The Realization of Virtual Reality of Launching Rocket Based on Simulink and VRML

7/27/2019 The Realization of Virtual Reality of Launching Rocket Based on Simulink and VRML

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International Journal of Advanced Computer Science, Vol. 2, No. 3, Pp.110-113, Mar. 2012.

Manuscript Received:20, Jun. 2011

Revised:

29,Sep., 2011

Accepted:25,Feb., 2012

Published: 15,Apr., 2012

Keywords Simulink,

6DOF

equation of

exterior

ballistics

Virtual

Reality

Abstract _ The course of simulation is

establishing mathematics model of exterior

ballistics, creating simulation platform

using Simulink and establishing 3D visual

scene using VRML (Virtual Reality

Modeling Language) and V-Realm Build

2.0. The input signal can be accepted by

output module of VR Sink, because of the

technology of combination of Simulink

and VRML. It can display the movement

of rocket in the way of virtual reality. The

flight trajectory reflects the flight state of

rocket. The technology of Virtual Reality

is significant for designers to design

exterior ballistics of rocket.

1. Introduction

VRML (Virtual Reality Modeling Language) is often

used for describing virtual reality. The visual world of

compute system can be created and experienced by virtual

reality which generates 3D space. In the 3D space users canintercommunicate with it. VRML has 6+1 DOF, so we

move and rotate images in three directions, also creates 3Dspace hyperlink [1].

VRML files are text attribute of describing virtual

space, which is generated by text editor. The center of

browser is default origin. It is X, Y, Z axis positive direction

from origin point to right, up, down. If you want to create

objects that are in default position, you have to adjust the

position of origin.

A typical VRML file includes head file, remark, nodes,field, circumstance and route [2].

In the past, high level program language is introduced

to solve the traditional exterior ballistics calculation, whichemphasizes on the arithmetic of model [3], a great deal ofdates are come into being when the simulation ends; Now

by the technology of combination of Simulink and VRML,

users can not only get the simulation dates, but also observe

the virtual movement of rocket.

This work was supported by Bei Jing Institute of Technology.

Wei-Ling Yang and Chun-Lan Jiang are with Bei Jing Institute of

Technology, School of Mechatronical Engineering ([email protected]; [email protected])

2. 6DOF Equation of Exterior

Ballistic

All expressions of forces and moments are introduced

to general equation of rigid movement. The format of

6DOF equation has been got. This equation is so-called 6D

equation [4].In this paper, we quote equations of exterior ballistics

from reference [4]. So, according to our demand we will

predigest these equations, and next steps to establish platform of simulation.

A. Coordinate system

1) Ground coordinate system o xyz

Ground coordinate system linking with earth, which

origin is the point at which something begins to move is

right-hand right-angle coordinate system. Confirming

moving direction is positive, the positive direction of

ox -axis, oy -axis, oz -axis is confirmed by right-hand

principle.

2) Rocket coordinate system'o

Its origin locates at the center of mass of rocket.

Positive direction of'o -axis is along the positive

direction of axis of rocket.'o -axis and

'o -axis are in

the plane which crosses center of mass of rocket and is

vertical to axis of rocket. This coordinate system is linked

with rocket and reflects space gesture of rocket.

3) Velocity coordinate system2 2 2

o x y z

In velocity coordinate system, origin is the center of

mass of rocket, the direction of 2ox -axis is the same as

velocity vector; 2oy -axis is vertical to 2

ox -axis; 2oz -axis is

confirmed by right-hand principle. This coordinate system

is also called natural coordinate system or ballistic

coordinate system.

The Realization of Virtual Reality of

Launching Rocket Based on Simulink and VRMLWei-Ling Yang, & Chun-Lan Jiang



Yang et al .: The Realization of Virtual Reality of Launching Rocket Based on Simulink and VRML

International Journal Publishers Group (IJPG) ©

111

Fig.1 Relation between velocity coordinate system and rocket coordinate

system

B. Dynamic equation of movement of center of mass of

projectiles, rockets, missiles

2 x F dv

dt m

=

(Equ.1)

22

1

cosad

F dt mv

= (Equ.2)

22 z F

mv

d

dt

= (Equ.3)

1

C

d

dt

= (Equ.4)

2

...

