CN112528410B - Landing gear retraction track determining method and system - Google Patents

Landing gear retraction track determining method and system Download PDF

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Publication number
CN112528410B
CN112528410B CN202011451958.4A CN202011451958A CN112528410B CN 112528410 B CN112528410 B CN 112528410B CN 202011451958 A CN202011451958 A CN 202011451958A CN 112528410 B CN112528410 B CN 112528410B
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landing gear
coordinate
end point
coordinate system
strut
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CN112528410A (en
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印寅
邹泽铧
朱林昊
刘相阳
蔡新之
魏小辉
聂宏
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Nanjing University of Aeronautics and Astronautics
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Nanjing University of Aeronautics and Astronautics
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/10—Geometric CAD
    • G06F30/15—Vehicle, aircraft or watercraft design
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation

Abstract

The invention provides a method and a system for determining a retraction track of an undercarriage, wherein the method comprises the following steps: determining a coordinate q1 of the last end point of the landing gear strut when being put down, a desired coordinate q2 of the last end point of the landing gear strut when being taken up, a third triangle network and a fourth triangle network under a global coordinate system; constructing a unit vector formula of the rotating shaft according to the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down and the expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is taken up under a global coordinate system; and determining an optimal receiving and releasing path according to a unit vector formula of the rotating shaft by adopting an optimization algorithm. Compared with the traditional manual design-dependent method, the method can automatically design and solve, save the effort of the people in the design process, shorten the design time, and solve the optimal receiving and releasing path without depending on experience.

Description

Landing gear retraction track determining method and system
Technical Field
The invention relates to the technical field of track planning in aerospace engineering, in particular to a method and a system for determining a landing gear retraction track.
Background
Landing gear assembly design is one of the core technologies of aircraft design throughout the design process of the aircraft. Conventional landing gear designs typically employ a "design-manufacture-test-improvement-design" serial design process, with design means often based on empirical retrofitting and mapping methods, and verification of the improvement through prototype testing. For an aircraft with a larger aircraft cabin, the method is more feasible, however, facing some aircrafts with higher requirements on maneuvering performance, such as supersonic aircrafts, the traditional landing gear design method cannot meet special requirements of narrow space, high approach speed and the like, and even the operational performance of the hypersonic aircrafts needs to be sacrificed to realize the functions of a landing system, and particularly the problem of limitation of the landing gear storage space becomes an important bottleneck for restricting the development of the hypersonic aircrafts.
With the development of digital prototype technology, design proofing, mechanism motion analysis, dynamics analysis, finite element analysis, optimization design and the like of a complex mechanism are performed through multidisciplinary collaborative simulation technology, even corresponding virtual tests are completed, more uncertain factors can be considered in the design stage, the performance of each system can be fully evaluated, test verification is not needed, development cost is greatly reduced, and development period is shortened. But the saved time is only the time of the prototype manufacturing experiment, and the design process still highly depends on the experience and the manual of people. With the improvement of the performance requirements of the aircraft, the complexity of the landing gear mechanism is continuously improved due to a plurality of limiting factors, and effective support is difficult to be provided for the selection of each key parameter rapidly in the initial design stage by the virtual simulation technology.
For example, in order to obtain a larger lift-drag ratio, the aircraft adopts thin wings, and has smaller wing aspect ratio, so that a cabin for taking up and paying off the landing gear is narrower, i.e. the landing gear is difficult to take up and paying off, and the landing gear is easy to interfere with the cabin or the engine and other instruments. Aiming at the problems that the landing gear recovery path is long in solving the actual problems of certain projects, the experience of engineers is excessively relied on, the optimal solution is difficult to find, the solution cannot be found, and the like, the method capable of rapidly determining the landing gear retraction track is urgently designed at present, and further, the situation that the cabin is repeatedly designed due to the non-optimality of the landing gear retraction mode is avoided.
Disclosure of Invention
Based on the above, the invention aims to provide a method and a system for determining the retraction track of a landing gear, so as to improve the rapid and automatic solving of the optimal retraction track of the landing gear.
In order to achieve the above object, the present invention provides a landing gear retraction track determining method, which includes:
step S1: determining a coordinate q1 of the last end point of the landing gear strut when being put down, a desired coordinate q2 of the last end point of the landing gear strut when being taken up, a third triangle network and a fourth triangle network under a global coordinate system;
step S2: constructing a unit vector formula of the rotating shaft according to the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down and the expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is taken up under a global coordinate system;
step S3: and determining an optimal receiving and releasing path according to a unit vector formula of the rotating shaft by adopting an optimization algorithm.
Optionally, step S1 specifically includes:
step S11: acquiring a coordinate Q1 of a landing gear mounting point position under an initial coordinate system, a coordinate Q2 of a landing gear strut end point when the landing gear is put down, and an expected coordinate Q3 of the landing gear strut end point when the landing gear is taken up;
step S12: acquiring a first three-dimensional model and a second three-dimensional model; the first three-dimensional model is a three-dimensional model describing the aircraft cabin environment; the second three-dimensional model is a three-dimensional model describing the landing gear in a down state;
Step S13: triangular mesh division is respectively carried out on the first three-dimensional model and the second three-dimensional model by using creo paramias software, so as to obtain a first triangular mesh and a second triangular mesh; the first triangular mesh and the second triangular mesh each comprise a plurality of triangular patches;
step S14: and converting the coordinate Q2 of the final end point of the landing gear strut in the initial coordinate system, the expected coordinate Q3 of the final end point of the landing gear strut in the retraction, the first triangular mesh and the second triangular mesh into the global coordinate system to obtain the coordinate Q1 of the final end point of the landing gear strut in the retraction, the expected coordinate Q2 of the final end point of the landing gear strut in the retraction, the third triangular network and the fourth triangular network in the global coordinate system.
