Self-adaptive suspension type outer wall cleaning unmanned aerial vehicle system and method based on constant tension control

Abstract

The invention discloses a self-adaptive suspension type outer wall cleaning unmanned aerial vehicle system and method based on constant tension control, and relates to the technical field of outer wall cleaning unmanned aerial vehicles. The system comprises a cleaning unmanned aerial vehicle subsystem, a water and electricity supply guarantee subsystem and an intelligent suspension retraction subsystem which are connected through a photoelectric liquid composite mooring rope; the intelligent suspension take-up and pay-off subsystem comprises a constant-tension take-up and pay-off device which monitors and adjusts the tension of a mooring rope in real time so as to maintain a constant micro-tension state, and it is ensured that the unmanned aerial vehicle flies stably. The water and electricity supply guarantee subsystem provides high-voltage direct-current electric energy and high-voltage fluid; the cleaning unmanned aerial vehicle subsystem comprises a self-adaptive telescopic spraying rod, and the position of a nozzle is dynamically adjusted according to the building facade structure so as to execute cleaning operation. By integrating constant tension control, high-voltage power supply and a self-adaptive cleaning mechanism, high efficiency, flight stability and operation safety of outer wall cleaning operation are achieved.

Description

Technical Field

[0001] This invention relates to the field of exterior wall cleaning drone technology, and in particular to an adaptive suspended exterior wall cleaning drone system and method based on constant tension control. Background Technology

[0002] With the acceleration of global urbanization, a large number of super high-rise buildings and large commercial complexes have emerged. The exterior walls of these buildings, such as glass curtain walls, aluminum composite panels, and stone facades, are exposed to the natural environment for a long time, accumulating pollutants such as dust, oil stains, acid rain residue, and bird droppings. These pollutants not only affect the urban landscape, but more importantly, corrosive pollutants, if not removed in time, will erode the building's surface materials, damage the structural integrity of the exterior walls, shorten the lifespan of the facade, increase maintenance and replacement costs, and may also cause safety hazards such as falling objects from heights, threatening the lives of pedestrians.

[0003] For a long time, the cleaning and maintenance of the exterior walls of high-rise buildings has mainly relied on two traditional methods: First, there's the "spider-man" high-altitude rope work, which is currently the most common method. Workers are suspended hundreds of meters in the air, their safety dependent on a single rope. This makes them highly vulnerable to sudden strong winds, rope breakage due to aging, and human error, resulting in high safety risks. Furthermore, manual cleaning is inefficient, labor-intensive, and it's difficult to guarantee uniform cleaning quality.

[0004] Secondly, there are window cleaning machines (aerial work platforms), which offer improved safety compared to "spider-men," but the equipment is large and cumbersome, requiring significant manpower and resources for transportation and installation. They also necessitate the installation of expensive track systems on the building's rooftop, increasing construction and maintenance costs. For older buildings with unique shapes, complex facades, or those without pre-installed tracks, window cleaning machines leave numerous blind spots, making thorough cleaning impossible.

[0005] In recent years, drone technology has developed rapidly, and using drones to replace manual labor for high-altitude operations has become an industry consensus. Drones are flexible, efficient, and safe, providing a new solution for cleaning the exterior walls of high-rise buildings. However, existing cleaning drone technologies face serious challenges in practical engineering applications: First, there are limitations in energy supply and payload range. Most multi-rotor drones on the market are powered by onboard lithium polymer batteries, which consume a lot of energy for cleaning operations. The energy density of traditional batteries limits the flight time, usually only 15-25 minutes. When carrying a cleaning payload, the flight time is even shorter, less than 10 minutes. The "take-off and return" mode results in poor operational continuity, and frequent battery replacements reduce overall cleaning efficiency and increase costs.

[0006] Secondly, there are shortcomings in the "passive" cable management of traditional tethered technologies. Current tethered drone technology uses ground-based power supply to address energy issues, but its cable management suffers from technical flaws. The control logic of "cable length = flight altitude + fixed safety margin" results in slack cables in the air. High-altitude wind fields are complex, and slack cables sway and drift under crosswinds (whiplash effect), generating nonlinear drag forces that disrupt flight stability. Furthermore, due to the lack of constant tension control, cables may become entangled near complex building facades, causing equipment damage and hindering cleaning operations. Summary of the Invention

[0007] In view of this, the present invention proposes an adaptive suspended exterior wall cleaning drone system and method based on constant tension control to solve the problems of insufficient endurance, stability and complex facade cleaning capabilities of existing tethered drones.

