matrix design, which includes multiple combinations of the following factors: cargo weight, cargo loading position, airdrop altitude, airdrop speed, and parachute deployment method. The cargo weight includes at least two levels: light weight and heavy weight; the cargo loading position includes at least front loading position, middle loading position and rear loading position; the airdrop altitude includes at least normal altitude and low altitude; the airdrop speed includes at least low speed, medium speed and high speed; and the parachute opening method includes at least first-stage opening and second-stage opening.

5. The method according to claim 1, characterized in that, The interval airdrop function verification test flight in step S5 and the continuous airdrop function verification test flight in step S6 both adopt a multi-cargo loading configuration and are verified according to the test point matrix design. The term "interval airdrop" refers to the sequential delivery of multiple goods with adjustable intervals, while "continuous delivery" refers to the continuous delivery of multiple goods without any intervals. Before conducting interval or consecutive airdrop verification, it is necessary to conduct assessments of the interrupted takeoff distance, takeoff distance, and landing distance under the corresponding total weight.

6. An airdrop test flight system for performing the rear-door airdrop test flight method for a large fixed-wing unmanned aerial vehicle as described in any one of claims 1 to 5, characterized in that, include: The data acquisition module is used to collect aircraft status parameters, airdrop system status parameters, environmental parameters, and cargo landing point parameters during the test flight. The test point matrix generation module is used to automatically generate a test point matrix containing different combinations of cargo weight, loading position, airdrop altitude, airdrop speed, and parachute deployment method based on the input aircraft configuration parameters and mission requirements. The test flight process control module is used to control the execution of each test flight subject in the order of steps S1 to S8 as described in claim 1, and to determine whether the conditions for entering the next subject are met based on the data fed back by the data acquisition module after each subject is completed. The accuracy tuning and verification module is used to adjust the parameters of the airdrop algorithm based on the accuracy requirements of the airdrop landing point, and to perform accuracy verification test flights after the software configuration is frozen, and output the accuracy assessment results. The risk warning module is used to issue risk warnings during flight tests based on pre-set hazard identification rules and real-time collected data.

7. The system according to claim 6, characterized in that, The data acquisition module includes: a crosswind radar and a theodolite for measuring the layer wind at the airdrop site, a flight control data interface for acquiring aircraft attitude and position information, and an airborne camera device for recording the cargo unloading process.

8. The system according to claim 6, characterized in that, The test point matrix generation module supports the generation of three test matrices: single-drop mode, interval airdrop mode, and continuous-drop mode, and allows users to configure the number of repetitions for each test point. The test point matrix generation module also has a built-in center of gravity envelope verification unit, which is used to automatically verify whether the aircraft's center of gravity is within the safety envelope when generating test points containing different cargo loading positions. If it exceeds the safety envelope, an alarm will be issued.

9. The system according to claim 6, characterized in that, In the accuracy adjustment and verification module, the landing accuracy requirement for interval airdrops is ≤100 meters, and the dispersion distance requirement for consecutive airdrops is ≤500 meters. The precision verification test flights must be conducted after the software configuration is frozen, with no fewer than four verification flights for each airdrop mode, and the precision assessment results output in the form of average value or circular error.

10. The system according to claim 6, characterized in that, The risk warning module contains the following pre-stored hazards: cargo jamming, accidental unlocking of limit locks, loss of aircraft control, collision between cargo and aircraft body after cargo leaves the cabin, and collision between aircraft and obstacles. The risk warning module issues a warning when it detects any of the following situations: wind speed in the airdrop area exceeds 6 m / s, aircraft attitude exceeds the preset safety threshold, door opening / closing command and status feedback are inconsistent, or cargo exit sequence is abnormal.

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