A cable tension fault-tolerant distribution method and system of a multi-unmanned aerial vehicle hoisting system

Abstract

This invention belongs to the field of multi-UAV hoisting control technology, specifically relating to a fault-tolerant cable tension allocation method and system for a multi-UAV hoisting system. The method first detects the operating status of the multi-UAV hoisting system in real time to determine whether it is in a normal thrust mode or a thrust failure mode. If in the normal thrust mode, a zero-space cable tension allocation method is used for cable tension allocation; if in the thrust failure mode, a cable tension allocation method incorporating load safety constraints is used. The load safety constraint method aims to minimize the deviation between the actual tension vector of the cable to be optimized and the desired tension vector of the cable. The load safety constraint is a second-order CBF constraint constructed for the multi-UAV hoisting system facing obstacles. This invention can achieve fault-tolerant cable tension allocation while ensuring the safety of the load and UAV obstacle avoidance.

Description

Technical Field

[0001] This invention belongs to the field of multi-UAV hoisting control technology, specifically relating to a cable tension fault-tolerant distribution method and system for a multi-UAV hoisting system. Background Technology

[0002] Multi-rotor unmanned aerial vehicles (UAVs) are widely used in both military and civilian fields such as reconnaissance and surveillance, aerial patrol, disaster relief, and cargo transportation due to their superior vertical takeoff and landing capabilities, excellent maneuverability, and high adaptability to complex scenarios. Robust control strategies such as sliding mode control (SMC), two-stage active disturbance rejection control (ADRC), control Lyapunov function (CLF), and nonlinear model predictive control (NMPC) have become the focus of current research. The paper "A Multi-UAV Load-Bearing Full Attitude Control Method Based on Nonlinear Model Predictive Control (NMPC)" considers UAV obstacle avoidance and cable tension constraints in system modeling. However, this method does not consider the cable tension distribution problem under UAV thrust-limited fault scenarios, and cannot achieve active fault tolerance, resulting in an imbalance in cable tension distribution. Summary of the Invention

[0003] The purpose of this invention is to address the aforementioned problems in the existing technology by providing a method and system for cable tension fault-tolerant distribution in a multi-UAV hoisting system that can achieve cable tension fault-tolerant distribution in UAV thrust-limited fault scenarios while meeting load obstacle avoidance requirements.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] In a first aspect, the present invention provides a cable tension fault-tolerant distribution method for a multi-UAV hoisting system, the cable tension fault-tolerant distribution method comprising:

[0006] S1. Real-time detection of the operating status of the multi-UAV hoisting system, and determination of whether the multi-UAV hoisting system is in normal thrust mode or thrust failure mode based on the operating status of the multi-UAV hoisting system.

[0007] S2. If the thrust is in normal mode, the zero-space cable tension distribution method is used for cable tension distribution; if the thrust is in fault mode, the cable tension distribution method with load safety constraints is used for cable tension distribution.

[0008] The cable tension allocation method incorporating load safety constraints includes: allocating cable tension with the optimization objective of minimizing the deviation between the actual cable tension vector and the desired cable tension vector; solving the optimization objective under load safety constraints, maximum cable tension constraints of the UAV, and spatial obstacle avoidance constraints to obtain the optimal actual cable tension vector; and allocating cable tension based on the optimal actual cable tension vector. The load safety constraint is a second-order CBF constraint constructed for the multi-UAV hoisting system facing obstacles.

[0009] The cable tension distribution method that introduces load safety constraints specifically includes:

[0010] The cable tension distribution method that introduces load safety constraints specifically includes:

[0011] A1. Define the desired resultant force vector. ,in This indicates the expected resultant force of the load. The desired resultant torque of the load is represented by a row vector in the load coordinate system consisting of all desired tension vectors of the cables. ,in For the first The desired tension vector of the cable in the load coordinate system is then: , ,in For the first The position vector of the suspension point of the cable in the load coordinate system. The number of cables is equal to the number of drones.

[0012] set up for The antisymmetric matrix, then , ,in It is a 3-order identity matrix;

[0013] definition If is a constant full-rank matrix, then ,in A constant full-rank matrix The pseudo-inverse matrix;

[0014] A2. The optimized objective function expression is constructed as follows:

[0015] ;

[0016] In the above formula, This is a column vector consisting of the actual tension of all cables. These are the weighting coefficients; , All are gain coefficients; For the first The position of an obstacle in an inertial coordinate system; For relaxation terms, This is the rotation matrix used to transfer a vector from the load coordinate system to the inertial coordinate system; For relaxation term The weight matrix, , , These are the tension matching weights and the torque matching weights, respectively. For load speed; For the nominal case, the first The maximum cable tension that a drone can provide, , For the first The maximum thrust of the drone; , The first frame and the first The desired position of the drone in the inertial coordinate system; For load location; , These are the safe distance thresholds between drones and the safe distance thresholds between drones and obstacles, respectively. The threshold for safe obstacle avoidance distance for the load; For the first The maximum cable tension that a thrust-failed drone can provide. For the first The maximum cable tension that a normally thrusting drone can provide; For the first The actual tension of the cable; Indicates the sensor's actual measurement of the first The actual tension direction of the cable. ; It is the acceleration due to gravity; For the first The length of the cable; For load quality;

[0017] Solving the above objective function yields the optimal actual tension vector of the cable, and the cable tension is then distributed based on this optimal actual tension vector.

