CN109077803A - It bleeds in a kind of virtual operation the modeling method of simulation model - Google Patents

It bleeds in a kind of virtual operation the modeling method of simulation model Download PDF

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CN109077803A
CN109077803A CN201810519551.7A CN201810519551A CN109077803A CN 109077803 A CN109077803 A CN 109077803A CN 201810519551 A CN201810519551 A CN 201810519551A CN 109077803 A CN109077803 A CN 109077803A
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particle
bleeding
grid
radius
revision
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CN109077803B (en
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石文
刘小平
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Yangtze River Delta Research Institute Of Beijing Jiaotong University
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/10—Computer-aided planning, simulation or modelling of surgical operations
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/10—Computer-aided planning, simulation or modelling of surgical operations
    • A61B2034/101—Computer-aided simulation of surgical operations

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  • Health & Medical Sciences (AREA)
  • Surgery (AREA)
  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biomedical Technology (AREA)
  • Robotics (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Medical Informatics (AREA)
  • Molecular Biology (AREA)
  • Animal Behavior & Ethology (AREA)
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Abstract

The invention discloses a kind of modeling methods for simulation model of bleeding in virtual operation, comprising: Step 1: determining particIe system, and particIe system is divided into using SPH method operating radius as the grid of side length；Step 2: determining particle i and judging particle i whether in the grid, when the particle i is in the grid, determine that the particle i's closes on particle；Step 3: the viscosity and the operating radius to particle i are revised, obtains revision viscosity and revise operating radius, the model is established according to the particle i stress, acceleration, the revision viscosity and the revision operating radius.It bleeds in virtual operation provided by the invention the modeling method of simulation model, the method for passing through grid dividing accelerates the efficiency that SPH method searches for point of proximity；By the improvement to model physical property of bleeding, making to bleed, it is more preferable to emulate smoothness of the surface, solves the problems, such as Boundary Distortion, improves the real-time and authenticity of emulation of bleeding；Keep simulated effect more smooth.

