A multi-rotor load-carrying unmanned aerial vehicle and an adaptive fault-tolerant flight control method thereof

Abstract

The application discloses a multi-rotor load-carrying unmanned aerial vehicle and a self-adaptive fault-tolerant flight control method thereof, and relates to the technical field of flight control of load-carrying unmanned aerial vehicles. The multi-rotor load-carrying unmanned aerial vehicle obtains a pulling force value signal through a plurality of load-carrying pull rings, and comprises the following steps: calculating the projection position coordinates of a load resultant force action point in a body coordinate system based on the position coordinates of the load-carrying pull rings, and determining a load center of gravity offset; calculating a pitch compensation moment and a roll compensation moment, correcting the original attitude controller output basic control quantity of a flight control device through the obtained compensation moment, and the flight control device can obtain a target thrust according to the corrected control quantity to complete flight control. The application can obtain the weight distribution of six arm connection regions in real time, can pre-compensate before the attitude is obviously deflected by calculating the load resultant force action point and the load center of gravity offset, and introducing the load resultant force action point and the load center of gravity offset into a multi-rotor thrust distribution process, and can reduce attitude lag and control oscillation in heavy load hanging flight.

Description

Technical Field

[0001] This invention relates to the technical field of flight control for heavy-duty unmanned aerial vehicles (UAVs), and more particularly to a multi-rotor heavy-duty UAV and its adaptive fault-tolerant flight control method. Background Technology

[0002] Multi-rotor drones have advantages such as vertical takeoff and landing, strong hovering ability, flexible structural layout, and fast control response, and have been widely used in fields such as inspection, aerial photography, agricultural plant protection, surveying and mapping, and material transportation. With the increasing demand for drone payloads, hexacopter drones, due to their greater lift reserve and certain power redundancy compared to quadcopters, are gradually being used for medium and large-scale payload transportation tasks.

[0003] For a hexacopter heavy-duty drone with a wheelbase of approximately two meters, its large fuselage size, long arms, and wide rotor power assembly layout provide high lift and ample load suspension space. However, in actual sling-load transportation, large hexacopter drones still face the following challenges: For long-wheelbase multirotor UAVs, the root of the arms is the primary stress-bearing area. Rotor lift is transmitted from the outer ends of the arms to the central frame, while load weight diffuses from the central frame to the arm regions. If the load acts on the frame center only through a single hook, the load transmission path is concentrated, which is detrimental to fully utilizing the structural load-bearing capacity of the multiple arm connection areas. Furthermore, the UAV is prone to swaying during takeoff, acceleration, deceleration, turning, and landing while carrying the load. When the load sways or becomes eccentric, the UAV will experience additional roll and pitch moments. Existing multirotor flight control systems typically rely on inertial measurement units to detect attitude deviations before providing feedback control, failing to determine the direction and degree of eccentricity in advance based on the load's stress state, resulting in lag in attitude control. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] To address the technical problems of insufficient utilization of the structural bearing capacity of the arm connection area and lag in attitude control when multiple loads are suspended, this invention provides a multi-rotor heavy-duty unmanned aerial vehicle (UAV) and its adaptive fault-tolerant flight control method. The invention provides the following technical solution: the multi-rotor heavy-duty UAV acquires tension value signals through multiple load-bearing rings, including the following steps: Based on the vertical component of the tension value of the bearing ring Calculate the total load weight or equivalent load weight G; and calculate the projected position coordinates of the resultant load point in the body coordinate system based on the position coordinates of the bearing ring. : ; ; In the formula, The tensile force value obtained for the i-th load-bearing pull ring; , (i) represents the initial position coordinates of the i-th load-bearing pull ring; n represents the number of load-bearing pull rings. According to the above Determine the load center of gravity offset, including the offset in the front-to-back direction. offset in the left and right directions ; Based on the aforementioned G, , Calculate pitch compensation moment With roll compensation torque : ; ; In the formula, and All are compensation coefficients; The obtained compensation torque is used to correct the basic control quantity output by the original attitude controller of the flight control device. The flight control device can then obtain the target thrust based on the corrected control quantity and complete the flight control.

[0006] As a preferred embodiment of the adaptive fault-tolerant flight control method for a multi-rotor heavy-duty unmanned aerial vehicle (UAV) according to the present invention, the method further includes designing a load safety judgment mechanism, specifically: If the load center of gravity offset exceeds the takeoff allowable threshold, it indicates that the load hanging position is unreasonable, the branch support rope lengths are inconsistent, or the load itself is severely unbalanced; the flight control device prohibits takeoff and prompts the operator to readjust the hanging position or redistribute the branch support rope lengths.

[0007] As a preferred embodiment of the adaptive fault-tolerant flight control method for a multi-rotor heavy-duty unmanned aerial vehicle (UAV) according to the present invention, the load safety judgment mechanism further includes: If the total load exceeds the maximum allowable load of the drone, the flight control device will prevent the drone's rotor power components from being unlocked and will output an overload alarm. The flight control device determines whether the tension signals from multiple load-bearing rings are unbalanced. If the tension in one line is significantly lower than the others, it indicates that the corresponding branch load-bearing rope is not taut, the load-bearing ring connection is abnormal, or the suspension rope is incorrectly attached. If the tension in one line is significantly higher than the others, it indicates that the load on the corresponding arm connection area is too high, posing a structural risk. At this time, the flight control device issues an abnormality warning to prevent the drone from taking off with a malfunction.