Optionally, step S2 specifically includes:
step S21: the normal vector under the global coordinate system is determined according to the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down and the expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is taken up, and the specific formula is as follows:
where q1 is the coordinate of the extreme end point of the landing gear leg at the time of extension in the global coordinate system, q2 is the desired coordinate of the extreme end point of the landing gear leg at the time of retraction in the global coordinate system, (X) f ,Y f ,Z f ) Normal vectors F (X) representing the planes of the landing gear, respectively f ,Y f ,Z f ) Is included in the three components of (a);
step S22: constructing a unit vector formula of the rotating shaft based on the normal vector, wherein the specific formula is as follows:
wherein ρ is the projection length of the rotation axis per unit length on the global coordinate xy plane, (X) f ,Y f ,Z f ) Normal vector F (X) to the plane of the landing gear f ,Y f ,Z f ) And θ is the angle between the projection of the rotation axis per unit length on the global coordinate xy plane and the x-axis, x r 、y r And z r Respectively the unit vectors R (x r ,y r ,z r ) Three values on each axis, R (x r ,y r ,z r ) Is a unit vector of rotation axes in a global coordinate system from the coordinate q1 of the landing gear leg end point at the time of lowering to the desired coordinate q2 of the landing gear leg end point at the time of raising.
Optionally, step S3 specifically includes:
step S31: inputting a given theta into a unit vector formula of the rotating shaft to determine a unit vector of the rotating shaft; θ is the angle between the projection of the rotation axis of unit length on the global coordinate xy plane and the x axis;
step S32: determining a rotation matrix of the third triangular network of the landing gear each time the third triangular network rotates by an alpha degree around the origin based on the unit vector of the rotation axis;
step S33: multiplying the rotation matrix by the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down under a global coordinate system to obtain the current position of the landing gear;
Step S34: calculating a distance between the rotated landing gear and the cabin environment based on the triangular patches in the third triangular network and the triangular patches in the fourth triangular network after rotation;
step S35: judging whether the cosine function value of the included angle between the current position of the undercarriage and the target position is smaller than a first preset value or not; if the distance between the landing gear and the landing gear is smaller than a first preset value, indicating that the landing gear reaches a target position, and taking the minimum distance in the whole take-off and landing process as an evaluation index of the retraction path; if the rotation angle is greater than or equal to the first preset value, alpha=alpha+phi, and returning to the step S32, wherein phi is a given rotation angle; the target position is an expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is retracted under a global coordinate system;
step S36: judging whether the evaluation index of the receiving and releasing path is smaller than or equal to a second preset value; if the evaluation index of the retraction path is smaller than or equal to the second preset value, the landing gear is considered to be capable of collision, and step S37 is executed; if the evaluation index of the retraction path is larger than a second preset value, the landing gear is indicated to be capable of achieving retraction without collision, and the retraction path corresponding to the angle theta is output as an optimal retraction path;
Step S37: converting the expected coordinate q2 of the final end point of the landing gear strut when the global coordinate system is retracted into the spherical coordinate system to obtain the new expected coordinate q of the final end point of the landing gear strut when the global coordinate system is retracted x ；
Step S38: let q2=q x And returns to "step S2".
Optionally, converting the desired coordinates q2 of the extreme end point of the landing gear leg when the global coordinate system is retracted into the global coordinate system to obtain new desired coordinates of the extreme end point of the landing gear leg when retractedq x The specific formula is as follows:
wherein (x, y, z) is landing gear spherical coordinate q x And r represents the length of the landing gear itself,representing yaw and pitch angles of the landing gear in the spherical coordinate system, respectively, +.>Are all translational angle variables.
The invention also provides a landing gear retraction track determining system, which comprises:
the parameter determining module is used for determining a coordinate q1 of the final end point of the landing gear strut when being put down, a desired coordinate q2 of the final end point of the landing gear strut when being taken up, a third triangle network and a fourth triangle network under the global coordinate system;
the unit vector formula construction module is used for constructing a unit vector formula of the rotating shaft according to the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down and the expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is taken up under the global coordinate system;
And the optimal receiving and releasing path determining module is used for determining the optimal receiving and releasing path according to the unit vector formula of the rotating shaft by adopting an optimization algorithm.
Optionally, the parameter determining module specifically includes:
a first acquisition unit configured to acquire a coordinate Q1 of a landing gear mounting point position in an initial coordinate system, a coordinate Q2 of a landing gear leg end point when the landing gear is put down, and an expected coordinate Q3 of the landing gear leg end point when the landing gear is taken up;
a second acquisition unit configured to acquire a first three-dimensional model and a second three-dimensional model; the first three-dimensional model is a three-dimensional model describing the aircraft cabin environment; the second three-dimensional model is a three-dimensional model describing the landing gear in a down state;
the triangle mesh dividing unit is used for dividing the triangle mesh of the first three-dimensional model and the triangle mesh of the second three-dimensional model by using creo paramias software to obtain a first triangle mesh and a second triangle mesh; the first triangular mesh and the second triangular mesh each comprise a plurality of triangular patches;
the first coordinate conversion unit is used for converting the coordinate Q2 of the last end point of the landing gear strut when being put down, the expected coordinate Q3 of the last end point of the landing gear strut when being taken up, the first triangle mesh and the second triangle mesh under the global coordinate system to obtain the coordinate Q1 of the last end point of the landing gear strut when being put down, the expected coordinate Q2 of the last end point of the landing gear strut when being taken up, the third triangle network and the fourth triangle network under the global coordinate system.
