presentation introduction to virtual reality in simulink

8/17/2019 Presentation Introduction to Virtual Reality in Simulink

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Intro to Matlab-Simulink Virtual Reality

How to…

Objective:

Show you how to simulate a mathematical system in Simulink and

visually check your equation on a real-virtual system.

on: 2016/04/29

Problem Description:Let’s assume we let a ball freely falls from an initial height . We want to find the equation of

the motion, and then simulate it in Simulink Virtual Reality to check if our equation really drive

the physical ball as expected.

By: Shck Rodrigue Tchamna

Step 1: Equation of motion: Free Fall motion without initial velocity

0 20h m

0h

Note: y is measured from the

ground to the center of the ball.

2

2dy gdt

Free fall motion

1.5r mr

Watch the Video here: Youtbe link

https://www.youtube.com/watch?v=XaCRp2Dbzzs&feature=youtu.behttps://www.youtube.com/watch?v=XaCRp2Dbzzs&feature=youtu.be


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Collision equation

2 2

02 2

2

0

2

, y

dy dyif y r F m K r y mg m

dt dt

K dyr y g

m dt

Volume conservation equation

4

3 x y z

r r r

Ellipse Volume

34

3r

Sphere Volume

Before bouncing After bouncing

Let’s assume x z

r r

ywith r y

3

2 34 4

3 3 x x z

r

r y r r r y

3

; x z y

r r r r y

y

Scale equations

0K

K m

2

2,

dy

if y r K r y gdt Collision equation

Before collision

x y zr r r r

yr y

Note: There is a ballcompression!

After collision

is the amount

of compression

y

x r

yr

x r

yr

; x z y

r r r y

Assumption: after collision, the deformation in the x and z direction are equal.


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Step 2: Build this model in Simulink

2

2

dyg

dt

Free fall motion

2

2,

dyif y r f g

dt

3

; x z y

r r r r y

y

Scale equations

Collision equation f K r y

function [f, rx, ry,rz] = fcn(y)

%#codegen

% % f is the ground reaction. The

compression of the ball bring about

a repell force from the ground,

equal to the ball compression

K = 500;

r = 1.5;

% % To avoid division by zero

if y= r

f = 0;

rx = r; ry = r; rz = r;

else %% y


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Step 3: drag and drop the Simulink Virtual Reality Sink block from the Simulink 3D

Animation Library


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Step 5: Double-click on the VR Sink block, then Click on New

Step 4: Install the Virtual reality editor by typing the following command in the Matlab prompt

vrinstall -install editor

Starting editor installation ...

Done.

And you will have

the following

Step 6: Right click on Add Node, then open Group Transform


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This Transform node is for the Sphere-Ball. To rename the Transform node: 1) Right-click

the Transform node. 2) Select the Edit Name menu item. 3) In the edit box to the left of

the Transform node, type Ball.

Step 7: Add a Shape node

Expand the Ball Transform node. Then Select the children node. Then add a Shape node, usingthe following sequence of menu selections:

Step 8: Expand the Children Node, then the Shape and right-click on the Appearance node in

order to add an appearance under the appearance node.


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Step 9: Add a Sphere Node under the Geometry Node


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Step 10: Add Material under material node

Change the Ball colour if you wish


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Step 11 : Change the Size of the Ball; r=1.5m

Step 12: Click on Translation and Set the ball to its initial position, at 20 m

Note: After clicking on Apply, the Ball will Vanish from the Screen. Do not Panic. Do the following

to bring the ball back.

It is also advisable to save your file Now before continuing!!!

Step 13: Right click on Root and Add a Viewpoint


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Note: Change the Viewpoint so as to have a good vision of the Ball. You can set different

viewpoint from the above viewpoint.

Step 14: Let’s add our floor where the Ball is going to bounce. The Floor is nothing but a Box

Node.

Lets copy the Ball Transform Node and make change from this Node. Right Click the

Ball(Transform), Then Copy it. Then go to the Edit menu, then Paste

Step 15: Refer to previous steps and rename it as “Floor”. Then expand all, Go to the Shape

node and delete the Sphere, then add a Box instead.

You should have something like this


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You should have something like this


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Step 16: Change the Floor size

Step 17: Then Go to Translation and bring the Floor position down


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Note. You can Click on the wheel of your mouse and drag the mouse in order to slightly roatate and see

The system in 3D.

Note. We can also add Background Node if we want to do so


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Step 18: Close it and save it when it prompts to do so, then go back in your Simulink Model,

Double-click on the VR Sink, then Browse and find the location of the file you just saved.

Step 19: Click on the View button


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Step 20: Now Real things Start!!! We want to link our Simulink output signals to the Virtual Reality

Block. Since we are interested in the translation of the Ball, let’s thick the Translation checkbox of

the Ball.

You should be able to see this Figure


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Note that the translation node is a 3 by 1 vector, representing the translation on the x, y and z

axis. Since we only have one translation here on the y axis, we sill use a VR Signal Expander. The

output width is 3 and the non-zero index is 2, meaning the value of y.

The VR Signal Expander can be found in the Simulink 3D Animation Tab


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Watch the Video

Step 21: We want to see the actual deformation of the ball. It can be done using the Scale along

the x, y and z axis

Step 22: we need a bus in order to make a 3 by 1 deformation vector

Watch the Video here: Youtbe link
https://www.youtube.com/watch?v=XaCRp2Dbzzs&feature=youtu.behttps://www.youtube.com/watch?v=XaCRp2Dbzzs&feature=youtu.be

presentation introduction to virtual reality in simulink

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