[0008] The specific technical solution of this invention is as follows: An adaptive suspended exterior wall cleaning drone system based on constant tension control includes: a cleaning drone subsystem, a water and power supply subsystem, and an intelligent suspension and retraction subsystem. These three subsystems are connected by a photoelectric-hydraulic composite tethering cable. The intelligent suspension and retraction subsystem includes a constant tension retraction device that monitors and adjusts the tension of the tethering cable in real time to maintain a constant micro-tension state, ensuring stable drone flight. The water and power supply subsystem provides high-voltage DC power and high-pressure fluid. The cleaning drone subsystem includes an adaptive telescopic spray boom that dynamically adjusts the nozzle position according to the building facade structure to perform cleaning operations.

[0009] Specifically, the constant tension take-up and release device includes a servo drive system, a precision cable winding mechanism, and a high-precision tension sensor. The servo drive system responds to tension deviations to perform take-up or release actions, the precision cable winding mechanism ensures orderly cable winding, and the high-precision tension sensor directly measures the cable tension and feeds it back to the closed-loop control circuit.

[0010] Specifically, the photoelectric-hydraulic composite tethering cable adopts a multi-layer composite structure, including a central high-pressure infusion tube, an outer conductive layer, an embedded optical fiber communication unit, a reinforcing layer, and a wear-resistant sheath. The conductive layer is used to transmit high-voltage DC power, the optical fiber communication unit enables high-speed data interaction, the reinforcing layer withstands mechanical tension, and the wear-resistant sheath resists external friction damage.

[0011] Specifically, the adaptive telescopic spray bar adopts a three-stage sleeve structure, driven by a micro linear stepper motor, combined with modular nozzles; the modular nozzles can be quickly replaced to adapt to different cleaning scenarios, including fan-shaped nozzles, cone-shaped nozzles and atomizing nozzles, which are used for large-area flat curtain walls, dead corner cleaning and cleaning agent pre-wetting, respectively.

[0012] An adaptive suspended exterior wall cleaning UAV method based on constant tension control includes: a constant tension flight stability control method and an adaptive cleaning operation control process; the constant tension flight stability control method adjusts the tether cable tension collaboratively by setting a target tension value, a closed-loop control algorithm, and a feedforward compensation mechanism; the adaptive cleaning operation control process includes environmental perception and positioning, distance calculation and telescopic boom planning, pressure and attitude coordinated control, and graded cleaning strategy execution to achieve adaptive operation of exterior wall cleaning.

[0013] Specifically, the steps of the constant tension flight stability control method include: activating the pre-tensioning mode before takeoff to slightly tension the cable; switching to the constant tension operation mode after takeoff and setting a constant target tension value; and applying a closed-loop proportional-integral-differential algorithm to calculate the tension deviation and generate servo commands.

[0014] Specifically, the vertical speed of the UAV is introduced as a feedforward quantity for compensation, and the take-up and release actions are adjusted in real time to eliminate tension fluctuations. This includes converting the real-time vertical speed of the UAV into an additional speed command through a proportional gain; superimposing it on the PID output to generate the final speed command of the servo motor, thereby reducing dynamic response lag.

[0015] Specifically, the environmental perception and positioning steps utilize a forward-facing binocular vision sensor and an ultrasonic ranging module to collaboratively scan the building facade, construct a three-dimensional depth map to identify the boundaries and groove depths of different components; at the same time, a real-time dynamic differential positioning module maintains the UAV's horizontal position with centimeter-level accuracy.

[0016] Specifically, the pressure-attitude coordinated control steps include: pre-calculating the reaction force of the high-pressure water jet and its pitching moment; synchronously injecting a reverse torque command into the UAV flight control system when the jet is activated; and offsetting the effect of the reaction force by adjusting the rotor speed difference to ensure the stability of the fuselage attitude.

[0017] Specifically, the graded cleaning strategy includes three steps: pre-wetting mode, main wash mode, and rinsing mode. In the pre-wetting mode, the fluid pressure is adjusted to a low value and the cleaning agent is mixed to quickly scan the wall. In the main wash mode, the pressure is increased to a high point and pure water is used to remove stains. In the rinsing mode, medium pressure is set to rinse away residue with a large flow rate.

[0018] The beneficial effects of this invention are as follows: 1. By combining rooftop voltage boosting and airborne voltage step-down conversion, the cross-sectional area of ​​cables required for power transmission is significantly reduced, achieving overall lightweighting of tethered cables and reducing power transmission losses over long distances.

[0019] 2. The dual-tank mixing system enables precise control of the cleaning fluid composition. Combined with the continuous pressure output characteristics of the variable frequency drive high-pressure pump, it effectively suppresses fluid pressure pulsation, reduces the risk of hydraulic shock in pipelines, and extends the service life of the system.

