Layout optimization method for undercarriage system of unmanned aerial vehicle

Abstract

The invention discloses a layout optimization method for an undercarriage system of an unmanned aerial vehicle, and the method specifically comprises the following steps: S1, simplifying the undercarriage system, and determining the type of a connection pair of the undercarriage system; s2, acquiring point coordinates, undercarriage system performance limitation and operation conditions required for constructing the undercarriage system model; s3, according to the undercarriage system point position coordinates, design variables are determined, and a parameterized model is generated; s4, an undercarriage ground load, gravity and a cabin door folding and unfolding load are applied, and the effective conditions of all the loads are set; s5, according to the folding and unfolding stroke, the undercarriage folding and unfolding angle limitation and the undercarriage system installation shipping space limitation, a corresponding related constraint function is constructed; s6, an objective function is determined according to the fuselage cross-linking load, the retracting and releasing load and the retracting and releasing efficiency; and S7, optimizing the target function, namely optimizing the mounting point position of the undercarriage and the mounting point position of the retracting and releasing actuator cylinder, and finally obtaining the optimal overall arrangement of the undercarriage system.

Description

Technical Field

[0001] The invention relates to the field of aviation technology, and in particular to a layout optimization method for a landing gear system of a drone. Background Art

[0002] As drones are light, fuel-efficient, short re-deployment time, and easy to maintain, the demand for drones is increasing as they are used in various fields at home and abroad. Various drones have customized space arrangements, which means that the landing gear system of drones also needs to be designed individually according to the space arrangement.

[0003] The landing gear system of a drone is mainly composed of a landing gear and a retractable actuator. The landing gear system is usually installed in the limited cabin of the drone, and the spatial layout is greatly restricted. The spatial layout of the landing gear system not only needs to consider that there is no interference with other components in the cabin during the retraction process, but also needs to consider that the retraction stroke, retraction load, etc. meet the design requirements during the entire retraction process. This is a difficult problem for the design layout of the landing gear system.

[0004] Conventional landing gear system spatial layout usually uses the establishment of associated motion for three-dimensional digital models to give priority to non-interference requirements, and then repeatedly adjusts them to make the retraction and extension stroke, retraction and extension load, etc. reach acceptable ranges. However, such a design method is time-consuming and laborious, and it is impossible to uniformly consider all constraints in a short period of time. Sometimes after the design is completed, one of the key constraints or design requirements cannot be met, and the design needs to be iterated repeatedly. When one or more design requirements change, the design iteration of the spatial layout needs to confirm whether the design requirements are met by adjusting the digital model, which is not conducive to the rapid update of the spatial layout. Summary of the invention

[0005] In view of the technical problem that the layout design of the UAV landing gear system in the prior art is time-consuming, the present invention proposes a layout optimization method for the UAV landing gear system.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for optimizing the layout of a UAV landing gear system comprises the following steps:

[0008] S1: Simplify the landing gear system and confirm the landing gear system connection sub-category;

[0009] S2: Obtain the point coordinates, landing gear system performance limitations and operating conditions required to build a landing gear system model;

[0010] S3: According to the point coordinates of the landing gear system, confirm the design variables and generate a parameterized model;

[0011] S4: Apply landing gear ground load, gravity and door retraction load, and set the effectiveness of each load;

[0012] S5: Construct corresponding related constraint functions according to the retraction and extension stroke, the landing gear retraction and extension angle limit, and the landing gear system installation compartment space limit;

[0013] S6: Confirm the objective function based on the fuselage cross-linking load, stowage load, and stowage efficiency;

[0014] S7: Optimize the objective function, that is, optimize the installation points of the landing gear and the installation points of the retractable actuator, and finally obtain the optimal overall layout of the landing gear system.

[0015] Preferably, in S1, making simplified assumptions on the landing gear system includes:

[0016] Assumption 1: The shapes of all components in the UAV landing gear system are replaced by point-line models, ignoring fit and clearance;

[0017] Assumption 2: The coordinates of the connection points of all components in the UAV landing gear system are taken as the center point of the connection area;

[0018] Assumption 3: The loads applied to the UAV landing gear system are all concentrated forces or moments;

[0019] Assumption 4: The lowering status and lowering angle of the front landing gear and main landing gear of the UAV landing gear system have been determined;

[0020] Assumption 5: The UAV's door retracting mechanism is linked to the landing gear, and the load applied by the door retracting mechanism to the landing gear has been determined;

[0021] Assumption 6: The three-side layout of the landing gear system in the extended state has been determined.

