CN103455661A - Spray simulation method based on cloud simulation of droplets - Google Patents

Abstract

The invention discloses a spray simulation method based on cloud simulation of droplets. The spray simulation method includes the steps: adopting a three-dimensional stereo camera to acquire three-dimensional point cloud data of plant bodies, and simulating actual crop plants through a point cloud deleting method and coordinate transformation processing; describing spray droplet particle motion trajectories through Lagrangian trajectory description operators under the conditions of determining nozzle type, nozzle coordinates and spray technology parameters; designing a point cloud intersection algorithm of the spray droplet particle motion trajectories and the plants and judging whether the droplets drop on the plant bodies or not and calculating drop point positions thereof; according to requirements of spray operation speed, constantly changing the space coordinates of a nozzle to complete dynamic simulation till a stop condition is reached, outputting droplet deposition rate, and optimizing spraying height. By the spray simulation method, visual operation indexes of spray operation can be analyzed, and the optimal spraying operation height is achieved by taking the effective deposition rate of the droplets as an objective function, so that certain reference is offered to reduce application amount of pesticides during an actual plant protection process.

Description

A kind of spraying emulation mode based on the simulation of droplet cloud

Technical field

The present invention relates to spray method, especially a kind of spraying emulation mode based on the simulation of droplet cloud.

Background technology

In order to ensure the stable yields volume increase of grain, the personnel that are engaged in agriculture often adopt rough formula plant protection spraying operation mode in field, a large amount of chemical agents can accurately be applied on the crop target, and excessive chemical agent brings serious environment and food-safety problem.

The people such as what male Kui of China Agricultural University just " measure the impact of spray technique parameter on spray effect ", and this problem is done excessive quantity research under laboratory environment, experimental results show that the impact of the spray technique parameter of Fan spray head on spray effect, particularly the anti-drift of droplet had to significant impact.

Large-scale development Ansys Fluent has comprised the particle analogue simulation system, there is the scholar to use this software to design with the assistant spray machine through the emulation of row droplet both at home and abroad, but, because the limitation of this system can not be in conjunction with actual job object and operating environment, therefore application often is restricted.

Summary of the invention

The object of the present invention is to provide a kind of spraying emulation mode based on the simulation of droplet cloud, by simulating actual farmland operation complex environment, set up virtual spraying analogue system, can provide spraying operation multinomial visual operational indicator analysis, and to take the effective deposition of droplet be objective function, optimize every technical parameter in spraying system, thereby provide certain reference for actual plant protection operation process.

In order to achieve the above object, the technical solution used in the present invention is:

The step of the inventive method is as follows:

1) the applying three-dimensional stereoscopic camera obtains plant body three dimensional point cloud, and deletes method and coordinate transform processing by a cloud, simulates actual crop plant;

2), under definite shower nozzle model, shower nozzle coordinate and spray technique Parameter Conditions, describe operator by Lagrangian track and describe spraying droplet Particles Moving track;

3) design a kind of spraying droplet Particles Moving track and plant point cloud intersection algorithm, differentiate droplet and whether drop on the plant body and calculate its drop point site;

4), according to the spraying operation rate request, constantly change the shower nozzle volume coordinate and complete dynamic similation, until export the mist droplet deposition rate and optimize spray height after reaching stop condition.

AB+AC-BC＜2AD

Described continuous variation shower nozzle volume coordinate completes dynamic similation, can simulate the Dynamic spraying process, nozzle position is changed according to the spraying operation rate request, after reaching the emulation step number Maxstep that stop condition complete requirement, calculate the sprayed deposit rate of this operation height condition lower nozzle, by repeatedly analog result comparison, realize the optimization of spray height parameter, the computing formula of droplet product rate is as follows:

$C=\frac{\underset{j=1}{\overset{p}{\mathrm{\Σ}}}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{N}_{\mathrm{ij}}^1{m}_{\mathrm{ij}}}{\underset{j=1}{\overset{p}{\mathrm{\Σ}}}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{N}_{\mathrm{ij}}{m}_{\mathrm{ij}}}$

Wherein C is the mist droplet deposition rate;

for the droplet mark vector, dropping on value on plant is 1, and the value on the ground that falls is 0, N _ijfor all droplet mark vector values are 1, m _ijfor Quality of fogdrop corresponding to droplet identification number.