[0018] The first The maximum cable tension that a faulty drone can provide It is generated based on the fault discount factor:

[0019] ;

[0020] In the above formula, This is a fault discount factor, which is set according to the thrust fault type of the faulty UAV. .

[0021] The zero-space cable tension distribution method includes:

[0022] B1. Define the desired resultant force vector ,in This indicates the expected resultant force of the load. Represents the expected resultant torque of the load, and is defined as a column vector consisting of the expected tension vectors of all cables in the load coordinate system. ,in For the first The desired tension vector of the cable in the load coordinate system. Let be the number of cables; then we have , ,in For the first The position vector of the suspension point of the cable in the load coordinate system;

[0023] Define a full-rank matrix ,in It is a 3-order identity matrix. for For an antisymmetric matrix, then we have ;

[0024] Define the zero-space tension vector ,in A full-rank matrix The zero-space constant basis matrix, Let be the corresponding coordinate vector, then we have ,in A full-rank matrix The pseudo-inverse matrix, ;

[0025] B2. Construct an optimization model for the desired thrust scalar value, solve the model to obtain the optimal null coordinate vector, and calculate the optimal actual cable tension vector for each UAV based on the optimal null coordinate vector; the expression of the optimization model for the desired thrust scalar value is:

[0026] ;

[0027] In the above formula, for The adjustment amount; For the nominal case, the first The maximum cable tension that a drone can provide, , For the first The maximum thrust of the drone; This is the gain coefficient; , The first frame and the first The desired position of the drone in the inertial coordinate system; For load location; , These are the safe distance thresholds between drones and the safe distance threshold between a drone and an obstacle, respectively. For the first The position of an obstacle in an inertial coordinate system; This is the rotation matrix used to transfer a vector from the load coordinate system to the inertial coordinate system; For the first The length of the cable.

[0028] Secondly, the present invention provides a cable tension fault-tolerant distribution system for a multi-UAV hoisting system, the cable tension fault-tolerant distribution system comprising:

[0029] The thrust status detection module is used to detect the operating status of the multi-UAV hoisting system in real time, and determine whether the multi-UAV hoisting system is in normal thrust mode or thrust failure mode based on the operating status of the multi-UAV hoisting system.

[0030] The first cable tension distribution module is used to distribute cable tension using the zero-space cable tension distribution method when the multi-UAV hoisting system is in thrust normal mode.

[0031] The second cable tension distribution module is used to distribute cable tension in a load-safety-constrained cable tension distribution method when the multi-UAV hoisting system is in thrust failure mode. This load-safety-constraint method includes: optimizing the cable tension distribution by minimizing the deviation between the actual cable tension vector and the desired cable tension vector; solving the optimization objective under load safety constraints, maximum cable tension constraints of the UAVs, and spatial obstacle avoidance constraints to obtain the optimal actual cable tension vector; and then distributing cable tension based on this optimal actual cable tension vector. The load safety constraints are second-order CBF constraints constructed for the multi-UAV hoisting system facing obstacles.

[0032] The second cable tension distribution module distributes cable tension according to the following steps:

[0033] A1. Define the desired resultant force vector. ,in This indicates the expected resultant force of the load. The desired resultant torque of the load is represented by a row vector in the load coordinate system consisting of all desired tension vectors of the cables. ,in For the first The desired tension vector of the cable in the load coordinate system is then: , ,in For the first The position vector of the suspension point of the cable in the load coordinate system. The number of cables is equal to the number of drones.

[0034] set up for The antisymmetric matrix, then , ,in It is a 3-order identity matrix;

[0035] definition If is a constant full-rank matrix, then ,in A constant full-rank matrix The pseudo-inverse matrix;

[0036] A2. The optimized objective function expression is constructed as follows:

[0037] ;

[0038] In the above formula, This is a column vector consisting of the actual tension of all cables. These are the weighting coefficients; , All are gain coefficients; For the first The position of an obstacle in an inertial coordinate system; For relaxation terms, This is the rotation matrix used to transfer a vector from the load coordinate system to the inertial coordinate system; For relaxation term The weight matrix, , , These are the tension matching weights and the torque matching weights, respectively. For load speed; For the nominal case, the first The maximum cable tension that a drone can provide, , For the first The maximum thrust of the drone; , The first frame and the first The desired position of the drone in the inertial coordinate system; For load location; , These are the safe distance thresholds between drones and the safe distance thresholds between drones and obstacles, respectively. The threshold for safe obstacle avoidance distance for the load; For the first The maximum cable tension that a thrust-failed drone can provide. For the first The maximum cable tension that a normally thrusting drone can provide; For the first The actual tension of the cable; Indicates the sensor's actual measurement of the first The actual tension direction of the cable. ; It is the acceleration due to gravity; For the first The length of the cable; For load quality;

[0039] Solving the above objective function yields the optimal actual tension vector of the cable, and the cable tension is then distributed based on this optimal actual tension vector.