[0020] 3. Using real-time cable tension as the control target, the cable is kept under slight tension through the linkage response between the rooftop deployment and take-up device and the UAV flight control system. This suppresses aeroelastic swaying caused by wind disturbance or UAV maneuvering, ensuring stable flight attitude.

[0021] 4. The aerial support point of the extended cable of the multi-degree-of-freedom strut device forms an isolation zone in the wall gap, reducing frictional damage between the cable and the building surface, optimizing the direction of cable tension, and reducing the additional load on the UAV lift system.

[0022] 5. By integrating environmental perception, distance calculation, and attitude coordination control, the system can dynamically match the extension and retraction length of the spray boom to the structural features of the building facade, simultaneously counteract the interference of the high-pressure jet reaction force on the flight attitude, and improve the cleaning efficiency and coverage under different pollution conditions through a graded cleaning strategy. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram illustrating the use of the adaptive suspended external wall cleaning drone system based on constant tension control according to the present invention. Figure 2 This is a schematic diagram of the structure of the adaptive suspended external wall cleaning drone system based on constant tension control of the present invention.

[0025] The attached figures are labeled as follows: 1-Clean-up drone subsystem; 2-Water and electricity supply subsystem; 21-High voltage DC power supply unit; 22-Intelligent fluid supply unit; 3-Intelligent suspension and retraction subsystem; 31-Electro-hydraulic composite tethering cable; 32-Constant tension retraction and retraction device; 33-Multi-degree-of-freedom strut device. Detailed Implementation

[0026] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0027] This invention proposes an adaptive suspended external wall cleaning drone system based on constant tension control. The core components of the system include a cleaning drone subsystem 1, a water and electricity supply subsystem 2, and an intelligent suspension and deployment subsystem 3. The three subsystems are physically connected and exchange energy information through a photoelectric-liquid composite tethering cable 31 that integrates power transmission, data communication (optical signal), and fluid transport functions.

[0028] The water and electricity supply subsystem 2, serving as the energy and water source center for the entire system, is located on the rooftop. It includes a high-voltage DC power supply unit 21 and an intelligent fluid supply unit 22. The water and electricity supply subsystem 2 is responsible for converting mains electricity / fuel power into suitable high-voltage electrical energy and high-voltage fluid for transmission.

[0029] The high-voltage DC power supply unit 21 provides a power transmission architecture based on AC-DC rectification boost (to 400V DC) and airborne lightweight DC-DC buck (to 24V / 5V), achieving extreme lightweighting and low-loss long-distance transmission of the tethered cable. The high-voltage DC power supply unit 21 is responsible for converting the input 220V / 380V AC mains power into stable and reliable high-voltage DC power. In specific implementation, the 220V / 380V AC input first passes through an EMI filter to suppress electromagnetic interference, and then enters a three-phase full-wave rectifier bridge and its matching LC filter network to convert the AC power into a 400V DC bus voltage. This rectifier must have a rated current value not less than the system's maximum operating current and a withstand voltage value higher than the 400V bus voltage. To ensure safety, a high-voltage DC contactor and an insulation monitoring device (IMD) are connected in series at the DC output terminal. The insulation monitoring device continuously monitors the insulation resistance value of the tethered cable; once this value falls below a preset safety threshold, the high-voltage DC contactor immediately cuts off the 400V DC output, ensuring the safety of operators and equipment.

[0030] The intelligent fluid supply unit 22 is responsible for providing high-pressure cleaning fluid. Its core components include a dual-tank system and a high-pressure pump set. The dual-tank system independently stores clean water and concentrated cleaning agent. Automatic and precise mixing of water and cleaning agent is achieved through a Venturi tube principle or a proportioning pump. The high-pressure pump set uses a three-plunger high-pressure pump, which, compared to a diaphragm pump, significantly reduces output pressure pulsation, effectively suppressing vibrations caused by fluid pressure fluctuations within the tethered hose. The high-pressure pump is driven by a variable frequency motor. By precisely adjusting the motor speed, continuous and stable control of the output fluid flow rate (500-900 L / h) and pressure (up to 25 MPa) is achieved. This variable frequency drive not only saves energy but also enables soft starting of the pump set, reducing hydraulic shock and protecting the pipeline system.

[0031] The intelligent suspension and deployment subsystem 3 is a key link connecting the rooftop and the aerial platform, and is crucial for ensuring the flight stability of the UAV. Its core components are the electro-hydraulic composite tether cable 31, the constant tension deployment and deployment device 32, and the multi-degree-of-freedom strut device 33.

