Adaptive return-to-home positioning system for tethered drones for aerial work

Abstract

The present invention discloses an adaptive return positioning system for a tethered UAV for high-altitude operations, which relates to the technical field of UAVs, including a data acquisition unit, a control analysis unit, and a return execution unit; in terms of safety, the present invention uses hierarchical control analysis to ensure accurate return, rationally plans the trajectory at the high-level stage, and stably adjusts the state at the low-level stage to reduce the risk of collision and falling. In terms of adaptability, the layered landing strategy can cope with different altitudes, the high-level focuses on preliminary adjustments, and the low-level flexibly controls speed and direction to adapt to a variety of initial altitudes; real-time update of instructions can cope with environmental changes, such as airflow interference. In terms of operational efficiency, layered planning improves efficiency, reduces unnecessary adjustments, and shortens return time; automatic generation of control instructions simplifies the operating process, reduces the burden on operators and reduces the risk of human errors, improves operational efficiency while ensuring that the UAV completes the return mission safely and stably.

Description

Technical Field

[0001] The invention relates to the technical field of unmanned aerial vehicles, in particular to an adaptive return home positioning system for a tethered unmanned aerial vehicle for high-altitude operations. Background Art

[0002] Drones are widely used in high-altitude operations such as power inspection, communication base station maintenance, and building inspection, but there are challenges in returning to the home position. The high-altitude environment is complex, and factors such as wind direction, unstable airflow, and signal interference affect the safe return of drones.

[0003] Traditional return-to-home positioning systems have limitations and mostly use a single control strategy. Navigation is based only on the general direction, lacking comprehensive consideration of multiple factors such as altitude, speed, and flight attitude. In complex high-altitude environments, this single strategy can easily cause the drone to deviate from its route, land unsteadily, or collide, and cannot adapt to the special environmental requirements of different altitudes. At higher altitudes, when the wind speed is high, more precise direction and attitude adjustments are required; in low-altitude areas close to the landing platform, fine speed and altitude control are required. In actual high-altitude operations, environmental factors at different altitudes have a large impact on the return of the drone. Therefore, an adaptive return-to-home positioning system is needed that can adjust the return strategy according to the altitude and flight parameters of the drone. Different control instructions are used at different altitudes to ensure safe and stable return to the landing platform in complex environments. At the high-level stage, the flight direction and attitude must be adjusted quickly and accurately to cope with complex airflows; at the low-level stage, precise altitude and speed control is emphasized to achieve a smooth landing. At the same time, the system needs to obtain key data such as the drone's position, speed, and landing platform position in real time, and quickly and accurately analyze and calculate to generate appropriate control instructions to ensure safe and accurate return. In summary, the development of this system has important practical significance. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art; to this end, the present invention proposes an adaptive return positioning system for a tethered drone for high-altitude operations.

[0005] The adaptive return home positioning system for tethered drones for aerial work includes:

[0006] A data acquisition unit, which obtains the position coordinates and speed information of the UAV, as well as the position coordinates of the landing platform;

[0007] A control analysis unit, used to perform hierarchical control analysis based on the results obtained by the data acquisition unit, and obtain a plurality of corresponding control instructions for the UAV;

[0008] The return execution unit is used to control the UAV to perform corresponding actions according to the corresponding control instructions calculated by the hierarchical planning unit.

[0009] As a further solution of the present invention: the hierarchical control analysis method is as follows:

[0010] Step 1. Obtain coordinates

[0011] Get the position coordinates of the drone in real time and mark them as (X w , Y w , Z w );

[0012] At the same time, obtain the location coordinates of the landing platform and mark it as (X t , Y t , Z t );

[0013] Step 2: Obtaining strategies

[0014] Get pre-set layered landing strategies;

[0015] The layered landing strategy includes the high-level stage and the low-level stage divided according to the height layered threshold, and the stage landing strategies corresponding to the high-level stage and the low-level stage;

[0016] The height stratification threshold is labeled HFy;

[0017] Step 3: High-level landing operation

[0018] Z in the drone's position coordinates w When the height stratification threshold of the high-level stage is exceeded, the stage landing strategy corresponding to the high-level stage is obtained;

[0019] Then the stage landing strategy corresponding to the high-level stage is executed, and the high-level flight control instructions of the UAV are obtained;