[0022] Preferably, in said S1, the types of connection pairs of the landing gear system include ball pairs, translation pairs and rotation pairs;

[0023] The landing gear system comprises a landing gear (1), a retractable actuator cylinder piston rod (2) and a retractable actuator cylinder outer cylinder (3); wherein the retractable actuator cylinder outer cylinder (3) and the fuselage, the retractable actuator cylinder piston rod (2) and the landing gear are connected by a ball pair, the retractable actuator cylinder outer cylinder (3) and the retractable actuator cylinder piston rod (2) are connected by a moving pair, and the landing gear (1) and the fuselage are connected by a left rotation pair and a right rotation pair.

[0024] Preferably, the S2 includes:

[0025] S2-1: Establish the Cartesian coordinate system of the drone landing gear system: the positive direction of the X axis is from the tail to the nose of the drone, the positive direction of the Y axis is perpendicular to the X axis and located in the same horizontal plane; the positive direction of the Z axis is the sky direction;

[0026] S2-2: After assembling the landing gear system to the correct Cartesian coordinate system, the connection pairs of the landing gear system are identified by category, and the number of points required is confirmed by category and point overlap; then the coordinates of each required point are measured and recorded to form the original point coordinate matrix X:

[0027]

[0028] In formula (1), x1 represents the x-axis coordinate of the first point; y1 represents the y-axis coordinate of the first point; z1 represents the z-axis coordinate of the first point; n Indicates the x-axis coordinate of the nth point; y n Indicates the y-axis coordinate of the nth point; z n Indicates the z-axis coordinate of the nth point.

[0029] Preferably, in S2-2, the number of points required is: 1 point required for the ball joint, 2 points required for the rotation joint, 2 points required for the translation joint, 1 point required for the single load application, and 1 point required for the center of mass of a single component; 2 points are required for constructing a single cylindrical component, 3 points are required for constructing a single triangular prism component, and 2 points are required for constructing a single rectangular component.

[0030] Preferably, S3 includes:

[0031] S3-1: Parameterize the original point coordinate matrix and determine the design variables;

[0032] S3-2: Establish a parametric model based on design variables.

[0033] Preferably, the S3-1 includes:

[0034] S3-1-1: Identify the relevant points, then parameterize and determine the design variables;

[0035] The related points include symmetrical relationships, coplanar relationships, and colinear relationships; the design variables include a first design variable DV1, a second design variable DV2, a third design variable DV3, and a fourth design variable DV4;

[0036] S3-1-2: Set the valid value range for the design variables:

[0037] The point coordinates must ensure that the landing gear system can maintain avoidance space in the cabin space during the entire movement process. Regular shapes are drawn using the set points to simplify the modeling of the landing gear system.

[0038] Preferably, in S4, the gravity is applied to the center of gravity of the landing gear;

[0039] The ground load includes the apical load F y , heading load F x and the lateral load F z , axial load F y , heading load F x Applied at the center of the landing gear axle, the lateral load F z Applied to the landing gear tire contact point;

[0040] The door retraction and extension load includes single-side door retraction and extension and double-side door retraction and extension; among them, single-side door retraction means that only one side of the door of the landing gear system opens and closes, and the force application point is the center point of the connection pair between the door mechanism and the landing gear; double-side door retraction means that the landing gear system has double-side doors opening and closing, and the force application points are respectively the center points of the connection pairs between the door mechanisms on both sides and the landing gear.