[0032] The photoelectric-hydraulic composite tethering cable 31 adopts a multi-layer composite structure: the core layer is a high-pressure infusion tube made of high-strength nylon or Teflon material, used to transport high-pressure cleaning fluid; the conductive layer is tightly spirally wound around the infusion tube and consists of 6 silver-plated copper wires with a cross-sectional area of ​​0.5mm², of which 2 are dedicated to transmitting 400V positive (+) DC power, 2 are used to transmit 400V negative (-) DC power, and the remaining 2 are used as spares or signal ground wires; this small wire diameter design benefits from the characteristic of significantly reduced current under high-voltage transmission. The communication layer embeds a single-mode fiber optic unit to realize high-speed, interference-resistant bidirectional data communication between the rooftop control station and the airborne flight controller, transmitting real-time video streams, flight control commands, and sensor data. The reinforcing layer uses a high-strength Kevlar fiber braided mesh to bear all the mechanical tension borne by the cable during operation. The outermost sheath is made of wear-resistant polyurethane (TPU) material, providing excellent wear resistance and resisting friction and cutting damage from the sharp edges of the building facade.

[0033] The constant tension cable winding and unwinding device 32 is the core actuator for achieving intelligent constant tension control. It is an active cable management mechanism integrating a servo drive system, a precision cable arrangement mechanism, a sensor group, and rotating connecting components. This device does not rely on traditional distance calculations but uses cable tension as the sole control target, responding in real-time to the movement of the UAV to ensure that the cable maintains a constant micro-tension under any operating condition, eliminating aeroelastic sway. The servo drive system uses a high-dynamic-response AC servo motor in conjunction with a precision planetary reducer to drive the drum. The servo motor operates in "torque control mode," ensuring a fast and accurate response to tension commands, especially with excellent performance at low speeds. The cable arrangement mechanism uses a reciprocating screw-type automatic cable arranger, which ensures that the cable is tightly, flat, and orderly wound layer by layer on the drum during cable winding and unwinding, effectively preventing mechanism jamming or cable length measurement errors caused by tangled wires. The sensor group includes a high-precision tension sensor and a high-resolution encoder. The tension sensor uses a "three-point" pressure sensor installed at the guide wheel assembly of the cable arranger to measure the tension value of the tethered cable in real-time and directly. The servo motor has a built-in high-resolution absolute encoder for real-time measurement of the drum's rotation angle and speed, accurately calculating the cable's winding and unwinding length and speed. To ensure uninterrupted transmission of power, signals, and fluids while the drum is rotating, a high-voltage, high-current conductive slip ring and a high-pressure water rotary joint are integrated at the drum's shaft.

[0034] The multi-degree-of-freedom strut device 33 is fixedly installed on the edge of the parapet wall on the top floor of the building. The main body of the device is a telescopic strut made of carbon fiber, with a length adjustable from 1.2 meters to 2.0 meters. A universal cable pulley is installed at the top of the telescopic strut. The core function of the strut is to extend the aerial fulcrum of the tethered cable from the edge of the floor outward, creating a "safe corridor" on the outer side of the building facade. This design effectively avoids damage caused by direct friction between the cable and the wall surface when hovering or operating at low altitudes, while significantly optimizing the direction angle of the cable's pull on the drone, minimizing the burden of the vertical upward tension component on the drone's lift system.

[0035] The cleaning drone subsystem 1 is the terminal platform for the entire system to perform aerial flight and exterior wall cleaning operations. It is a lightweight three-stage telescopic spray boom system integrated into the drone platform. This system, combined with onboard visual perception, can automatically adjust the nozzle extension length according to the wall's depth of field. With multi-module quick-release nozzles, it achieves precise cleaning of facades made of different materials (glass, stone, aluminum) and with different structures (flat, recessed). Its design focuses on high thrust-to-weight ratio, lightweight construction, environmental adaptability, and precise control capabilities. The frame structure adopts an X-shaped quadcopter symmetrical layout. Compared to a cross-shaped configuration, this layout has theoretical and practical advantages in terms of maneuverability and yaw control responsiveness. The fuselage and arms are made of high-modulus carbon fiber composite materials (such as pitch-based carbon fiber). These materials possess extremely high specific modulus (stiffness / density ratio) and excellent damping characteristics, achieving not only extreme lightweighting (weight reduction) but also effectively absorbing the high-frequency vibration energy generated during the operation of the airborne high-pressure water pump. This prevents such vibrations from interfering with the data acquisition accuracy of the flight controller (IMU - Inertial Measurement Unit), ensuring flight stability. To meet the operational requirements of long-term exposure to water mist environments, the entire aircraft is designed strictly according to the IP55 protection rating. Core electronic circuit boards are coated with a nano-level waterproof coating, and the drive motor bearings employ a fully enclosed waterproof structure. The cleaning drone subsystem 1 includes a propulsion unit, an onboard power management unit, a cleaning actuator, and a flight control system.