[0020] Step 4: Low-level landing operation

[0021] After high-level flight control instructions are executed;

[0022] Z in the drone's position coordinates w When the height stratification threshold of the high-level stage is not exceeded, the stage landing strategy corresponding to the low-level stage is obtained;

[0023] Then the stage landing strategy corresponding to the low-level stage is executed, and the low-level flight control instructions of the UAV are obtained;

[0024] Step 5. Real-time update control

[0025] After the low-level flight control command is executed, the control is updated based on the position coordinates and speed information of the UAV, combined with the corresponding stage landing strategy of the low-level stage, and then the corresponding real-time update control command is obtained.

[0026] As a further solution of the present invention: in Step 4, the low flight control instruction includes a low-level flight control instruction one and a low-level flight control instruction two.

[0027] As a further solution of the present invention: in Step 3, the stage landing strategy of the high-level stage is as follows:

[0028] Step 3.1, through , calculate the direction adjustment angle θa1 of the UAV’s flight direction;

[0029] Step 3.4, through , calculate the direction adjustment angle θa1 of the UAV’s flight direction;

[0030] Step 3.4, through , calculate the pitch adjustment angle θb1 of the UAV’s flight attitude;

[0031] Step 3.5, generate high-level flight control instructions based on the flight time T1 of the UAV flying at the horizontal distance D1, the direction adjustment angle θa1 of the UAV's flight direction, and the pitch adjustment angle θb1 of the UAV's flight attitude, and mark it as K1 = [T1, θa1, θb1];

[0032] Among them, in the stage landing strategy of the high-level stage, (X w , Y w , Z w ) are the position coordinates of the UAV at the high-level stage.

[0033] As a further solution of the present invention: in Step 4, the stage landing strategy of the low-level stage is as follows:

[0034] Step 4.1. Calculate the horizontal distance between the current position of the drone and the landing platform according to the method in Step 3.1, and mark it as D2;

[0035] Among them, in the stage landing strategy of the low-level stage, the (X w , Y w , Z w ) is the position coordinate of the UAV in the bottom layer after executing the control instruction K1;

[0036] Step 4.2, then compare D2 with the preset distance threshold D2y:

[0037] When D2>D2y, the flight time of the UAV flying at the horizontal distance D2 is calculated according to the method from Step 3.2 to Step 3.3, and it is marked as T2, and the direction adjustment angle of the UAV flight direction is calculated and marked as θa2;

[0038] Step 4.2, then generate the bottom-level flight control instruction 1 according to the flight time T2 of the UAV at the horizontal distance D2 and the direction adjustment angle θa2 of the UAV's flight direction, and mark it as K2 = [T2, θa2];

[0039] Until D2<D2y;

[0040] Step 4.3, get the position coordinates of the drone after executing the underlying flight control command 1, and replace the X w Subtract the X coordinate of the landing platform position t , and get the current height difference Hc, and then compare the current height difference with the preset height threshold Hy:

[0041] When Hc ≥ Hy, the drone descends at the current flight speed V in the bottom stage;

[0042] When Hc<Hy, then through , calculate the adjustment speed V1 of the UAV in the bottom stage, and the UAV descends according to the adjustment speed V1 in the bottom stage, and generate the bottom-level flight control instruction 2 according to the adjustment speed V1 of the UAV in the bottom stage, and mark it as K20=[V1].

[0043] As a further solution of the present invention: the update control method is as follows:

[0044] Step 5.1, according to the method from Step 3.1 to Step 3.2, calculate the flight time of the UAV at the corresponding horizontal distance and mark it as T3;

[0045] Among them, in the stage landing strategy of the low-level stage, the flight time T3 of the UAV flying at the corresponding horizontal distance is calculated as the position coordinates of the UAV at the corresponding position in the bottom-level stage after executing the control instruction K1;

[0046] Step 5.2, obtain half of the flight time corresponding to T3, that is, T3 / 2;

[0047] Then, based on Step 5.1, the flight time of the UAV at the corresponding horizontal distance, the direction adjustment angle of the UAV's flight direction, and the pitch adjustment angle of the UAV's flight attitude are calculated in accordance with the method of Step 3.3 to Step 3.4;