2

1tan

( ) D D

d C M

dt A A

A C

A

= + +

+

(Equ.5)

2

...2

1tan

( ) D D

d C M

dt A A

A C

A

= + +

+

(Equ.6)

C. Kinematics equation of movement of center of mass of projectiles, rockets, missiles

2cos cos

a

dxv

dt = (Equ.7)

2cos sin a

dy

dt v = (Equ.8)

2sin

dz v

dt = (Equ.9)

2cos

ad

dt

= (Equ.10)

2d

dt

= (Equ.11)

2tand

dt

= (Equ.12)

D. Connection equation

2 2 2 2 2sin cos sin sin cos .

cos( )a a

=

(Equ.13)

1 2 2sin cos sin( ) / cosa a = (Equ.14)

2 2sin sin sin( ) / cosa a = (Equ.15)

In above equations,2 x

F ,2

F and2

F are the force

in the ground coordinate; v is initial velocity;2

and

1 are orientation attack angel and high-low attack angel ;

is rotation orientation angel;a

and2

are high-low

angle of velocity and orientation angel of velocity;

a and 2 are high-low angle of projectile axes and

orientation angel of projectile axes;

,

and

are

rotation velocity in the projectile coordinate;

There are fifteen equations and fifteen variables.

When the parameters of structure, dynamics, shoot

condition, initial condition are given, we can solve the

movement trajectory by integral method. By predigesting

these equations, other format of equation of exterior

ballistics is given.

3. Create Simulink Simulation Model

The main function of Simulink is describing dynamicscharacteristics of system, realizing dynamics modeling and

simulation [7]. The course of Simulink is system, modeling,arithmetic, program design and displaying of simulation

results.

A. Establish 6DOF dynamics equation module and exterior

forces and moments based on Simulink Units

6DOF dynamics equation can be expressed by a group

of non-linear differential equations, the core of which isdynamics equation and kinematics equation. The exterior

forces and moments can be expressed in the ground

coordination and in the rocket coordination separately. You

can create a module which exports speed, coordinationvalue, and rate of rolling, orientation cosine and Euler

angel.The basal parameter of 6DOF dynamics equation

includes initial angel, initial speed, and curve of thrust,

aerodynamics parameter, mass and movement of inertia,

center of mass. After these parameters are confirmed and

simulation platform are established ，it can be simulated in

the way of visualization.

When complicated system occurs in the course of

modeling and simulation, the model is difficulty to be

described by single system. It is also divided into some

separate subsystems. In addition users can encapsulate subsystems in a module [8]. In this paper there have 15

equations of exterior ballistics, so we need to encapsulate

them into two subsystems modules, as follows (see Fig.2and Fig.3).



International Journal of Advanced Computer Science, Vol. 2, No. 3, Pp.110-113, Mar. 2012.


112

Fig. 2 Model of exterior force and exterior moment

Fig.3 Model of 6DOF Equation

4. Encapsulation of visualization

simulation module

Visualization simulation module (see Fig.4) consists of

exterior forces and moments module, 6DOF dynamics

equation module, XY-Graph module, visualization module.In order to modify variable parameter, all parameters are in

the same M-file [5]. The purpose is to increase readability.

Encapsulation of module has the advantage of

readability and transplant. According to concrete conditions,

adding other module make the result more closed to real

phenomenon.

Fig.4 Visualization simulation

The modules concerning virtual reality toolbox consistof core module, special module, special input module,single module [8]. The core module includes VR Sink and

VR Source, VR Sink module supports the single from

Simulink to virtual reality and VR Source supports

interface technology from virtual reality to Simulink.Virtual reality toolbox can work in two work environment

such as MATLAB interface technology, Simulink interface

technology. Rotation MATRIX2VR can transformorientation cosine matrix to rotation vector. In this paper we

select Simulink interface technology and virtual reality

toolbox.

