CN113378251A - Unit structure curved surface array laying modeling method suitable for multiple continuous curved surface types - Google Patents

Abstract

The invention relates to a unit structure curved surface array laying modeling method suitable for various continuous curved surface types, which can conveniently lay a structural material unit structure array on a curved surface of a rotating body, ensures that the unit structure is not deformed, has stable period intervals and a large laying range, is very suitable for the laying requirement of non-developable curved surfaces, does not need Boolean operation in the modeling process, does not need to carry out plane-to-curved surface wrapping calculation, has very high laying speed, and can be finished by more than 1000 units in only a few seconds. The method has the advantages of weak unit deformation, more consistent periodic intervals, wide adaptive curved surface types and capability of laying unit arrays on continuous curved surfaces.

Description

Unit structure curved surface array laying modeling method suitable for multiple continuous curved surface types

Technical Field

The invention relates to an electromagnetic design technology, in particular to a unit structure curved surface array laying modeling method suitable for various continuous curved surface types.

Background

In modern electromagnetic design, a large amount of "curved surface conformal electromagnetic structure materials" are used, for example, Frequency Selective Surface (FSS) materials, meta-materials (meta-materials), honeycomb wave-absorbing materials, conformal antenna arrays and the like are attached to curved surfaces, which is one of research hotspots of electromagnetic technology, especially in the field of electromagnetic stealth design. They have the common feature of "all being composed of a series of 'units' according to a certain rule". Normally, the unit design of these electromagnetic structural materials is performed on a plane, but in practice, these structural materials may be laid on the surfaces of the radomes, wings, cabins and the like of airplanes, ships, missiles, vehicles, and these surfaces are often various complex curved surfaces, and strict periodic arrangement (except few 'developable surfaces') on these complex curved surfaces is often impossible. Then, "how to 'quasi-periodically' arrange the cell arrays on a complex curved surface, and ensure electromagnetic performance? The method is an international modeling problem, namely how to construct a curved conformal array laying method which is efficient, has certain universality and ensures specific electromagnetic performance is a related modeling problem.

On the other hand, currently, some paving modeling technical methods for electromagnetic design software in Europe and America have the following steps: planar projection methods and curved surface winding methods. Both of these methods have some significant drawbacks in the type of surface being laid, and in the electromagnetic properties after laying. Therefore, a new "unit-placement method that is efficient, simple, versatile, and ensures unit and array pitch" would be an important electromagnetic material modeling advance.

Currently, European and American professional electromagnetic design software has a curved surface laying modeling method for some structural materials such as FSS materials, metamaterials and the like, and mainly comprises the following steps: planar projection and curved surface slicing winding. The planar projection method is characterized in that the projection of the unit on the curved surface on the lower plane is consistent with the plane period interval, the method has the advantages that the implementation method is simple, when the curvature of the curved surface is larger or the curved surface is steeper, the unit shape and the interval between the units can be changed greatly, the electromagnetic performance is deteriorated rapidly, and when the method corresponds to a multi-layer FSS, the unit size difference of different layers can be caused more, and the effect of the multi-layer design can be also deteriorated rapidly. The other method is a curved surface winding method, which comprises the steps of firstly establishing curved surface coordinates on a curved surface, then establishing a mapping relation from the curved surface to a plane, then establishing a periodic structure on the plane, and finally realizing the winding and attaching of the plane to the curved surface according to the mapping relation. The method has the advantages that: the periodic cell structure and spacing remain relatively accurate. If the surface to be laid is an expandable surface (such as a cylindrical surface or a conical surface), a uniform mapping relation from all the surfaces to the plane can be established, and the quality of the FSS can be ensured very high. However, the curved surface of the surface of an aircraft, a ship, a vehicle, etc. is often an undevelopable curved surface (for example, a spherical surface, an ellipsoid surface, a hyperboloid surface, a more complex curved surface, etc.), when the curved surface is laid on the undevelopable curved surface by a winding method, only a plurality of projections of the partial curved surface to a plane can be established, that is, the projections are carried out by a 'slicing' attaching method, and the partial curved surface is mapped to the limited large plane, so that a plurality of problems can occur: 1. when the inextensible curved surface is attached, a blank gap area (without a structure in the blank gap area) can appear between different patches, and the whole electromagnetic performance can be deteriorated due to the gap area; 2. the big region of curvature of inextensible surface, single paster often is less, needs more little pasters to attach, and blank gap area accounts for and also can obviously increase, leads to the electromagnetic property worsen more. Therefore, the curved surface winding method has obvious weaknesses for (very common) non-developable curved surfaces, and especially, the problem is more serious in the case of larger curvature.