Optionally, the unit vector formula construction module specifically includes:
the normal vector formula construction unit is used for determining a normal vector under the global coordinate system according to the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down and the expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is taken up, and the specific formula is as follows:
where q1 is the coordinate of the extreme end point of the landing gear leg at the time of extension in the global coordinate system, q2 is the desired coordinate of the extreme end point of the landing gear leg at the time of retraction in the global coordinate system, (X) f ,Y f ,Z f ) Normal vectors F (X) representing the planes of the landing gear, respectively f ,Y f ,Z f ) Is included in the three components of (a);
the unit vector formula construction unit is used for constructing a unit vector formula of the rotating shaft based on the normal vector, and the specific formula is as follows:
wherein ρ is the projection length of the rotation axis per unit length on the global coordinate xy plane, (X) f ,Y f ,Z f ) Normal vector F (X) to the plane of the landing gear f ,Y f ,Z f ) And θ is the angle between the projection of the rotation axis per unit length on the global coordinate xy plane and the x-axis, x r 、y r And z r Respectively the unit vectors R (x r ,y r ,z r ) Three values on each axis, R (x r ,y r ,z r ) Is a unit vector of rotation axes in a global coordinate system from the coordinate q1 of the landing gear leg end point at the time of lowering to the desired coordinate q2 of the landing gear leg end point at the time of raising.
Optionally, the optimal receiving and releasing path determining module specifically includes:
an input unit for inputting a given θ into a unit vector formula of the rotation shaft to determine a unit vector of the rotation shaft; θ is the angle between the projection of the rotation axis of unit length on the global coordinate xy plane and the x axis;
a rotation matrix determining unit for determining a rotation matrix of the third triangle network of the landing gear each time the third triangle network rotates by α degrees around the origin based on the unit vector of the rotation axis;
the multiplying unit is used for multiplying the rotation matrix with a coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down in a global coordinate system to obtain the current position of the landing gear;
a distance determining unit for calculating a distance between the landing gear after rotation and the cabin environment based on the triangular patches in the third triangular network and the triangular patches in the fourth triangular network after rotation;
the first judging unit is used for judging whether the cosine function value of the included angle between the current position and the target position of the landing gear is smaller than a first preset value or not; if the distance between the landing gear and the landing gear is smaller than a first preset value, indicating that the landing gear reaches a target position, and taking the minimum distance in the whole take-off and landing process as an evaluation index of the retraction path; if the rotation matrix is greater than or equal to the first preset value, alpha=alpha+phi, and returning to a rotation matrix determining unit, wherein phi is a given rotation angle; the target position is an expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is retracted under a global coordinate system;
The second judging unit is used for judging whether the evaluation index of the receiving and releasing path is smaller than or equal to a second preset value; if the evaluation index of the retraction path is smaller than or equal to a second preset value, the landing gear is considered to be capable of collision, and a second coordinate conversion unit is executed; if the evaluation index of the retraction path is larger than a second preset value, the landing gear is indicated to be capable of achieving retraction without collision, and the retraction path corresponding to the angle theta is output as an optimal retraction path;
a second coordinate conversion unit for converting the expected coordinate q2 of the landing gear post end point when the global coordinate system is down and up to the spherical coordinate system to obtain a new expected coordinate q of the landing gear post end point when the landing gear post is up and down x ；
Assignment unit for letting q2=q x And returns a "unit vector formula construction module".
Optionally, converting the desired coordinate q2 of the extreme end point of the landing gear leg when the global coordinate system is retracted into the global coordinate system to obtain a new desired coordinate q of the extreme end point of the landing gear leg when retracted x The specific formula is as follows:
wherein (x, y, z) is landing gear spherical coordinate q x And r represents the length of the landing gear itself,representing yaw and pitch angles of the landing gear in the spherical coordinate system, respectively, +. >Are all translational angle variables.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention provides a method and a system for determining a retraction track of an undercarriage, wherein the method comprises the following steps: determining a coordinate q1 of the last end point of the landing gear strut when being put down, a desired coordinate q2 of the last end point of the landing gear strut when being taken up, a third triangle network and a fourth triangle network under a global coordinate system; constructing a unit vector formula of the rotating shaft according to the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down and the expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is taken up under a global coordinate system; and determining an optimal receiving and releasing path according to a unit vector formula of the rotating shaft by adopting an optimization algorithm. Compared with the traditional manual design-dependent method, the method can automatically design and solve, save the effort of the people in the design process, shorten the design time, and solve the optimal receiving and releasing path without depending on experience.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flowchart of a landing gear retraction track determination method according to embodiment 1 of the present invention;
FIG. 2 shows the distribution angle of the shaft according to embodiment 1 of the present invention;
fig. 3 is a block diagram of a landing gear retraction trajectory determination system according to embodiment 2 of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention aims to provide a method and a system for determining a landing gear retraction track, which are used for improving the rapid and automatic solving of the optimal retraction track of a landing gear.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
Example 1
As shown in fig. 1, the invention discloses a landing gear retraction track determining method, which comprises the following steps:
step S1: the coordinates q1 of the landing gear leg end point when lowered, the desired coordinates q2 of the landing gear leg end point when retracted, the third triangle network and the fourth triangle network in the global coordinate system are determined.
Step S2: and constructing a unit vector formula of the rotation shaft according to the coordinate q1 of the final end point of the landing gear strut when the landing gear strut is put down and the expected coordinate q2 of the final end point of the landing gear strut when the landing gear strut is taken up in under the global coordinate system.
Step S3: and determining an optimal receiving and releasing path according to a unit vector formula of the rotating shaft by adopting an optimization algorithm.