[0040] The second cable tension distribution module generates the first cable tension distribution module according to the following formula. The maximum cable tension that a faulty drone can provide :

[0041] ;

[0042] In the above formula, This is a fault discount factor, which is set according to the thrust fault type of the faulty UAV. .

[0043] The first cable tension distribution module distributes cable tension according to the following steps:

[0044] B1. Define the desired resultant force vector ,in This indicates the expected resultant force of the load. Represents the expected resultant torque of the load, and is defined as a column vector consisting of the expected tension vectors of all cables in the load coordinate system. ,in For the first The desired tension vector of the cable in the load coordinate system. Let be the number of cables; then we have , ,in For the first The position vector of the suspension point of the cable in the load coordinate system;

[0045] Define a full-rank matrix ,in It is a 3-order identity matrix. for For an antisymmetric matrix, then we have ;

[0046] Define the zero-space tension vector ,in A full-rank matrix The zero-space constant basis matrix, Let be the corresponding coordinate vector, then we have ,in A full-rank matrix The pseudo-inverse matrix, ;

[0047] B2. Construct an optimization model for the desired thrust scalar value, solve the model to obtain the optimal null coordinate vector, and calculate the optimal actual cable tension vector for each UAV based on the optimal null coordinate vector; the expression of the optimization model for the desired thrust scalar value is:

[0048] ;

[0049] In the above formula, for The adjustment amount; For the nominal case, the first The maximum cable tension that a drone can provide, , For the first The maximum thrust of the drone; This is the gain coefficient; , The first frame and the first The desired position of the drone in the inertial coordinate system; For load location; , These are the safe distance thresholds between drones and the safe distance threshold between a drone and an obstacle, respectively. For the first The position of an obstacle in an inertial coordinate system; This is the rotation matrix used to transfer a vector from the load coordinate system to the inertial coordinate system; For the first The length of the cable.

[0050] Thirdly, the present invention proposes a cable tension fault-tolerant distribution device for a multi-UAV hoisting system, the cable tension fault-tolerant distribution device comprising a memory and a processor; the memory is used to store computer program code and transmit the computer program code to the processor; the processor is used to execute the cable tension fault-tolerant distribution method as described above according to the instructions in the computer program code.

[0051] Fourthly, the present invention proposes a computer-readable storage medium storing a computer program that, when executed by a processor, implements the aforementioned cable tension fault-tolerant allocation method.

[0052] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0053] 1. The cable tension fault-tolerant allocation method described in this invention detects the thrust state and, for typical fault scenarios where UAV thrust is limited, adopts a cable tension allocation method that introduces load safety constraints. This method uses the actual cable tension vector as the optimization variable, and the optimization process is carried out under load safety constraints, UAV maximum cable tension constraints, and spatial obstacle avoidance constraints. The load safety constraint is a second-order CBF constraint constructed for multi-UAV hoisting systems facing obstacles, which can achieve fault-tolerant allocation of cable tension while ensuring the load and UAV obstacle avoidance safety. In addition, a thrust discount coefficient is introduced into the UAV maximum cable tension constraint to better refine the difference between faulty UAVs and normal UAVs, thereby improving the final cable tension allocation accuracy.

[0054] 2. The cable tension fault-tolerant distribution method described in this invention uses the zero-space cable tension distribution method to distribute cable tension under normal working conditions, and uses the redundant tension provided by the zero-space tension vector to adjust the position of the UAV to achieve obstacle avoidance. Attached Figure Description

[0055] Figure 1 This is a flowchart of the cable tension tolerance distribution method described in this invention.

[0056] Figure 2 The cable tension for all drones obtained from the calculation example.

[0057] Figure 3 The load obtained from the calculation example is compared with the motion of all drones.

[0058] Figure 4 The load obtained from the calculation example is the z-axis height of UAV No. 1.

[0059] Figure 5 The calculation example shows the single-step solution time obtained by applying the method described in this invention.

[0060] Figure 6This is a structural block diagram of the cable tension tolerance distribution system described in this invention.

[0061] Figure 7 This is a structural block diagram of the cable tension tolerance distribution device described in this invention. Detailed Implementation

[0062] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0063] Example 1:

[0064] See Figure 1 A method for fault-tolerant cable tension distribution in a multi-UAV hoisting system, comprising the following steps:

[0065] S1. Real-time detection of the operating status of the multi-UAV hoisting system, and determination of whether the multi-UAV hoisting system is in normal thrust mode or thrust failure mode based on the operating status of the multi-UAV hoisting system.