[0008] As a preferred embodiment of the adaptive fault-tolerant flight control method for a multi-rotor heavy-duty unmanned aerial vehicle (UAV) according to the present invention, the method further includes: defining a body coordinate system with the x-axis pointing forward of the UAV; the y-axis pointing to the right of the UAV; and the z-axis pointing vertically upward; generating an additional pitch moment when the load shifts forward, i.e., Δx>0; and generating an additional roll moment when the load shifts to the right, i.e., Δy>0. When the load center of gravity offset changes periodically and the amplitude of the change exceeds a set threshold, the flight control device determines that the load is in a swinging state and then introduces the offset change rate: ; ; in, Given the sampling period, the compensation torque after adding dynamic damping is: ; ; in, This is the offset compensation coefficient. This is the offset change rate compensation coefficient; The compensation torque is superimposed on the original attitude controller output: ; ; in, and This is the final control torque used for thrust distribution across the six rotor power units.

[0009] As a preferred embodiment of the adaptive fault-tolerant flight control method for a multi-rotor heavy-duty unmanned aerial vehicle (UAV) according to the present invention, wherein: when the flight control device determines that the load is in a swinging state, the control strategy includes: limiting the horizontal acceleration of the UAV; limiting the maximum tilt angle of the UAV; based on the... and Superimposed onto the attitude controller output; The overall load swing amplitude is calculated based on the amplitude of the forward and backward offset and the amplitude of the left and right offset within the preset sliding time window of the load resultant force application point. When the overall load swing amplitude continuously exceeds the safety threshold, the flight control device stops the current horizontal acceleration or turning action and controls the UAV to enter the hovering and swing reduction state. After the overall load swing amplitude is reduced to below the recovery threshold and remains below the preset time, the flight mission can continue, the flight can return to base at a limited speed, or the UAV can land safely.

[0010] As a preferred embodiment of the adaptive fault-tolerant flight control method for a multi-rotor heavy-duty unmanned aerial vehicle (UAV) described in this invention, the method further includes: the flight control device calculating a health score based on the deviation between the target speed and the actual speed of the motor, the operating current of the motor or ESC, the temperature of the motor or ESC, and the voltage of the power bus or corresponding power branch, including a speed health score. Current health score Temperature health score and voltage health score ; Based on all the above health scores, the health coefficient of the rotor power assembly is calculated using a weighted summation method: ; in, The value range is from 0 to 1; ,when When the value is close to 1, it indicates that the rotor power assembly is working normally; when... A decrease indicates a risk of reduced efficiency or abnormality in the rotor power assembly; when When the value is close to 0, it indicates that the rotor power component is seriously abnormal or has failed.

[0011] The flight control system redistributes fault-tolerant thrust in the following manner: ; Where W is the health weight matrix; when the health coefficient of a certain rotor power component decreases, the flight control device reduces the thrust allocation weight of that rotor power component and transfers some of the thrust demand to other healthy rotor power components.

[0012] As a preferred embodiment of the adaptive fault-tolerant flight control method for a multi-rotor heavy-duty unmanned aerial vehicle (UAV) described in this invention, wherein: the rotational speed health score Designed as follows: ; ; in, The rotational speed tracking error of the i-th group of rotor power components, For the target speed, This refers to the actual rotational speed. To prevent constants with a denominator of zero, The maximum permissible relative speed error; Current health rating Designed as follows: ; in, This is the current warning value. For the maximum allowable current, Ii The value of the current for the i-th rotor power component; Temperature Health Score Designed as follows: ; in, This is the temperature warning value. For the maximum allowable temperature, T i The temperature value of the i-th rotor power assembly; Voltage health rating Designed as follows: ; in, This is the voltage warning value. For the minimum permissible operating voltage, V i Let be the voltage value of the i-th rotor power component.

[0013] The present invention also discloses a multi-rotor heavy-duty unmanned aerial vehicle (UAV) for use in the above-mentioned adaptive fault-tolerant flight control method. The multi-rotor heavy-duty UAV includes a central carrier body, arm assemblies, rotor power assemblies, carrier assemblies, and landing gear assemblies. The landing gear assemblies are disposed below the central carrier body. One end of each arm assembly is connected to the central carrier body, and the other end is installed and connected to a set of rotor power assemblies. The boom assembly is evenly distributed around the central support body. The support component is located below the boom assembly. The support component includes multiple branch support ropes and a main support rope. Each branch support rope corresponds to a six-ring support. The six branch support ropes are connected to the six rings respectively, and then the six branch support ropes converge into a main support rope. The lower end of the main support rope is used to connect the heavy object to be lifted.