The steps are discussed in detail below:
step S1: determining a coordinate q1 of the landing gear leg end point when being put down, a desired coordinate q2 of the landing gear leg end point when being taken up, a third triangle network and a fourth triangle network under a global coordinate system, specifically comprising:
step S11: acquiring a coordinate Q1 of a landing gear mounting point position under an initial coordinate system, a coordinate Q2 of a landing gear strut end point when the landing gear is put down, and an expected coordinate Q3 of the landing gear strut end point when the landing gear is taken up; the initial coordinate system in the invention is set according to actual requirements.
Step S12: acquiring a first three-dimensional model and a second three-dimensional model; the first three-dimensional model is a three-dimensional model describing the aircraft cabin environment; the second three-dimensional model is a three-dimensional model describing when the landing gear is in a down state.
Step S13: triangular mesh division is respectively carried out on the first three-dimensional model and the second three-dimensional model by using creo paramias software, so as to obtain a first triangular mesh and a second triangular mesh; the first triangular mesh and the second triangular mesh each comprise a plurality of triangular patches; the first triangle mesh and the second triangle mesh are stored in an STL file format or an OBJ file format.
Step S14: converting the coordinate Q2 of the final end point of the landing gear strut in the initial coordinate system, the expected coordinate Q3 of the final end point of the landing gear strut in the retraction, the first triangular mesh and the second triangular mesh into the global coordinate system to obtain the coordinate Q1 of the final end point of the landing gear strut in the retraction, the expected coordinate Q2 of the final end point of the landing gear strut in the retraction, the third triangular network and the fourth triangular network in the global coordinate system; the third triangle network is an LG triangle network and the fourth triangle network is an RE triangle network.
That is, a global coordinate system is constructed with the coordinate Q1 of the landing gear mounting point position as the origin. And subtracting the coordinates of Q1 from the coordinates of each vertex of each patch in the first triangular mesh under the global coordinate system to generate a third triangular network, and subtracting the coordinates of Q1 from the coordinates of each vertex of each patch in the second triangular mesh to generate a fourth triangular network.
Step S2: the unit vector formula of the rotation shaft is constructed according to the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down and the expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is taken up in under a global coordinate system, and specifically comprises the following steps:
Step S21: the normal vector under the global coordinate system is determined according to the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down and the expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is taken up, and the specific formula is as follows:
wherein q1 is the coordinate of the end point of the landing gear strut when being put down in the global coordinate system, and q2 is the end point of the landing gear strut when being taken up in the global coordinate systemDesired coordinates, (X) f ,Y f ,Z f ) Normal vectors F (X) representing the planes of the landing gear, respectively f ,Y f ,Z f ) Is included in the three components of (a).
Step S22: constructing a unit vector formula of the rotating shaft based on the normal vector, wherein the specific formula is as follows:
wherein ρ is the projection length of the rotation axis per unit length on the global coordinate xy plane, (X) f ,Y f ,Z f ) Normal vector F (X) to the plane of the landing gear f ,Y f ,Z f ) And θ is the angle between the projection of the rotation axis per unit length on the global coordinate xy plane and the x-axis, x r 、y r And z r Respectively the unit vectors R (x r ,y r ,z r ) Three values on each axis, R (x r ,y r ,z r ) Is a unit vector of rotation axes in a global coordinate system from the coordinate q1 of the landing gear leg end point at the time of lowering to the desired coordinate q2 of the landing gear leg end point at the time of raising.
For a rotation axis in three-dimensional space, it can be described by a two-dimensional vector given the modulo length. The rotation axis is a unit vector, and the specific formula is: r (x) r ,y r ,z r ) And (2) andwherein x is r 、y r And z r Three values on each axis.
Determining a rotation axis satisfying the condition; the conditional formula is:
wherein,unit vector R (x r ,y r ,z r ) Shorthand for->Is normal vector F (X f ,Y f ,Z f ) Is abbreviated as x r 、y r And z r Respectively the unit vectors R (x r ,y r ,z r ) Three values on each axis, (X) f ,Y f ,Z f ) Respectively represent normal vectors F (X) f ,Y f ,Z f ) Is included in the three components of (a).
All rotation axes meeting the conditions are necessarily distributed on an angular bisection plane, and as shown in fig. 2, the specific formula of the angular bisection plane is:
X f x+Y f y+Z f z＝0；
wherein, (X f ,Y f ,Z f ) Respectively represent normal vectors F (X) f ,Y f ,Z f ) Q1 is the coordinate of the extreme end point of the landing gear leg at the time of lowering in the global coordinate system, and q2 is the desired coordinate of the extreme end point of the landing gear leg at the time of raising in the global coordinate system. The rotation axis distribution plane can be obtained by passing the normal vector of the plane through the origin of coordinates Q1.
Step S3: an optimization algorithm is adopted, and an optimal receiving and releasing path is determined according to a unit vector formula of the rotating shaft, and the method specifically comprises the following steps:
the optimization algorithm is a gradient descent algorithm, a conjugate gradient descent algorithm, a heuristic algorithm, a genetic algorithm, an adam algorithm or a simulated annealing algorithm.
Step S31: inputting the projection of a given unit length rotating shaft on a global coordinate xy plane and an angle theta clamped by an x axis into a unit vector formula of the rotating shaft to determine a unit vector of the rotating shaft; the unit vector R (x r ,y r ,z r ) Representing one retraction path of the landing gear, that is, one retraction path for each θ.
Step S32: the rotation matrix of the third triangular network of the landing gear is determined on the basis of the unit vector of the rotation shaft, and the specific formula is as follows:
where α is the number of degrees, x, of each rotation of the landing gear triangle network LG about the origin r 、y r And z r Respectively the unit vectors R (x r ,y r ,z r ) Three values on each axis.