[0048] At the same time, multiply the current speed of the drone by 0.75 to get the updated speed of the drone;

[0049] Then, a real-time update control instruction is generated according to the flight time of the UAV flying at the corresponding horizontal distance, the direction adjustment angle of the UAV's flight direction, and the pitch adjustment angle of the UAV's flight attitude, and the update speed of the UAV;

[0050] Step 5.3, after the unmanned real-time update control instructions are generated, the corresponding real-time update control instructions are generated according to the method from Step 5.1 to Step 5.2 until the UAV reaches the landing platform.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] Precise return guarantee: Through hierarchical control analysis, corresponding landing strategies are formulated at different altitudes. This precise hierarchical control can ensure that the drone gradually approaches the landing platform according to a reasonable trajectory during the return process. For example, the distance to the landing platform is calculated, and the flight direction and attitude are adjusted at the high-level stage, avoiding blind flight and improving the safety of the return process.

[0053] Stable landing control: At the low level, different low-level flight control instructions are generated through detailed horizontal distance judgment and height difference processing. This helps the drone to adjust the flight state more stably when approaching the landing platform, avoid the risk of falling due to excessive speed or improper attitude adjustment, and ensure that the drone lands safely and smoothly on the landing platform.

[0054] Flexible response to different altitudes: The layered landing strategy can adapt to the flight characteristics of the drone at different altitudes. At the high-level stage, due to the long distance from the landing platform, the main focus is on the initial adjustment of the flight direction and attitude, such as calculating the direction adjustment angle and pitch adjustment angle to ensure that the drone flies in the correct direction of the landing platform. At the low-level stage, the flight speed and direction are flexibly adjusted according to the distance and height difference from the landing platform. This control method based on altitude layering enables the system to adapt to various initial return altitudes and improves the system's adaptability to drones at different operating altitudes.

[0055] Adaptability to environmental changes: During the entire return process, the system can continuously adjust the flight status according to the real-time position coordinates and speed information of the drone by updating the control instructions in real time. For example, when encountering sudden airflow interference or other environmental changes, the system can generate appropriate control instructions based on the new situation to ensure that the drone can still return according to the predetermined trajectory, showing good environmental adaptability.

[0056] Efficient hierarchical planning: The hierarchical control analysis method improves the efficiency of return positioning. Compared with a single overall control strategy, the landing process is divided into high-level and low-level stages, and strategies are formulated separately, which can be controlled more targeted. Quickly adjust to the roughly correct flight direction and attitude in the high-level stage, and gradually control accurately in the low-level stage, reducing unnecessary adjustments and circuitous flights, thereby shortening the return time of the drone and improving operational efficiency.

[0057] Simplified operation process: Control analysis is performed and control instructions are generated according to the preset layered landing strategy, so the operator does not need to perform complex manual operations during the return process. This not only reduces the workload of the operator, but also reduces the risk caused by human error, making the return operation of the drone simpler and more efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 is a system block diagram of the present invention;

[0059] Figure 2 It is a schematic diagram of the module flow of the control and analysis unit in the present invention. DETAILED DESCRIPTION

[0060] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0061] The present invention is composed of a data acquisition unit, a control analysis unit and a return execution unit; this modular design makes the system structure clear, the functions of each unit clear, and is convenient for system development, maintenance and upgrading. The data acquisition unit is responsible for acquiring necessary flight data, the control analysis unit performs complex hierarchical control analysis, and the return execution unit executes control instructions, each performing its own duties, thereby improving the reliability and operability of the entire system.

[0062] Embodiment 1

[0063] See also Figure 1 and Figure 2 As shown, the present invention is an adaptive return home positioning system for a tethered UAV for high-altitude operations, comprising:

[0064] A data acquisition unit, which obtains the position coordinates and speed information of the UAV, as well as the position coordinates of the landing platform;

[0065] A control analysis unit, used to perform hierarchical control analysis based on the results obtained by the data acquisition unit, and obtain a plurality of corresponding control instructions for the UAV;

[0066] The hierarchical control analysis method is as follows:

[0067] Step 1. Get the position coordinates of the drone in real time and mark them as (X w , Y w , Z w );

[0068] At the same time, obtain the location coordinates of the landing platform and mark it as (X t , Y t , Z t );