[0041] Preferably, the S5 includes:

[0042] S4-1: Construct the length constraint function of the retractable actuator:

[0043]

[0044] In formula (2), L min Indicates the minimum length allowed for the retractable actuator; the first design variable DV1, the second design variable DV2, the third design variable DV3, the fourth design variable DV4; S indicates the retracted displacement;

[0045] S4-2: Construct the landing gear retraction angle limit constraint function:

[0046] g2(X)=Sc min -r wheel -Sc(X) t＝ts ≤0 (3)

[0047] In formula (3), g2(X) represents the landing gear retraction angle limit constraint function; Sc min Indicates the minimum distance between the wheel center and the door when the landing gear is fully retracted; r wheel Indicates the maximum radius of the tire; ts is the time when the landing gear is fully retracted; Sc(X) t＝ts Indicates the distance between the wheel center and the door when the landing gear is fully retracted;

[0048] S4-3: Construct point space restriction constraint function:

[0049]

[0050] In formula (4), g3(X) represents the point space constraint function; CONTACT(X) i represents the i-th contact force; n represents the number of contact forces;

[0051] S4-4: Construct the relative position constraint function of each component of the landing gear system:

[0052] PO=z1-z2-5≥0 (5)

[0053] In formula (5), PO represents the position constraint between two points; z1 represents the z-direction distance of the first point; z2 represents the z-direction distance of the second point;

[0054] Based on the above, we can infer:

[0055]

[0056] In formula (6), g4(X) represents the relative position constraint function of each component of the landing gear system; PO(X) i represents the position constraint of the i-th point; m represents the number of relative position constraints of the points.

[0057] Preferably, in S6, the objective function is the fuselage load, the stowage load and the stowage efficiency;

[0058] The fuselage load is divided into the combined force of the load at the connection between the fuselage and the components of the take-off and landing system:

[0059]

[0060] In formula (7), F1 represents the load on the fuselage; n represents the total number of connections, K i are the penalty factors of each objective function, and their magnitude and value need to be adjusted according to the actual working conditions. 1,i is the resultant load at each connection;

[0061] The magnitude of the retracting load F2 is the same as the resultant force on the fuselage at the connection of the retracting actuator;

[0062] Assume that the retractable actuator is in the maximum extension state in the initial state, and the maximum contraction displacement is S max , then the retractable efficiency is:

[0063]

[0064] In formula (8), η represents the retraction efficiency; S max represents the maximum contraction displacement; Indicates the maximum combined force on the fuselage at the connection point of the retracting and extending actuator;

[0065] To simplify the calculation, the objective function is transformed from multi-objective optimization to a single-objective optimization problem:

[0066] Q=α1F1+α2F2+α3η (9)

[0067] In formula (9), α1, α2, and α3 are the penalty factors of each objective function.

[0068] In summary, due to the adoption of the above technical solution, compared with the prior art, the present invention has at least the following beneficial effects:

[0069] The present invention saves time and calculation cost for the initial layout design of the landing gear system, provides a guarantee for the rapid iteration of the layout of the landing gear system, and simplifies the load analysis and motion state analysis of the landing gear system. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 Schematic diagram of a layout optimization method for a UAV landing gear system according to an exemplary embodiment of the present invention.

[0071] Figure 2 FIG. 2 is a schematic diagram of a landing gear system connection according to an exemplary embodiment of the present invention.

[0072] Figure 3 Schematic diagram of a parameterized model of a landing gear system according to an exemplary embodiment of the present invention.

[0073] Figure 4 Schematic diagram of a cabin space restriction import model according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0074] The present invention is further described in detail below in conjunction with the examples and specific implementation methods. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0075] In the description of the present invention, it is necessary to understand that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0076] like Figure 1 As shown, the present invention provides a layout optimization method for a UAV landing gear system, which specifically includes the following steps:

[0077] S1: Make simplifying assumptions about the UAV landing gear system and confirm the landing gear system connection subcategory.

[0078] In this embodiment, simplified assumptions are made about the drone landing gear system including:

[0079] Assumption 1: The shapes of all components in the UAV landing gear system are replaced by point-line models, ignoring irrelevant parameters such as fit and clearance;

[0080] Assumption 2: The coordinates of the connection points of all components in the UAV landing gear system are taken as the center point of the connection area;

[0081] Assumption 3: The loads applied to the UAV landing gear system are all concentrated forces or moments;

[0082] Assumption 4: The lowering status and lowering angle of the front landing gear and main landing gear of the UAV landing gear system have been determined;

[0083] Assumption 5: The UAV's door retracting mechanism is linked to the landing gear, and the load applied by the door retracting mechanism to the landing gear has been determined;

[0084] Assumption 6: The three-side layout of the landing gear system in the extended state has been determined.