[0014] In a preferred embodiment of the multi-rotor heavy-duty unmanned aerial vehicle (UAV) of the present invention, the frame of the central supporting body includes: an upper supporting plate, a lower supporting plate, a circumferential reinforcing beam, and a center of gravity detection component; the upper and lower supporting plates are spaced apart vertically, and the circumferential reinforcing beam connects the upper and lower supporting plates; the center of gravity detection component is located inside the central supporting body on the side near the arm mounting cavity, and is connected to a tension detection element at the supporting pull ring for collecting, filtering, and processing tension signals; The central support body is also provided with a battery installation area, an arm installation cavity, and a flight control installation area. The battery installation area is located on the central support body and is used to install the power battery pack. The flight control installation area is used to install the flight control device, inertial measurement unit, positioning module, communication module and related control circuits. The arm installation cavity is used to insert, sleeve or fix the corresponding arm components.

[0015] In a preferred embodiment of the multi-rotor heavy-duty unmanned aerial vehicle (UAV) of the present invention, the arm assembly is configured as six groups, and the included angle between two adjacent groups of arm assemblies is 60°.

[0016] The beneficial effects of this invention are: 1. The method of the present invention can obtain the load distribution of the six arm connection areas in real time. It can not only estimate the total load weight, but also calculate the point of application of the load resultant force and the center of gravity offset, and introduce them into the multi-rotor thrust distribution process. It can perform pre-compensation before the attitude deflection is obvious, and reduce attitude lag and control oscillation during heavy load sling flight.

[0017] 2. This invention utilizes multiple branched load-bearing ropes that engage with load-bearing pull rings, allowing the load weight to be shared by multiple arm connection areas, reducing localized stress concentration on the central frame caused by single-point loading. Furthermore, the main load-bearing rope, when taut and vertical, is located near the UAV's central axis, which helps to bring the resultant load force closer to the aircraft's center, reducing the initial eccentric moment caused by the suspended load on the UAV's attitude.

[0018] 3. This invention combines load eccentricity compensation and power anomaly fault-tolerant control, which can redistribute thrust when the efficiency of a certain rotor power component decreases or malfunctions, thereby improving the emergency safety of heavy-load UAVs. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a schematic diagram of the overall structure of a multi-rotor heavy-duty unmanned aerial vehicle proposed in this invention; Figure 2 for Figure 1 A schematic diagram of the state of a multi-rotor heavy-duty drone when it is carrying a load; Figure 3 for Figure 1 A schematic diagram of the frame structure of the central supporting body of a multi-rotor unmanned aerial vehicle with heavy load capacity; Figure 4 This is a schematic diagram of the overall process of an adaptive fault-tolerant flight control method for a multi-rotor heavy-duty unmanned aerial vehicle proposed in this invention; In the diagram: 1. Central load-bearing frame; 2. Arm assembly; 3. Rotor power assembly; 4. Load-bearing assembly; 5. Landing gear assembly; 6. Branch load-bearing rope; 7. Main load-bearing rope; 1-1. Upper load-bearing plate; 1-2. Lower load-bearing plate; 1-3. Circumferential reinforcing beam; 1-4. Battery mounting area; 1-5. Load-bearing pull ring; 1-6. Arm mounting cavity; 1-7. Flight control mounting area; 1-8. Center of gravity detection assembly. Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0023] Example 1 Reference Figures 1-2 In one embodiment of the present invention, a multi-rotor heavy-duty unmanned aerial vehicle (UAV) is provided, which includes a central load-bearing body 1, an arm assembly 2, six sets of rotor power assemblies 3, a load-bearing assembly 4, and a landing gear assembly 5.

[0024] The central support body 1 is located in the middle of the UAV's fuselage and serves as the main load-bearing foundation for the entire aircraft. Arm assemblies 2 are evenly distributed along the circumference of the central support body 1. For example, there are six sets of arm assemblies 2, and the included angle between adjacent sets of arm assemblies 2 is preferably 60°. One end of each set of arm assemblies 2 is connected to the central support body 1, and the other end is equipped with a set of rotor power assemblies 3. The six sets of rotor power assemblies 3 together generate the lift required for the UAV's takeoff, hovering, attitude adjustment, and flight.

[0025] In this embodiment, the UAV's wheelbase is approximately two meters. Wheelbase can be understood as the distance between the motor axes of the two opposing sets of rotor power components 3. The two-meter wheelbase gives the UAV a larger power layout radius and payload mounting space, but it also lengthens the arm assembly 2, causing the arm root and central load-bearing body 1 to bear greater bending and torque moments. Therefore, in this embodiment, the central load-bearing body 1 adopts a box-type structure with upper and lower plates and circumferential reinforcing beams to improve overall bending and torsional resistance.

[0026] The load-bearing assembly 4 is located below the boom assembly 2, that is, below the central load-bearing body 1. Unlike the traditional single-point hook structure, the six load-bearing assemblies 4 adopt a six-point force-sharing method, that is, six branch load-bearing ropes 6 are respectively connected to six load-bearing pull rings 1-5, and the six branch load-bearing ropes 6 are then converged into a main load-bearing rope 7. The main load-bearing rope 7 is used to connect to the heavy object, hook, cargo box or sling.

