A truss aerial transportation system and construction method thereof

Abstract

The present invention discloses a truss aerial transportation system and a construction method thereof, the system comprising: a plurality of drones; at least one ball joint, the ball joint being arranged on the drone; at least one tether, the tether being connected to the ball joint and used to connect the ball joint to a load; at least one rod, the rod being arranged between drones, and the two ends of the rod being respectively connected to the drones; the drones, the rods, the tethers and the loads forming a truss rigid structure. In the present invention, the drones are connected by rods, and the drones and the loads are connected by tethers, so that the drones, the rods, the tethers and the loads form a truss rigid structure, which improves the transportation efficiency of small-sized and heavy-weight loads.

Description

Technical Field

[0001] The invention relates to the field of robot technology, and in particular to a truss aerial transportation system and a construction method thereof. Background Art

[0002] In recent years, drones have demonstrated their great potential in air transportation. Compared with a single drone, a multi-drone system can carry heavier loads, and the system becomes more complex. At present, there are two types of mainstream multi-drone cooperative transportation methods: rope-tethered cooperative transportation framework and rigid cooperative transportation framework. However, for small and heavy loads, the rope-tethered cooperative transportation framework has useless lateral tension, resulting in partial efficiency loss; and drones cannot be directly connected to the load to form a rigid cooperative transportation framework.

[0003] Therefore, the existing technology still needs to be improved and developed. Summary of the invention

[0004] The technical problem to be solved by the present invention is that, in view of the above-mentioned defects of the prior art, a truss aerial transportation system and a construction method thereof are provided, aiming to solve the problem in the prior art that for small-sized and heavy loads, the rope-based cooperative transportation framework has useless lateral tension, resulting in partial efficiency loss; and the drone cannot be directly connected to the load to form a rigid cooperative transportation framework.

[0005] The technical solution adopted by the present invention to solve the problem is as follows:

[0006] In a first aspect, an embodiment of the present invention provides a truss aerial transportation system, wherein the system includes: a plurality of unmanned aerial vehicles, a ball joint arranged on the unmanned aerial vehicles, a plurality of tethers and a plurality of rods; the ball joint is connected to the load through the tether; the unmanned aerial vehicles are connected through the rod; the unmanned aerial vehicles, the rods, the tethers and the load constitute a truss rigid structure.

[0007] In one implementation, the rod is a lightweight rod.

[0008] In a second aspect, an embodiment of the present invention further provides a method for constructing a truss aerial transportation system, wherein the method comprises:

[0009] Obtaining the payload gravity, and determining the total number of drones according to the payload gravity;

[0010] Based on the total number of drones, a truss rigid structure diagram is constructed according to a number of tethers, a number of rods and loads;

[0011] Based on the truss rigid structure diagram, the stress of each rod is calculated, and the yield strength of each rod is determined according to the stress of each rod, wherein the yield strength is a strength index of each rod in the truss rigid structure diagram.

[0012] In one implementation, determining the total number of drones according to the load gravity includes:

[0013] Obtaining the gravity of each of the drones and the maximum thrust of the drones;

[0014] The total number of drones is determined according to the gravity of each drone, the payload gravity and the maximum thrust.

[0015] In one implementation, determining the total number of drones according to the gravity of each drone, the load gravity, and the maximum thrust includes:

[0016] Multiplying the maximum thrust by a preset coefficient to obtain an intermediate thrust;

[0017] The intermediate thrust is subtracted from the gravity of each of the drones to obtain an intermediate resultant force;

[0018] The total number of drones is determined according to the intermediate resultant force and the load gravity.

[0019] In one implementation, determining the total number of drones according to the intermediate resultant force and the load gravity includes:

[0020] Dividing the load gravity by the intermediate resultant force to obtain a quotient;

[0021] According to the quotient, the total number of drones is determined.

[0022] In one implementation, determining the total number of drones according to the quotient includes:

[0023] The quotient is rounded up to obtain an integer value, and the integer value is used as the total number of drones.

[0024] In one implementation, constructing a truss rigid structure diagram based on the total number of drones, a number of tethers, a number of rods, and a load includes:

[0025] Determine the initial nodes and initial edges based on loads, ties and members;

[0026] Add a drone as a new node;

[0027] Count the number of drones in the initial node and the number of drones in the newly added node to obtain the number of drones in use;

[0028] According to the added drones, loads, tethers and rods, the newly added edges are obtained;

[0029] When the number of drones in use is less than the total number of drones, continue to perform the step of adding a drone as a newly added node;

[0030] When the number of drones in use is equal to the total number of drones, the step of adding a drone as a newly added node is stopped, and the initial node, initial edge, all newly added nodes and all newly added edges are generated into a truss rigid structure diagram.