[0085] In this embodiment, the landing gear system connection pair categories include ball joints, translation joints and rotation joints.

[0086] like Figure 2 As shown, a set of actuator direct push landing gear system includes landing gear 1, retractable actuator piston rod 2 and retractable actuator outer cylinder 3; the landing gear system needs to be bilaterally symmetrical on the XY plane of the drone. The actuator outer cylinder 3 and the fuselage, the actuator piston rod 2 and the landing gear are connected by ball joints, the actuator outer cylinder 3 and the piston rod 2 are connected by moving joints, and the landing gear 1 and the fuselage are connected by left and right revolute joints.

[0087] S2: Acquire the landing gear system point coordinates, relevant performance limitations of the landing gear system, and operating conditions (including load and working status) to establish an original point coordinate matrix.

[0088] In this embodiment, a Cartesian coordinate system of the drone landing gear system is established: the positive direction of the X axis is from the tail to the nose of the drone, the positive direction of the Y axis is perpendicular to the X axis and located in the same horizontal plane; the sky direction is the positive direction of the Z axis;

[0089] In this embodiment, after the landing gear system is assembled to the correct rectangular coordinate system, the connection pairs of the landing gear system are identified by category, and the required number of points is confirmed by the category and point overlap (reusable points, thereby reducing point settings).

[0090] In this embodiment, two ball joints and one movable joint can share two points to establish, and two rotational joints can be determined by two shared points. Therefore, the number of points required is: 1 point required for the ball joint, 2 points required for the rotational joint, 2 points required for the movable joint, 1 point required for single load application, and 1 point required for the center of mass of a single component; 2 points are required to construct a single cylindrical component, 3 points are required to construct a single triangular prism component, and 2 points are required to construct a single rectangular component.

[0091] Then measure and record the coordinates of each required point, as shown in Table 1, to form the original point coordinate matrix X:

[0092]

[0093] In formula (1), x1 represents the x-axis coordinate of the first point; y1 represents the y-axis coordinate of the first point; z1 represents the z-axis coordinate of the first point; n Indicates the x-axis coordinate of the nth point; y n Indicates the y-axis coordinate of the nth point; z n Indicates the z-axis coordinate of the nth point.

[0094] Table 1. Point coordinates

[0095]

[0096]

[0097] S3: Confirm the design variables based on the original point coordinate matrix and establish a parametric model.

[0098] S3-1: Parameterize the original point coordinate matrix and determine the design variables.

[0099] S3-1-1: Identify the related points, then parameterize and determine the design variables.

[0100] In this embodiment, the associated points include points with symmetrical relationships, coplanar relationships, colinear relationships, etc. These points need to be identified in advance before parameterization in order to simplify the number of parameterized variables.

[0101] In this embodiment, the point coordinates in Table 1 are parameterized to obtain a first design variable DV1, a second design variable DV2, a third design variable DV3, and a fourth design variable DV4, as shown in Table 2.

[0102] Table 2. Design variables determination

[0103]

[0104]

[0105] S3-1-2: Set the valid value range for the design variables.

[0106] According to the landing gear system structure and rapid update iteration, the valid value range of the design variables is set as follows: the point coordinates must satisfy the requirement that a certain avoidance space can be maintained in the cabin space during the entire movement of the landing gear system. The set points are used to draw regular shapes such as rectangles, triangular prisms, cylinders, etc. to simplify the modeling of the landing gear system.

[0107] In this embodiment, comprehensive table 2 can set the effective value range for the first design variable DV1, the second design variable DV2, the third design variable DV3, and the fourth design variable DV4:

[0108] -270≥DV1≥-330, 210≥DV2≥170, -530≥DV3≥-555, -255≥DV4≥-315.

[0109] S3-2: Establish a parametric model based on design variables.

[0110] Use the design variables of the set points to draw regular shapes such as cuboids, triangular prisms, cylinders, etc. to perform parametric modeling of the landing gear system. Figure 3 For example, the retractable actuator can be replaced by two cylinders and a cuboid, the two cylinders represent the piston rod and the outer cylinder respectively, and the cuboid represents the motor assembly; the connection pairs between the components are set at the center point of the connection between the components.

[0111] S4: Apply landing gear ground load, gravity and door retraction load, and set the effectiveness of each load.