[0066] Specifically, the condition for determining that the multi-UAV hoisting system is in thrust failure mode is as follows: if at least one UAV in the multi-UAV hoisting system experiences a thrust failure, then the multi-UAV hoisting system is determined to be in thrust failure mode. The thrust failure includes, but is not limited to, motor efficiency degradation and insufficient battery power.

[0067] S2. If the thrust failure mode is in effect, the cable tension distribution method that introduces load safety constraints shall be used to distribute the cable tension.

[0068] Specifically, the cable tension allocation method incorporating load safety constraints includes: allocating cable tension with the optimization objective of minimizing the deviation between the actual cable tension vector and the desired cable tension vector; solving the optimization objective under load safety constraints, the maximum cable tension constraint of the UAV, and spatial obstacle avoidance constraints to obtain the optimal actual cable tension vector; and allocating cable tension based on the optimal actual cable tension vector. The load safety constraint is a second-order CBF constraint constructed for the multi-UAV hoisting system facing obstacles. Specifically, the cable tension allocation method incorporating load safety constraints is performed sequentially according to the following steps:

[0069] A1. Define the desired resultant force vector. ,in This indicates the expected resultant force of the load. The desired resultant torque of the load is represented by a row vector in the load coordinate system consisting of all desired tension vectors of the cables. ,in For the first The desired tension vector of the cable in the load coordinate system is then: , ,in For the first The position vector of the suspension point of the cable in the load coordinate system. The number of cables is equal to the number of drones.

[0070] set up for The antisymmetric matrix, then , ,in It is a 3-order identity matrix;

[0071] definition If is a constant full-rank matrix, then ,in A constant full-rank matrix The pseudo-inverse matrix;

[0072] A2. The optimized objective function expression is constructed as follows:

[0073] ;

[0074] In the above formula, This is a column vector consisting of the actual tension of all cables. These are the weighting coefficients; , All are gain coefficients; For the first The position of an obstacle in an inertial coordinate system; For relaxation terms, This is the rotation matrix used to transfer a vector from the load coordinate system to the inertial coordinate system; For relaxation term The weight matrix, , , These are the tension matching weights and the torque matching weights, respectively. For load speed; For the nominal case, the first The maximum cable tension that a drone can provide, , For the first The maximum thrust of the drone; , The first frame and the first The desired position of the drone in the inertial coordinate system; For load location; , These are the safe distance thresholds between drones and the safe distance thresholds between drones and obstacles, respectively. The threshold for safe obstacle avoidance distance for the load; For the first The maximum cable tension that a thrust-failed drone can provide. For the first The maximum cable tension that a normally thrusting drone can provide; For the first The actual tension of the cable; Indicates the sensor's actual measurement of the first The actual tension direction of the cable. ; It is the acceleration due to gravity; For the first The length of the cable; For load quality;

[0075] In the above optimization objective function, The load safety constraint is based on the CBF function. This load safety constraint requires that when the load is close to the obstacle, a reverse acceleration is generated through tension distribution to ensure that the load is always in the safe zone. The maximum cable tension constraint for drones is used to distinguish between the maximum cable tension of drones with normal thrust and those with malfunctions. This requires that the tension distribution be coordinated and complementary among multiple drones based on the drone malfunction situation to avoid the tension allocated to a drone exceeding its execution capacity. To address spatial obstacle avoidance constraints, while meeting load requirements, the system ensures a safe distance between each UAV and obstacles, forming a complementary two-layer safety barrier with the load safety constraint based on the CBF function. This ultimately improves the overall load safety performance of the hoisting system.

[0076] Solving the above objective function yields the optimal actual tension vector of the cable, and the cable tension is then distributed based on this optimal actual tension vector.

[0077] Specifically, the first The maximum cable tension that a faulty drone can provide It is generated based on the fault discount factor:

[0078] ;

[0079] In the above formula, This is a fault discount factor, which is set according to the thrust fault type of the faulty UAV. .

[0080] S3. If the thrust is in the normal mode, the zero-space cable tension distribution method is used to distribute the cable tension.