[0031] In one implementation, the initial edge includes a first initial edge and a second initial edge; and determining the initial node and the initial edge according to the load, the tether and the rod includes:

[0032] The two drones and the payload form three initial nodes;

[0033] Take the rod between the two drones as the first initial edge;

[0034] The tether between the two drones and the payload is used as the second initial edge.

[0035] In one implementation, the obtaining of the newly added edges according to the added drone, payload, tether, and rod includes:

[0036] Add the tether between the drone and the payload as the first added edge;

[0037] The rod between the added UAV and the adjacent UAV is used as the second added edge.

[0038] In one implementation, the calculating the stress of each rod based on the truss rigid structure diagram includes:

[0039] Obtaining a connection matrix and an adjacency matrix defined by a user based on the truss rigid structure diagram;

[0040] According to the adjacency matrix, a configuration mass corresponding to the UAV is obtained; wherein the configuration mass is the mass of the rods assigned to the UAV;

[0041] Get the mass of a drone;

[0042] Adding the mass of a drone and the mass of the configuration corresponding to the drone to obtain the node mass;

[0043] Get the thrust of a drone in a balanced state;

[0044] Obtaining node gravity according to the node mass, and decomposing the node gravity and the thrust on the coordinate axis to obtain an X-axis external force component, a Y-axis external force component, and a Z-axis external force component, respectively;

[0045] The X-axis external force component, the Y-axis external force component and the Z-axis external force component form an external force vector;

[0046] Obtaining node coordinate values, and performing a mixed operation on the connection matrix and the node coordinate values ​​to obtain an intermediate matrix;

[0047] Inverting the intermediate matrix and multiplying the matrix with the external force vector to obtain a force density vector;

[0048] According to the force density vector, the stress of each rod is obtained.

[0049] In one implementation, obtaining the configuration quality corresponding to the drone according to the adjacency matrix includes:

[0050] Obtaining the masses of several rods connected to the drone;

[0051] Based on the adjacency matrix, a distribution operation is performed on the masses of a plurality of rods connected to the drone to obtain a configuration mass corresponding to the drone.

[0052] In one implementation, obtaining the stress of each rod according to the force density vector includes:

[0053] Obtaining the side length of the rod corresponding to each force density in the force density vector;

[0054] Each force density is multiplied by the side length of the rod corresponding to the force density to obtain the stress of each rod.

[0055] In one implementation, determining the yield strength of the rod according to the stress includes:

[0056] Determining the yield strength of each rod member according to the stress of each rod member includes:

[0057] Obtain the cross-sectional area of ​​each rod corresponding to the stress of each rod;

[0058] Obtaining a safety factor; wherein the safety factor is used to characterize the safety of the rod;

[0059] The product obtained by multiplying the stress of each rod by the safety factor is divided by the cross-sectional area of ​​the rod corresponding to the stress of each rod to obtain a number of strength values;

[0060] A value that meets a preset condition is selected from the several strength values ​​as the yield strength.

[0061] In a third aspect, an embodiment of the present invention further provides an intelligent terminal, comprising a memory and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by one or more processors, and the one or more programs include a method for executing a construction method of a truss aerial transportation system as described in any one of the above items.

[0062] In a fourth aspect, an embodiment of the present invention further provides a non-temporary computer-readable storage medium, which, when instructions in the storage medium are executed by a processor of an electronic device, enables the electronic device to execute a method for constructing a truss aerial transportation system as described in any one of the above.

[0063] Beneficial effects of the present invention: The system of the embodiment of the present invention includes: a number of drones; at least one ball joint, which is arranged on the drone; at least one tether, which is connected to the ball joint and is used to connect the ball joint to a load; at least one rod, which is arranged between drones, and the two ends of the rod are respectively connected to the drones; the drones, the rods, the tethers and the loads constitute a truss rigid structure. It can be seen that in the embodiment of the present invention, the drones are connected by rods, and the drones and the loads are connected by tethers, so that the drones, the rods, the tethers and the loads constitute a truss rigid structure, which improves the transportation efficiency of small-sized and heavy-weight loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0065] Figure 1 A structural diagram of a truss aerial transportation system provided in an embodiment of the present invention.