[0112] In this embodiment, a lateral load F is applied to the center point of the wheel axle. y , heading load F x , apply a lateral load F to the tire contact point z , a gravity load is applied to the center of mass of the landing gear retracting and extending actuator, and a door mechanism load is applied to the door mechanism connection on the landing gear. The model is as follows Figure 3 shown.

[0113] The gravity is applied to the center of gravity of the landing gear; the ground load is divided into the axial load F y , heading load F x and the lateral load F Z, the azimuth load and heading load are applied to the center of the landing gear axle, and the lateral load is applied to the ground contact point of the landing gear tire; the door retraction and extension load is divided into two cases: single-side door retraction and extension and double-sided door retraction and extension. Single-side door retraction means that only one side of the landing gear system has a door opening and closing, so only the door retraction and extension load of one side of the door needs to be established, and the force application point is the center point of the connection pair between the door mechanism and the landing gear. Double-sided door retraction means that the landing gear system has doors opening and closing on both sides, so the door retraction and extension load of both sides of the door needs to be established, and the force application points are the center points of the connection pairs between the door mechanisms and the landing gear.

[0114] In this embodiment, the payload validity is set as follows:

[0115] The static load analysis of the landing gear system and the retraction and extension load analysis are integrated to transform into an optimization model of the landing gear system working state affected by time. When the optimization reaches the static load analysis stage of the landing gear system, the landing gear system is locked in the down state, and the load applies the landing gear ground load and the door fixed angle load; when the optimization reaches the system retraction and extension load analysis, the landing gear system is retracted and extended, and the load applies gravity and the door retraction and extension load. The details are as follows:

[0116] Static load analysis mainly analyzes the situation when the landing gear is subjected to static load. At this time, the actuator is locked in a fully extended state. Since gravity is already included in the landing gear ground load calculation, gravity load is not applied during the static load analysis of the landing gear system.

[0117] The static load of the landing gear system is divided into loads of various working conditions. After analyzing the static load conditions, they are programmed as a function of load and time to achieve simulation of all static load conditions within a certain period of time; the door retraction load changes with the door opening and closing angle, and the door opening and closing angle changes with the landing gear rotation angle. The door retraction load is set to a load that changes with the landing gear rotation angle, and the door retraction load is simulated; gravity can be expressed as a force fixed in the negative direction of the Y-axis above the center of mass.

[0118] When performing static load analysis on the landing gear system, the static load is valid and the landing gear system is locked in the lowered state. At this time, the actuator is locked in the fully extended state. Since gravity is already included in the landing gear ground load calculation, the gravity load is not applied during the static load analysis of the landing gear system.

[0119] When analyzing the landing gear retraction and extension load of the landing gear system, the door retraction and extension load and gravity are valid. When the landing gear system is retracted and extended, the static load is invalid. The door retraction and extension load changes with the door opening and closing angle, and the door opening and closing angle changes with the landing gear rotation angle. The door retraction and extension load is set to the load that changes with the landing gear rotation angle, and the door retraction and extension load is simulated. Gravity can be expressed as a force fixed in the negative direction of the Y axis on the center of mass, with a magnitude of mg.

[0120] That is, assuming that the static load simulation duration is t1, the load application is:

[0121] Ift≤t1, static load is valid, door retraction load and gravity are 0;

[0122] Ift>t1, the door retraction and extension load and gravity are effective, and the static load is 0.

[0123] S5: Construct corresponding related constraint functions according to the retraction and extension stroke, the landing gear retraction and extension angle limit, and the landing gear system installation compartment space limit.

[0124] S5-1: Construct the length constraint function of the retractable actuator.

[0125] In this embodiment, the retracting and extending stroke is affected by the structural characteristics of the retracting and extending actuator and has a minimum length restriction, namely:

[0126]

[0127] In formula (2), L min Indicates the minimum length allowed for the retractable actuator; the first design variable DV1, the second design variable DV2, the third design variable DV3, the fourth design variable DV4; S represents the retracted displacement.

[0128] S5-2: Construct a landing gear retraction and extension angle limit constraint function.