[0027] Specifically, the load-bearing assembly 4 includes six branch load-bearing ropes 6 and one main load-bearing rope 7. The six branch load-bearing ropes 6 correspond to six load-bearing loops 1-5. One end of each branch load-bearing rope 6 is connected to the corresponding load-bearing loop 1-5, or passes through the corresponding load-bearing loop 1-5 and extends downwards; the other ends of the six branch load-bearing ropes converge below the central load-bearing body 1 and then connect to the main load-bearing rope 7. The lower end of the main load-bearing rope 7 is used to connect to the load to be lifted. The load to be lifted can be a cargo box, equipment, material package, basket, agricultural materials, or other loads. The main load-bearing rope 7 can be connected to the load to be lifted via a hook, lock, shackle, quick-release connector, or safety locking device.

[0028] Under ideal load-bearing conditions, the six branch load-bearing ropes 6 are of equal length or matched according to a preset length, so that the main load-bearing rope 7 is located near the central axis of the UAV body in a taut and vertical state. Here, the central axis of the body refers to the axis that passes through the geometric center of the central load-bearing body 1 and is perpendicular to the upper load-bearing plate 1-1. By bringing the main load-bearing rope close to the central axis of the body, the resultant force of the load to be lifted can pass through the central area of ​​the UAV as much as possible, reducing the initial eccentric moment.

[0029] Compared to single-point mounting, the six-point load-bearing system offers better structural stress distribution. When a load is pulled downwards by the main load-bearing rope, this force is distributed to six branch load-bearing ropes, which then transmit it to six load-bearing rings 1-5. These six load-bearing rings 1-5 are positioned near the six boom mounting cavities 1-6, allowing the load force to be transmitted to the central load-bearing body 1 along the six circumferential support positions, thereby improving load distribution and load-bearing stability.

[0030] Furthermore, when the load experiences slight swaying or is affected by external wind disturbances, the tension distribution of the six branch load-bearing ropes will change. By detecting the tension changes at the six load-bearing rings 1-5, it is possible to determine whether the load is eccentric, swaying, or experiencing abnormal impacts, providing a basis for the flight control device to perform attitude compensation.

[0031] The landing gear assembly 5 is located below the central load-bearing body 1 and is used to support the entire aircraft on the ground. The landing gear assembly 5 can adopt a skid-type, outrigger-type, or combined structure to provide sufficient installation and swing space for the load-bearing assembly 4 and the load to be lifted during takeoff and landing.

[0032] Reference Figure 3 The frame of the central support body 1 includes: upper support plate 1-1, lower support plate 1-2, circumferential reinforcing beam 1-3 and center of gravity detection component 1-8; the central support body 1 also has a battery mounting area 1-4, an arm mounting cavity 1-6 and a flight control mounting area 1-7.

[0033] The upper bearing plate 1-1 and the lower bearing plate 1-2 are spaced apart vertically, and the circumferential reinforcing beam 1-3 connects the upper bearing plate 1-1 and the lower bearing plate 1-2. The upper bearing plate 1-1, the lower bearing plate 1-2, and the circumferential reinforcing beam 1-3 together form a closed bearing structure similar to a box girder. This structure can increase the moment of inertia of the central bearing body 1, giving it better bending and torsional resistance during heavy-load flight.

[0034] Battery mounting areas 1-4 are located on the central supporting body 1 and are used to mount the power battery pack. Preferably, battery mounting areas 1-4 are arranged close to the center of the central supporting body 1 to reduce the impact of battery weight on the airframe's center of gravity. Flight control mounting areas 1-7 are used to mount the flight control unit, inertial measurement unit, positioning module, communication module, and related control circuits. Preferably, flight control mounting areas 1-7 are located in a position with less vibration and close to the airframe center to improve attitude measurement and control stability.

[0035] There are six arm mounting cavities 1-6, located in the six circumferential connection areas of the central supporting body 1. Each arm mounting cavity 1-6 is used for insertion, sleeve connection, or fixation of the corresponding arm assembly 2. The arm assembly 2 can be connected to the arm mounting cavity 1-6 via bolts, locating pins, sleeves, snap-fit ​​fittings, or adhesive fittings. For a two-meter wheelbase UAV, the arm mounting cavities 1-6 not only serve a connecting function but also bear the responsibility of transmitting bending moment and torque at the root of the arm.

[0036] Six load-bearing pull rings 1-5 are provided, respectively arranged near the six boom mounting cavities 1-6. Each load-bearing pull ring 1-5 is located below the central load-bearing body 1, or it can be located below the boom assembly 2 near the root. Because the load-bearing pull rings 1-5 are arranged close to the boom root, the tensile force generated by the suspended load can be directly transmitted to the boom connection area and the central load-bearing body 1, thereby forming a distributed load-bearing path and reducing local stress concentration caused by single-point loading.

[0037] The center of gravity detection assembly 1-8 is located inside the central support body 1 near the arm mounting cavity 1-6 or near the flight control mounting area 1-7. The center of gravity detection assembly 1-8 is connected to the tension detection elements at the six support rings 1-5, used for acquiring, filtering, and processing six tension signals. Each support ring 1-5 has a tension detection element at its mounting position. The tension detection element can be located between the support ring 1-5 and the central support body 1, at the pin connection position of the support ring 1-5, or integrated with the support ring 1-5. The tension detection element can be a pin-type tension sensor, a ring-type tension sensor, a tension / compression sensor, a strain gauge sensor, or a load cell. The tension detection element is used to detect the tension value borne by the corresponding support ring 1-5.

