CN104656078A - Sea surface ship method based on ray tracing - Google Patents

Abstract

The invention belongs to a tracing method and particularly relates to a sea surface ship method based on ray tracing. The sea surface ship method comprises the following steps: step 1: ray division and wave beam equivalence: firstly, building a sea-surface target integrated geometric model composed of triangular surface elements, and then calculating beamlet; step 2: ray tracing and multi-path reflection calculation; step3: far field contribution calculation of multi-path reflection: forming far field scattering contribution when electromagnetic beam irradiates on elements visible in a receiving direction during multi-path reflection of a target and a sea surface. Since the receiving distance is far, incoherent diffuse reflection contribution is taken as a major, and a GO method taking coherent weight as a major cannot be considered for calculation. Finally, far field scattering contribution of all visible elements can be overlapped in a coherent way, namely a total scattering field is obtained. After the use of the method provided by the invention, the effect that quick calculation to coupling scattering of different ships and a dynamic ocean surface under any sea conditions can be achieved.

Description

A kind of method of the surface vessel based on ray tracing

Technical field

The invention belongs to method for tracing, be specifically related to a kind of method of the surface vessel based on ray tracing.

Background technology

Surface vessel, aircraft carrier electromagnetic characteristic of scattering will directly support the radar detection of aircraft carrier target, tracking, identification and guidance.Due to the super electrically large sizes of Ship Target and extra large background, structure onlap polygamy, the impact of the factors such as coupling between the two and relative motion, the electromagnetic scattering modeling of sea and Ship Target is a challenging difficult problem in target and environment Electromagnetic Scattering Characteristics field always.Current research is limited to the simplify processes based on " four paths " model more, and efficiency and precision also do not have effective computation model that can meet engineer applied demand.

In sea-surface target and background characteristics development test, research work is mainly to follow the tracks of foreign technology.Aerospace Science and Industry Corporation 207 propose the quick high frequency algorithm of a kind of surface vessel coupling scattering based on HPP/PO, effectively can solve the static combination scattering problem of the two, but owing to relating to the precise geometrical modeling on sea on a large scale, limit by calculated amount, be difficult to be generalized to dynamic situation.Beijing Institute of Aeronautics becomes sea Radar Target Scatter phenomenological model when proposing one, can carry out rational qualitative interpretation, but can't meet engineer applied demand from physical phenomenon and Scattering Rules to surface vessel scattering properties in quantitative test.Fudan University combines before and after broad sense with Green function spectral integral accelerated method (SAA) to alternative manner (GFBM), and the EM scattering that the wind for head-down radar monitoring under complicated sea conditions drives sea and Ship Target complex composite moulding calculates; Fast Iterative is used for the poor field that two dimension target and large scale one dimension PM compose sea to calculate.But above-mentioned numerical algorithm all takes dimensionality reduction and is similar to, namely set up the combination scattering model of the two dimension target on one-dimensional sea surface, although obtain some valuable conclusions, the further research that needs is generalized in practical engineering application.

Summary of the invention

This object is for prior art defect, provides a kind of method of the surface vessel based on ray tracing.

The present invention is achieved in that a kind of method of the surface vessel based on ray tracing, comprises the steps:

Step one: ray divides and beam equivalent

First the sea-surface target integration geometric model be made up of Triangular object model is set up, during calculating, plane electromagnetic wave incident direction adopts the Z-buffer algorithm accelerated based on video card carry out blanking to composite model, identify electromagnetic irradiation area, i.e. all visible Triangular object model.

Then, can according to electromagnetism Scattering Calculation accuracy requirement, in units of bin, each visible face is determined several intersection points as ray and bin, thus the electromagnetic wave be irradiated on bin is subdivided into the identical minor beam of yardstick.Each for visible bin limit is divided into m decile, and get the intersection point of the little triangle core after decile as ray and bin, then the number of rays be transmitted on each bin is m ².

Because the division of ray is in units of bin, different visible bins is generally different in the projected area of the surface of emission (from the plane that incident direction is vertical), and the beam size usable area therefore representated by incident ray is expressed as

$d{A}_k=\frac{S_k({\hat{k}}_0\·{\hat{n}}_k)}{m^2}---\left(1\right)$

In formula, k is bin number, S _kfor bin area, for panel method to, for electromagnetic wave incident direction, m is the isodisperse on bin limit.According to target and sea binning yardstick separately, different m values can be set respectively, thus obtain different radiographic density.