The beneficial effect that the present invention has is:

The present invention can provide spraying operation visual operational indicator analysis, and to take the effective deposition of droplet be objective function, acquisition optimum spraying operation height, thereby provide certain reference for reducing actual plant protection operation process Pesticides use amount.

The accompanying drawing explanation

Fig. 1 means specific implementation process flow diagram of the present invention.

Fig. 2 is three-dimensional collected by camera plant point Yun Yuantu.

Fig. 3 be through deleting and coordinate transform after the plant point cloud chart.

Fig. 4 is the Dynamic spraying design sketch.

Fig. 5 is spray height and mist droplet deposition rate graph of a relation.

Embodiment

Below in conjunction with drawings and Examples, the invention will be further described.

As shown in Figure 1, realization flow of the present invention is as follows:

1) the applying three-dimensional stereoscopic camera obtains plant body three dimensional point cloud, and deletes method and coordinate transform processing by a cloud, simulates actual crop plant;

2), under definite shower nozzle model, shower nozzle coordinate and spray technique Parameter Conditions, describe operator by Lagrangian track and describe spraying droplet Particles Moving track;

3) design a kind of spraying droplet Particles Moving track and plant point cloud intersection algorithm, differentiate droplet and whether drop on the plant body and calculate its drop point site;

4), according to the spraying operation rate request, constantly change the shower nozzle volume coordinate and complete dynamic similation, until export the mist droplet deposition rate and optimize spray height after reaching stop condition.

S110: use the 3 D stereo camera to get and obtain the plant cloud data, utilize the distance samples method to complete a cloud and delete, sampled distance is r, and the some cloud after deleting is carried out to coordinate transform, and coordinate transformation algorithm is described below:

Choosing plant model root is some N, and the stem that chooses upwards growth is some M, vector for the normal vector of plane Π, N is a bit in the Π plane, and the formula of establishing Π is Ax+By+Cz+D=0, $\frac{x-x_o}{l}=\frac{y-y_o}{m}=\frac{z-z_o}{n},$ ? $\mathrm{MN}\⊥\mathrm{\Π}\⇔S//n$ ? $\frac{A}{l}=\frac{B}{m}=\frac{C}{n},$ Bring the N point coordinate into and obtain the XOY plane formula, select two uneven vectors on XOY plane, and carry out orthogonalization unit by Schmidt orthogonalization, the Schmidt orthogonalization procedure is as follows:

If α ₁, α ₂..., α _slinear independence, construct β ₁, β ₂..., β _smake its pairwise orthogonal, and β _ionly α ₁, α ₂..., α _ilinear combination, i=1,2 ..., s, then β _iunit, note

γ ₁, γ ₂..., γ _sthe standard Orthogonal Vectors,

β wherein ₁=α ₁, ${\mathrm{\β}}_2={\mathrm{\α}}_2-\frac{({\mathrm{\α}}_2,{\mathrm{\β}}_1)}{({\mathrm{\β}}_1,{\mathrm{\β}}_1)}{\mathrm{\β}}_1,$

${\mathrm{\β}}_3={\mathrm{\α}}_3-\frac{({\mathrm{\α}}_3,{\mathrm{\β}}_1)}{({\mathrm{\β}}_1,{\mathrm{\β}}_1)}{\mathrm{\β}}_1-\frac{({\mathrm{\α}}_3,{\mathrm{\β}}_2)}{({\mathrm{\β}}_2,{\mathrm{\β}}_2)}{\mathrm{\β}}_2,$