[0038] Example 2 Reference Figure 4 The adaptive fault-tolerant flight control method for a multi-rotor heavy-duty unmanned aerial vehicle (UAV) applied in Example 1, taking a six-rotor heavy-duty UAV as an example, specifically includes the following steps: Step 1: Collect the tension value signals corresponding to the 6 load-bearing pull rings 1-5 to obtain six channels, which are recorded as follows: The positions of the six load-bearing pull rings 1-5 in the body coordinate system are denoted as follows: ; Calculate the total load weight or equivalent load weight G based on the vertical component tensile force values ​​from the six channels (collected by a multi-axis force sensor): In the formula, This represents the vertical component corresponding to the six tension value signals.

[0039] Step 2: Calculate the projected coordinates of the point of application of the resultant load in the body coordinate system based on the six tensile force values, the vertical component, and the position coordinates of the six load-bearing rings 1-5. : ; ; When the load is centered and the main load-bearing rope remains vertical, the tension distribution at the six load-bearing rings 1-5 is approximately symmetrical, and the calculated... Approaching the center of the machine body. When the load shifts or swings in a certain direction, the tension of the load-bearing pull ring 1-5 closer to that direction increases, and the tension of the load-bearing pull ring 1-5 farther away from that direction decreases, as calculated. It then shifts.

[0040] Let the reference position under standard conditions be: ; The load center of gravity offset is: ; .

[0041] in, This indicates the offset of the load in the forward and backward directions. This indicates the offset of the load in the left-right direction.

[0042] To reduce the impact of propeller vibration, instantaneous load impact, and sensor noise, the six-channel thrust signals are filtered. Filtering methods can include moving average filtering, first-order low-pass filtering, median filtering, or Kalman filtering. For example: ;in, This represents the filtered tension value of the i-th path. This is the filtering result from the previous time step. These are the filter coefficients.

[0043] Step 3: The flight control system calculates the compensation torque based on the load center of gravity offset obtained in Step 2. When the load shifts forward, the UAV will generate an additional pitch torque; when the load shifts to the left or right, the UAV will generate an additional roll torque. If the flight control system only makes feedback adjustments after a significant change in attitude angle, it is prone to attitude lag and control oscillation.

[0044] Therefore, in this invention, the load center of gravity offset is directly incorporated into the thrust distribution process. The flight control unit calculates the compensation torque as follows: ; ; in, To compensate for pitch torque, G is the roll compensation torque, and G is the equivalent weight of the load. and This is the compensation coefficient.

[0045] Step 4: The original attitude controller of the flight control unit outputs the basic control quantity. for: ;in For total lift requirements, Based on the rolling moment, Based on the pitching moment, Based on the yaw moment.

[0046] After introducing the compensation torque calculated in the above process, the control quantity will be... Revised to: The flight control system can then calculate the target thrust of the six rotor power units 3 based on the corrected control quantity U. ,in, For the first The target thrust of rotor power assembly 3.

[0047] Through the above-mentioned step three process, when the load becomes eccentric or swings, the flight control device can adjust the thrust output of the six sets of rotor power components 3 in advance according to the changes in the six-point pull, so that the UAV has a faster compensation capability for load disturbances.

[0048] In summary, before the drone takes off, the flight control system first reads the tension values ​​at points 1-5 of the six load-bearing rings and performs a load safety assessment. Specifically, this includes: 1. The flight control unit calculates the total load weight or equivalent load weight based on the six-channel thrust values. If the total load weight exceeds the maximum permissible load of the UAV, the flight control unit will prevent the rotor power assembly 3 from being unlocked and will output an overload alarm.

[0049] 2. The flight control system calculates the point of application of the resultant load force and the center of gravity offset. If the load center of gravity offset exceeds the allowable takeoff threshold, it indicates that the load's suspension position is unreasonable, the branch support rope lengths are inconsistent, or the load itself is severely unbalanced. In this case, the flight control system can prohibit takeoff and prompt the operator to readjust the suspension position or redistribute the branch support rope lengths.

[0050] 3. The flight control system determines whether the six tension values ​​are significantly unbalanced. If the tension in one direction is significantly lower than the others, it may indicate that the corresponding branch's load-bearing rope is not taut, the load-bearing ring connection is abnormal, or the suspension rope is incorrectly attached. If the tension in one direction is significantly higher than the others, it may indicate that the corresponding arm connection area is under excessive load, posing a structural risk. In this case, the flight control system can issue an abnormality warning to prevent the drone from taking off with a malfunction.

[0051] This pre-flight safety assessment can detect overload, off-center loading, and abnormal hoisting before the drone takes off, improving the safety of heavy-load flights.

[0052] During flight, if the load to be hoisted swings, the tension values ​​at the six load-bearing rings 1-5 will change periodically. For example, when the load swings forward, the tension at the front load-bearing ring 1-5 increases, and the tension at the rear load-bearing ring 1-5 decreases; when the load swings backward, the rear tension increases, and the front tension decreases.

[0053] The center of gravity detection components 1-8 can identify the load oscillation state based on the amplitude and frequency of the changes in the six-channel tension values. When the load center of gravity offset changes periodically and the amplitude of the change exceeds a set threshold, the flight control device determines that the load is in an oscillation state.