[0069] Step 2, obtain the pre-set layered landing strategy;

[0070] The layered landing strategy includes the high-level stage and the low-level stage divided according to the height layered threshold, and the stage landing strategies corresponding to the high-level stage and the low-level stage;

[0071] The height stratification threshold is labeled HFy;

[0072] Step 3. Z in the drone's position coordinates w When the height stratification threshold of the high-level stage is exceeded, the stage landing strategy corresponding to the high-level stage is obtained;

[0073] Then the stage landing strategy corresponding to the high-level stage is executed, and the high-level flight control instructions of the UAV are obtained;

[0074] The stage landing strategy at the high level is as follows:

[0075] Step 3.1, through , calculate the horizontal distance D1 between the current position of the UAV and the landing platform;

[0076] Step 3.2, simultaneously obtain the current UAV flight speed V1;

[0077] Then, the flight time T1 of the drone flying at the horizontal distance D1 is calculated by dividing the horizontal distance D1 by the flight speed V;

[0078] Step 3.3, through , calculate the direction adjustment angle θa1 of the UAV’s flight direction;

[0079] Step 3.4, through , calculate the pitch adjustment angle θb1 of the UAV’s flight attitude;

[0080] Step 3.5, generate high-level flight control instructions based on the flight time T1 of the UAV flying at the horizontal distance D1, the direction adjustment angle θa1 of the UAV's flight direction, and the pitch adjustment angle θb1 of the UAV's flight attitude, and mark it as K1 = [T1, θa1, θb1];

[0081] Among them, in the stage landing strategy of the high-level stage, (X w , Y w , Z w ) is the position coordinate of the UAV at the high-level stage:

[0082] Step 4. Z in the drone's position coordinates w When the height stratification threshold of the high-level stage is not exceeded, the stage landing strategy corresponding to the low-level stage is obtained;

[0083] Then, the stage landing strategy corresponding to the low-level stage is executed, and the low-level flight control instructions of the UAV are obtained; wherein the low-level flight control instructions include the low-level flight control instruction 1 and the low-level flight control instruction 2;

[0084] The stage landing strategy for the low-level stage is as follows:

[0085] Step 4.1. Calculate the horizontal distance between the current position of the drone and the landing platform according to the method in Step 3.1, and mark it as D2;

[0086] Among them, in the stage landing strategy of the low-level stage, the (X w , Y w , Z w ) is the position coordinate of the UAV in the bottom layer after executing the control instruction K1;

[0087] Step 4.2, then compare D2 with the preset distance threshold D2y:

[0088] When D2>D2y, the flight time of the UAV flying at the horizontal distance D2 is calculated according to the method from Step 3.2 to Step 3.3, and it is marked as T2, and the direction adjustment angle of the UAV flight direction is calculated and marked as θa2;

[0089] Step 4.2, then generate the bottom-level flight control instruction 1 according to the flight time T2 of the UAV at the horizontal distance D2 and the direction adjustment angle θa2 of the UAV's flight direction, and mark it as K2 = [T2, θa2];

[0090] Until D2<D2y;

[0091] Step 4.3, get the position coordinates of the drone after executing the underlying flight control command 1, and replace the X w Subtract the X coordinate of the landing platform position t , and get the current height difference Hc, and then compare the current height difference with the preset height threshold Hy:

[0092] When Hc ≥ Hy, the drone descends at the current flight speed V in the bottom stage;

[0093] When Hc<Hy, then through , calculate the adjustment speed V1 of the drone in the bottom stage, and the drone descends according to the adjustment speed V1 in the bottom stage, and generate the bottom flight control instruction 2 according to the adjustment speed V1 of the drone in the bottom stage, and mark it as K20 = [V1];

[0094] The return execution unit is used to control the UAV to perform corresponding actions according to the corresponding control instructions calculated by the hierarchical planning unit.