Step 2: ray tracing and multipath reflection calculate

In plane wave incidence situation, omit time-harmonic factor e ^{j ω t}, incident electric fields can be expressed as

$E^i=\hat{a}{E}_0{e}^{-j{k}_{0}r}---\left(2\right)$

In formula, for incident electric fields polarised direction, E ₀for electric field amplitude, k ₀for incident wave number, r is wave propagation distance.

Electromagnetic wave is when target surface reflects, and the direction of propagation, E field polarization direction and phase place all can change.If r _nfor true origin is to T _nthe vector of upper any point, then wave beam is at T _ngO mirror field after reflection is

In formula

Step 3: the far field contributor of multipath reflection calculates

Electromagnetic beam is irradiated to reciever in the multipath reflection on target and sea can form far field contribution of scatters to during visible bin.Because receiving range is far away, based on incoherent diffuse reflection contribution, can not again to consider that the GO method of coherent component calculates.

For target, if T _nbe visible face at radar receive direction, utilize physical optical method approximate treatment wave beam at T _nthe far field contribution of scatters of upper formation.Integrating range equivalence is set to T _nbin interval, and do weighting to amplitude, weighting factor is

$A_l=\frac{{\mathrm{dA}}_k}{S_n({\hat{k}}_i\·\hat{n})}---\left(5\right)$

In formula, dA _kfor the area that ray carries, determined by formula (1), S _nfor T _narea.For conductive object, the far field scattered field of this secondary reflection is

In formula, s is T _nbin interval, for T _nnormal direction.

For sea, according to two yardstick scattering models of the applicable medium rough surface that F.G.Bass and I.M.Fuks proposes, obtain the scattered field of the Rough Sea Surfaces being applicable to EM scattering:

$\stackrel{\→}{E_s}=\frac{k^2{e}^{\mathrm{ik}{R}_s}}{\mathrm{\π}{R}_s}{E}_0\underset{S}{\∫}F(\stackrel{^^^}{p_i,}{p}_r,\stackrel{^^^}{k_i,}{k}_r,n)\mathrm{\ζ}\left(\stackrel{\→}{r}\right)\mathrm{\η}(\stackrel{\→}{r},k_r)e^{-i\stackrel{\→}{q}\·\stackrel{\→}{r}}{d}^{\→}---\left(7\right)$

In formula:

Wherein, for polarization vector, be respectively the unit vector in incident direction and scattering direction, for bin per unit system to; for considering to block and the step function introduced, its value 1,0 corresponds respectively to a r ∈ S and to be irradiated by incident wave or not illuminated; a ₀=cos θ _i, $b_0=\sqrt{\mathrm{\ϵ}-{\sin }^2{\mathrm{\θ}}_i},a=\hat{n}\·\widehat{\mathrm{\β}},b=\sqrt{\mathrm{\ϵ}-1+a^2}.$

Finally, coherence stack is carried out in the contribution of the Far Field Scattering of all visible face and can obtain total scattering field.

Effect of the present invention is used to be: by carrying out Geometric Modeling and mesh generation to sea and naval vessel class target, form the surface vessel integration triangle face-units corresponding with actual scene, adopt the adaptive beam dividing mode directly determined by bin structure, carry out equivalence to the electromagnetic wave energy representated by every bar wave beam to be similar to, in ray multiple reflections integrated application for target high frequency algorithm and for the two-scale method of Rough Sea Surfaces calculate between target and sea multipath coupling scattering contribution, under any sea condition of final realization, the coupling scattering of different naval vessel and Dynamic offing calculates fast.

Embodiment

Based on a method for the surface vessel of ray tracing, comprise the steps:

Step one: ray divides and beam equivalent

First the sea-surface target integration geometric model be made up of Triangular object model is set up, during calculating, plane electromagnetic wave incident direction adopts the Z-buffer algorithm accelerated based on video card carry out blanking to composite model, identify electromagnetic irradiation area, i.e. all visible Triangular object model.