[0081] Specifically, the zero-space cable tension distribution method is performed in sequence according to the following steps:

[0082] B1. Define the desired resultant force vector ,in This indicates the expected resultant force of the load. Represents the expected resultant torque of the load, and is defined as a column vector consisting of the expected tension vectors of all cables in the load coordinate system. ,in For the first The desired tension vector of the cable in the load coordinate system. Let be the number of cables; then we have , ,in For the first The position vector of the suspension point of the cable in the load coordinate system;

[0083] Define a full-rank matrix ,in It is a 3-order identity matrix. for For an antisymmetric matrix, then we have ;

[0084] Define the zero-space tension vector ,in A full-rank matrix The zero-space constant basis matrix, Let be the corresponding coordinate vector, then we have ,in A full-rank matrix The pseudo-inverse matrix, ;

[0085] B2. Construct an optimization model for the desired thrust scalar value, solve the model to obtain the optimal null coordinate vector, and calculate the optimal actual cable tension vector for each UAV based on the optimal null coordinate vector; the expression of the optimization model for the desired thrust scalar value is:

[0086] ;

[0087] In the above formula, for The adjustment amount; For the nominal case, the first The maximum cable tension that a drone can provide, , For the first The maximum thrust of the drone; This is the gain coefficient; , The first frame and the first The desired position of the drone in the inertial coordinate system; For load location; , These are the safe distance thresholds between drones and the safe distance threshold between a drone and an obstacle, respectively. For the first The position of an obstacle in an inertial coordinate system; This is the rotation matrix used to transfer a vector from the load coordinate system to the inertial coordinate system; For the first The length of the cable.

[0088] The optimal solution is obtained through QP. and optimal Substitute At this time, the result is This is the optimal actual tension vector of the cable.

[0089] Performance verification:

[0090] To fully verify the control performance of the proposed method, a simulation experimental platform was constructed based on the Matlab platform. The experimental parameters are shown in Table 1. The sampling period was 0.02s, and the total simulation time was 24s. The initial position and attitude angle of the load were (-3, -2, 0)m and (0, 0, 0)deg, respectively. The expected height of the load was 8m, the expected speed was 1.5m / s, and the expected attitude angle was (0, 0, 0)deg. The expected trajectory was a rectangle with four vertices: A(-5, -3, 8)m, B(5, -3, 8)m, C(5, 3, 8)m, and D(-5, 3, 8)m. The load moved cyclically in the order A→B→C→D→A. Four static obstacles were set up. Obstacles 1 and 2 were located near the expected trajectory of the load, and obstacles 3 and 4 were located near the flight area of ​​the UAV. To simplify collision detection, the UAV and the load were treated as point masses in the experiment, and their radii were superimposed on the obstacles. Nonlinear bounded perturbations were applied throughout the experiment, and the first UAV was set to malfunction at t=14s.

[0091] Table 1 Experimental parameter settings

[0092] ;

[0093] 1. Obtain the tension of all drone cables as follows: Figure 2 As shown, before the fault onset at t=14s, the average cable tension output of the four drones was 28.1N, and their trajectories maintained good consistency. After the fault onset at t=14s, the average cable tension of drone 1 actively decreased from 28.1N to 13.9N, a decrease of 50.5%. The average tension of drones 2, 3, and 4 actively increased to 42.2N, 42.2N, and 40.6N respectively, to compensate for the thrust loss of drone 1.

[0094] 2. Obtain the load and the movement status of all drones, such as Figure 3 As shown, the load and the z-axis height of UAV No. 1 are as follows: Figure 4 As shown, after the fault onset at t=14s, the z-axis height of UAV 1 rapidly decreased from 13.5m to 9.5m, while the load's z-axis height only decreased by 0.5m and recovered to 8m after 1s. This demonstrates that the controller can maintain the load's position tracking accuracy by actively adjusting the formation position of the faulty UAVs.

[0095] 3. Before the fault was triggered, the number of load-obstacle collisions, drone-obstacle collisions, and drone-drone collisions were all 0, indicating good obstacle avoidance performance.

[0096] 4. Obtain the time consumed in a single step solution, such as... Figure 5 As shown in the figure. Further calculations revealed an average single-step time of 1.03 ms and a maximum solution time of 2.34 ms. It can be seen that the method described in this invention has high computational efficiency and better real-time deployment capabilities.

[0097] Example 2:

[0098] See Figure 6 A cable tension fault-tolerant distribution system for a multi-UAV hoisting system includes a thrust state detection module, a first cable tension distribution module, and a second cable tension distribution module. The thrust state detection module is used to detect the operating status of the multi-UAV hoisting system in real time and determine whether the system is in a normal thrust mode or a thrust failure mode based on the operating status. The second cable tension distribution module is used to distribute cable tension using a cable tension distribution method incorporating load safety constraints when the multi-UAV hoisting system is in a thrust failure mode. The cable tension distribution method incorporating load safety constraints includes: optimizing the cable tension by minimizing the deviation between the actual cable tension vector and the desired cable tension vector; solving the optimization objective under load safety constraints, maximum cable tension constraints of the UAVs, and spatial obstacle avoidance constraints to obtain the optimal actual cable tension vector; and distributing cable tension based on the optimal actual cable tension vector. The load safety constraints are second-order CBF constraints constructed for the multi-UAV hoisting system facing obstacles. The second cable tension distribution module specifically performs cable tension distribution according to the following steps:

[0099] A1. Define the desired resultant force vector. ,in This indicates the expected resultant force of the load. The desired resultant torque of the load is represented by a row vector in the load coordinate system consisting of all desired tension vectors of the cables. ,in For the first The desired tension vector of the cable in the load coordinate system is then: , ,in For the first The position vector of the suspension point of the cable in the load coordinate system. The number of cables is equal to the number of drones.