[0095] This embodiment divides the landing process into a high-level stage and a low-level stage according to the height layer threshold, and formulates corresponding stage landing strategies respectively, so that the UAV can take more targeted control measures at different height stages. This hierarchical control method can more accurately adapt to the flight characteristics and environmental requirements of the UAV at different altitudes, and improve the accuracy and stability of the return positioning. In the stage landing strategy of the high-level stage, a variety of flight parameters such as the horizontal distance between the current position of the UAV and the landing platform, the flight speed, the direction adjustment angle of the flight direction, and the pitch adjustment angle of the flight attitude are comprehensively considered to generate a high-level flight control instruction. This helps to fully adjust the flight state of the UAV, ensure accurate flight toward the landing platform in the high-level stage, and reduce deviations. In the low-level stage, the horizontal distance, the preset distance threshold, the height difference, the preset height threshold, and the flight speed are also considered to generate the low-level flight control instructions. This comprehensive consideration of multiple parameters enables the UAV to more accurately adjust the flight attitude and speed in the process of approaching the landing platform, and land safely and stably.

[0096] Embodiment 2

[0097] As the second embodiment of the present invention, when the present application is specifically implemented, compared with the first embodiment, the difference between the technical solution of the present embodiment and the first embodiment is that in the present embodiment, the control analysis unit also includes after the low flight control instruction is executed, according to the position coordinates and speed information of the UAV, and combined with the stage landing strategy corresponding to the low-level stage, and then update control, and obtain the corresponding real-time update control instruction;

[0098] Update control is as follows:

[0099] Step 5.1, according to the method from Step 3.1 to Step 3.2, calculate the flight time of the UAV at the corresponding horizontal distance and mark it as T3;

[0100] Among them, in the stage landing strategy of the low-level stage, the flight time T3 of the UAV flying at the corresponding horizontal distance is calculated as the position coordinates of the UAV at the corresponding position in the bottom-level stage after executing the control instruction K1;

[0101] Step 5.2, obtain half of the flight time corresponding to T3, that is, T3 / 2;

[0102] Then, based on Step 5.1, the flight time of the UAV at the corresponding horizontal distance, the direction adjustment angle of the UAV's flight direction, and the pitch adjustment angle of the UAV's flight attitude are calculated in accordance with the method of Step 3.3 to Step 3.4;

[0103] At the same time, multiply the current speed of the drone by 0.75 to get the updated speed of the drone;

[0104] Then, a real-time update control instruction is generated according to the flight time of the UAV flying at the corresponding horizontal distance, the direction adjustment angle of the UAV's flight direction, and the pitch adjustment angle of the UAV's flight attitude, and the update speed of the UAV;

[0105] Step 5.3, after the unmanned real-time update control instructions are generated, the corresponding real-time update control instructions are generated according to the method from Step 5.1 to Step 5.2 until the UAV reaches the landing platform.

[0106] In this embodiment, based on the first embodiment, the control analysis unit adds an update control function after the execution of the low-level flight control instruction. In the low-level stage, the update control is performed according to the position coordinates and speed information of the UAV, combined with the corresponding stage landing strategy of the low-level stage, and the real-time update control instruction is obtained. This dynamic adjustment mechanism can continuously optimize the control instructions according to the actual state of the UAV during the flight process, better adapt to various changes in the flight process, such as airflow interference, navigation errors, etc., and further improve the accuracy of the UAV return positioning; in the update control mode, by calculating the flight time, obtaining half of its value, and recalculating the flight direction and attitude adjustment angle on this basis, and adjusting the speed at the same time, and then generating a real-time update control instruction. This method can more flexibly adjust the flight parameters of the UAV, so that the UAV can land more smoothly and accurately in the process of approaching the landing platform. The corresponding real-time update control instructions are continuously generated in a specific way until the UAV arrives at the landing platform. This continuous optimization process can ensure that the flight state of the UAV is always in the optimal or near-optimal state during the entire return landing process, effectively reducing the risk of landing failure and improving the safety and reliability of the system.

[0107] Embodiment 3

[0108] As the third embodiment of the present invention, when the present application is specifically implemented, compared with the first and second embodiments, the technical solution of this embodiment is to combine the solutions of the first and second embodiments mentioned above for implementation.