Step S33: multiplying the rotation matrix by the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down under a global coordinate system to obtain the current position of the landing gear;
step S34: calculating a distance between the rotated landing gear and the cabin environment based on the triangular patches in the third triangular network and the triangular patches in the fourth triangular network after rotation; that is to say: and taking the distance between two triangular patches closest to the two sets as the distance between the landing gear and the cabin environment, forming one set by the triangular patches of the third triangular network after rotation, and forming the other set by the triangular patches of the fourth triangular network.
Step S35: judging whether cosine function value cos beta of an included angle between the current position and the target position of the undercarriage is smaller than a first preset value or not; if the distance between the landing gear and the landing gear is smaller than a first preset value, indicating that the landing gear reaches a target position, and taking the minimum distance in the whole take-off and landing process as an evaluation index of the retraction path; the target position is an expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is retracted under a global coordinate system; if the value is greater than or equal to the first preset value, α=α+Φ, and return to "step S32", where Φ is a given rotation angle. The target position is the desired coordinate q2 of the last end point of the landing gear leg when stowed in the global coordinate system.
Step S36: judging whether the evaluation index of the receiving and releasing path is smaller than or equal to a second preset value; if the evaluation index of the retraction path is smaller than or equal to the second preset value, the landing gear is considered to be capable of collision, and step S37 is executed; if the evaluation index of the retraction path is larger than the second preset value, the landing gear is indicated to be capable of achieving retraction without collision, and the retraction path corresponding to the angle theta is output as the optimal retraction path.
The geometric meaning of the evaluation index f is that when the landing gear rotates along the optimal path obtained by the given parameters, the shortest distance D exists between the landing gear and the cabin environment when the landing gear is closest to the cabin environment on the whole path. If the evaluation index is less than or equal to the second preset value, this indicates that the landing gear is moving along the path, and the landing gear is crashed, indicating that the path is not viable. In this embodiment, the first preset value and the second preset value are set according to actual requirements.
In the optimization of the last step, the optimal parameter theta can be calculated, but the selected optimal parameter path still has the possibility of generating a scene that the landing gear cannot be received and the collision occurs. This means that if the landing gear is retrieved in a spatially rotated manner at the initially given stow desired position q2, further optimisation is required, also for a partially stowable scenario if the shortest distance f between the landing gear and the cabin environment is smaller than a second preset value for the optimal path movement by the designer according to the optimal parameter θ. The optimal track is better by fine tuning the final receiving expected position q2 or the landing gear can avoid the income of collision under the condition that the optimal track obtained in the last step cannot avoid collision, and the specific steps are as follows:
Step S37: converting the expected coordinate q2 of the final end point of the landing gear strut when the global coordinate system is retracted into the spherical coordinate system to obtain the new expected coordinate q of the final end point of the landing gear strut when the global coordinate system is retracted x The specific formula is as follows:
wherein (x, y, z) is landing gear spherical coordinate q x And r represents the length of the landing gear itself,representing yaw and pitch angles of the landing gear in the spherical coordinate system, respectively, +.>Are all translational angle variables. R, # in the formula>And->Is determined from the desired coordinates q2 initially given by the extreme end points of the landing gear leg when stowed in the global coordinate system. The spherical coordinate system is constructed with landing gear mounting points as the origin.
Step S38: let q2=q x And returns to "step S2".
Example 2
As shown in fig. 3, the present invention further provides a landing gear retraction trajectory determination system, the system including:
the parameter determination module 301 is configured to determine a coordinate q1 of a final end point of the landing gear leg when being put down, a desired coordinate q2 of a final end point of the landing gear leg when being taken up, a third triangle network, and a fourth triangle network in the global coordinate system.
The unit vector formula construction module 302 is configured to construct a unit vector formula of the rotation axis according to the coordinate q1 of the landing gear leg end point when the landing gear leg is put down and the expected coordinate q2 of the landing gear leg end point when the landing gear leg is taken up in.
And the optimal receiving and releasing path determining module 303 is configured to determine an optimal receiving and releasing path according to a unit vector formula of the rotation shaft by adopting an optimization algorithm.
As an embodiment, the parameter determining module 301 of the present invention specifically includes:
a first acquisition unit for acquiring the coordinates Q1 of the landing gear mounting point position in the initial coordinate system, the coordinates Q2 of the landing gear leg end point at the time of being put down, and the desired coordinates Q3 of the landing gear leg end point at the time of being taken up.
A second acquisition unit configured to acquire a first three-dimensional model and a second three-dimensional model; the first three-dimensional model is a three-dimensional model describing the aircraft cabin environment; the second three-dimensional model is a three-dimensional model describing when the landing gear is in a down state.
The triangle mesh dividing unit is used for dividing the triangle mesh of the first three-dimensional model and the triangle mesh of the second three-dimensional model by using creo paramias software to obtain a first triangle mesh and a second triangle mesh; the first triangular mesh and the second triangular mesh each include a plurality of triangular patches.
The first coordinate conversion unit is used for converting the coordinate Q2 of the last end point of the landing gear strut when being put down, the expected coordinate Q3 of the last end point of the landing gear strut when being taken up, the first triangle mesh and the second triangle mesh under the global coordinate system to obtain the coordinate Q1 of the last end point of the landing gear strut when being put down, the expected coordinate Q2 of the last end point of the landing gear strut when being taken up, the third triangle network and the fourth triangle network under the global coordinate system.
As an embodiment, the unit vector formula construction module 302 of the present invention specifically includes:
the normal vector formula construction unit is used for determining a normal vector under the global coordinate system according to the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down and the expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is taken up, and the specific formula is as follows:
where q1 is the coordinate of the extreme end point of the landing gear leg at the time of extension in the global coordinate system, q2 is the desired coordinate of the extreme end point of the landing gear leg at the time of retraction in the global coordinate system, (X) f ,Y f ,Z f ) Normal vectors F (X) representing the planes of the landing gear, respectively f ,Y f ,Z f ) Is included in the three components of (a).