[0129] In this embodiment, in order to ensure that the landing gear can be completely retracted into the landing gear system compartment and keep a clearance distance from the door area when retracted, the minimum retraction angle of the landing gear is constrained, and the constraint function is converted into the minimum distance Sc between the wheel center and the door when the landing gear is fully retracted. min constraint:

[0130] g2(X)=Sc min -r wheel -Sc(X) t＝ts ≤0 (3)

[0131] In formula (3), g2(X) represents the landing gear retraction angle limit constraint function; Sc min Indicates the minimum distance between the wheel center and the door when the landing gear is fully retracted; r wheel Indicates the maximum radius of the tire; ts is the time when the landing gear is fully retracted; Sc(X) t＝ts Indicates the distance between the wheel center and the cabin door when the landing gear is fully retracted.

[0132] S5-3: Construct point space restriction constraint function.

[0133] In this embodiment, the layout of the landing gear system is restricted by the point space. During the entire retraction and extension process, it is necessary not to interfere with the point space and maintain a certain avoidance distance. For this purpose, the point space constraint is transformed: the point space is reduced so that the reduced point space and the original point space always maintain the avoidance distance requirement, and the reduced point space is in contact with the various components of the landing gear system. The final constraint function is:

[0134]

[0135] In formula (4), g3(X) represents the point space restriction constraint function; represents the i-th contact force; n represents the number of contact forces.

[0136] For example, space constraints can be imported into the model, such as Figure 4 As shown, mutual contact forces CONTACT1, CONTACT2, and CONTACT3 are established between the cabin space and the landing gear, the cabin space and the retracting actuator, and the retracting actuator and the landing gear, respectively, and the point space restriction function is established:

[0137] CONTACT1+CONTACT2+CONTACT3≤0.

[0138] S5-4: Construct the relative position constraint function of each component of the landing gear system.

[0139] In this embodiment, in order to ensure that the relative positions of the components of the landing gear system meet the design requirements, the relative positions of the components are constrained, which is converted into the relationship between the points of the components: if point 1 is required to be always above point 2, and the z-direction distance must not be less than 5 mm, then the position constraint between point 1 and point 2 is:

[0140] PO=z1-z2-5≥0 (5)

[0141] In formula (5), PO represents the position constraint between two points; z1 represents the z-direction distance of the first point; z2 represents the z-direction distance of the second point;

[0142] Based on the above content, it can be deduced that:

[0143]

[0144] In formula (6), g4(X) represents the relative position constraint function of each component of the landing gear system; PO(X) i represents the position constraint of the i-th point; m represents the number of relative position constraints of the points.

[0145] S6: Confirm the objective function based on the fuselage cross-linking load, stowage load, and stowage efficiency.

[0146] Among them, the fuselage load (i.e., the fuselage cross-link load) is divided into the landing gear left shaft fuselage load force F 1,1 , landing gear right shaft fuselage load force F 1,2 , the combined force F on the fuselage at the connection between the retractable and extended actuator 1,3 , then the load on the fuselage is:

[0147]

[0148] In formula (7), F1 represents the load on the fuselage; n represents the total number of connections; K i are the penalty factors of each objective function, and their magnitude and value need to be adjusted according to the actual working conditions; F 1,i is the resultant force of the loads at each connection, for example, F 1,1 Indicates the resultant force on the fuselage of the left shaft of the landing gear; F 1,2 Indicates the resultant force on the fuselage of the right shaft of the landing gear; F 1,3 Indicates the combined force on the fuselage at the connection between the retractable and extended actuators.

[0149] In this embodiment, the retraction load refers to the driving force required when the retraction actuator drives the landing gear to be retracted or lowered, which is expressed as F2; ​​if the retraction load F2 is the same as the resultant force on the fuselage at the connection between the retraction actuator and the landing gear, it does not need to be applied separately.

[0150] In this embodiment, it is assumed that the retractable actuator is in the maximum extension state in the initial state, and the contraction displacement is S, then:

[0151]

[0152] In formula (8), η represents the retraction efficiency; S max represents the maximum contraction displacement; Indicates the maximum combined force on the fuselage at the connection point of the retracting and extending actuator;

[0153] In this embodiment, in order to simplify the calculation, the objective function is transformed from a multi-objective (fuselage load, stowage load, stowage efficiency) optimization into a single-objective optimization problem, that is, the objective function:

[0154] Q=α1F1+α2F2+α3η (9)

[0155] In formula (9), α1, α2, and α3 are the penalty factors of each objective function; F1 represents the load on the fuselage; F2 represents the retraction load; and η represents the retraction efficiency.