Description

It bleeds in a kind of virtual operation the modeling method of simulation model
Technical field
The invention belongs to the virtual operation technical field in virtual reality, in particular to emulation of bleeding in a kind of virtual operation The modeling method of model.
Background technique
Virtual reality technology is a kind of virtual world created by Computer Simulation, and true sense can be provided for user Feel.Virtual reality technology includes computer graphics, and the subjects such as artificial intelligence and mechanics pass through analog vision, the sense of hearing and tactile Deng realization to environment, the emulation of perception.User raises one's hand to wait behavior acts as input, computer is handled simultaneously by yaw It responds, feedback arrives the sense organ of user.An important research direction of the virtual operation as virtual reality technology is cured for surgery Life provides the training platform of an immersion, can it is safer, efficiently cultivate surgeon, and cost reduces, and avoids Use animal as research object, is protected the censure of animal association.It, can not as needed for treatment in true operation It needs to handle histoorgan with avoiding, this results in the certainty bled.If operator's training is bad, meeting It to a large amount of the case where bleeding is likely to that correct processing mode can not be made, generates serious consequence.Therefore, virtual operation platform Build, emulation of bleeding is important component part, not only can increase the sense of reality of virtual surgical environment visual aspects, moreover it is possible to add The ability of hemorrhage is handled surgeon by force.
Currently, for emulation of bleeding, there are some problems, and the real-time of emulation is poor, and real-time is that virtual operation must expire The requirement of foot, any delay can all influence the precision of operation, and with the increase of population in emulation of bleeding, calculation amount increases, Directly affect the real-time of emulation；The authenticity emulated in the case where real-time is met the requirements is to be improved, including right The deficiency of physical property of bleeding research, and the shortcoming in terms of programming realization.
Summary of the invention
An object of the present invention is to accelerate the efficiency that SPH method searches for point of proximity by the method for grid dividing, is improved It bleeds the real-time of emulation.
The second object of the present invention is to revise, make to particle properties parameter by the research to physical property of bleeding Bleeding, it is more preferable to emulate smoothness of the surface, solves the problems, such as Boundary Distortion, improves the authenticity for emulation of bleeding.
Technical solution provided by the invention are as follows:
It bleeds in a kind of virtual operation the modeling method of simulation model, comprising:
Step 1: determining particIe system and the particIe system being divided into using SPH method operating radius as side length Grid；
Step 2: determining particle i and judging the particle i whether in the grid, when the particle i is described When in grid, determine that the particle i's closes on particle；When the particle i is not in the grid, then increase more nets by several times Lattice, until being in particle i in grid；
Step 3: the viscosity and the operating radius to particle i are revised, revision viscosity and revision are obtained Operating radius, according to the foundation of the particle i stress, acceleration, the revision viscosity and the revision operating radius Model；
Wherein, the revision viscosity of the particle i are as follows:
μ=bexp (- aPi)；
In formula, a, b are coefficient, and a > 0, b > 0；PiFor the blood platelet nature parameters of particle i；
The revision operating radius are as follows:
In formula, λ is constant；miFor the quality of particle i；ρiFor the density of particle i；D is dimension；
Wherein, when the particle i is in bleeding surface, the particle i stress further includes tension, the particle i by Tension are as follows:
In formula, C (ri) be particle i tension field；For the unit normal vector of bleeding surface；δ is constant；
Particle i is due to the acceleration that is generated by the tension:
In formula, fi tFor the tension that particle i is subject to, ρiFor the density of particle i.
Preferably, in the step 2 further include: if surrounding's grid of grid where the particle i exists, count The particle in the surrounding grid is calculated at a distance from particle i, the point within the scope of the operating radius of particle i is found out, as grain Sub- i's closes on particle.
Preferably, increased grid number is 1 every time.
Preferably, in the step 2, judge the method whether particle i is in bleeding surface are as follows:
Calculate the tension field of particle i:
Wherein, particle j, A are closed on if existed around particle ij=1, otherwise Aj=0；mjFor closing on for particle i The quality of particle j；ρjFor the density of particle i；W(ri-rj, h) and it is kernel function；riFor the radius of particle i；rjFor the radius of particle j； H is the operating radius of particle i；
If C (ri)=0, then particle i is not at bleeding surface；If C (ri) ≠ 0, then particle i is in bleeding surface.
It preferably, further include the blood platelet nature parameters P in the step 3iValue changes over time:
Wherein, k is carry-over factor；mjFor the quality for closing on particle j of particle i；PiFor the blood platelet property of particle i Parameter；PjFor the blood platelet nature parameters for closing on particle j of particle i；W(ri-rj, h) and it is kernel function；riFor the radius of particle i；rj For the radius of particle j；H is the operating radius of particle i.
Preferably, in the step 3, taking the value that the value of a is 200, b is 0.5.
The beneficial effects of the present invention are:
It bleeds in virtual operation provided by the invention the modeling method of simulation model, by being ground to physical property of bleeding Study carefully, by Navier-Stokes (N-S) equation for being used to simulate fluid and for solving Navier-Stokes (N-S) equation SPH method is improved, and accelerates the efficiency that SPH method searches for point of proximity by the method for grid dividing；By to model of bleeding The improvement of physical property, making to bleed, it is more preferable to emulate smoothness of the surface, solves the problems, such as Boundary Distortion, improves emulation of bleeding Real-time and authenticity；Keep simulated effect more smooth.
Detailed description of the invention
Fig. 1 is grid dividing figure of the present invention.
Fig. 2 is to be compared using the FPS of the method for search point of proximity of the present invention and the FPS of traversal particle point of proximity Comparison diagram.
Fig. 3 is the simulated effect figure of bleeding using modeling method of the present invention.
Fig. 4 is the simulated effect figure of bleeding for being not introduced into the tension that particle is subject to.
Fig. 5 is the simulated effect figure of bleeding for being not introduced into the viscosity that blood platelet property calculates particle.
Operating radius in SPH is not changed to function of particle density post-simulation effect picture by Fig. 6.
Specific embodiment
Present invention will be described in further detail below with reference to the accompanying drawings, to enable those skilled in the art referring to specification text Word can be implemented accordingly.