The unit vector formula construction unit is used for constructing a unit vector formula of the rotating shaft based on the normal vector, and the specific formula is as follows:
wherein ρ is the projection length of the rotation axis per unit length on the global coordinate xy plane, (X) f ,Y f ,Z f ) Normal vector F (X) to the plane of the landing gear f ,Y f ,Z f ) And θ is the angle between the projection of the rotation axis per unit length on the global coordinate xy plane and the x-axis, x r 、y r And z r Respectively the unit vectors R (x r ,y r ,z r ) Three values on each axis, R (x r ,y r ,z r ) Is a unit vector of rotation axes in a global coordinate system from the coordinate q1 of the landing gear leg end point at the time of lowering to the desired coordinate q2 of the landing gear leg end point at the time of raising.
As an implementation manner, the optimal receive-and-release path determining module 303 of the present invention specifically includes:
an input unit for inputting a given θ into a unit vector formula of the rotation shaft to determine a unit vector of the rotation shaft; θ is the angle between the projection of the rotation axis of unit length on the global coordinate xy plane and the x axis;
and a rotation matrix determining unit for determining a rotation matrix of the third triangular network of the landing gear each time the third triangular network rotates by an alpha degree around the origin based on the unit vector of the rotation axis.
And the multiplication unit is used for multiplying the rotation matrix with a coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down in a global coordinate system to obtain the current position of the landing gear.
And the distance determining unit is used for calculating the distance between the landing gear and the cabin environment after rotation based on the triangular patches in the third triangular network and the triangular patches in the fourth triangular network after rotation.
The first judging unit is used for judging whether the cosine function value of the included angle between the current position and the target position of the landing gear is smaller than a first preset value or not; if the distance between the landing gear and the landing gear is smaller than a first preset value, indicating that the landing gear reaches a target position, and taking the minimum distance in the whole take-off and landing process as an evaluation index of the retraction path; if the rotation angle is greater than or equal to the first preset value, alpha=alpha+phi, and returning to a rotation matrix determining unit, wherein phi is a given rotation angle, and alpha degrees are changed; the target position is the desired coordinate q2 of the last end point of the landing gear leg when stowed in the global coordinate system.
The second judging unit is used for judging whether the evaluation index of the receiving and releasing path is smaller than or equal to a second preset value; if the evaluation index of the retraction path is smaller than or equal to a second preset value, the landing gear is considered to be capable of collision, and a second coordinate conversion unit is executed; if the evaluation index of the retraction path is larger than the second preset value, the landing gear is indicated to be capable of achieving retraction without collision, and the retraction path corresponding to the angle theta is output as the optimal retraction path.
A second coordinate conversion unit for converting the expected coordinate q2 of the landing gear post end point when the global coordinate system is down and up to the spherical coordinate system to obtain a new expected coordinate q of the landing gear post end point when the landing gear post is up and down x The specific formula is as follows:
wherein (x, y, z) is landing gear spherical coordinate q x And r represents the length of the landing gear itself,representing yaw and pitch angles of the landing gear in the spherical coordinate system, respectively, +.>Are all translational angle variables.
Assignment unit for letting q2=q x And returns a "unit vector formula construction module".
Example 3
In the embodiment, taking the design of a landing gear retraction mechanism of a hypersonic aircraft as an example, the optimization design calculation of the landing gear movement path is carried out. Due to the air inlet channel structure, the airborne equipment and the heat insulation layer of the aircraft, the storage space of the landing gear is extremely narrow, and the design of the retraction path of the landing gear is very difficult. The model of this embodiment is simplified as follows, and for the landing gear itself, only the strut and tyre portions thereof are retained by simplifying unnecessary additional mechanisms, to obtain a model for covering the complex connection portion by the envelope when the door is in the open state, by intercepting the cabin section of the landing gear mounting position portion for the complex cabin environment constituted by the intake duct together with the aeroengine and the skin outside the aircraft, etc.
And S1, performing grid division on the obtained landing gear model (a first three-dimensional model) and the obstacle cabin model (a second three-dimensional model) by using creo paramias software, and exporting the landing gear model and the obstacle cabin model into an STL file. The following triangle network is generated. The angle 0 ° and the chord height 1000mm were chosen, dividing the landing gear into 150 panels, and the angle 0.0 and the chord height 800mm were chosen to divide the cut cabin section into 634 panels.
S2, as an initial ideal pickup position coordinate vector, q2 (0.00,0.00,2500) mm, and the corresponding tail end position of the landing gear in the down state, wherein the vector coordinate is q1 (2201.37,1180.98, -94.09) mm. Taking the ideal collection state position vector q2 (0.00,0.00,2500) mm as a target position and the tail end position vector q1 (2201.37,1180.98, -94.09) mm when the corresponding landing gear is in the down state, the normal vector of the rotating shaft distribution plane can be obtained to be R (-0.6113, -0.3279,0.7203). Thus, the rotational axis of the landing gear can be obtained by the normal vector to this plane.
S3, optimizing the parameter theta through an adam and other optimization algorithms, wherein the value of the parameter is [0,2 pi ]]Finally, the result is
S4, selecting two angles,the direction angle coordinate of the current ideal target position qx can be obtained to be (28.21, -2.15) through a direction angle-Cartesian coordinate conversion formula. Taking the optimization as a starting point, optimizing by using adam algorithm to obtain the following table 1:
Table 1 results obtained by optimization
The landing gear has a small angular deviation from the original target position, so that the shortest distance between the motion recovery path and the cabin can achieve the optimal result under the radian limitation.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other.
The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to assist in understanding the methods of the present invention and the core ideas thereof; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.