Disclosure of Invention

Aiming at the problem that the unit structure of the inextensible curved surface laying period is difficult in the electromagnetic design, the unit structure curved surface array laying modeling method suitable for various continuous curved surface types is provided, the requirements that unit deformation is weak, the period interval is kept consistent, the adaptive curved surface type is wide, and the unit structure array can be laid on the continuous curved surface.

The technical scheme of the invention is as follows: a unit structure curved surface array laying modeling method suitable for various continuous curved surface types specifically comprises the following steps:

1) according to the shape of a carrier object needing to be paved with structural materials, establishing a continuous curved surface, wherein the continuous curved surface is formed by splicing an axisymmetric rotating curved surface or a part thereof, a non-axisymmetric non-repetitive rotating curved surface or a part thereof and a plurality of parts of the curved surface into a carrier object rotating body;

2) building a structural material unit structure needing array laying;

3) establishing local coordinates of points on the curved surface: each rotating body surface established in the step 1) comprises two orthogonal dimension directions, the two orthogonal dimensions of each rotating body surface before extraction are respectively a u direction along a rotating body generatrix direction and a v direction perpendicular to the generatrix direction, when the generatrix is a curve, the u direction is defined as being along a curve tangent direction, and v is defined as being perpendicular to the generatrix tangent direction, and for a point P on any given curved surface, the local coordinate of the point is determined to be (u, v, n), wherein the n vector is a normal vector of the two orthogonal dimensions u and v; step 2), the unit structure can be set to be embedded or floated on the surface by a distance h, the x axis and the u axis of the coordinate system of the unit structure are aligned, the y axis and the v axis are aligned, the unit structure is moved by a distance h from a point P along the direction of an n vector, the unit structure floats when h is larger than 0, otherwise, the array unit structure can be deployed on the curved surface;

4) starting to lay the unit structure from the top of the rotating body in the step 1), if the curvature of the top of the rotating body is not consistent with the size of the laid unit structure, starting to lay the unit structure from a distance away from the top, and firstly, laying the unit structure along a local v-shaped ring direction at equal intervals along arc lengths, wherein the arc length intervals take an array period of planar design as reference; the surface of the unit structure is parallel to a tangent plane formed by u and v of the laying position point, and the suspension height h or the embedding surface depth h is determined according to the value of h in the step 3);

after one circle of laying is finished along the v direction, a certain length is arranged along the u direction at intervals, next annular laying is started, the length can refer to the periodic interval of the planes, and after a specified height range is fully laid, laying modeling can be finished, so that the unit structure array is conformal to the curved surface;

5) and covering the rotator material with the material of the unit structure to complete the laying modeling of the curved surface array.

Preferably, the unit structure in the step 2) selects any one of FSS materials, metamaterials and honeycomb wave-absorbing materials.

The invention has the beneficial effects that: the invention is suitable for the modeling method for laying the unit structure curved surface array of various continuous curved surface types, can conveniently lay the curved surface array on the curved surface of the rotating body, ensures that the units are not deformed, has stable period interval and large laying range, is very suitable for the laying requirement of the non-developable curved surface, does not need Boolean operation in the modeling process, does not need to carry out wrapping calculation from a plane to the curved surface, has very high laying speed, and can be finished by more than 1000 units in only a few seconds.

Drawings

FIG. 1a is a view of an axisymmetric curved rotating body of the present invention;

FIG. 1b is a non-axisymmetric non-repeating rotator diagram of the present invention;

FIG. 2 is a continuous curved view of multiple sections of the present invention spliced together;

FIG. 3 is a diagram of an embodiment of an array unit of the present invention;

FIG. 4 is a schematic view of the u-direction and v-direction of the present invention;

FIG. 5 is a single row hoop lay down of the present invention;

FIG. 6 is a diagram of multiple rows of circumferential layers according to the present invention;

FIG. 7 is a schematic diagram of a curved array of objects laid in accordance with the present invention;

FIG. 8 is a schematic view of a plurality of partially spliced continuous curved arrays of the present invention after they are laid.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

The method is suitable for the unit structure curved surface array laying modeling method of various continuous curved surface types, and comprises the following concrete implementation steps:

(1) according to the shape of the carrier object needing to be laid with the structural material, a continuous curved surface is established, and the curved surface can be: an axisymmetric surface of revolution or a part thereof, a non-axisymmetric non-repeating surface of revolution (the projection curve is not repeated for the center) or a part thereof, a body of revolution of a carrier object (with discontinuous polygonal line edges) formed by splicing a plurality of parts of the aforementioned curved surfaces, and the like. The curved surface is a moving line, and under a given condition, the moving line generating a curve is called a bus in a space continuous motion track, and the bus can be a straight line or a curve. The curved surface is used as a paved object and is formed by a bus of the curved surface around a rotating shaft along any closed curve, and the curved surface can be an expandable curved surface or an unexpanded curved surface. The axisymmetrical rotating curved surface and the non-axisymmetrical non-repetitive curved surface are shown in fig. 1a and 1b, the generatrix of fig. 1a and 1b is a straight line, one end of the generatrix is on the axis, the other end of the generatrix is on the closed curve, the closed curve of the axisymmetrical rotating curved surface is a circle, and the closed curve of the non-axisymmetrical non-repetitive curved surface is an irregular curve.

Definition of non-axisymmetric non-repeating surface of revolution: the term "non-repetitive" means that when a cylindrical projection coordinate established by a selected reference axis (for an axisymmetric radome reference axis, generally, a rotation axis is selected, and for a non-axisymmetric radome, the selected reference axis is not necessarily the rotation axis for establishing a radome curved surface) is used for parameterizing the curved surface, an angle parameter has a characteristic of being univocal (also called a rotation curved surface with a cylindrical projection coordinate parameter being univocal, that is, the height and the rotation angle of any point on the curved surface have uniqueness under the cylindrical coordinate); the reference axis is chosen arbitrarily, and for a typical radome, the reference axis is usually chosen to pass through the vertex of the radome and through a portion of the bottom surface of the radome closer to the center.

Cylindrical projection coordinate system: the method is a double-parameter curved surface coordinate system, and any point on a certain curved surface is projected by a cylindrical surface height parameter h and a rotating angle parameter theta. A continuous curved surface (possibly with discontinuous fold line edges) with multiple sections spliced together is shown in fig. 2.

(2) And establishing a structural material unit structure needing array laying, wherein the array unit is an object laid to the continuous curved surface. Fig. 3 shows a structural form of an array unit, and the structural form of the array unit depends on the design of electromagnetic performance, and can have various structural forms.

(3) Establishing local coordinates on a curved surface: each rotating body surface established in the step (1) comprises two orthogonal dimension directions, the two orthogonal dimensions of each rotating body surface before extraction are respectively a u direction along a bus direction of the rotating body and a v direction perpendicular to the bus direction, and the two orthogonal dimensions are shown in fig. 4; when the generatrix is a curve, the u direction is defined as the direction along the tangent line of the curve, and v is defined as the direction perpendicular to the tangent line of the generatrix (the normal n, u and v directions of the curved surface form a right-hand orthogonal coordinate system);

the tangent direction of the curve is as follows: the vector (unit vector) of the coordinates of the points on the curve versus the coordinates t of the isocratic curve on the curve. On a geometric surface of a discrete expression, the parameters of the tangential direction are generally obtained in a differential manner.

The unit can be set to a distance h to embed or float to the surface. According to the convention, the normal vector of the curved surface faces to the outside of the curved surface, in this case, for a point P on any given curved surface, the local coordinates (u, v, n) of the point are determined, wherein the n vector is the normal vector of two orthogonal dimensions u and v; aligning the x axis and the u axis of the coordinate system of the unit, aligning the y axis and the v axis, moving a distance h (floating when h is more than 0, or embedding) from the point P along the direction of the n vector, and then arranging the array units on the curved surface. (see FIG. 4)

(4) The units are laid from the top of the rotating body, if the curvature of the top of the rotating body is large, the units can be laid from a certain height away from the top (the height value is selected by a user, the relative size of the units is integrated, the product of the curvature multiplied by the unit size is small enough, if the product is smaller than 5 degrees), the laying is firstly carried out along the local v direction (hoop), the laying mode is that the laying mode is equal intervals along the arc length, and the arc length intervals use the array period of the plane design as the reference. The surface of the element is parallel to the section formed by u and v of the point of laying, the value of h according to (3), the height of suspension h or the depth of the embedding surface h, as shown in fig. 5.