[0066] Figure 2 A schematic flow chart of a method for constructing a truss aerial transportation system provided in an embodiment of the present invention.

[0067] Figure 3 This is a block diagram of the internal structure principle of the intelligent terminal provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0068] The present invention discloses a truss aerial transportation system and a construction method thereof. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0069] It will be understood by those skilled in the art that, unless expressly stated, the singular forms "one", "said", and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or wireless coupling. The term "and / or" used herein includes all or any unit and all combinations of one or more associated listed items.

[0070] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined as herein.

[0071] Since in the existing technology, in the rope-based cooperative transport framework, the drone and the load are connected by cables, the system can be controlled by formation (K. Klausen, C. Meissen, TIFossen, M. Arcak and T. A. Johansen, “Cooperative Control for Multirotors Transporting an Unknown Suspended Load Under Environmental Disturbances,” IEEE Trans. Control Syst. Technol., vol. 28, no. 2, pp. 653-660, Mar. 2020.) and inverse kinematics (Q. Jiang and V. Kumar, “The Inverse Kinematics of Cooperative Transport With Multiple Aerial Robots,” IEEE Trans. Robot., vol. 29, no. 1, pp. 136-145, Feb. 2013.) methods, and the control technology is relatively mature. However, from a structural point of view, if the load size is small, then these cables will always be diagonal, that is, only a part of the tension on the rope is used to balance the gravity of the load, and the other part is used to maintain the diagonal formation, which is called "useless lateral tension" here. Obviously, due to the existence of these useless lateral tensions, the drone cannot use all of its lift output to offset gravity, which means a partial loss of efficiency.

[0072] However, in the rigid cooperative transport framework, the UAV will be directly fixed to the load or connected with a ball joint, so there will be no problem of inclined pull, and there will be no useless lateral pull. There are many literatures at home and abroad that have studied its control problem, such as (YHTan, S. Lai, K. Wang, and BMChen, "Cooperative control of multiple unmanned aerial systems for heavy duty carrying," Annu. Rev. Control, vol. 46, pp. 44-57, Apr. 2018.) (A. Tagliabue, M. Kamel, R. Siegwart, and J. Nieto, "Robust collaborative object transportation using multiple MAVs," Int. J. Robot. Res., vol. 38, no. 9, pp. 1020-1044, Aug. 2019.). However, for smaller loads, there will not be enough space for the UAV to be placed on the load, and the rigid frame will not be suitable for smaller and heavier loads.

[0073] In order to solve the problems of the prior art, this embodiment provides a truss aerial transportation system, in which drones are connected by rods, and drones are connected to loads by tethers, so that the drones, the rods, the tethers and the loads constitute a truss rigid structure, which improves the transportation efficiency of small-sized and heavy loads. The system in a specific embodiment includes: a number of drones; at least one ball joint, which is arranged on the drone; at least one tether, which is connected to the ball joint and is used to connect the ball joint to the load; at least one rod, which is arranged between drones and has two ends connected to the drones respectively; the drones, the rods, the tethers and the loads constitute a truss rigid structure.

[0074] like Figure 1 As shown in, an embodiment of the present invention provides a truss aerial transportation system, which includes: a plurality of drones; at least one ball joint, which is arranged on the drone; at least one tether, which is connected to the ball joint and is used to connect the ball joint to a load; at least one rod, which is arranged between the drones and has two ends connected to the drones respectively; the drones, the rods, the tethers and the loads constitute a truss rigid structure.