Claims (6)

1. A landing gear retraction trajectory determination method, the method comprising:
step S1: determining a coordinate q1 of the last end point of the landing gear strut when being put down, a desired coordinate q2 of the last end point of the landing gear strut when being taken up, a third triangle network and a fourth triangle network under a global coordinate system;
Step S2: constructing a unit vector formula of the rotating shaft according to the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down and the expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is taken up under a global coordinate system;
step S3: an optimization algorithm is adopted, and an optimal receiving and releasing path is determined according to a unit vector formula of the rotating shaft;
the step S1 specifically comprises the following steps:
step S11: acquiring a coordinate Q1 of a landing gear mounting point position under an initial coordinate system, a coordinate Q2 of a landing gear strut end point when the landing gear is put down, and an expected coordinate Q3 of the landing gear strut end point when the landing gear is taken up;
step S12: acquiring a first three-dimensional model and a second three-dimensional model; the first three-dimensional model is a three-dimensional model describing the aircraft cabin environment; the second three-dimensional model is a three-dimensional model describing the landing gear in a down state;
step S13: triangular mesh division is respectively carried out on the first three-dimensional model and the second three-dimensional model by using creo paramias software, so as to obtain a first triangular mesh and a second triangular mesh; the first triangular mesh and the second triangular mesh each comprise a plurality of triangular patches;
step S14: converting the coordinate Q2 of the final end point of the landing gear strut in the initial coordinate system, the expected coordinate Q3 of the final end point of the landing gear strut in the retraction, the first triangular mesh and the second triangular mesh into the global coordinate system to obtain the coordinate Q1 of the final end point of the landing gear strut in the retraction, the expected coordinate Q2 of the final end point of the landing gear strut in the retraction, the third triangular network and the fourth triangular network in the global coordinate system;
The step S3 comprises the following steps:
step S31: inputting a given theta into a unit vector formula of the rotating shaft to determine a unit vector of the rotating shaft; θ is the angle between the projection of the rotation axis of unit length on the global coordinate xy plane and the x axis;
step S32: determining a rotation matrix of the third triangular network of the landing gear each time the third triangular network rotates by an alpha degree around the origin based on the unit vector of the rotation axis;
step S33: multiplying the rotation matrix by the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down under a global coordinate system to obtain the current position of the landing gear;
step S34: calculating a distance between the rotated landing gear and the cabin environment based on the triangular patches in the third triangular network and the triangular patches in the fourth triangular network after rotation;
step S35: judging whether the cosine function value of the included angle between the current position of the undercarriage and the target position is smaller than a first preset value or not; if the distance between the landing gear and the landing gear is smaller than a first preset value, indicating that the landing gear reaches a target position, and taking the minimum distance in the whole take-off and landing process as an evaluation index of the retraction path; if the rotation angle is greater than or equal to the first preset value, alpha=alpha+phi, and returning to the step S32, wherein phi is a given rotation angle; the target position is an expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is retracted under a global coordinate system;
Step S36: judging whether the evaluation index of the receiving and releasing path is smaller than or equal to a second preset value; if the evaluation index of the retraction path is smaller than or equal to the second preset value, the landing gear is considered to be capable of collision, and step S37 is executed; if the evaluation index of the retraction path is larger than a second preset value, the landing gear is indicated to be capable of achieving retraction without collision, and the retraction path corresponding to the angle theta is output as an optimal retraction path;
step S37: converting the expected coordinate q2 of the final end point of the landing gear strut when the global coordinate system is retracted into the spherical coordinate system to obtain the new expected coordinate q of the final end point of the landing gear strut when the global coordinate system is retracted x ；
Step S38: let q2=q x And returns to "step S2".
2. The landing gear retraction trajectory determination method according to claim 1, wherein step S2 comprises:
step S21: the normal vector under the global coordinate system is determined according to the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down and the expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is taken up, and the specific formula is as follows:
where q1 is the coordinate of the extreme end point of the landing gear leg at the time of extension in the global coordinate system, q2 is the desired coordinate of the extreme end point of the landing gear leg at the time of retraction in the global coordinate system, (X) f ,Y f ,Z f ) Normal vectors F (X) representing the planes of the landing gear, respectively f ,Y f ,Z f ) Is included in the three components of (a);
step S22: constructing a unit vector formula of the rotating shaft based on the normal vector, wherein the specific formula is as follows:
wherein ρ is the projection length of the rotation axis per unit length on the global coordinate xy plane, (X) f ,Y f ,Z f ) Normal vector F (X) to the plane of the landing gear f ,Y f ,Z f ) And θ is the angle between the projection of the rotation axis per unit length on the global coordinate xy plane and the x-axis, x r 、y r And z r Respectively the unit vectors R (x r ,y r ,z r ) Three values on each axis, R (x r ,y r ,z r ) Is a unit vector of rotation axes in a global coordinate system from the coordinate q1 of the landing gear leg end point at the time of lowering to the desired coordinate q2 of the landing gear leg end point at the time of raising.
3. A method of determining a landing gear retraction trajectory according to claim 1 wherein the transformation of the desired coordinate q2 of the landing gear leg tip point when the global coordinate system is retracted and extended to the spherical coordinate system results in a new desired coordinate q of the landing gear leg tip point when retracted and extended x The specific formula is as follows:
wherein (x, y, z) is landing gear spherical coordinate q x Is represented by the three-axis coordinate value of r, r represents the landing gear itselfLength of θ,Representing yaw and pitch angles of the landing gear in the spherical coordinate system, respectively, +. >Δθ is a translational angle variable.