5. Establish 3D visual scene

3D visual scene (see Fig.5) consists of vehicle, rocket,

radar and background. VRML has difficult in constructing

more complicated 3D model because VRML is strict in

syntax-language and has better function. So in this paper

we can add the Object Library, which is the most important

part of V-Realm Builder, to visual scene, also add the object

that we create to Object Library.The criterion of VRML is that father nodes have child

nodes and child nodes have child nodes. Each node consists

of field, which has specified value, all these values definecharacter of a scene.

Fig.5 3D Visual scene

6. Visual Simulation

In Figure 4, select the VR Sink module, in VR Sink

dialog box, Knock Browse button and select “my .WRL”

file （see Fig.6） and open it. In the right you’ll see

directory tree, then select the rocket, in the subdirectorytree, make a marker on center and rotation. When the modelis run, observers can view from different visual angles (see

Fig.8). We also get the movement curve by XY-Graph

module (see Fig.7).



Yang et al .: The Realization of Virtual Reality of Launching Rocket Based on Simulink and VRML


113

Fig.6 VRML directory tree

Fig.7 Movement curve

Fig.8 The result of trajectory simulation

7. Conclusion

From Fig.7 we can get the top point of trajectory and

set up range table. So we can intercalate initialized

launching parameters according to needs of launching.

From Fig.8 we see the movement of rocket directly.Visual simulation of weapon system is an important

research method in the field of weapon design [9] includingwarhead evaluation visualization, interior ballistics

visualization、terminal ballistics visualization、vulnerability

visualization and so on.

It is easy to establish simulation model and decrease

amount of work and is also convenient for users to modify

any module in the method mentioned in this paper, so all

factors can be reflected in concrete way. Output result hasthe characteristic of visualization.

In this paper visual simulation reflects trajectory of

rocket directly and characteristics of exterior ballistics. Itaccords with real phenomenon of launching rocket basically.

Visual simulation is significant for designers to design

products.

References

[1] D.W. Long, "6-DOF motion SIMULINK for projectiles based on MATALB/SIMULINK," (2009) Journal ofChongqing Institute of Technology (Natural science), vol. 23,

no.4, pp. 146-147.[2] ZH. JunMin, H. Y. Juan, "The incorporate simulation of the

missile trajectory based on MATALB/SIMULINK,"

(2003) Journal of Projectiles, Rockets, Missiles andGuidance, vol. 21, no.36, pp. 134-138.

[3] M. Works, MATLAB the language of technical computing,

using MATLAB. Release, 2001.[4] H.Z. Peng. "Exterior Ballistics of Projectiles, Rockets and

Missiles" (2008) Press of Beijing institute of Technology, pp.

141-143[5] X.D. Yu, & CH.Y. Quan, "Technology and Application of

system simulation based on MATLAB/SIMULINK," (2006) pp. 36-38

[6] H.H. Rosenbrock, Computer aided control systems design.

London: Academic Press (1973), pp. 442-448[7] L. Hua, CH.W. Wei, Simulation of Trajectory Visualization

Based on VRML Language.[8] H. Quebec, TEQSIM International. Power system block set,

for use with SIMULINK.[9] ZH.J. Xiang, & L. XueShan. "The Plane Flying-off

Simulation Using Virtual Reality Toolbox of MATLAB,"

(2003) Compute Simulation, vol. 10, no. 34, pp. 168-173.

Wei-Ling Yang was born in

ShanDong province, China, in 1981.

He received the B.Sc. and M.Sc.

degrees from North University of

China in 2006 and Bei Jing Institute

of Technology in 2008, respectively.He is the author or coauthor of more

than ten national and international

papers. He is with flight mechanics

Center Group, since 2006. He is

currently pursuing his Ph.D. degree in Bei Jing Institute ofTechnology, School of Mechatronic Engineering. His

current research interests include explosion mechanics,

flight mechanics, engineering mechanics and Numerical

Simulation.

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The Realization of Virtual Reality of Launching Rocket Based on Simulink and VRML