[0036] The propulsion unit consists of a motor, an electronic speed controller (ESC), and a propeller. The motor is a high-torque, low-KV (speed constant) external rotor brushless DC motor (BLDC). The inherently large moment of inertia of the external rotor structure helps provide more stable speed maintenance and enhances robustness against irregular high-altitude gusts. The ESC uses a vector ESC that supports FOC (Field-Oriented Control) algorithms. Compared to traditional square wave drive, FOC drive significantly reduces motor operating noise and improves thrust efficiency (thrust per unit power consumption) by approximately 10%. The propeller is equipped with large carbon fiber blades, using a "CW-CCW-CW-CCW" adjacent blade counter-rotation layout to counteract the anti-torque generated by rotor rotation, ensuring directional stability of the UAV. The overall system design thrust-to-weight ratio (maximum lift / total system weight) ≥ 2.5. The total system weight includes: the weight of the drone's own structure, the weight of the onboard cleaning actuator, the weight of the tether cable at maximum operating altitude, and the fluid weight of the infusion tube inside the tether cable when it is filled with fluid at maximum altitude. This ensures that the drone still has sufficient lift margin to maintain controllable flight under extreme conditions (such as maximum load, maximum altitude, and strong winds).

[0037] The onboard power management unit (HMU) is responsible for efficiently and reliably converting the high-voltage DC power transmitted via the tether to the operating voltage required by various components of the UAV, and also provides emergency power supply capabilities. Its core is the high-voltage step-down module (onboard DC-DC converter). This module receives 350V-400V high-voltage DC power transmitted via the electro-hydraulic composite tether 31. It employs a high-density isolated DC-DC converter chip, achieving a zero-voltage switching (ZVS) topology with an operating frequency up to the MHz level. This design results in extremely high power density (>1000 W / m³) and conversion efficiency (>93%). The converter's main output provides a stable 24V DC power to the drive motor and high-pressure water pump; the auxiliary output, through a two-stage step-down circuit, provides 5V DC power to the flight control computer and various sensors. To address the heat dissipation challenges posed by the high power density, the DC-DC module is installed tightly against the fuselage's aluminum alloy heat sink frame and positioned directly below the rotor disk, fully utilizing the downwash airflow generated by the rotor for forced air cooling. The emergency backup power supply uses a high-rate 6S lithium polymer battery (nominal voltage 22.2V), connected in parallel to the 24V main DC bus via an ideal diode controller (or equivalent circuit). This battery features "online hot backup": when the tethered power supply is normal, the battery is in a float charge state; once the system detects that the 24V voltage on the main line (from the tethered cable) has dropped below a preset safety threshold (e.g., a power outage), the ideal diode controller instantly turns on, and the emergency battery seamlessly takes over the power supply to the 24V bus, ensuring the continuous operation of the UAV's critical systems (flight control, communication, core sensors). The design capacity of this emergency battery must be strictly guaranteed to maintain the UAV at full load (including maximum cable weight and tubing fluid weight) for the minimum time required for a safe hovering and landing from the system's preset highest operating point to the ground (in practice, this is set to at least 15 minutes).

[0038] The cleaning actuator, a key component that directly acts on the cleaning target, consists of a telescopic spray boom and modular nozzles. The telescopic spray boom employs a three-stage aluminum alloy sleeve structure driven by a miniature linear stepper motor, resulting in a lightweight yet rigid design. High-pressure cleaning fluid is delivered to the nozzles via a built-in Teflon high-pressure hose. The spray boom is designed with a telescopic stroke ranging from 150mm to 500mm. When the drone hovers stably at a safe distance of 1.5 meters from the building wall, the spray boom can extend sufficiently to clean hard-to-reach areas such as window frames and decorative strips up to 300mm deep. To reduce the weight and inertia of moving parts, the end effector of the spray boom features a hollowed-out weight-reduction design. The modular nozzles use stainless steel V-shaped clamp quick-connect interfaces, supporting rapid on-site replacement (completed in seconds) according to different cleaning needs. Specific categories are shown in Table 1. Table 1. Modular Cleaning Nozzle Selection and Applicable Scenarios

[0039] A miniature proportional control valve is connected in series in the airborne hydraulic circuit. This valve receives flight control commands and adjusts the spray pressure to the set value in real time and precisely according to different stages of the cleaning operation (pre-wetting, main washing, rinsing), with an adjustment range covering 0.5MPa to 3.0MPa.