4. A landing gear retraction trajectory determination system, the system comprising:
the parameter determining module is used for determining a coordinate q1 of the final end point of the landing gear strut when being put down, a desired coordinate q2 of the final end point of the landing gear strut when being taken up, a third triangle network and a fourth triangle network under the global coordinate system;
the unit vector formula construction module is used for constructing a unit vector formula of the rotating shaft according to the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down and the expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is taken up under the global coordinate system;
the optimal receiving and releasing path determining module is used for determining an optimal receiving and releasing path according to a unit vector formula of the rotating shaft by adopting an optimization algorithm;
the parameter determining module specifically comprises:
a first acquisition unit configured to acquire a coordinate Q1 of a landing gear mounting point position in an initial coordinate system, a coordinate Q2 of a landing gear leg end point when the landing gear is put down, and an expected coordinate Q3 of the landing gear leg end point when the landing gear is taken up;
a second acquisition unit configured to acquire a first three-dimensional model and a second three-dimensional model; the first three-dimensional model is a three-dimensional model describing the aircraft cabin environment; the second three-dimensional model is a three-dimensional model describing the landing gear in a down state;
The triangle mesh dividing unit is used for dividing the triangle mesh of the first three-dimensional model and the triangle mesh of the second three-dimensional model by using creo paramias software to obtain a first triangle mesh and a second triangle mesh; the first triangular mesh and the second triangular mesh each comprise a plurality of triangular patches;
the first coordinate conversion unit is used for converting the coordinate Q2 of the final end point of the landing gear strut when being put down, the expected coordinate Q3 of the final end point of the landing gear strut when being taken up, the first triangular mesh and the second triangular mesh under the global coordinate system to obtain the coordinate Q1 of the final end point of the landing gear strut when being put down, the expected coordinate Q2 of the final end point of the landing gear strut when being taken up, the third triangular network and the fourth triangular network under the global coordinate system;
the optimal receiving and releasing path determining module specifically comprises:
an input unit for inputting a given θ into a unit vector formula of the rotation shaft to determine a unit vector of the rotation shaft; θ is the angle between the projection of the rotation axis of unit length on the global coordinate xy plane and the x axis;
a rotation matrix determining unit for determining a rotation matrix of the third triangle network of the landing gear each time the third triangle network rotates by α degrees around the origin based on the unit vector of the rotation axis;
The multiplying unit is used for multiplying the rotation matrix with a coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down in a global coordinate system to obtain the current position of the landing gear;
a distance determining unit for calculating a distance between the landing gear after rotation and the cabin environment based on the triangular patches in the third triangular network and the triangular patches in the fourth triangular network after rotation;
the first judging unit is used for judging whether the cosine function value of the included angle between the current position and the target position of the landing gear is smaller than a first preset value or not; if the distance between the landing gear and the landing gear is smaller than a first preset value, indicating that the landing gear reaches a target position, and taking the minimum distance in the whole take-off and landing process as an evaluation index of the retraction path; if the rotation angle is larger than or equal to the first preset value, alpha=alpha+phi, and returning to a rotation matrix determining unit, wherein phi is a given rotation angle; the target position is an expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is retracted under a global coordinate system;
the second judging unit is used for judging whether the evaluation index of the receiving and releasing path is smaller than or equal to a second preset value; if the evaluation index of the retraction path is smaller than or equal to a second preset value, the landing gear is considered to be capable of collision, and a second coordinate conversion unit is executed; if the evaluation index of the retraction path is larger than a second preset value, the landing gear is indicated to be capable of achieving retraction without collision, and the retraction path corresponding to the angle theta is output as an optimal retraction path;
A second coordinate conversion unit for converting the expected coordinate q2 of the landing gear post end point when the global coordinate system is down and up to the spherical coordinate system to obtain a new expected coordinate q of the landing gear post end point when the landing gear post is up and down x ；
Assignment unit for letting q2=q x And returns a "unit vector formula construction module".
5. The landing gear retraction trajectory determination system according to claim 4, wherein the unit vector formula construction module specifically comprises:
the normal vector formula construction unit is used for determining a normal vector under the global coordinate system according to the coordinate q1 of the last end point of the landing gear strut when the landing gear strut is put down and the expected coordinate q2 of the last end point of the landing gear strut when the landing gear strut is taken up, and the specific formula is as follows:
where q1 is the coordinate of the extreme end point of the landing gear leg at the time of extension in the global coordinate system, q2 is the desired coordinate of the extreme end point of the landing gear leg at the time of retraction in the global coordinate system, (X) f ,Y f ,Z f ) Normal vectors F (X) representing the planes of the landing gear, respectively f ,Y f ,Z f ) Is included in the three components of (a);
the unit vector formula construction unit is used for constructing a unit vector formula of the rotating shaft based on the normal vector, and the specific formula is as follows:
wherein ρ is the projection length of the rotation axis per unit length on the global coordinate xy plane, (X) f ,Y f ,Z f ) Normal vector F (X) to the plane of the landing gear f ,Y f ,Z f ) And θ is the angle between the projection of the rotation axis per unit length on the global coordinate xy plane and the x-axis, x r 、y r And z r Respectively the unit vectors R (x r ,y r ,z r ) Three values on each axis, R (x r ,y r ,z r ) Is a unit vector of rotation axes in a global coordinate system from the coordinate q1 of the landing gear leg end point at the time of lowering to the desired coordinate q2 of the landing gear leg end point at the time of raising.
6. The landing gear retraction trajectory determination system according to claim 4 wherein the conversion of the desired coordinate q2 of the landing gear leg end point when the global coordinate system is retracted and extended to the global coordinate system results in a new desired coordinate q of the landing gear leg end point when retracted and extended x The specific formula is as follows:
wherein (x, y, z) is landing gear spherical coordinate q x And (2) the triaxial coordinate value of r represents the length of the landing gear itself, θ,Representing yaw and pitch angles of the landing gear in the spherical coordinate system, respectively, +.>Δθ is a translational angle variable.
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