[0109] This embodiment combines the solutions of embodiment one and embodiment two, and combines the advantages of embodiment one, namely, precise hierarchical control, comprehensive consideration of multiple flight parameters, and unitized design, and embodiment two, namely, dynamic adjustment, flexible adjustment of flight parameters, and continuous optimization until landing. This allows the adaptive return home positioning system of the tethered drone for high-altitude operations of the present invention to operate in a more precise, stable, and safe manner during the entire return process, from high altitude to low altitude until landing, and comprehensively improves the adaptive return home positioning capability of the system. In complex environments and flight conditions, it can better ensure the smooth return and landing of the drone, reduce the risk of landing failure caused by various factors, and improve the reliability and safety of drone operations.

[0110] The above formulas are all dimensionless and numerical calculations. The formula is a formula for the most recent real situation obtained by collecting a large amount of data and performing software simulation. The preset parameters and thresholds in the formula are set by technicians in this field according to actual conditions.

[0111] The above embodiments are only used to illustrate the technical method of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical method of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical method of the present invention.

Claims

1. The adaptive return home positioning system for tethered drones for aerial work is characterized by: include: A data acquisition unit, which obtains the position coordinates and speed information of the UAV, as well as the position coordinates of the landing platform; The control analysis unit is used to perform hierarchical control analysis based on the results obtained by the data acquisition unit. The hierarchical control analysis method is as follows: Step 1. Obtain the position coordinates of the drone and the landing platform in real time; Step 2, obtain the pre-set layered landing strategy; Step 3. When the Z-axis coordinate value in the position coordinate of the UAV exceeds the height stratification threshold of the high-level stage, the stage landing strategy corresponding to the high-level stage is obtained, and then the stage landing strategy corresponding to the high-level stage is executed, and the high-level flight control instruction of the UAV is obtained. The layered landing strategy includes the high-level stage and the bottom-level stage divided according to the height stratification threshold, and the stage landing strategies corresponding to the high-level stage and the bottom-level stage; Step 4. After the high-level flight control command is executed, if the Z-axis coordinate value in the position coordinate of the UAV does not exceed the height layer threshold of the high-level stage, the stage landing strategy corresponding to the low-level stage is obtained, and then the stage landing strategy corresponding to the low-level stage is executed, and the low-level flight control command of the UAV is obtained; Step 5. After the low-level flight control instructions are executed, the low-level flight control instructions include the low-level flight control instructions 1 and the low-level flight control instructions 2. According to the position coordinates and speed information of the UAV, combined with the corresponding stage landing strategy of the low-level stage, the update control is performed and the corresponding real-time update control instructions are obtained; The return execution unit is used to control the UAV to perform corresponding actions according to the corresponding control instructions calculated by the hierarchical planning unit.

2. The adaptive return home positioning system for a tethered drone for aerial work according to claim 1, characterized in that: In Step 3, the stage landing strategy of the high-level stage is as follows: Step 3.1, calculate the horizontal distance between the current position of the drone and the landing platform through the position coordinates of the drone at the high-level stage and the landing platform, and mark it as D1; Step 3.2, simultaneously obtain the current UAV flight speed V1; Then, the flight time T1 of the drone flying at the horizontal distance D1 is calculated by dividing the horizontal distance D1 by the flight speed V1; Step 3.3, calculate the direction adjustment angle of the UAV's flight direction through the position coordinates of the UAV at the high-level stage and the position coordinates of the landing platform, and mark it as θa1; Step 3.4, calculate the pitch adjustment angle of the UAV's flight attitude through the position coordinates of the UAV at the high-level stage, the position coordinates of the landing platform, and the height stratification threshold, and mark it as θb1; Step 3.5, generate high-level flight control instructions based on the flight time T1 of the UAV at the horizontal distance D1, the direction adjustment angle θa1 of the UAV's flight direction, and the pitch adjustment angle θb1 of the UAV's flight attitude, and mark it as K1 = [T1, θa1, θb1].

3. The adaptive return home positioning system for a tethered drone for aerial work according to claim 1, characterized in that: In Step 4, the stage landing strategy of the low-level stage is as follows: Step 4.