[0075] In practice, when transporting small and heavy loads, the existing traditional rope-based cooperative transport frame has useless lateral tension, resulting in low efficiency in transporting heavy loads, and drones cannot be fixed to small and heavy loads to form a rigid cooperative transport frame. Trusses are an important structure in modern construction engineering, which consists of rod elements connected by pin joints to form a rigid diagram. In trusses, there is no shear force, and all stresses are along the axial direction of the rods, which makes trusses a lightweight and strong mechanical structure with a small amount of material. In addition, the external forces on the truss nodes will be distributed to the tensile network, thereby reducing the mechanical strength of individual rods. Due to these structural advantages, trusses have been applied to robotics, such as tensegrity robots (M. Vespignani, JM Friesen, V. Sunspiral, and J. Bruce, "Design of SUPERball v2, a Compliant Tensegrity Robot for Absorbing Large Impacts," in Proc. IEEE / RSJ Int. Conf. Intell. Robots Syst., Oct. 2018, pp. 2865-2871.), joint design (JM Friesen, JL Dean, T. Bewley, and V. Sunspiral, "A Tensegrity-Inspired Compliant 3-DOF Compliant Joint," in Proc. Int. Conf. Robot. Autom., May 2018, pp. 3301-3306.). Therefore, the present invention adopts a truss structure to construct a truss aerial transport system. The system is improved on the basis of the traditional rope-tethered cooperative transport framework. Considering the existence of lateral tension in the rope-tethered cooperative transport framework, rods are added between the drones. In one implementation, the rod is a lightweight rod. In this embodiment, the drone is a rotary-wing drone, and the tether is connected to a ball joint provided on the drone, so that the drone and the load are connected through the tether; wherein the ball joint includes a base, a cover body and a ball rod, wherein a rotating ball is provided at the bottom end of the ball rod. Through the above arrangement, during time calculation, the drone, the rod, the tether and the load form a truss rigid structure, which can eliminate useless lateral tension, thereby greatly improving the transportation efficiency of small-sized and heavy-weight loads.

[0076] Exemplary Methods

[0077] This embodiment provides a method for constructing a truss aerial transportation system, which can be applied to a robot's intelligent terminal. Figure 1 As shown, the method includes:

[0078] Step S100, obtaining the load gravity, and determining the total number of drones according to the load gravity;

[0079] Specifically, first obtain the load mass m L According to the relationship between mass and gravity, we can get the gravity G of the load L The greater the weight of the load, the more drones are needed. The number of drones that are reasonable to use in practice (reasonable conditions: not wasting drone resources and meeting the requirements of actual transportation) is determined based on the weight of the load.

[0080] In order to obtain the total number of drones, determining the total number of drones according to the load gravity includes the following steps:

[0081] S101, obtaining the gravity of each drone and the maximum thrust of the drone;

[0082] S102: Determine the total number of drones according to the gravity of each drone, the payload gravity, and the maximum thrust.

[0083] Each drone has its own gravity, and it is assumed that the gravity of all drones is equal, so we only need to obtain the gravity G of one drone. u In addition, the drone has thrust during flight. In order to accurately calculate the total number of drones, it is necessary to obtain the maximum thrust f of the drone. max . Then according to the gravity G of each drone u , the load gravity G L and the maximum thrust f max , determine the total number of drones. Accordingly, determining the total number of drones according to the gravity of each drone, the load gravity and the maximum thrust includes the following steps: multiplying the maximum thrust by a preset coefficient to obtain an intermediate thrust; subtracting the gravity of each drone from the intermediate thrust to obtain an intermediate resultant force; and determining the total number of drones according to the intermediate resultant force and the load gravity.

[0084] In practice, in order to reserve margin for the weight of the rod and reserve margin for the mobility of the transportation system, the maximum thrust is multiplied by a preset coefficient to obtain an intermediate thrust, wherein, due to the high resistance to axial force of the truss structure, the weight of the rod can be light, and its proportion is very small compared to the weight of the drone and the load, but a margin must also be reserved for the weight of the rod; the margin for mobility of the transportation system is to allow the system to climb upwards, thereby realizing the transportation function. In this embodiment, the preset coefficient is 0.7. Therefore, the intermediate thrust is 0.7*f max , the intermediate thrust will be subtracted from the gravity of each drone to obtain the intermediate resultant force, such as the intermediate resultant force is f 合 =0.7*f max-G u , the load gravity G L Divide by the intermediate force f 合 , get the quotient H, which may be an integer or a decimal, and the total number of drones is an integer, so the quotient H is rounded up to get an integer value, and the integer value is used as the total number of drones. If the quotient H is 5, the total number of drones is 5; if the quotient H is 5.3, the total number of drones is 6.

[0085] After getting the total number of drones, you can execute Figure 2 The following steps are shown: S200, based on the total number of drones, a number of tethers, a number of rods and loads, a truss rigid structure diagram is constructed;

[0086] Since the system is composed of drones, several tethers, several rods and loads, after the number of drones is determined, the number of tethers is determined, and then the number and length of the rods can be used to construct the truss rigid structure diagram of the nodes formed by the drones and the loads and the edges formed by the tethers and the rods. In practice, although the rods can be made lightweight, they will also occupy part of the load capacity, so the added rods should be as few as possible; in addition, the rod length is the drone flight spacing, which is related to the actual system size configuration. The construction method of the present invention is applicable to any rod length, and is applicable to 1m rods as well as 10m rods.