[0100] set up for The antisymmetric matrix, then , ,in It is a 3-order identity matrix;

[0101] definition If is a constant full-rank matrix, then ,in A constant full-rank matrix The pseudo-inverse matrix;

[0102] A2. The optimized objective function expression is constructed as follows:

[0103] ;

[0104] In the above formula, This is a column vector consisting of the actual tension of all cables. These are the weighting coefficients; , All are gain coefficients; For the first The position of an obstacle in an inertial coordinate system; For relaxation terms, This is the rotation matrix used to transfer a vector from the load coordinate system to the inertial coordinate system; For relaxation term The weight matrix, , , These are the tension matching weights and the torque matching weights, respectively. For load speed; For the nominal case, the first The maximum cable tension that a drone can provide, , For the first The maximum thrust of the drone; , The first frame and the first The desired position of the drone in the inertial coordinate system; For load location; , These are the safe distance thresholds between drones and the safe distance thresholds between drones and obstacles, respectively. The threshold for safe obstacle avoidance distance for the load; For the first The maximum cable tension that a thrust-failed drone can provide. For the first The maximum cable tension that a normally thrusting drone can provide; For the first The actual tension of the cable; Indicates the sensor's actual measurement of the first The actual tension direction of the cable. ; It is the acceleration due to gravity; For the first The length of the cable; For load quality;

[0105] Solving the above objective function yields the optimal actual cable tension vector, and cable tension is allocated based on the optimal actual cable tension vector.

[0106] The second cable tension distribution module generates the following formula: The maximum cable tension that a faulty drone can provide :

[0107] ;

[0108] In the above formula, This is a fault discount factor, which is set according to the thrust fault type of the faulty UAV. ;

[0109] The first cable tension distribution module is used to distribute cable tension using a zero-space cable tension distribution method when the multi-UAV hoisting system is in normal thrust mode; the first cable tension distribution module specifically distributes cable tension according to the following steps:

[0110] B1. Define the desired resultant force vector ,in This indicates the expected resultant force of the load. Represents the expected resultant torque of the load, and is defined as a column vector consisting of the expected tension vectors of all cables in the load coordinate system. ,in For the first The desired tension vector of the cable in the load coordinate system. Let be the number of cables; then we have , ,in For the first The position vector of the suspension point of the cable in the load coordinate system;

[0111] Define a full-rank matrix ,in It is a 3-order identity matrix. for For an antisymmetric matrix, then we have ;

[0112] Define the zero-space tension vector ,in A full-rank matrix The zero-space constant basis matrix, Let be the corresponding coordinate vector, then we have ,in A full-rank matrix The pseudo-inverse matrix, ;

[0113] B2. Construct an optimization model for the desired thrust scalar value, solve the model to obtain the optimal null coordinate vector, and calculate the optimal actual cable tension vector for each UAV based on the optimal null coordinate vector; the expression of the optimization model for the desired thrust scalar value is:

[0114] ;

[0115] In the above formula, for The adjustment amount; For the nominal case, the first The maximum cable tension that a drone can provide, , For the first The maximum thrust of the drone; This is the gain coefficient; , The first frame and the first The desired position of the drone in the inertial coordinate system; For load location; , These are the safe distance thresholds between drones and the safe distance threshold between a drone and an obstacle, respectively. For the first The position of an obstacle in an inertial coordinate system; This is the rotation matrix used to transfer a vector from the load coordinate system to the inertial coordinate system; For the first The length of the cable.

[0116] Example 3:

[0117] See Figure 7A cable tension fault-tolerant distribution device for a multi-UAV hoisting system includes a memory and a processor; the memory is used to store computer program code and transmit the computer program code to the processor; the processor is used to execute the cable tension fault-tolerant distribution method described in Embodiment 1 according to the instructions in the computer program code.

[0118] Example 4:

[0119] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the cable tension fault-tolerant allocation method described in Embodiment 1.

[0120] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program goods. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program goods embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0121] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, as well as combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0122] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0123] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process.Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for fault-tolerant cable tension distribution in a multi-UAV hoisting system, characterized in that: The cable tension tolerance distribution method includes: S1. Real-time detection of the operating status of the multi-UAV hoisting system, and determination of whether the multi-UAV hoisting system is in normal thrust mode or thrust failure mode based on the operating status of the multi-UAV hoisting system. S2. If the thrust is in normal mode, the zero-space cable tension distribution method is used for cable tension distribution; if the thrust is in fault mode, the cable tension distribution method with load safety constraints is used for cable tension distribution. The cable tension allocation method incorporating load safety constraints includes: allocating cable tension with the optimization objective of minimizing the deviation between the actual cable tension vector and the desired cable tension vector; solving the optimization objective under load safety constraints, maximum cable tension constraints of the UAV, and spatial obstacle avoidance constraints to obtain the optimal actual cable tension vector; and allocating cable tension based on the optimal actual cable tension vector. The load safety constraint is a second-order CBF constraint constructed for the multi-UAV hoisting system facing obstacles.