……

${\mathrm{\β}}_s={\mathrm{\α}}_s=-\frac{({\mathrm{\α}}_s,{\mathrm{\β}}_1)}{({\mathrm{\β}}_1,{\mathrm{\β}}_1)}{\mathrm{\β}}_1-\frac{({\mathrm{\α}}_s,{\mathrm{\β}}_2)}{({\mathrm{\β}}_2,{\mathrm{\β}}_2)}{\mathrm{\β}}_2-\·\·\·\frac{({\mathrm{\α}}_s,{\mathrm{\β}}_{s-1})}{({\mathrm{\β}}_{s-1},{\mathrm{\β}}_{s-1})}{\mathrm{\β}}_{s-1}$

To two groups of bases that obtain, use transformation for mula to obtain the coordinate of millet cake cloud under new coordinate system, transformation for mula is as follows: if vectorial γ is the arbitrary vector in the n-dimensional vector SPACE V, it is at base α ₁, α ₂..., α _swith base β ₁, β ₂..., β _scoordinate be respectively X=(x ₁, x ₁..., x _n) ^t, Y=(y ₁, y ₁..., y _n) ^t,

Be γ=x ₁α ₁+ x ₂α ₂+ ... + x _nα _n=y ₁β ₁+ y ₂β ₂+ ... + y _nβ _n,

The vectorial coordinate transformation for mula is Y=C ^-1x

Wherein C is from base α ₁, α ₂..., α _sto base β ₁, β ₂..., β _sexcessive matrix, excessively Matrix Formula is as follows:

C=(α ₁，α ₂，…，α _n) ^T(β ₁，β ₂，…，β _n)。

S120: under definite shower nozzle model, shower nozzle coordinate and spray technique Parameter Conditions, take particIe system as basic description means, by Lagrangian method, calculate droplet Particles Moving track, it is as follows that Lagrange is described the Particles Moving equation:

${\stackrel{\→}{F}}_g+{\stackrel{\→}{F}}_f+{\stackrel{\→}{F}}_w=m\frac{d{\stackrel{\→}{v}}_p}{\mathrm{dt}}$

$\left\{\begin{array}{c}{m}_p\frac{{\mathrm{dv}}_{\mathrm{px}}}{\mathrm{dt}}=F_{\mathrm{fx}}+F_{\mathrm{wx}}\\ m_p\frac{{\mathrm{dv}}_{\mathrm{py}}}{\mathrm{dt}}=F_{\mathrm{fy}}+F_{\mathrm{wy}}\\ m_p\frac{{\mathrm{dv}}_{\mathrm{pz}}}{\mathrm{dt}}=F_{\mathrm{fz}}+F_{\mathrm{wz}}+F_g\end{array}\right.$

V wherein _px, v _py, v _pzfor droplet particle rapidity vector at x, y, the speed component on the z direction, t is the time, F _gfor droplet particle gravity

m wherein _ρfor the droplet mass particle, D is the droplet particle diameter, and ρ is the droplet particle density, and g is acceleration of gravity, F _fx, F _fy, F _fzfor the droplet particle is subject to air resistance

at x, y, the component on the z direction, air resistance

wherein μ is aerodynamic force viscosity,

for droplet Particles Moving velocity, F _wx, F _wy, F _wzfor the droplet particle is subject to the wind drag force

at x, y, the component on the z direction,

for the wind drag force

wherein for wind vector, when indoor calm experiment, think by time increment method, the Particles Moving in each time step is done to certain simplification, think according to every step just the motion state of particle determine the motion state of every step end particle, by the time, every step is progressively followed the tracks of, obtain the movement locus of particle in whole flight course, the droplet equation of motion is one group of nonlinear ordinary differential equation group, here adopt easy Local approximation solution, by time increment method, publicity is simplified, solution formula is as follows:

$\left\{\begin{array}{c}{v}_{\mathrm{px}}^{n+1}=v_{\mathrm{px}}^n{e}^{-\frac{\mathrm{\Δt}}{\mathrm{\τ}}}+\frac{F_{\mathrm{fx}}\mathrm{\τ}}{m_p}(1-e^{-\frac{\mathrm{\Δt}}{\mathrm{\τ}}})\\ v_{\mathrm{py}}^{n+1}=v_{\mathrm{py}}^n{e}^{-\frac{\mathrm{\Δt}}{\mathrm{\τ}}}+\frac{F_{\mathrm{fy}}\mathrm{\τ}}{m_p}(1-e^{-\frac{\mathrm{\Δt}}{\mathrm{\τ}}})\\ v_{\mathrm{pz}}^{n+1}=v_{\mathrm{pz}}^n{e}^{-\frac{\mathrm{\Δt}}{\mathrm{\τ}}}+\frac{F_{\mathrm{fz}}\mathrm{\τ}}{m_p}(1-e^{-\frac{\mathrm{\Δt}}{\mathrm{\τ}}})\end{array}\right.$

Wherein, the τ momentum relaxation time, Δ t time step,

for at n constantly at x, y, the projection on the z direction,

for at n+1 constantly at x, y, the projection on the z direction, n+1 Δ t constantly, in the locus of known shower nozzle coordinate (x0, y0, z0), single step spraying droplet number num situation, tried to achieve by following system of equations by the locus of each droplet point:

$\left\{\begin{array}{c}{x}_{n+1}=x_n+(v_{\mathrm{px}}^n+v_{\mathrm{px}}^{n+1})\frac{\mathrm{\Δt}}{2}\\ y_{n+1}=y_n+(v_{\mathrm{py}}^n+v_{\mathrm{py}}^{n+1})\frac{\mathrm{\Δt}}{2}\\ z_{n+1}=z_n+(v_{\mathrm{pz}}^n+v_{\mathrm{pz}}^{n+1})\frac{\mathrm{\Δt}}{2}\end{array}\right.$

Wherein, x _n, y _n, z _nfor the volume coordinate position at n moment droplet particle, x _n+1, y _n+1, z _n+1for the volume coordinate position at n+1 moment droplet particle, droplet particle life cycle shows that this particle participates in the cycle of track emulation, and in the spraying simulation process, droplet particle life cycle ends up being following three kinds of situations:

(1) particle falls earthward;

(2) particle is fallen on target or on manipulating object;

(3) particle rapidity approaches 0.

S130: a kind of droplet track and plant point cloud intersection algorithm are to utilize plant point and directed line segment spatial relation, a Rule of judgment is set and realizes whether droplet drops on plant and drop point site is calculated, suppose: droplet track directed line segment BC is arranged in space, one plant point cloud A is arranged, if the vertical line that AD is triangle ABC, the D point is intersection point, by triangular nature, is obtained:

AD+BD＞AB

AD+DC＞AC

The addition of binomial formula obtains

2AD+DC+BD＞AB+AC

That is: 2AD+BC>AB+AC

Judge whether droplet reaches in a cloud, and drop point site is thought the point of Z-direction numerical value maximum in all mid points that satisfy condition if therefore obtain meeting following formula, wherein by the distance samples method, learn that AD should be greater than 3r.

AB+AC-BC＜2AD

AB+AC-BC＜2AD

S140, S150, S160: constantly change the shower nozzle volume coordinate and complete dynamic similation, can simulate the Dynamic spraying process, nozzle position is changed according to the spraying operation rate request, after reaching the emulation step number Maxstep that stop condition complete requirement, calculate the sprayed deposit rate of this operation height condition lower nozzle, by repeatedly analog result comparison, realize the optimization of spray height parameter, the computing formula of droplet product rate is as follows:

$C=\frac{\underset{j=1}{\overset{p}{\mathrm{\Σ}}}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{N}_{\mathrm{ij}}^1{m}_{\mathrm{ij}}}{\underset{j=1}{\overset{p}{\mathrm{\Σ}}}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{N}_{\mathrm{ij}}{m}_{\mathrm{ij}}}$

Wherein C is the mist droplet deposition rate;

for the droplet mark vector, dropping on value on plant is 1, and the value on the ground that falls is 0, N _ijfor all droplet mark vector values are 1, m _ijfor Quality of fogdrop corresponding to droplet identification number.