[0040] The flight control system is the brain of the drone's operation, employing a flight controller deeply customized based on a mature multi-rotor control architecture. The controller integrates multiple sensors: a three-axis MEMS accelerometer, a three-axis MEMS gyroscope, a three-axis magnetometer (electronic compass), and a high-precision barometric altimeter (for measuring relative altitude). The positioning system features an RTK-GPS / BDS dual-mode differential positioning module, combined with correction signals from ground base stations, providing centimeter-level accuracy in horizontal positioning to ensure high-altitude hovering stability. The environmental perception system integrates multiple sensors: a forward-mounted binocular stereo vision sensor and an ultrasonic ranging module work together to identify the distance to the wall in front of the drone, construct a local 3D depth map, and accurately identify the boundaries and groove depths of window frames, glass seams, and decorative strips; a downward-mounted laser optical flow module detects changes in ground texture optical flow to assist in precise hovering at low altitudes (or in environments with obstructed GPS signals). This perception system is the foundation for adaptive cleaning operations.

[0041] This invention also proposes an adaptive suspended exterior wall cleaning drone method based on constant tension control. This method is a collaborative control method used to protect the adaptive suspended exterior wall cleaning drone system of this invention. Its core lies in coordinating the intelligent suspension deployment and take-up subsystem 3 with the aerial cleaning drone subsystem 1 to achieve stable tethered flight and efficient, adaptive cleaning operations. Specifically, it includes a constant tension flight stability control method and an adaptive cleaning operation control process.

[0042] The core of the constant tension flight stability control method lies in introducing the tension of the tether cable as a key state variable into the entire flight control loop, transforming the cable from a potential "passive interference source" into a "controllable constraint force." When tension fluctuations are detected, the deployment / retraction system and the in-flight flight control system interact and adjust collaboratively to achieve integrated "aircraft-cable" interference mitigation. The specific implementation steps are as follows: Step 1: Tension Setting and Mode Activation. Before the drone takes off, the system enters "pre-tensioning mode." At this time, the servo motor of the constant tension cable reel 32 outputs a small, constant torque to eliminate any slack in the cable on the drum, putting the cable in a slightly tensioned initial state. After the drone takes off, the system automatically switches to "constant tension operation mode." In this mode, a constant target tension value is set. (In specific implementation, the range is set to 5N to 10N). The principle for setting this target value is: it should be large enough to ensure that the cable remains taut at all times, effectively preventing it from swaying aeroelastically (whiplash effect) under wind force; at the same time, the tension value must be much smaller than the maximum available lift margin of the UAV under the current operating conditions, ensuring that it does not significantly limit or interfere with the UAV's vertical maneuverability.

[0043] Step 2: Closed-loop PID control. The controller (located in the intelligent suspension retraction subsystem 3 or the water and electricity supply guarantee subsystem 2) reads the measured values ​​of the tension sensor installed at the guide wheel assembly of the cable guide in real time at a high frequency of 1kHz. Calculate the deviation between the current measured tension value and the set target tension value. The proportional (P), integral (I), and derivative (D) control algorithms are used to calculate this deviation and generate speed control commands for the servo motor. : ; The correct execution logic is: when the measured tension is greater than the target tension (the cable is too tight), i.e. At this time, the servo motor performs the cable release action, releasing the cable to reduce tension; when the measured tension is less than the target tension (cable slack), that is... At this time, the servo motor performs the winding action, tightening the cable to increase tension.

[0044] Step 3: Feedforward Compensation. Simple tension feedback closed-loop control inherently suffers from mechanical transmission lag, resulting in an insufficient response speed to fully follow the rapid movements of the UAV. To overcome this lag, this method introduces UAV state feedforward. Specifically, the UAV flight control system uses an optical fiber communication link in the electro-hydraulic composite tethering cable 31 to transmit its real-time measured vertical velocity. The speed information is then transmitted to the controller, which in turn transmits this speed information. (After a proportional gain) This is converted into an additional speed feedforward, and the final speed command applied to the servo motor is the sum of the PID output and the feedforward: ; This control law enables the wire take-up and take-down device to predict and respond to the vertical motion trend of the UAV (such as accelerating upward or downward) in near real time, significantly reducing the tension fluctuation amplitude and greatly improving the stability of the system during dynamic flight.