[0054] First, define the aircraft coordinate system so that the x-axis points forward of the UAV; the y-axis points to the right of the UAV; and the z-axis points vertically upward. When the load shifts forward (Δx > 0), an additional pitching moment will be generated; when the load shifts to the right (Δy > 0), an additional roll moment will be generated. The additional moments generated by the load shift are: ; ; Where G is the total load weight or equivalent load weight. Add torque in the roll direction, An additional torque is applied in the pitch direction. To counteract this additional torque, the flight control system applies a compensating torque in the opposite direction: ; ; in, This refers to the roll compensation torque during the oscillating state. The pitch compensation torque occurs during the oscillation state. and These are compensation coefficients set based on the UAV's load, wheelbase, and attitude response characteristics. A rate of change of offset is introduced to account for load oscillation. ; ; in, Given the sampling period, the compensation torque after adding dynamic damping is: ; ; in, This is the offset compensation coefficient. This is the offset change rate compensation coefficient.

[0055] The compensation torque is then superimposed on the original attitude controller output: ; ; in, and This is the final control torque used for thrust distribution across the six rotor power units.

[0056] In load oscillation suppression mode, the flight control system can adopt the following control strategies: First, limit the horizontal acceleration of the drone to avoid further excitation of load swing due to rapid acceleration and deceleration of the airframe; Second, limit the maximum tilt angle of the drone to keep the main support rope as close to vertical as possible; Third, based on the static offset components (Δx and Δy in step four), dynamic offset components (Δx and Δy in the swing state in step five), and dynamic offset change rate of the load resultant force point, the roll anti-sway compensation torque and pitch anti-sway compensation torque are calculated by combining static off-center load feedforward compensation and dynamic swing proportional-differential damping compensation, and the anti-sway compensation torque is superimposed on the attitude controller output.

[0057] Fourth, the overall load swing amplitude is calculated based on the amplitudes of the forward and backward and left and right offsets of the load resultant force application point within a preset sliding time window. When the overall load swing amplitude continuously exceeds the safety threshold, the flight control device stops the current horizontal acceleration or turning action and controls the UAV to enter a hovering and sway-reducing state. After the overall load swing amplitude decreases below the recovery threshold and remains below it for a preset time, the flight mission continues, the flight returns at a limited speed, or the UAV lands safely. Specifically: Within a sliding time window containing N sampling points, the amplitude of the forward and backward oscillation is: Forward and backward swing amplitude A x for: ; Left and right swing amplitude A y for: ; Comprehensive swing amplitude A s for: ; Through the above methods, this embodiment can not only detect static load eccentricity, but also identify dynamic swaying during flight, thereby improving the stability of sling transport.

[0058] In one embodiment, the hexacopter heavy-duty UAV experiences a significant load on its rotor power assembly 3 under heavy load conditions. If a rotor power assembly 3 experiences insufficient motor speed, ESC current limiting, motor overheating, blade damage, or decreased thrust response, the actual thrust generated by that power shaft may be lower than the target thrust commanded by the flight control system.

[0059] The flight control system calculates a health score based on the deviation between the target speed and the actual speed of the motor, the operating current of the motor or ESC, the temperature of the motor or ESC, and the voltage of the power bus or corresponding power branch. Speed ​​Health Rating for: ; ; in, The rotational speed tracking error of the i-th group of rotor power components, For the target speed, This refers to the actual rotational speed. To prevent constants with a denominator of zero, This represents the maximum permissible relative speed error.

[0060] Current health rating It can be represented as: ; in, This is the current warning value. For the maximum allowable current, I iLet be the current value of the i-th rotor power component.

[0061] Temperature Health Score for: ; in, This is the temperature warning value. For the maximum allowable temperature, T i Let be the temperature value of the i-th rotor power assembly.

[0062] Voltage health rating for: ; in, This is the voltage warning value. For the minimum permissible operating voltage, V i Let be the voltage value of the i-th rotor power component.

[0063] Based on all the above health scores, the health status of the six groups of rotor power components 3 is determined. The health coefficient of the i-th group of rotor power components 3 is calculated by weighted summation and denoted as: ; in, The value range is from 0 to 1; .when When the value is close to 1, it indicates that the rotor power assembly 3 is working normally; when... A decrease indicates a risk of reduced efficiency or abnormality in the rotor power assembly 3; when When the value is close to 0, it indicates that the rotor power component 3 is seriously abnormal or has failed.

[0064] The flight control system can redistribute fault-tolerant thrust in the following manner: ; Where W is the health weight matrix.

[0065] When the health coefficient of a certain rotor power component 3 decreases, the flight control device reduces the thrust distribution weight of that rotor power component 3 and transfers some thrust demand to other healthy rotor power components 3. If the abnormality is minor, the UAV maintains mission flight or enters a speed-limited flight state; if the abnormality is severe, the UAV enters a speed-limited return-to-home or safe landing mode.

[0066] During fault-tolerant control, the flight control system prioritizes roll and pitch stability, followed by altitude maintenance, and then yaw control. For heavy-load sling-mounted UAVs, roll and pitch stability are directly related to load sway and overall aircraft safety, and therefore should be given the highest priority.