2. The cable tension tolerance distribution method for a multi-UAV hoisting system according to claim 1, characterized in that: The cable tension distribution method that introduces load safety constraints specifically includes: A1. Define the desired resultant force vector. ,in This indicates the expected resultant force of the load. The desired resultant torque of the load is represented by a row vector in the load coordinate system consisting of all desired tension vectors of the cables. ,in For the first The desired tension vector of the cable in the load coordinate system is then: , ,in For the first The position vector of the suspension point of the cable in the load coordinate system. The number of cables is equal to the number of drones. set up for The antisymmetric matrix, then , ,in It is a 3-order identity matrix; definition If is a constant full-rank matrix, then ,in A constant full-rank matrix The pseudo-inverse matrix; A2. The optimized objective function expression is constructed as follows: ； In the above formula, This is a column vector consisting of the actual tension of all cables. These are the weighting coefficients; , All are gain coefficients; For the first The position of an obstacle in an inertial coordinate system; For relaxation terms, This is the rotation matrix used to transfer a vector from the load coordinate system to the inertial coordinate system; For relaxation term The weight matrix, , , These are the tension matching weights and the torque matching weights, respectively. For load speed; For the nominal case, the first The maximum cable tension that a drone can provide, , For the first The maximum thrust of the drone; , The first frame and the first The desired position of the drone in the inertial coordinate system; For load location; , These are the safe distance thresholds between drones and the safe distance thresholds between drones and obstacles, respectively. The threshold for safe obstacle avoidance distance for the load; For the first The maximum cable tension that a thrust-failed drone can provide. For the first The maximum cable tension that a normally thrusting drone can provide; For the first The actual tension of the cable; Indicates the sensor's actual measurement of the first The actual tension direction of the cable. ; It is the acceleration due to gravity; For the first The length of the cable; For load quality; Solving the above objective function yields the optimal actual tension vector of the cable, and the cable tension is then distributed based on this optimal actual tension vector.

3. The cable tension tolerance distribution method for a multi-UAV hoisting system according to claim 2, characterized in that: The first The maximum cable tension that a faulty drone can provide It is generated based on the fault discount factor: ； In the above formula, This is a fault discount factor, which is set according to the thrust fault type of the faulty UAV. .

4. The cable tension tolerance distribution method for a multi-UAV hoisting system according to claim 1, characterized in that: The zero-space cable tension distribution method includes: B1. Define the desired resultant force vector ,in This indicates the expected resultant force of the load. Represents the expected resultant torque of the load, and is defined as a column vector consisting of the expected tension vectors of all cables in the load coordinate system. ,in For the first The desired tension vector of the cable in the load coordinate system. Let be the number of cables; then we have , ,in For the first The position vector of the suspension point of the cable in the load coordinate system; Define a full-rank matrix ,in It is a 3-order identity matrix. for For an antisymmetric matrix, then we have ; Define the zero-space tension vector ,in A full-rank matrix The zero-space constant basis matrix, Let be the corresponding coordinate vector, then we have ,in A full-rank matrix The pseudo-inverse matrix, ; B2. Construct an optimization model for the desired thrust scalar value, solve the model to obtain the optimal null coordinate vector, and calculate the optimal actual cable tension vector for each UAV based on the optimal null coordinate vector; the expression of the optimization model for the desired thrust scalar value is: ； In the above formula, for The adjustment amount; For the nominal case, the first The maximum cable tension that a drone can provide, , For the first The maximum thrust of the drone; This is the gain coefficient; , The first frame and the first The desired position of the drone in the inertial coordinate system; For load location; , These are the safe distance thresholds between drones and the safe distance threshold between a drone and an obstacle, respectively. For the first The position of an obstacle in an inertial coordinate system; This is the rotation matrix used to transfer a vector from the load coordinate system to the inertial coordinate system; For the first The length of the cable.

5. A cable tension tolerance distribution system for a multi-UAV hoisting system, characterized in that: The cable tension tolerance distribution system includes: The thrust status detection module is used to detect the operating status of the multi-UAV hoisting system in real time, and determine whether the multi-UAV hoisting system is in normal thrust mode or thrust failure mode based on the operating status of the multi-UAV hoisting system. The first cable tension distribution module is used to distribute cable tension using the zero-space cable tension distribution method when the multi-UAV hoisting system is in thrust normal mode. The second cable tension distribution module is used to distribute cable tension in a load-safety-constrained cable tension distribution method when the multi-UAV hoisting system is in thrust failure mode. This load-safety-constraint method includes: optimizing the cable tension distribution by minimizing the deviation between the actual cable tension vector and the desired cable tension vector; solving the optimization objective under load safety constraints, maximum cable tension constraints of the UAVs, and spatial obstacle avoidance constraints to obtain the optimal actual cable tension vector; and then distributing cable tension based on this optimal actual cable tension vector. The load safety constraints are second-order CBF constraints constructed for the multi-UAV hoisting system facing obstacles.