[0087] In order to obtain a truss rigid structure diagram, the truss rigid structure diagram is constructed based on the total number of drones, a number of tethers, a number of rods and loads, including the following steps:

[0088] S201, determining initial nodes and initial edges according to loads, tethers and rods;

[0089] S202, adding a drone as a new node;

[0090] S203, counting the number of drones in the initial node and the number of drones in the newly added node to obtain the number of drones in use;

[0091] S204, obtaining newly added edges according to the added drone, load, tether and rod;

[0092] S205, when the number of the drones in use is less than the total number of the drones, continue to execute the step of adding a drone as a new node;

[0093] S206. When the number of drones in use is equal to the total number of drones, the step of adding a drone as a newly added node is stopped, and the initial node, initial edge, all newly added nodes and all newly added edges are generated into a truss rigid structure diagram.

[0094] Specifically, the initial edges include the first initial edges and the second initial edges. First, two drones are selected, and the two drones and the load are composed of three initial nodes. The drones and the load constitute the node set V, and the tethers and rods constitute the edge set E. A minimum rigid graph needs to be constructed. Among them, the n+1 nodes including the load and the n drones have been determined, and the edges corresponding to the n tethers have also been determined. What needs to be determined is the edge composed of the added rods. In order to build a rigid structure, a rod is added between the two drones. The rod is used as the first initial edge, and the tether between each drone and the load is used as the second initial edge. There are two second initial edges, so that the three nodes of the two drones and the load constitute a rigid subgraph. The truss rigid structure diagram of the entire system starts with the subgraph composed of these three nodes. Then, based on the above subgraph, a drone is added as a new node; the number of drones in the initial node and the number of drones in the new node are counted to obtain the number of drones in use; the tether between the added drone and the load is determined, and the tether between the added drone and the load is used as the first new edge; two additional rods are also added as edges to the drone nodes that are not yet connected to the drone in the rigid subgraph, and the rods between the added drone and the adjacent drones are used as the second new edges, that is, there are two second new edges, so that the newly generated subgraph remains rigid. This process continues until all drones are added to the rigid subgraph, specifically: when the number of drones in use is less than the total number of drones, continue to execute the step of adding a drone as a new node; when the number of drones in use is equal to the total number of drones, stop executing the step of adding a drone as a new node, and generate a truss rigid structure diagram with the initial node, initial edge, all new nodes and all new edges.

[0095] After the truss rigid structure diagram is constructed, you can execute Figure 2 The following steps are shown: S300, based on the truss rigid structure diagram, calculate the stress of each rod, and determine the yield strength of each rod according to the stress of each rod, wherein the yield strength is the strength index of each rod in the truss rigid structure diagram.

[0096] Specifically, the yield strength is an important indicator of the strength of each rod in the truss rigid structure diagram, which is used to characterize whether the rod is easy to break or deform. Once the rod is broken or deformed, it will inevitably affect the normal use of the truss air transportation system. After the truss rigid structure diagram is constructed, it is necessary to select appropriate rods so that the strength of the rods can meet the needs of actual transportation. Therefore, it is required to solve the stress of each rod. After obtaining the stress of each rod, the yield strength of each rod is obtained according to the relationship between stress and yield strength.

[0097] To obtain the stress, calculating the stress of each rod based on the rigid structure diagram of the truss includes the following steps: Obtain the connection matrix and the adjacency matrix defined by the user based on the rigid structure diagram of the truss; According to the adjacency matrix, obtain the configured mass corresponding to the drone; wherein, the configured mass is the mass of the rod assigned to the drone; Obtain the mass of a drone; Add the mass of a drone and the configured mass corresponding to the drone to obtain the node mass; Obtain the thrust of a drone in the equilibrium state; Obtain the node gravity according to the node mass, and decompose the node gravity and the thrust on the coordinate axes to respectively obtain the external force components on the X-axis, the Y-axis, and the Z-axis; Combine the external force components on the X-axis, the external force components on the Y-axis, and the external force components on the Z-axis to form an external force vector; Obtain the node coordinate values, and perform a mixed operation on the connection matrix and the node coordinate values to obtain an intermediate matrix; Multiply the inverted intermediate matrix by the external force vector to obtain a force density vector; According to the force density vector, obtain the stress of each rod.