The present invention provides a kind of modeling methods for simulation model of bleeding in virtual operation, can be improved in virtual operation It bleeds the real-time and authenticity of emulation, comprising:
Firstly, the point of proximity of the method search particle i with grid division.
As shown in Figure 1, particIe system is divided into using SPH method operating radius as the grid of side length by the present invention, by drawing The method of subnetting lattice improves the efficiency that point of proximity is searched in SPH method, improves the computational efficiency for emulation of bleeding.The basis in programming The method that the position of calculative particle i determines grid dividing region saves memory to reduce unnecessary grid.Specifically It include: that particIe system determining first judges grain after particIe system is divided into using SPH method operating radius as the grid of side length Whether sub- i is in grid；If particle i is in grid, find out particle i other particles within a grid as particle i Close on particle (point of proximity)；If particle i is not in grid, increase more grids, until making particle i be in grid In；To save memory, increases grid several times, increase by 1 grid (200 particles can be accommodated) every time, until making at particle i In grid.Later, surrounding's grid of grid whether there is where judging particle i, if the surrounding grid exists, calculate Particle in the surrounding grid finds out the point within the scope of the operating radius of particle i, as particle i at a distance from particle i Close on particle (point of proximity).
Use the FPS and traversal FPS pairs of particle point of proximity of the method simulation result of search point of proximity provided by the invention Than as shown in Fig. 2, passing through the comparison in figure, it can be seen that the method for search point of proximity provided by the invention searched closes on Point can cover all practical point of proximity of particle i substantially.
Later, the viscosity to particle i and the operating radius are revised, and obtain revision viscosity and revision is made With radius, the mould is established according to the particle i stress, acceleration, the revision viscosity and the revision operating radius Type.It specifically includes:
When calculating particle i stress, first determine whether particle i is in bleeding surface, when whether particle i is in bleeding surface When, introduce the tension that particle i is subject to.
Judge the method whether particle i is in bleeding surface are as follows:
Calculate the tension field of particle i:
Wherein, particle j, A are closed on if existed around particle ij=1, otherwise Aj=0；mjFor closing on for particle i The quality of particle j；ρjFor the density of particle i；W(ri-rj, h) and it is kernel function；riFor the radius of particle i；rjFor the radius of particle j； H is the operating radius of particle i；
If C (ri)=0, then particle i is not at bleeding surface；If C (ri) ≠ 0, then particle i is in bleeding surface.
When particle i is in bleeding surface, the tension that particle i is subject to is calculated:
Wherein, κ is the surface curvature of particle；For the unit normal vector of bleeding surface, δ is constant, for the meter that standardizes It calculates；
Further calculate the surface curvature of particleThat is the tension that particle i is subject to
Later, particle i is calculated due to the acceleration that is generated by the tension:
Wherein, fi tFor the tension that particle i is subject to, ρiFor the density of particle i.
Blood platelet property is introduced, the viscosity of particle i is revised.It is small in blood because containing blood platelet in blood Blood can gradually solidify under the action of plate.As the time increases, viscous force suffered by particle can be increasing, therefore, introduce with Platelet-related Property P, effect directly affect viscosity μ.
Firstly, calculating P according to SPH methodiValue changes over time:
Wherein, k is carry-over factor,
I.e.
Wherein, k is carry-over factor；mjFor the quality for closing on particle j of particle i；PiFor the blood platelet property of particle i Parameter；PjFor the blood platelet nature parameters for closing on particle j of particle i；W(ri-rj, h) and it is kernel function；riFor the radius of particle i；rj For the radius of particle j；H is the operating radius of particle i.
The viscosity of revised particle i: μ=bexp (- aPi)。
Wherein, a, b are coefficient, and a > 0, b > 0；PiFor the blood platelet property of particle i.
In the present embodiment, taking the value that the value of a is 200, b is 0.5, works as PiWhen value reduces, viscosity μ increases.
Since during Particles Moving, as the distance between particle increases, the density of particle becomes relatively small.This Result in using the operating radius in tradition SPH method modeled in Force Calculation when, when the distance between particle approaches When operating radius, close to zero, this is not inconsistent with actual conditions for intergranular viscous force and pressure.
Therefore, the operating radius in SPH is changed to function of particle density, revised operating radius are as follows:
Wherein, λ is constant；miFor the quality of particle i；ρiFor the density of particle i；D is dimension.
Later, using above-mentioned revision parameter, simulation model of bleeding is established.
Using the modeling method for simulation model of bleeding in virtual operation provided by the invention, in traditional Navier- Introduced in Stokes (N-S) equation particle by tension, blood platelet viscous force viscosity is influenced, and by the side SPH After invariable operating radius is changed to the function of particle density in method, the result for emulation of bleeding is as shown in Figure 3.It is not introduced into grain The simulated effect of bleeding for the tension (not including step 2) that sub- i is subject to, as shown in Figure 4.It is not introduced into blood platelet property, calculates particle The simulated effect of bleeding of the viscosity (not including step 3) of i, as shown in Figure 5.The operating radius in SPH grain is not changed to The simulated effect of sub- density function (not including step 4), as shown in Figure 6.It can be seen with the comparison of Fig. 3 respectively by Fig. 4-6 Out, using method provided by the invention, improvement to model physical property of bleeding, can make to bleed emulates smoothness of the surface more It is good, solve the problems, such as Boundary Distortion.
It bleeds in virtual operation provided by the invention the modeling method of simulation model, by being ground to physical property of bleeding Study carefully, by Navier-Stokes (N-S) equation for being used to simulate fluid and for solving Navier-Stokes (N-S) equation SPH method is improved, and accelerates the efficiency that SPH method searches for point of proximity by the method for grid dividing；By to model of bleeding The improvement of physical property, making to bleed, it is more preferable to emulate smoothness of the surface, solves the problems, such as Boundary Distortion, improves emulation of bleeding Real-time and authenticity；Keep simulated effect more smooth.
Although the embodiments of the present invention have been disclosed as above, but its is not only in the description and the implementation listed With it can be fully applied to various fields suitable for the present invention, for those skilled in the art, can be easily Realize other modification, therefore without departing from the general concept defined in the claims and the equivalent scope, the present invention is simultaneously unlimited In specific details and legend shown and described herein.