1. Calculate the horizontal distance between the current position of the drone and the landing platform according to the method in Step 3.1, and mark it as D2; Step 4.2, then compare D2 with the preset distance threshold D2y: When D2>D2y, the flight time of the UAV flying at the horizontal distance D2 is calculated according to the method from Step 3.2 to Step 3.3, and it is marked as T2, and the direction adjustment angle of the UAV flight direction is calculated and marked as θa2; Step 4.2, then generate the bottom-level flight control instruction 1 according to the flight time T2 of the UAV at the horizontal distance D2 and the direction adjustment angle θa2 of the UAV's flight direction, and mark it as K2 = [T2, θa2]; Until D2<D2y; Step 4.3, get the position coordinates of the drone after executing the underlying flight control command 1, and replace the X w Subtract the X coordinate of the landing platform position t , and get the current height difference Hc, and then compare the current height difference with the preset height threshold Hy: When Hc ≥ Hy, the drone descends at the current flight speed V in the bottom stage; When Hc<Hy, then through , calculate the adjustment speed V1 of the UAV in the bottom stage, and the UAV descends according to the adjustment speed V1 in the bottom stage, and generate the bottom-level flight control instruction 2 according to the adjustment speed V1 of the UAV in the bottom stage, and mark it as K20=[V1].

4. The adaptive return home positioning system for a tethered drone for aerial work according to claim 3 is characterized in that: Update control is as follows: Step 5.1, according to the method from Step 3.1 to Step 3.2, calculate the flight time of the UAV at the corresponding horizontal distance and mark it as T3; Step 5.2, obtain half of the flight time corresponding to T3, that is, T3 / 2; Then, based on Step 5.1, the flight time of the UAV at the corresponding horizontal distance, the direction adjustment angle of the UAV's flight direction, and the pitch adjustment angle of the UAV's flight attitude are calculated in accordance with the method of Step 3.3 to Step 3.4; At the same time, multiply the current speed of the drone by 0.75 to get the updated speed of the drone; Then, a real-time update control instruction is generated according to the flight time of the UAV flying at the corresponding horizontal distance, the direction adjustment angle of the UAV's flight direction, and the pitch adjustment angle of the UAV's flight attitude, and the update speed of the UAV; Step 5.3, after the unmanned real-time update control instructions are generated, the corresponding real-time update control instructions are generated according to the method from Step 5.1 to Step 5.2 until the UAV reaches the landing platform.

5. The adaptive return home positioning system for a tethered aerial work drone according to claim 4, characterized in that: In Step 4.1, in the stage landing strategy of the low-level stage, the position coordinates of the UAV used to calculate the horizontal distance D2 are the position coordinates of the UAV in the low-level stage after executing the control instruction K1; In Step 5.1, in the stage landing strategy of the low-level stage, the flight time T3 of the UAV flying at the corresponding horizontal distance is calculated as the position coordinates of the UAV at the corresponding position in the low-level stage after executing the control instruction K1.

6. The adaptive return home positioning system for a tethered drone for aerial work according to claim 2, characterized in that: The horizontal distance between the current position of the drone and the landing platform is calculated as follows: First, the square of the difference between the X-axis coordinate value of the position coordinate of the drone at the high-level stage and the position coordinate of the landing platform is calculated; At the same time, the square of the difference between the Y-axis coordinate value in the position coordinates of the drone at the high-level stage and the position coordinates of the landing platform is calculated; Then add the squares of the two differences and take the square root; The final result is the horizontal distance between the current position of the drone and the landing platform.

7. The adaptive return home positioning system for a tethered drone for aerial work according to claim 2, characterized in that: The calculation method of the direction adjustment angle of the drone's flight direction is as follows: First, the difference between the X-axis coordinate value of the position coordinate of the UAV at the high-level stage and the position coordinate of the landing platform is calculated; At the same time, the difference between the Y-axis coordinate value of the position coordinate of the UAV at the high-level stage and the position coordinate of the landing platform is obtained; Then divide the difference corresponding to the X-axis coordinate value by the difference corresponding to the Y-axis coordinate value, and then use the inverse tangent function to combine the result to calculate the direction adjustment angle of the drone's flight direction.

8. The adaptive return home positioning system for a tethered drone for aerial work according to claim 2, characterized in that: The calculation method of the pitch adjustment angle of the drone's flight attitude is as follows: First, the Z-axis coordinate value of the landing platform's position coordinates in the high-level stage is subtracted from the height layer threshold, and then the result is divided by the horizontal distance between the current position of the drone and the landing platform. The inverse tangent function is then used to combine the result to calculate the pitch adjustment angle of the drone's flight attitude.

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