6. The cable tension tolerance distribution system for a multi-UAV hoisting system according to claim 5, characterized in that: The second cable tension distribution module distributes cable tension according to the following steps: A1. Define the desired resultant force vector. ,in This indicates the expected resultant force of the load. The desired resultant torque of the load is represented by a row vector in the load coordinate system consisting of all desired tension vectors of the cables. ,in For the first The desired tension vector of the cable in the load coordinate system is then: , ,in For the first The position vector of the suspension point of the cable in the load coordinate system. The number of cables is equal to the number of drones. set up for The antisymmetric matrix, then , ,in It is a 3-order identity matrix; definition If is a constant full-rank matrix, then ,in A constant full-rank matrix The pseudo-inverse matrix; A2. The optimized objective function expression is constructed as follows: ； In the above formula, This is a column vector consisting of the actual tension of all cables. These are the weighting coefficients; , All are gain coefficients; For the first The position of an obstacle in an inertial coordinate system; For relaxation terms, This is the rotation matrix used to transfer a vector from the load coordinate system to the inertial coordinate system; For relaxation term The weight matrix, , , These are the tension matching weights and the torque matching weights, respectively. For load speed; For the nominal case, the first The maximum cable tension that a drone can provide, , For the first The maximum thrust of the drone; , The first frame and the first The desired position of the drone in the inertial coordinate system; For load location; , These are the safe distance thresholds between drones and the safe distance thresholds between drones and obstacles, respectively. The threshold for safe obstacle avoidance distance for the load; For the first The maximum cable tension that a thrust-failed drone can provide. For the first The maximum cable tension that a normally thrusting drone can provide; For the first The actual tension of the cable; Indicates the sensor's actual measurement of the first The actual tension direction of the cable. ; It is the acceleration due to gravity; For the first The length of the cable; For load quality; Solving the above objective function yields the optimal actual tension vector of the cable, and the cable tension is then distributed based on this optimal actual tension vector.

7. The cable tension tolerance distribution system for a multi-UAV hoisting system according to claim 6, characterized in that: The second cable tension distribution module generates the first cable tension distribution module according to the following formula. The maximum cable tension that a faulty drone can provide : ； In the above formula, This is a fault discount factor, which is set according to the thrust fault type of the faulty UAV. .

8. The cable tension fault-tolerant distribution system for a multi-UAV hoisting system according to claim 5, characterized in that: The first cable tension distribution module distributes cable tension according to the following steps: B1. Define the desired resultant force vector ,in This indicates the expected resultant force of the load. Represents the expected resultant torque of the load, and is defined as a column vector consisting of the expected tension vectors of all cables in the load coordinate system. ,in For the first The desired tension vector of the cable in the load coordinate system. Let be the number of cables; then we have , ,in For the first The position vector of the suspension point of the cable in the load coordinate system; Define a full-rank matrix ,in It is a 3-order identity matrix. for For an antisymmetric matrix, then we have ; Define the zero-space tension vector ,in A full-rank matrix The zero-space constant basis matrix, Let be the corresponding coordinate vector, then we have ,in A full-rank matrix The pseudo-inverse matrix, ; B2. Construct an optimization model for the desired thrust scalar value, solve the model to obtain the optimal null coordinate vector, and calculate the optimal actual cable tension vector for each UAV based on the optimal null coordinate vector; the expression of the optimization model for the desired thrust scalar value is: ； In the above formula, for The adjustment amount; For the nominal case, the first The maximum cable tension that a drone can provide, , For the first The maximum thrust of the drone; This is the gain coefficient; , The first frame and the first The desired position of the drone in the inertial coordinate system; For load location; , These are the safe distance thresholds between drones and the safe distance threshold between a drone and an obstacle, respectively. For the first The position of an obstacle in an inertial coordinate system; This is the rotation matrix used to transfer a vector from the load coordinate system to the inertial coordinate system; For the first The length of the cable.

9. A cable tension fault-tolerant distribution device for a multi-UAV hoisting system, the cable tension fault-tolerant distribution device comprising a memory and a processor; the memory is used to store computer program code and transmit the computer program code to the processor; the processor is used to execute the cable tension fault-tolerant distribution method as described in claim 1 according to the instructions in the computer program code.

10. A computer-readable storage medium storing a computer program that, when executed by a processor, implements the cable tension fault-tolerant allocation method as described in claim 1.

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