Claims (6)

1. a kind of modeling method for simulation model of bleeding in virtual operation characterized by comprising
Step 1: determining particIe system and the particIe system being divided into using SPH method operating radius as the grid of side length；
Step 2: determining particle i and judging the particle i whether in the grid, when the particle i is in the grid When, determine that the particle i's closes on particle；When the particle i is not in the grid, then increase more grids by several times, until It is in particle i in grid；
Step 3: the viscosity and the operating radius to particle i are revised, revision viscosity and revision effect are obtained Radius establishes the model according to the particle i stress, acceleration, the revision viscosity and the revision operating radius；
Wherein, the revision viscosity of the particle i are as follows:
μ=bexp (- aPi)；
In formula, a, b are coefficient, and a > 0, b > 0；PiFor the blood platelet nature parameters of particle i；
The revision operating radius are as follows:
In formula, λ is constant；miFor the quality of particle i；ρiFor the density of particle i；D is dimension；
Wherein, when the particle i is in bleeding surface, the particle i stress further includes tension, that the particle i is subject to Power are as follows:
In formula, C (ri) be particle i tension field；For the unit normal vector of bleeding surface；δ is constant；
Particle i is due to the acceleration that is generated by the tension:
In formula, fi tFor the tension that particle i is subject to, ρiFor the density of particle i.
2. the modeling method for simulation model of bleeding in virtual operation according to claim 1, which is characterized in that the step In two further include: if surrounding's grid of grid where the particle i exists, calculate the particle and grain in the surrounding grid The distance of sub- i, finds out the point within the scope of the operating radius of particle i, closes on particle as particle i.
3. the modeling method for simulation model of bleeding in virtual operation according to claim 2, which is characterized in that increase every time Grid number be 1.
4. the modeling method for simulation model of bleeding in virtual operation according to claim 1 or 3, which is characterized in that in institute It states in step 2, judges the method whether particle i is in bleeding surface are as follows:
Calculate the tension field of particle i:
Wherein, particle j, A are closed on if existed around particle ij=1, otherwise Aj=0；mjParticle j is closed on for particle i Quality；ρjFor the density of particle i；W(ri-rj, h) and it is kernel function；riFor the radius of particle i；rjFor the radius of particle j；H is grain The operating radius of sub- i；
If C (ri)=0, then particle i is not at bleeding surface；If C (ri) ≠ 0, then particle i is in bleeding surface.
5. the modeling method for simulation model of bleeding in virtual operation according to claim 4, which is characterized in that in the step It further include the blood platelet nature parameters P in rapid threeiValue changes over time:
Wherein, k is carry-over factor；mjFor the quality for closing on particle j of particle i；PiFor the blood platelet nature parameters of particle i；PjFor The blood platelet nature parameters for closing on particle j of particle i；W(ri-rj, h) and it is kernel function；riFor the radius of particle i；rjFor particle j Radius；H is the operating radius of particle i.
6. the modeling method for simulation model of bleeding in virtual operation according to claim 5, which is characterized in that in the step In rapid three, taking the value that the value of a is 200, b is 0.5.
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Cited By (1)

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Publication number Priority date Publication date Assignee Title
CN111047707A (en) * 2019-11-11 2020-04-21 南昌大学 Bleeding simulation method of mixed particle blood model based on SPH

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CN107633123A (en) * 2017-09-13 2018-01-26 浙江工业大学 A kind of method accelerated for smoothed particle method simulation bleeding and processing

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111047707A (en) * 2019-11-11 2020-04-21 南昌大学 Bleeding simulation method of mixed particle blood model based on SPH
CN111047707B (en) * 2019-11-11 2021-09-28 南昌大学 Bleeding simulation method of mixed particle blood model based on SPH

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