[0156] S7: Use existing analysis software (ADAMS / ANSYS MOTION / LMS VIRTUAL LAB / NASTRAN / ABAQUS) to optimize the objective function, that is, optimize the installation points of the landing gear and the installation points of the retractable actuator, and finally obtain the optimal overall layout of the landing gear system.

[0157] Those skilled in the art will appreciate that the above-mentioned embodiments are specific examples for implementing the present invention, and in actual applications, various changes may be made thereto in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A method for optimizing the layout of a UAV landing gear system, characterized in that: The specific steps include: S1: Simplify the landing gear system and confirm the landing gear system connection sub-category; S2: Obtain the point coordinates, landing gear system performance limitations and operating conditions required to build a landing gear system model; S3: According to the point coordinates of the landing gear system, confirm the design variables and generate a parameterized model; S4: Apply landing gear ground load, gravity and door retraction load, and set the effectiveness of each load; S5: Construct corresponding related constraint functions according to the retraction and extension stroke, the landing gear retraction and extension angle limit, and the landing gear system installation compartment space limit; S6: Confirm the objective function based on the fuselage cross-linking load, stowage load, and stowage efficiency; S7: Optimize the objective function, that is, optimize the installation points of the landing gear and the installation points of the retractable actuator, and finally obtain the optimal overall layout of the landing gear system.

2. The layout optimization method of a UAV landing gear system according to claim 1, characterized in that: In S1, simplified assumptions are made for the landing gear system including: Assumption 1: The shapes of all components in the UAV landing gear system are replaced by point-line models, ignoring fit and clearance; Assumption 2: The coordinates of the connection points of all components in the UAV landing gear system are taken as the center point of the connection area; Assumption 3: The loads applied to the landing gear system of the UAV are all concentrated forces or moments; Assumption 4: The lowering status and lowering angle of the front landing gear and main landing gear of the UAV landing gear system have been determined; Assumption 5: The UAV's door retracting mechanism is linked to the landing gear, and the load applied by the door retracting mechanism to the landing gear has been determined; Assumption 6: The three-side layout of the landing gear system in the extended state has been determined.

3. The layout optimization method of a UAV landing gear system according to claim 1, characterized in that: In S1, the landing gear system connection pair categories include ball joints, translation joints and rotation joints; The landing gear system comprises a landing gear (1), a retractable actuator cylinder piston rod (2) and a retractable actuator cylinder outer cylinder (3); wherein the retractable actuator cylinder outer cylinder (3) and the fuselage, the retractable actuator cylinder piston rod (2) and the landing gear are connected by a ball pair, the retractable actuator cylinder outer cylinder (3) and the retractable actuator cylinder piston rod (2) are connected by a moving pair, and the landing gear (1) and the fuselage are connected by a left rotation pair and a right rotation pair.

4. The layout optimization method of a UAV landing gear system according to claim 1, characterized in that: The S2 includes: S2-1: Establish the Cartesian coordinate system of the drone landing gear system: the positive direction of the X axis is from the tail to the nose of the drone, the positive direction of the Y axis is perpendicular to the X axis and located in the same horizontal plane; the positive direction of the Z axis is the sky direction; S2-2: After assembling the landing gear system to the correct Cartesian coordinate system, the connection pairs of the landing gear system are identified by category, and the number of points required is confirmed by category and point overlap; then the coordinates of each required point are measured and recorded to form the original point coordinate matrix X: In formula (1), x1 represents the x-axis coordinate of the first point; y1 represents the y-axis coordinate of the first point; z1 represents the z-axis coordinate of the first point; n Indicates the x-axis coordinate of the nth point; y n Indicates the y-axis coordinate of the nth point; z n Indicates the z-axis coordinate of the nth point.

5. The layout optimization method of a UAV landing gear system according to claim 4, characterized in that: In S2-2, the number of points required is: 1 point required for the ball joint, 2 points required for the rotation joint, 2 points required for the translation joint, 1 point required for the application of a single load, and 1 point required for the center of mass of a single component; 2 points are required to construct a single cylindrical component, 3 points are required to construct a single triangular prism component, and 2 points are required to construct a single rectangular component.