Then, can according to electromagnetism Scattering Calculation accuracy requirement, in units of bin, each visible face is determined several intersection points as ray and bin, thus the electromagnetic wave be irradiated on bin is subdivided into the identical minor beam of yardstick.Each for visible bin limit is divided into m decile, and get the intersection point of the little triangle core after decile as ray and bin, then the number of rays be transmitted on each bin is m ².

Because the division of ray is in units of bin, different visible bins is generally different in the projected area of the surface of emission (from the plane that incident direction is vertical), and the beam size usable area therefore representated by incident ray is expressed as

$d{A}_k=\frac{S_k({\hat{k}}_0\·{\hat{n}}_k)}{m^2}---\left(1\right)$

In formula, k is bin number, S _kfor bin area, for panel method to, for electromagnetic wave incident direction, m is the isodisperse on bin limit.According to target and sea binning yardstick separately, different m values can be set respectively, thus obtain different radiographic density.

Step 2: ray tracing and multipath reflection calculate

In plane wave incidence situation, omit time-harmonic factor e ^{j ω t}, incident electric fields can be expressed as

$E^i=\hat{a}{E}_0{e}^{-j{k}_{0}r}---\left(2\right)$

In formula, for incident electric fields polarised direction, E ₀for electric field amplitude, k ₀for incident wave number, r is wave propagation distance.

Electromagnetic wave is when target surface reflects, and the direction of propagation, E field polarization direction and phase place all can change.Coupling between target and the sea class dihedral angle structure that mainly hull and sea are formed causes, and can think that wave beam is followed in conjunction with optics (GO) principle at the multiple reflections of inside. for T _nouter normal vector, with be respectively ray at T _non incident direction and the unit vector of reflection direction, be respectively polarised direction and the phase place of incident electric fields, be respectively polarised direction and the phase place of reflected field.For target conductor, if r _nfor true origin is to T _nthe vector of upper any point, then wave beam is at T _ngO mirror field after reflection is

In formula

Step 3: the far field contributor of multipath reflection calculates

Electromagnetic beam is irradiated to reciever in the multipath reflection on target and sea can form far field contribution of scatters to during visible bin.Because receiving range is far away, based on incoherent diffuse reflection contribution, can not again to consider that the GO method of coherent component calculates.

For target, if T _nbe visible face at radar receive direction, physical optical method (PO) approximate treatment wave beam can be utilized at T _nthe far field contribution of scatters of upper formation.Integrating range equivalence is set to T _nbin interval, and do weighting to amplitude, weighting factor is

$A_l=\frac{{\mathrm{dA}}_k}{S_n({\hat{k}}_i\·\hat{n})}---\left(5\right)$

In formula, dA _kfor the area that ray carries, determined by formula (1), S _nfor T _narea.For conductive object, the far field scattered field of this secondary reflection is

In formula, s is T _nbin interval, for T _nnormal direction.

For sea, according to two yardstick scattering models of the applicable medium rough surface that F.G.Bass and I.M.Fuks proposes, obtain the scattered field of the Rough Sea Surfaces being applicable to EM scattering:

$\stackrel{\→}{E_s}=\frac{k^2{e}^{\mathrm{ik}{R}_s}}{\mathrm{\π}{R}_s}{E}_0\underset{S}{\∫}F(\stackrel{^^^}{p_i,}{p}_r,\stackrel{^^^}{k_i,}{k}_r,n)\mathrm{\ζ}\left(\stackrel{\→}{r}\right)\mathrm{\η}(\stackrel{\→}{r},k_r)e^{-i\stackrel{\→}{q}\·\stackrel{\→}{r}}{d}^{\→}---\left(7\right)$

In formula:

Wherein, for polarization vector, be respectively the unit vector in incident direction and scattering direction, for bin per unit system to; for considering to block and the step function introduced, its value 1,0 corresponds respectively to a r ∈ S and to be irradiated by incident wave or not illuminated; a ₀=cos θ _i, $b_0=\sqrt{\mathrm{\ϵ}-{\sin }^2{\mathrm{\θ}}_i},a=\hat{n}\·\widehat{\mathrm{\β}},b=\sqrt{\mathrm{\ϵ}-1+a^2}.$

Finally, coherence stack is carried out in the contribution of the Far Field Scattering of all visible face and can obtain total scattering field.

