Tutorial - Creating an Alpha Type Stirling Engine

Creating an alpha type Stirling

engine in virtual reality.

ing. Mátyás Attila Masterand – ISM

2012-2013

Creating the 3D model in virtual reality consists of the following

steps:

• Constructing and assembling the elements in SolidWorks to

obtain the 3D model

• Exporting the 3D CAD model to a SimMechanics model

• Exporting the SimMechanics model to the Virtual World

• Creating a Graphical User Interface(GUI), to view. And control

the mechanism

Creating the 3D model

The most complex part is the piston, you need to make some extruded cuts, to

create space for the connecting rod.


The next step is to create the two cilinders with the same inner diameter as the pistons,

you need a cold cilinder, and a hot cilinder.

You can place some ribs on the cold cilinder, for a better look.


After the cilinders, you need to create a connecting rod, a crankshaft and a flywheel.


You need to create a block for the engine and a support where you can place the engine

itself.


After you got the components you need to create an assembly file. When you place the

constraints with the “Mate” command, you have to work with the next hierarchy:

Block-CrankShaft-Connecting rods(2)-Pistons(2)-Cilinders(2). When the assembly is

ready you need to create the regenerator, with a 3D sketch.


When we finished the regenerator, save it.

Exporting from 3D model

• Click on “Save As”


• STL


• VRML(At the options menu, select VRML97, and uncheck the‟Save all

components of the assembly in a single file‟)


• SimMechanics Link Export SimMechanics First Generation

• Save it as *.XML


• Create screenshots from the assembly, and the main parts. Save the

assembly as „stirlingengine.jpg‟

Creating Simulink model

To open the SolidWorks model in SimMechanics, you have to do

th next:

• Open MATLAB, and set current folder the folder where you

have saved all the files previously.

• Click on the command line, and type

“mech_import(„stirlingengine.xml‟)”, or simply

“mech_import”, and browse for the *.xml file

• It will result a simulink model like this.

• You need to organize the blocks to get a better view on the model


• After ordering, select all components, and create Subsystem, or press Ctrl+G


• Right click on subsystem

image(imread(„stirlingengine.jpg‟));


• Duble click on the Revolute joint on „axa_principala‟, change nr. of ports

to 2


• Create this model from

simulink library browser.

• Change the second option at

the Joint Actuator to Motion.



• Go back to the main subsystem, open Simulink Library Browser, get the 3

blocks from there (Constant, Slider Gain, Display)

• Connect them in this order

• Change the simulation time from 10, to inf.

• Change the Slider Gain max value to 360, so that our engine can make a full rotation.



• Start the simulation, and move the slider, check if everthing works fine.

Creating the Virtual World

• Stop the simulation, and go back to the main Matlab window.

• Check if you are working in the correct current folder, if not change it.

• Type: „vrcadcleanup(„name of the assembly.wrl‟);


This command will clean up our wrl file in a fes seconds. cleaning the spaces and

making ready the file to be opened in the virtual reality toolbox.


• Open the virtual reality toolbox. You can find it in you Matlab folder or on

the following path:

C:\Program Files\MATLAB\R2012b\toolbox\sl3d\vrealm\program\vrbuilder2

• Open – stirlingengine.wrl


• After opening the file, click on New world, and click on Insert Background


• Click on the TEST button to visualize the engine

• With the help of the mooving tools, get a good viewpoint.


• Insert a Directional Light, if it is badly enlightened, modify the direction of the

Directional Light


• After getting the right position, create a viewpoint, and in the desciption, give it a

name, like View1

• Move the position of the engine, and create 2 other views: View2, and View3


• Insert Navigation info, and World info

• Save the file, and exit the virtual realm builder


• Go back to the main Matlab window, and enter the next command:

vrphysmod(„stirlingengine.wrl‟, stirlingengine);

• This command will add a Vrsink, and a sample connection to our simmechanics

model


• At the model, this sample connection will be added. Copy(Ctrl+C) the body sensor,

and the GOTO blocks.


• Rename the GOTO blocks to : - rod1_rot

- rod1_trans


• Duble click on the piston Add CS

• Make this step with the displacer, connecting_rod_2, axa_pricipala, volanta (You need

to do this with all moving parts; there are 6 moving parts)


• Paste(Ctrl+V) the blocks, and connect them with the CS4.

• Rename the GOTO blocks piston1_trans; piston1_rot;

• Do these steps with all the other moving parts

• Select the 4 blocks create a subsystem Mask it wit the

image(imread(„rod.jpg‟)); command.

• Repeat these steps with the other moving parts too.


• At last you create a subsystem from the root part, and you will get a similar model

like on the picture.



• Go back to the VR sink model

• Duble click the VR Sink

• Simulation

• Block parameters


• Browse select the

stirlingengine.wrl

• Thick the rotation and

translation icon at all

moving parts


• After you exit the Block Parameters window,

your VR sink will look like this.

• Copy the 3 blocks, and make an overall of 6

pairs of them.


• Connect them; rotations to rotations, and translations to translations, rotations need an

aditional block.


• Make the link between the vr sink and the simulink model

• Click Update Tags select the Tag you need

• Do this to all elements


• Open the VR Sink, Click reload, to refresh, check if you can switch between the view

points, and run a TEST, check if everything works fine, if you move the slider.


• Go back to your subsystem, delete the Slider Gain, and connect the Constant with

the subsystem.

Creating the Graphical User Interface

• Go back to main window, NEW Graphical User Iterface Blank GUI OK


• Save As GUI

• Duble click the background, change width to 180, height to 45


• Right click on background View CallbacksCreateFcn

• GUI.m will be opened


This is the part where the virtual reality engine will be aded to the GUI

• Copy this code under “function varargout”

• c1=vr.canvas(w,gcf, [“coordinates of the window”, “Dimension of the window”]);

• c1.Viewpoint=„Name of the view‟

• Create 3 views in total


• Create 3 buttons: “Start Simulation”, “Stop Siulation”, “Exit”

• Create a slider, an edit text, and statical text

• Change the Max value of the slider to 360


• Right click on the slider View callbacks Callback

set_param('stirlingengine/Constant','Value',num2str(get(hObject,'Value'))); a=get_param('stirlingengine/angle','RuntimeObject'); val_a=a.InputPort(1).Data; set(handles.angle,'String',round(val_a));

• Right click on the Start Button View callbacks Callback

set_param('stirlingengine','SimulationCommand','start'); • Right click on the Stop Button View callbacks Callback

set_param('stirlingengine','SimulationCommand','stop');


Right click on the Stop Button View callbacks Callback

save_system('stirlingengine'); close_system('stirlingengine'); close; • Save the GUI again • Run the GUI (F5 or Ctrl-T)


• Your GUI is ready to run!

Good Luck!

Documents

Tutorial - Creating an Alpha Type Stirling Engine