[0045] The adaptive cleaning operation control process is a closed-loop automated process encompassing sensing, planning, and execution, covering the entire process from pre-wetting and main washing to rinsing. The specific steps are as follows: Step 1: Environmental Perception and Positioning. The drone flies to the target wall area for cleaning. RTK-GPS module maintains centimeter-level precise positioning in the horizontal plane. Simultaneously, forward-facing binocular vision sensor and ultrasonic ranging module continuously and collaboratively scan the building facade to acquire depth information, construct a local high-precision 3D depth map, and identify and segment different components on the wall (such as glass curtain wall panels, window frames, stone / aluminum panel areas, decorative strips) and their boundaries and depth information (especially groove depth).

[0046] Step Two: Distance Calculation and Telescopic Arm Planning. Set the standard safe operating distance between the drone's center and the wall to be cleaned. (For example, 2.0 meters is set in the specific implementation). Based on the 3D depth map generated in step one, the flight control system calculates in real time the actual distance between the current target cleaning point (e.g., the deepest part of the window frame recess) and the center of the drone fuselage. Optimal spray distance based on nozzle type Calculate the required extension length of the telescopic spray boom: ; Then, a miniature linear stepper motor drives the telescopic spray bar to precisely position the nozzle tip to the target cleaning point.

[0047] Step 3: Pressure-Attitude Coordinated Control. Before activating the high-pressure water pump for injection, the flight control system pre-calculates the reaction force generated by the high-pressure water jet based on the currently set injection pressure, nozzle type, and flow rate. This involves the pitch moment generated on the drone. Simultaneously with issuing the "start water jet" command to the high-pressure water pump, the flight control system injects a pre-calculated pitch moment command in the opposite direction into the motor mixer. This command is achieved by coordinating and adjusting the speed difference of the four rotors (generating a pitch moment). This active torque compensation ensures that, at the instant the high-pressure water jet suddenly starts, the drone will not pitch backward due to the reaction force, maintaining a stable fuselage attitude (remaining completely still).

[0048] Step 4: Execution of graded cleaning strategy. The flight control system automatically calls different cleaning modes and controls the relevant actuators according to the cleaning task plan: (1) Pre-wetting mode: Adjust the proportion valve to set the water pressure to 0.5MPa, and mix the cleaning agent into the water flow in proportion through the liquid mixing system. The UAV scans the wall surface along the planned path at a relatively fast speed, so that the cleaning liquid covers and softens the stains evenly. (2) Main washing mode: Adjust the proportion valve to increase the water pressure to 3.0MPa (maximum value), and use pure water. The UAV reduces the scanning speed or performs fixed-point cleaning according to the degree of stains, and uses high-pressure water jet to remove the softened stubborn stains. (3) Rinsing mode: Adjust the proportion valve to set the water pressure to 1.5MPa, and use pure water with low total dissolved solids (TDS). Rinse the wall surface with a large flow rate to remove residual cleaning agent and stain particles and avoid water stains.

[0049] The beneficial effects of this invention are as follows: (1) It breaks through the physical limits of endurance and load capacity, and realizes continuous operation in all weather: by using the 400V high-voltage transmission architecture of the high-voltage DC transmission structure, the current is reduced by nearly 20 times (compared to the 24V system), according to Joule's law The significantly reduced current allows the use of extremely thin wires to transmit thousands of kilowatts of power with very low loss. This greatly reduces the weight of cables over hundreds of meters, freeing up the effective load for high-pressure water pumps and telescopic mechanisms, and theoretically enabling unlimited operation.

[0050] (2) The intelligent constant tension cable reeling and releasing device 32 and PID+feedforward control method are adopted to fundamentally solve the problem of flight stability of tethered UAVs in wind fields: through active servo control, the cable is kept at a constant micro tension. Physically, the stiffness of the taut cable is extremely high and it is not easily affected by crosswinds to cause displacement. Dynamically, the constant tension is a known and stable constant for the flight control system and is very easy to compensate. This allows the UAV to maintain centimeter-level hovering accuracy in crosswinds.

[0051] (3) Achieved deep cleaning of complex building facades without dead angles: Through the adaptive telescopic cleaning mechanism, the mode of "safe hovering of the drone and deep operation of the arm" was realized. The drone can always stay in the safe zone 2 meters away and rely on the telescopic arm to send the nozzle into the dead corner of the groove, which not only ensures the cleaning effect, but also eliminates the collision risk.