Claims (1)

1. based on a method for the surface vessel of ray tracing, it is characterized in that, comprise the steps:

Step one: ray divides and beam equivalent

First the sea-surface target integration geometric model be made up of Triangular object model is set up, during calculating, plane electromagnetic wave incident direction adopts the Z-buffer algorithm accelerated based on video card carry out blanking to composite model, identify electromagnetic irradiation area, i.e. all visible Triangular object model.

Then, can according to electromagnetism Scattering Calculation accuracy requirement, in units of bin, each visible face is determined several intersection points as ray and bin, thus the electromagnetic wave be irradiated on bin is subdivided into the identical minor beam of yardstick.Each for visible bin limit is divided into m decile, and get the intersection point of the little triangle core after decile as ray and bin, then the number of rays be transmitted on each bin is m ².

Because the division of ray is in units of bin, different visible bins is generally different in the projected area of the surface of emission (from the plane that incident direction is vertical), and the beam size usable area therefore representated by incident ray is expressed as

$d{A}_k=\frac{S_k({\hat{k}}_0\·{\hat{n}}_k)}{m^2}---\left(1\right)$

In formula, k is bin number, S _kfor bin area, for panel method to, for electromagnetic wave incident direction, m is the isodisperse on bin limit.According to target and sea binning yardstick separately, different m values can be set respectively, thus obtain different radiographic density.

Step 2: ray tracing and multipath reflection calculate

In plane wave incidence situation, omit time-harmonic factor e ^{j ω t}, incident electric fields can be expressed as

$E^i=\hat{a}{E}_0{e}^{-j{k}_{0}r}---\left(2\right)$

In formula, for incident electric fields polarised direction, E ₀for electric field amplitude, k ₀for incident wave number, r is wave propagation distance.

Electromagnetic wave is when target surface reflects, and the direction of propagation, E field polarization direction and phase place all can change.If r _nfor true origin is to T _nthe vector of upper any point, then wave beam is at T _ngO mirror field after reflection is

In formula

Step 3: the far field contributor of multipath reflection calculates

Electromagnetic beam is irradiated to reciever in the multipath reflection on target and sea can form far field contribution of scatters to during visible bin.Because receiving range is far away, based on incoherent diffuse reflection contribution, can not again to consider that the GO method of coherent component calculates.

For target, if T _nbe visible face at radar receive direction, utilize physical optical method approximate treatment wave beam at T _nthe far field contribution of scatters of upper formation.Integrating range equivalence is set to T _nbin interval, and do weighting to amplitude, weighting factor is

$A_l=\frac{{\mathrm{dA}}_k}{S_n({\hat{k}}_i\·\hat{n})}---\left(5\right)$

In formula, dA _kfor the area that ray carries, determined by formula (1), S _nfor T _narea.For conductive object, the far field scattered field of this secondary reflection is

In formula, s is T _nbin interval, for T _nnormal direction.

For sea, according to two yardstick scattering models of the applicable medium rough surface that F.G.Bass and I.M.Fuks proposes, obtain the scattered field of the Rough Sea Surfaces being applicable to EM scattering:

$\stackrel{\→}{E_s}=\frac{k^2{e}^{\mathrm{ik}{R}_s}}{\mathrm{\π}{R}_s}{E}_0\underset{S}{\∫}F(\stackrel{^^^}{p_i,}{p}_r,\stackrel{^^^}{k_i,}{k}_r,n)\mathrm{\ζ}\left(\stackrel{\→}{r}\right)\mathrm{\η}(\stackrel{\→}{r},k_r)e^{-i\stackrel{\→}{q}\·\stackrel{\→}{r}}{d}^{\→}---\left(7\right)$

In formula:

Wherein, for polarization vector, be respectively the unit vector in incident direction and scattering direction, for bin per unit system to; for considering to block and the step function introduced, its value 1,0 corresponds respectively to a r ∈ S and to be irradiated by incident wave or not illuminated; a ₀=cos θ _i, $b_0=\sqrt{\mathrm{\ϵ}-{\sin }^2{\mathrm{\θ}}_i},a=\hat{n}\·\widehat{\mathrm{\β}},b=\sqrt{\mathrm{\ϵ}-1+a^2}.$

Finally, coherence stack is carried out in the contribution of the Far Field Scattering of all visible face and can obtain total scattering field.