[0067] In summary, the complete workflow of a two-meter wheelbase hexacopter heavy-duty UAV is as follows: The operator connects the load to be hoisted to the main load-bearing rope; six branch load-bearing ropes are connected to or pass through six load-bearing pull rings 1-5 respectively, and converge below the central load-bearing frame 1. The flight control device reads the tension values ​​at the six load-bearing pull rings 1-5 and calculates the total load weight; the flight control device calculates the point of application of the resultant force of the load based on the six tension values ​​and the positions of the six load-bearing pull rings 1-5; the flight control device determines whether the load weight and the load center of gravity offset meet the takeoff conditions; if the takeoff conditions are met, the flight control device allows the rotor power assembly 3 to unlock and controls the UAV to take off; if the takeoff conditions are not met, takeoff is prohibited and an alarm is output; during flight, the center of gravity detection assembly 1-8 continuously collects the six tension values ​​and calculates the point of application of the resultant force of the load in real time, and estimates the load offset accordingly; the flight control device calculates the roll compensation moment and pitch compensation moment based on the load center of gravity offset. Compensating torque; the flight control unit superimposes the compensating torque onto the attitude control commands and recalculates the target thrust of the six sets of rotor power components 3; the flight control unit monitors the working status of the six sets of rotor power components 3 in real time and calculates the health coefficient of each rotor power component 3; when the health coefficient of any rotor power component 3 decreases, the flight control unit performs fault-tolerant thrust redistribution; when the load swing, load offset, or power anomaly exceeds the safety threshold, the flight control unit controls the UAV to enter the speed-limited return-to-home or safe landing mode; after the UAV lands, the flight control unit records the six-channel thrust change, maximum load weight, maximum center of gravity offset, and power anomaly information for subsequent maintenance and flight safety analysis.

[0068] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An adaptive fault-tolerant flight control method for a multi-rotor heavy-duty unmanned aerial vehicle, characterized in that, The multi-rotor heavy-duty drone acquires tension value signals through multiple load-bearing rings, including the following steps: Based on the vertical component of the tension value of the bearing ring Calculate the total load weight or equivalent load weight G; and calculate the projected position coordinates of the resultant load point in the body coordinate system based on the position coordinates of the bearing ring. : ； ； In the formula, The tensile force value obtained for the i-th load-bearing pull ring; (x i ,y i (i) represents the initial position coordinates of the i-th load-bearing pull ring; n represents the number of load-bearing pull rings. According to the above Determine the load center of gravity offset, including the offset in the front-to-back direction. , offset in the left and right directions ; Based on the aforementioned G, , Calculate pitch compensation moment With roll compensation torque : ； ； In the formula, and All are compensation coefficients; The obtained compensation torque is used to correct the basic control quantity output by the original attitude controller of the flight control device. The flight control device obtains the target thrust based on the corrected control quantity and completes flight control.

2. The adaptive fault-tolerant flight control method for a multi-rotor heavy-duty unmanned aerial vehicle according to claim 1, characterized in that: The method also includes designing a load safety judgment mechanism, specifically: If the load center of gravity offset exceeds the takeoff allowable threshold, it indicates that the load hanging position is unreasonable, the branch support rope lengths are inconsistent, or the load itself is severely unbalanced; the flight control device prohibits takeoff and prompts the operator to readjust the hanging position or redistribute the branch support rope lengths.

3. The adaptive fault-tolerant flight control method for a multi-rotor heavy-duty unmanned aerial vehicle according to claim 2, characterized in that: The load safety assessment mechanism also includes: If the total load exceeds the maximum allowable load of the drone, the flight control device will prevent the drone's rotor power components from being unlocked and will output an overload alarm. The flight control device determines whether the tension signals from multiple load-bearing rings are unbalanced. If the tension in one line is significantly lower than the others, it indicates that the corresponding branch load-bearing rope is not taut, the load-bearing ring connection is abnormal, or the suspension rope is incorrectly attached. If the tension in one line is significantly higher than the others, it indicates that the load on the corresponding arm connection area is too high, posing a structural risk. At this time, the flight control device issues an abnormality warning to prevent the drone from taking off with a malfunction.

4. The adaptive fault-tolerant flight control method for a multi-rotor heavy-duty unmanned aerial vehicle according to claim 1, characterized in that: The method also includes: defining a body coordinate system with the x-axis pointing forward of the UAV; the y-axis pointing to the right of the UAV; and the z-axis pointing vertically upward; generating an additional pitch moment when the load shifts forward, i.e., Δx>0; and generating an additional roll moment when the load shifts to the right, i.e., Δy>0. When the load center of gravity offset changes periodically and the amplitude of the change exceeds a set threshold, the flight control device determines that the load is in a swinging state and then introduces the offset change rate: ； ； in, Given the sampling period, the compensation torque after adding dynamic damping is: ； ； in, This is the offset compensation coefficient. This is the offset change rate compensation coefficient; The compensation torque is superimposed on the original attitude controller output: ； ； in, and This is the final control torque used for thrust distribution across the six rotor power units.