[0098] Specifically, the user can be an engineer or other designers. The user first defines the connection matrix: wherein, V is the set of points, E is the set of edges, and adding the absolute value indicates the size of the C matrix, indicating that C is a real matrix of size |E|*|V|. The first |V|-1 members represent the tethers, and the other row members represent the rods. If member k (since the matrix C has |E| rows, so k ranges from 1 to |E|) connects nodes i and j (i < j), then the i-th and j-th elements of the k-th row will be assigned 1 and -1, that is, the connection matrix:

[0099]

[0100] Then define the adjacency matrix, that is:

[0101]

[0102]

[0103] wherein, (v i ,v j ) represents the edge from node j to node i.

[0104] After obtaining the connection matrix and the adjacency matrix, the configured mass corresponding to the drone can be obtained according to the adjacency matrix; wherein, the configured mass is the mass of the rod assigned to the drone; correspondingly, obtaining the configured mass corresponding to the drone according to the adjacency matrix includes the following steps: Obtain the masses m of several rods connected by the drone ij; Based on the adjacency matrix, the mass of several rods connected to the UAV is distributed to obtain the configuration mass corresponding to the UAV. For example, in the truss air transportation system, the mass of the tether can be ignored, and the mass of the rod can be evenly distributed to the two adjacent nodes connected to it, so the configuration mass is:

[0105]

[0106] Among them, m ij is the mass of the rod connecting drones i and j. Then get the mass m of a drone u , and the mass of a drone m u Add the configuration mass corresponding to the UAV to get the node mass m i ; The node quality is:

[0107]

[0108] After obtaining the node mass, obtain the thrust of a drone in a balanced state; for example: f i represents the thrust of the i-th UAV in the equilibrium state, and the node gravity m is obtained according to the node mass i g, and the node gravity m i g and the thrust f i Decompose on the coordinate axis and obtain the X-axis external force component F x , Y-axis external force component F y and the Z-axis external force component F z ; For load nodes, only m L g. Since decomposing the resultant force on the coordinate axis is an existing technology, it will not be repeated here. For example: in the inertial coordinate system, F x , F y and F z Represents the external force components of the node along the three axes. The X-axis external force component, the Y-axis external force component and the Z-axis external force component form an external force vector; for example:

[0109]

[0110] In addition, the overall method is used to analyze the forces on each drone and solve the following optimization equations:

[0111] min f T f

[0112] and constraint equations

[0113]

[0114]

[0115] in I3 represents a 3*3 diagonal identity matrix, cos 2 δ represents cosδ squared, which is a number. 2 δI3 is cos 2 δ multiplies a matrix I3; δ represents the maximum active angle of the ball joint, n =

[001] T Indicates the direction of the center axis of the ball joint.

[0116] Obtain node coordinate values, and perform mixed operations on the connection matrix and the node coordinate values ​​to obtain an intermediate matrix; for example: in an inertial coordinate system, define x, y, is the coordinate value of the node on each axis, and the intermediate matrix is

[0117]

[0118] In addition, in the truss force network, there are the following equilibrium relations:

[0119] C T diag(q)Cx=F x

[0120] C T diag(q)Cy=F y

[0121] C T diag(q)Cz=F z

[0122] in

[0123]

[0124] Solve the upper force balance equation, using the property diag(a)b=diag(b)a, where a and b are two vectors of the same dimension, the original balance equation can be written as:

[0125] Hq=F

[0126] Then, the intermediate matrix is ​​inverted (pseudo-inverse in this embodiment) and multiplied with the external force vector to obtain a force density vector; then the force density vector q can be obtained:

[0127] q=H + F

[0128] in(·) + Represents the pseudo-inverse of the matrix. Finally, the stress of each rod is obtained according to the force density vector. Accordingly, the stress of each rod is obtained according to the force density vector, including the following steps: obtaining each force density q in the force density vector q k The corresponding side length of the rod is l kIn practice, the safe flight distance of the drone is first determined based on the performance of the drone, and then the flight distance between drones is determined based on the safe flight distance, which is the rod length l k . Each force density q k The side length l of the rod corresponding to the force density k Multiply them to get the stress T of each member k . Get the stress T of each rod k After that, the yield strength of each rod can be determined according to the stress of each rod. In one implementation, the yield strength of each rod according to the stress of each rod includes the following steps: obtaining the cross-sectional area S of the rod corresponding to the stress of each rod k (S k represents the cross-sectional area of ​​the kth rod); obtain the safety factor χ; wherein the safety factor is used to characterize the safety of the rod; the stress T of each rod k The product T obtained by multiplying the safety factor χ k *χ divided by the cross-sectional area S of each member corresponding to the stress of each member k , and obtain several intensity values 0<χ<1 is the safety factor (can be 0.8), from the several strength values ​​P k The value that meets the preset conditions is selected as the yield strength σ. The calculation process is as follows:

[0129] For the added member, the yield strength σ needs to meet the following preset conditions:

[0130] σ>max{P k}

[0131] Based on the above embodiments, the present invention further provides an intelligent terminal, whose principle block diagram can be shown as follows: Figure 3 As shown. The intelligent terminal includes a processor, a memory, a network interface, a display screen, and a temperature sensor connected through a system bus. Among them, the processor of the intelligent terminal is used to provide computing and control capabilities. The memory of the intelligent terminal includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The network interface of the intelligent terminal is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a method for constructing a truss air transportation system is implemented. The display screen of the intelligent terminal can be a liquid crystal display screen or an electronic ink display screen, and the temperature sensor of the intelligent terminal is pre-set inside the intelligent terminal to detect the operating temperature of the internal equipment.

[0132] Those skilled in the art will understand that Figure 3The schematic diagram in the figure is only a block diagram of a part of the structure related to the scheme of the present invention, and does not constitute a limitation on the smart terminal to which the scheme of the present invention is applied. The specific smart terminal may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0133] In one embodiment, a smart terminal is provided, comprising a memory and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by one or more processors. The one or more programs include instructions for performing the following operations: obtaining a load gravity, and determining the total number of drones according to the load gravity;

[0134] Based on the total number of drones, a truss rigid structure diagram is constructed according to a number of tethers, a number of rods and loads;

[0135] Based on the truss rigid structure diagram, the stress of each rod is calculated, and the yield strength of each rod is determined according to the stress of each rod, wherein the yield strength is a strength index of each rod in the truss rigid structure diagram.

[0136] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided by the present invention can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0137] In summary, the present invention discloses a truss aerial transportation system and a construction method thereof, the system comprising: a number of drones; at least one ball joint, the ball joint being arranged on the drone; at least one tether, the tether being connected to the ball joint and used to connect the ball joint to a load; at least one rod, the rod being arranged between drones, and the two ends of the rod being respectively connected to the drones; the drones, the rods, the tethers and the loads forming a truss rigid structure. In the present invention, the drones are connected by rods, and the drones and the loads are connected by tethers, so that the drones, the rods, the tethers and the loads form a truss rigid structure, which improves the transportation efficiency of small-sized and heavy-weight loads.

[0138] Based on the above embodiments, the present invention discloses a method for constructing a truss aerial transportation system. It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, it can be improved or transformed according to the above description. All these improvements and transformations should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for constructing a truss aerial transportation system, characterized in that: The system includes a plurality of drones, at least one ball joint, at least one tether, and at least one rod, wherein the ball joint is arranged on the drone, the tether is connected to the ball joint and is used to connect the ball joint to a load, the rod is arranged between the drones, and both ends of the rod are respectively connected to the drones, the drones, the rod, the tether and the load constitute a truss rigid structure, the rod is a lightweight rod, and the method includes: Obtaining the payload gravity, and determining the total number of drones according to the payload gravity; Based on the total number of drones, a truss rigid structure diagram is constructed according to a number of tethers, a number of rods and loads; Based on the truss rigid structure diagram, the stress of each rod is calculated, and the yield strength of each rod is determined according to the stress of each rod, wherein the yield strength is a strength index of each rod in the truss rigid structure diagram; Determining the total number of drones according to the load gravity includes: Obtaining the gravity of each of the drones and the maximum thrust of the drones; Determining the total number of drones according to the gravity of each drone, the payload gravity, and the maximum thrust; The step of calculating the stress of each rod based on the truss rigid structure diagram includes: Obtaining a connection matrix and an adjacency matrix defined by a user based on the truss rigid structure diagram; According to the adjacency matrix, a configuration mass corresponding to the UAV is obtained; wherein the configuration mass is the mass of the rods assigned to the UAV; Get the mass of a drone; Adding the mass of a drone and the mass of the configuration corresponding to the drone to obtain the node mass; Get the thrust of a drone in a balanced state; Obtaining node gravity according to the node mass, and decomposing the node gravity and the thrust on the coordinate axis to obtain an X-axis external force component, a Y-axis external force component, and a Z-axis external force component, respectively; The X-axis external force component, the Y-axis external force component and the Z-axis external force component form an external force vector; Obtaining node coordinate values, and performing a mixed operation on the connection matrix and the node coordinate values ​​to obtain an intermediate matrix; Inverting the intermediate matrix and multiplying the matrix with the external force vector to obtain a force density vector; According to the force density vector, the stress of each rod is obtained; Determining the yield strength of each rod member according to the stress of each rod member includes: Obtain the cross-sectional area of ​​each rod corresponding to the stress of each rod; Obtaining a safety factor; wherein the safety factor is used to characterize the safety of the rod, and the safety factor is greater than 0 and less than 1; The product obtained by multiplying the stress of each rod by the safety factor is divided by the cross-sectional area of ​​the rod corresponding to the stress of each rod to obtain a number of strength values; A value that meets a preset condition is selected from the several strength values ​​as the yield strength.