6. The method for optimizing the layout of a UAV landing gear system according to claim 1, characterized in that: The S3 includes: S3-1: Parameterize the original point coordinate matrix and determine the design variables; S3-2: Establish a parametric model based on design variables.

7. The method for optimizing the layout of a UAV landing gear system according to claim 6, characterized in that: The S3-1 includes: S3-1-1: Identify the relevant points, then parameterize and determine the design variables; The related points include symmetrical relationships, coplanar relationships, and colinear relationships; the design variables include a first design variable DV1, a second design variable DV2, a third design variable DV3, and a fourth design variable DV4; S3-1-2: Set the valid value range for the design variables: The point coordinates must ensure that the landing gear system can maintain avoidance space in the cabin space during the entire movement process. Regular shapes are drawn using the set points to simplify the modeling of the landing gear system.

8. The method for optimizing the landing gear system of a UAV according to claim 1, characterized in that: In S4, the gravity is applied to the center of gravity of the landing gear; The ground load includes the apical load F y , heading load F x and the lateral load F z , axial load F y , heading load F x Applied at the center of the landing gear axle, the lateral load F z Applied to the landing gear tire contact point; The door retraction and extension load includes single-side door retraction and extension and double-side door retraction and extension; among them, single-side door retraction means that only one side of the door of the landing gear system opens and closes, and the force application point is the center point of the connection pair between the door mechanism and the landing gear; double-side door retraction means that the landing gear system has double-side doors opening and closing, and the force application points are respectively the center points of the connection pairs between the door mechanisms on both sides and the landing gear.

9. The method for optimizing the layout of a UAV landing gear system according to claim 1, characterized in that: The S5 includes: S4-1: Construct the length constraint function of the retractable actuator: In formula (2), L min Indicates the minimum length allowed for the retractable actuator; the first design variable DV1, the second design variable DV2, the third design variable DV3, the fourth design variable DV4; S indicates the retracted displacement; S4-2: Construct the landing gear retraction angle limit constraint function: g2(X)=Sc min -r wheel -Sc(X) t＝ts ≤0 (3) In formula (3), g2(X) represents the landing gear retraction angle limit constraint function; Sc min Indicates the minimum distance between the wheel center and the door when the landing gear is fully retracted; r wheel Indicates the maximum radius of the tire; ts is the time when the landing gear is fully retracted; Sc(X) t＝ts Indicates the distance between the wheel center and the door when the landing gear is fully retracted; S4-3: Construct point space restriction constraint function: In formula (4), g3(X) represents the point space constraint function; CONTACT(X) i represents the i-th contact force; n represents the number of contact forces; S4-4: Construct the relative position constraint function of each component of the landing gear system: PO=z1-z2-5≥0 (5) In formula (5), PO represents the position constraint between two points; z1 represents the z-direction distance of the first point; z2 represents the z-direction distance of the second point; Based on the above, we can infer: In formula (6), g4(X) represents the relative position constraint function of each component of the landing gear system; PO(X) i represents the position constraint of the i-th point; m represents the number of relative position constraints of the points.

10. The method for optimizing the layout of a UAV landing gear system according to claim 1, characterized in that: In S6, the objective function is the fuselage load, the stowage load and the stowage efficiency; The fuselage load is divided into the combined force of the load at the connection between the fuselage and the components of the take-off and landing system: In formula (7), F1 represents the load on the fuselage; n represents the total number of connections, K i are the penalty factors of each objective function, and their magnitude and value need to be adjusted according to the actual working conditions. 1,i is the resultant load at each connection; The magnitude of the retracting load F2 is the same as the resultant force on the fuselage at the connection of the retracting actuator; Assume that the retractable actuator is in the maximum extension state in the initial state, and the maximum contraction displacement is S max , then the retractable efficiency is: In formula (8), η represents the retraction efficiency; S max represents the maximum contraction displacement; Indicates the maximum combined force on the fuselage at the connection point of the retracting and extending actuator; To simplify the calculation, the objective function is transformed from multi-objective optimization to a single-objective optimization problem: Q=α1F1+α2F2+α3η (9) In formula (9), α1, α2, and α3 are the penalty factors of each objective function.

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