5. The adaptive fault-tolerant flight control method for a multi-rotor heavy-duty unmanned aerial vehicle according to claim 4, characterized in that: When the flight control device determines that the load is in a swinging state, the control strategy includes: limiting the horizontal acceleration of the UAV; limiting the maximum tilt angle of the UAV; based on the... and Superimposed onto the attitude controller output; The overall load swing amplitude is calculated based on the amplitude of the forward and backward offset and the amplitude of the left and right offset within the preset sliding time window of the load resultant force application point. When the overall load swing amplitude continuously exceeds the safety threshold, the flight control device stops the current horizontal acceleration or turning action and controls the UAV to enter the hovering and swing reduction state. After the overall load swing amplitude is reduced to below the recovery threshold and remains below the preset time, the flight mission can continue, the flight can return to base at a limited speed, or the UAV can land safely.

6. The adaptive fault-tolerant flight control method for a multi-rotor heavy-duty unmanned aerial vehicle according to claim 1, characterized in that: The method also includes: the flight control device calculating a health score based on the deviation between the target speed and the actual speed of the motor, the operating current of the motor or ESC, the temperature of the motor or ESC, and the voltage of the power bus or corresponding power branch, including: speed health score. Current health score Temperature health score and voltage health score ; Based on all the above health scores, the health coefficient of the rotor power assembly is calculated using a weighted summation method: ; in, The value range is from 0 to 1; ,when When the value is close to 1, it indicates that the rotor power assembly is working normally; when... A decrease indicates a risk of reduced efficiency or abnormality in the rotor power assembly; when A value close to 0 indicates a serious malfunction or failure of the rotor power assembly; The flight control system redistributes fault-tolerant thrust in the following manner: ； Where W is the health weight matrix; when the health coefficient of a certain rotor power component decreases, the flight control device reduces the thrust allocation weight of that rotor power component and transfers some of the thrust demand to other healthy rotor power components.

7. The adaptive fault-tolerant flight control method for a multi-rotor heavy-duty unmanned aerial vehicle according to claim 6, characterized in that: The speed health score Designed as follows: ； ； in, The rotational speed tracking error of the i-th group of rotor power components, For the target speed, This refers to the actual rotational speed. To prevent constants with a denominator of zero, The maximum permissible relative speed error; Current health rating Designed as follows: ； in, This is the current warning value. For the maximum allowable current, I i The value of the current for the i-th rotor power component; Temperature Health Score Designed as follows: ； in, This is the temperature warning value. For the maximum permissible temperature, T i The temperature value of the i-th rotor power assembly; Voltage health rating Designed as follows: ； in, This is the voltage warning value. For the minimum permissible operating voltage, V i Let be the voltage value of the i-th rotor power component.

8. A multi-rotor heavy-duty unmanned aerial vehicle (UAV) using the adaptive fault-tolerant flight control method for a multi-rotor heavy-duty UAV as described in any one of claims 1-7, characterized in that: The multi-rotor heavy-duty UAV includes a central carrier body (1), arm assembly (2), rotor power assembly (3), carrier assembly (4), and landing gear assembly (5); the landing gear assembly (5) is located below the central carrier body (1); one end of each arm assembly (2) is connected to the central carrier body (1), and the other end is installed and connected to a set of rotor power assemblies (3); The boom assembly (2) is evenly distributed around the central load-bearing body (1). The load-bearing assembly (4) is located below the boom assembly (2). The load-bearing assembly (4) includes multiple branch load-bearing ropes (6) and a main load-bearing rope (7). Each branch load-bearing rope (6) corresponds to a six-ring load-bearing loop (1-5). The six branch load-bearing ropes (6) cooperate with the six ring load-bearing loops (1-5) respectively, and then the six branch load-bearing ropes (6) converge into a main load-bearing rope (7). The lower end of the main load-bearing rope (7) is used to connect the heavy object to be lifted.

9. A multi-rotor heavy-duty unmanned aerial vehicle according to claim 8, characterized in that: The frame of the central bearing body (1) includes: an upper bearing plate (1-1), a lower bearing plate (1-2), a circumferential reinforcing beam (1-3), and a center of gravity detection component (1-8); the upper bearing plate (1-1) and the lower bearing plate (1-2) are arranged at intervals, and the circumferential reinforcing beam (1-3) is connected between the upper bearing plate (1-1) and the lower bearing plate (1-2); the center of gravity detection component (1-8) is located inside the central bearing body (1) on the side near the arm mounting cavity (1-6), and the center of gravity detection component (1-8) is connected to the tension detection element at the bearing pull ring (1-5) for collecting, filtering, and processing tension signals; The central support body (1) is also provided with a battery installation area (1-4), an arm installation cavity (1-6), and a flight control installation area (1-7). The battery installation area (1-4) is located on the central support body (1) and is used to install the power battery pack. The flight control installation area (1-7) is used to install the flight control device, inertial measurement unit, positioning module, communication module and related control circuits. The arm installation cavity (1-6) is used to insert, sleeve or fix the corresponding arm assembly (2).

10. A multi-rotor heavy-duty unmanned aerial vehicle according to claim 8, characterized in that: The arm assembly (2) is configured as six groups, and the included angle between two adjacent groups of arm assemblies (2) is 60°.

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