As shown in Figure 2, be the rapeseed plants original point cloud atlas by the 3 D stereo collected by camera, have 45235 points.As shown in Figure 3, being over-sampling deletes and, through the plant point cloud chart of row-coordinate conversion, has 4574 points apart from the r=2mm sampling, and the spatial point number is reduced to original 10.1%, reduce the calculated amount of subsequent step, selecting the N point coordinate is (24.745010376 ,-158.550506592,1111.473999023), the N point of take is initial point, selecting the M point coordinate is that (32.594978333 ,-141.628906250,1091.062011719) carry out coordinate transform.As shown in Figure 4, be that shower nozzle is 0.2m in spray height, single step spraying cloud point number num is 50, and maximum emulation step number Maxstep is 100 steps, and the shower nozzle Changing Pattern is along the Dynamic spraying design sketch under x direction of principal axis 0.6m/s mobile condition.As shown in Figure 5, that shower nozzle is that 0.1m is to 0.3m in spray height, every the 0.025m altitude simulation once, single step spraying cloud point number num is 50, maximum emulation step number Maxstep is 100 steps, and the shower nozzle Changing Pattern is along the Dynamic spraying design sketch under x direction of principal axis 0.6m/s mobile condition, the relation between spray height and spraying droplet deposition, as can be seen from Figure 5, under current spraying environmental baseline, when spray height is 0.2m, the mist droplet deposition rate reaches maximal value.

Claims (5)

1. the spraying emulation mode based on the simulation of droplet cloud, is characterized in that, the step of the method is as follows:

1) the applying three-dimensional stereoscopic camera obtains plant body three dimensional point cloud, and deletes method and coordinate transform processing by a cloud, simulates actual crop plant;

2), under definite shower nozzle model, shower nozzle coordinate and spray technique Parameter Conditions, describe operator by Lagrangian track and describe spraying droplet Particles Moving track;

3) design a kind of spraying droplet Particles Moving track and plant point cloud intersection algorithm, differentiate droplet and whether drop on the plant body and calculate its drop point site;

4), according to the spraying operation rate request, constantly change the shower nozzle volume coordinate and complete dynamic similation, until export the mist droplet deposition rate and optimize spray height after reaching stop condition.

2. a kind of spraying emulation mode based on droplet cloud simulation according to claim 1, it is characterized in that: described use 3 D stereo camera is got and is obtained the plant cloud data, utilizing the distance samples method to complete a cloud deletes, sampled distance is r, point cloud after deleting is carried out to coordinate transform, and coordinate transformation algorithm is described below:

Choosing plant model root is some N, and the stem that chooses upwards growth is some M, vector

for the normal vector of plane Π, N is a bit in the Π plane, and the formula of establishing Π is Ax+By+Cz+D=0,

?

? bring the N point coordinate into and obtain the XOY plane formula, select two uneven vectors on XOY plane, and carry out orthogonalization unit by Schmidt orthogonalization, the Schmidt orthogonalization procedure is as follows:

If α ₁, α ₂..., α _slinear independence, construct β ₁, β ₂..., β _smake its pairwise orthogonal, and β _ionly α ₁, α ₂..., α _ilinear combination, i=1,2 ..., s, then β _iunit, note

γ ₁, γ ₂..., γ _sthe standard Orthogonal Vectors,

β wherein ₁=α ₁,

……

To two groups of bases that obtain, use transformation for mula to obtain the coordinate of millet cake cloud under new coordinate system, transformation for mula is as follows: if vectorial γ is the arbitrary vector in the n-dimensional vector SPACE V, it is at base α ₁, α ₂..., α _swith base β ₁, β ₂..., β _scoordinate be respectively X=(x ₁, x ₁..., x _n) ^t, Y=(y ₁, y ₁..., y _n) ^t,

Be γ=x ₁α ₁+ x ₂α ₂+ ... + x _nα _n=y ₁β ₁+ y ₂β ₂+ ... + y _nβ _n,

The vectorial coordinate transformation for mula is Y=C ^-1x

Wherein C is from base α ₁, α ₂..., α _sto base β ₁, β ₂..., β _sexcessive matrix, excessively Matrix Formula is as follows:

C=(α ₁，α ₂，…，α _n) ^T(β ₁，β ₂，…，β _n)。

3. a kind of spraying emulation mode based on droplet cloud simulation according to claim 1, it is characterized in that: described under definite shower nozzle model, shower nozzle coordinate and spray technique Parameter Conditions, take particIe system as basic description means, calculate droplet Particles Moving track by Lagrangian method, it is as follows that Lagrange is described the Particles Moving equation:

V wherein _px, v _py, v _pzfor droplet particle rapidity vector

at x, y, the speed component on the z direction, t is the time, F _gfor droplet particle gravity

m wherein _ρfor the droplet mass particle, D is the droplet particle diameter, and ρ is the droplet particle density, and g is acceleration of gravity, F _fx, F _fy, F _fzfor the droplet particle is subject to air resistance

at x, y, the component on the z direction, air resistance

wherein μ is aerodynamic force viscosity,

for droplet Particles Moving velocity, F _wx, F _wy, F _wzfor the droplet particle is subject to the wind drag force

at x, y, the component on the z direction,

for the wind drag force

wherein for wind vector, when indoor calm experiment, think

by time increment method, the Particles Moving in each time step is done to certain simplification, think according to every step just the motion state of particle determine the motion state of every step end particle, by the time, every step is progressively followed the tracks of, obtain the movement locus of particle in whole flight course, the droplet equation of motion is one group of nonlinear ordinary differential equation group, here adopt easy Local approximation solution, by time increment method, publicity is simplified, solution formula is as follows:

Wherein, the τ momentum relaxation time, Δ t time step,

for at n constantly

at x, y, the projection on the z direction,

for at n+1 constantly

at x, y, the projection on the z direction, n+1 Δ t constantly, in the locus of known shower nozzle coordinate (x0, y0, z0), single step spraying droplet number num situation, tried to achieve by following system of equations by the locus of each droplet point:

Wherein, x _n, y _n, z _nfor the volume coordinate position at n moment droplet particle, x _n+1, y _n+1, z _n+1for the volume coordinate position at n+1 moment droplet particle, droplet particle life cycle shows that this particle participates in the cycle of track emulation, and in the spraying simulation process, droplet particle life cycle ends up being following three kinds of situations:

(1) particle falls earthward;

(2) particle is fallen on target or on manipulating object;

(3) particle rapidity approaches 0.

4. a kind of spraying emulation mode based on droplet cloud simulation according to claim 1, it is characterized in that: described a kind of droplet track and plant point cloud intersection algorithm are to utilize plant point and directed line segment spatial relation, a Rule of judgment is set and realizes whether droplet drops on plant and drop point site is calculated, suppose: droplet track directed line segment BC is arranged in space, one plant point cloud A is arranged, if the vertical line that AD is triangle ABC, the D point is intersection point, by triangular nature, is obtained:

AD+BD＞AB

AD+DC＞AC

The addition of binomial formula obtains

2AD+DC+BD＞AB+AC

That is: 2AD+BC>AB+AC

Judge whether droplet reaches in a cloud, and drop point site is thought the point of Z-direction numerical value maximum in all mid points that satisfy condition if therefore obtain meeting following formula, wherein by the distance samples method, learn that AD should be greater than

AB+AC-BC＜2AD。

5. a kind of spraying emulation mode based on droplet cloud simulation according to claim 1, it is characterized in that: described continuous variation shower nozzle volume coordinate completes dynamic similation, can simulate the Dynamic spraying process, nozzle position is changed according to the spraying operation rate request, after reaching the emulation step number Maxstep that stop condition complete requirement, calculate the sprayed deposit rate of this operation height condition lower nozzle, by repeatedly analog result comparison, realize the optimization of spray height parameter, the computing formula of droplet product rate is as follows:

Wherein C is the mist droplet deposition rate; for the droplet mark vector, dropping on value on plant is 1, and the value on the ground that falls is 0, N _ijfor all droplet mark vector values are 1, m _ijfor Quality of fogdrop corresponding to droplet identification number.

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