[0052] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An adaptive suspended exterior wall cleaning drone system based on constant tension control, characterized in that, include: The cleaning drone subsystem, the water and electricity supply subsystem, and the intelligent suspension and deployment subsystem are connected by a photoelectric-hydraulic composite tethering cable. The intelligent suspension and deployment subsystem includes a constant tension tethering device that monitors and adjusts the tension of the tethering cable in real time to maintain a constant micro-tension state and ensure the stability of the drone flight. The water and electricity supply subsystem provides high-voltage DC power and high-pressure fluid. The cleaning drone subsystem includes an adaptive telescopic spray boom that dynamically adjusts the nozzle position according to the building facade structure to perform cleaning operations.

2. The adaptive suspended exterior wall cleaning drone system based on constant tension control as described in claim 1, characterized in that, The constant tension take-up and release device includes a servo drive system, a precision cable winding mechanism, and a high-precision tension sensor. The servo drive system responds to tension deviations to perform take-up or release actions, the precision cable winding mechanism ensures orderly cable winding, and the high-precision tension sensor directly measures the cable tension and feeds it back to the closed-loop control circuit.

3. The adaptive suspended exterior wall cleaning drone system based on constant tension control as described in claim 1, characterized in that, The photoelectric-hydraulic composite tethering cable adopts a multi-layer composite structure, including a central high-pressure infusion tube, an outer conductive layer, an embedded optical fiber communication unit, a reinforcing layer, and a wear-resistant sheath. The conductive layer is used to transmit high-voltage DC power, the optical fiber communication unit realizes high-speed data interaction, the reinforcing layer withstands mechanical tension, and the wear-resistant sheath resists external friction damage.

4. The adaptive suspended exterior wall cleaning drone system based on constant tension control as described in claim 1, characterized in that, The adaptive telescopic spray bar adopts a three-stage sleeve structure and is driven by a micro linear stepper motor, combined with modular nozzles. The modular nozzles can be quickly replaced to adapt to different cleaning scenarios, including fan-shaped nozzles, cone-shaped nozzles, and atomizing nozzles, which are used for large-area flat curtain walls, dead corner cleaning, and cleaning agent pre-wetting, respectively.

5. A method for an adaptive suspended external wall cleaning drone based on constant tension control, characterized in that, include: Constant tension flight stability control method and adaptive cleaning operation control process; The constant tension flight stability control method adjusts the tether cable tension in a coordinated manner by setting a target tension value, using a closed-loop control algorithm and a feedforward compensation mechanism; the adaptive cleaning operation control process includes environmental perception and positioning, distance calculation and telescopic arm planning, pressure and attitude coordinated control, and graded cleaning strategy execution to achieve adaptive operation of exterior wall cleaning.

6. The adaptive suspended exterior wall cleaning drone method based on constant tension control as described in claim 5, characterized in that, The specific steps of the constant tension flight stability control method include: activating the pre-tensioning mode before takeoff to slightly tension the cable; switching to the constant tension operation mode after takeoff and setting a constant target tension value; and applying a closed-loop proportional-integral-differential algorithm to calculate the tension deviation and generate servo commands.

7. The adaptive suspended exterior wall cleaning drone method based on constant tension control as described in claim 6, characterized in that, The vertical speed of the drone is introduced as a feedforward quantity for compensation, and the take-up and release actions are adjusted in real time to eliminate tension fluctuations. Specifically, the real-time vertical speed of the drone is converted into an additional speed command through proportional gain; it is superimposed on the PID output to generate the final speed command of the servo motor, thereby reducing dynamic response lag.

8. The adaptive suspended exterior wall cleaning drone method based on constant tension control as described in claim 5, characterized in that, The environmental perception and positioning steps utilize a forward-facing binocular vision sensor and an ultrasonic ranging module to collaboratively scan the building facade, construct a three-dimensional depth map to identify the boundaries and groove depths of different components; at the same time, a real-time dynamic differential positioning module maintains the UAV's horizontal position with centimeter-level accuracy.

9. The adaptive suspended exterior wall cleaning drone method based on constant tension control as described in claim 5, characterized in that, The pressure attitude coordinated control steps include: pre-calculating the reaction force and pitching moment of the high-pressure water jet; synchronously injecting a reverse torque command into the UAV flight control system when the jet is activated; and offsetting the effect of the reaction force by adjusting the rotor speed difference to ensure the stability of the fuselage attitude.

10. The adaptive suspended exterior wall cleaning drone method based on constant tension control as described in claim 5, characterized in that, The graded cleaning strategy includes three steps: pre-wetting mode, main wash mode, and rinsing mode. In the pre-wetting mode, the fluid pressure is adjusted to a low value and the cleaning agent is mixed to quickly scan the wall. In the main wash mode, the pressure is increased to a high point and pure water is used to remove stains. In the rinsing mode, the pressure is set to a medium pressure and a large flow rate to rinse away residue.

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