2. The method for constructing a truss aerial transportation system according to claim 1, characterized in that: Determining the total number of drones according to the gravity of each drone, the load gravity, and the maximum thrust includes: Multiplying the maximum thrust by a preset coefficient to obtain an intermediate thrust; The intermediate thrust is subtracted from the gravity of each of the drones to obtain an intermediate resultant force; The total number of drones is determined according to the intermediate resultant force and the load gravity.

3. The method for constructing a truss aerial transportation system according to claim 2, characterized in that: Determining the total number of drones according to the intermediate resultant force and the load gravity includes: Dividing the load gravity by the intermediate resultant force to obtain a quotient; According to the quotient, the total number of drones is determined.

4. The method for constructing a truss aerial transportation system according to claim 3, characterized in that: Determining the total number of drones according to the quotient includes: The quotient is rounded up to obtain an integer value, and the integer value is used as the total number of drones.

5. The method for constructing a truss aerial transportation system according to claim 1, characterized in that: The method of constructing a truss rigid structure diagram based on the total number of drones, a number of tethers, a number of rods and loads includes: Determine the initial nodes and initial edges based on loads, ties and members; Add a drone as a new node; Count the number of drones in the initial node and the number of drones in the newly added node to obtain the number of drones in use; According to the added drones, loads, tethers and rods, the newly added edges are obtained; When the number of drones in use is less than the total number of drones, continue to perform the step of adding a drone as a newly added node; When the number of drones in use is equal to the total number of drones, the step of adding a drone as a newly added node is stopped, and the initial node, initial edge, all newly added nodes and all newly added edges are generated into a truss rigid structure diagram.

6. The method for constructing a truss aerial transportation system according to claim 5, characterized in that: The initial edge includes a first initial edge and a second initial edge; and the determining of the initial node and the initial edge according to the load, the tether and the rod includes: The two drones and the payload form three initial nodes; Take the rod between the two drones as the first initial edge; The tether between the two drones and the payload is used as the second initial edge.

7. The method for constructing a truss aerial transportation system according to claim 5, characterized in that: According to the added drone, load, tether and rod, the newly added edges include: Add the tether between the drone and the payload as the first added edge; The rod between the added UAV and the adjacent UAV is used as the second added edge.

8. The method for constructing a truss aerial transportation system according to claim 1, characterized in that: The obtaining, according to the adjacency matrix, a configuration quality corresponding to the drone includes: Obtaining the masses of several rods connected to the drone; Based on the adjacency matrix, a distribution operation is performed on the masses of a plurality of rods connected to the drone to obtain a configuration mass corresponding to the drone.

9. The method for constructing a truss aerial transportation system according to claim 1, characterized in that: Obtaining the stress of each rod according to the force density vector includes: Obtaining the side length of the rod corresponding to each force density in the force density vector; Each force density is multiplied by the side length of the rod corresponding to the force density to obtain the stress of each rod.

10. An intelligent terminal, characterized in that: The invention comprises a memory and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by one or more processors, including the one or more programs for executing the method according to any one of claims 1 to 9.

11. A non-transitory computer-readable storage medium, characterized in that: When the instructions in the storage medium are executed by a processor of an electronic device, the electronic device is enabled to execute the method as claimed in any one of claims 1 to 9.

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