After finishing one circle of laying along the v direction, starting next hoop laying at certain intervals along the u direction, wherein the length can refer to the plane period intervals, as shown in fig. 6. And when the specified height range is fully paved, paving modeling can be completed. The effect that the unit array is conformal to the curved surface is achieved.

(5) And covering the rotator material with the material of the unit to complete the laying modeling of the curved surface array.

The unit is laid on the curved surface of the rotator according to a u-direction (along a generatrix) and a v-direction (along a surrounding axis), and the matrix material is covered by the array unit material instead of a Boolean operation method, and the laying of the quasi-periodic structure can be carried out for multiple times by the method. For example, the calculation result proves that most of the multilayer FSS performance designed by the method is slightly different from that of a flat plate multilayer.

The picture of the object is shown in FIG. 7. Fig. 7 shows a physical structure of the pipe-shaped unit laid on the tangent oval surface, the pipe-shaped unit is made of air, the tangent oval surface is made of metal, and after the laying is completed, a gap-type FSS array model is formed. FIG. 8 is a schematic view of a plurality of partially spliced continuous curved arrays after they are laid.

The Frequency Selective Surface (FSS) is a single-screen or multi-screen periodic array structure composed of a large number of passive resonance units and is composed of periodically arranged metal patch units or periodically arranged aperture units on a metal screen. Such a surface may exhibit total reflection (patch type) or full transmission characteristics (aperture type) in the vicinity of the resonant frequency of the cell.

Radar Cross Section (RCS) is the most critical concept in Radar stealth technology, and represents a physical quantity of the intensity of an echo generated by a target under the irradiation of Radar waves. The radar scattering cross section is also called a backscattering cross section, is a measure of the radar signal scattering capacity of a target in the radar incidence direction, and is expressed by the power density normalization of an incident field. RCS refers to the ratio of the return scattered power per unit solid angle in the radar incident direction to the power density of the target section.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (2)

1. A unit structure curved surface array laying modeling method suitable for various continuous curved surface types is characterized by comprising the following steps:

1) according to the shape of a carrier object needing to be paved with structural materials, establishing a continuous curved surface, wherein the continuous curved surface is formed by splicing an axisymmetric rotating curved surface or a part thereof, a non-axisymmetric non-repetitive rotating curved surface or a part thereof and a plurality of parts of the curved surface into a carrier object rotating body;

2) building a structural material unit structure needing array laying;

3) establishing local coordinates of points on the curved surface: each rotating body surface established in the step 1) comprises two orthogonal dimension directions, the two orthogonal dimensions of each rotating body surface before extraction are respectively a u direction along a rotating body generatrix direction and a v direction perpendicular to the generatrix direction, when the generatrix is a curve, the u direction is defined as being along a curve tangent direction, and v is defined as being perpendicular to the generatrix tangent direction, and for a point P on any given curved surface, the local coordinate of the point is determined to be (u, v, n), wherein the n vector is a normal vector of the two orthogonal dimensions u and v; step 2), the unit structure can be set to be embedded or floated on the surface by a distance h, the x axis and the u axis of the coordinate system of the unit structure are aligned, the y axis and the v axis are aligned, the unit structure is moved by a distance h from a point P along the direction of an n vector, the unit structure floats when h is larger than 0, otherwise, the array unit structure can be deployed on the curved surface;

4) starting to lay the unit structure from the top of the rotating body in the step 1), if the curvature of the top of the rotating body is not consistent with the size of the laid unit structure, starting to lay the unit structure from a distance away from the top, and firstly, laying the unit structure along a local v-shaped ring direction at equal intervals along arc lengths, wherein the arc length intervals take an array period of planar design as reference; the surface of the unit structure is parallel to a tangent plane formed by u and v of the laying position point, and the suspension height h or the embedding surface depth h is determined according to the value of h in the step 3);

after one circle of laying is finished along the v direction, a certain length is arranged along the u direction at intervals, next annular laying is started, the length can refer to the periodic interval of the planes, and after a specified height range is fully laid, laying modeling can be finished, so that the unit structure array is conformal to the curved surface;

5) and covering the rotator material with the material of the unit structure to complete the laying modeling of the curved surface array.

2. The method for laying and modeling the curved surface array of the unit structure suitable for multiple continuous curved surface types according to claim 1, wherein the unit structure in the step 2) is made of any one of FSS materials, metamaterials and honeycomb wave-absorbing materials.

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