Scilab/C2/Xcos-Introduction/English
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| Introduction Slide | Welcome to the spoken tutorial on Xcos, Scilab Connected Object Simulator.
Xcos is a Scilab package for modeling and simulation of dynamical systems. It includes both continuous and discrete systems. |
| Slide | In this tutorial you will learn
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| Slide | To practice this tutorial, Scilab should be installed on your system.
I am using Ubuntu Linux 12.04 and Scilab version 5.3.3 for demonstration |
| Open Scilab | Open the scilab console window on your computer
Go to applications and select Xcos or type “xcos” in your scilab console window and press enter
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| Palette | By doing this, two windows will open.
The two windows are
In palette browser you will find different types of blocks
The other window, Untitled-Xcos is blank with grids |
| Collecting the blocks from different Pallete | We will now simulate a first order system with a step input.
To begin I will select a transfer function block from the Continuous time systems palette. Drag this block to the Untitled-Xcos window. Select the required source in the Sources palette. I will scroll down and use the step function block I will drag and place it before the transfer function block. Similarly, the output is displayed using the CSCOPE block which is available in Sinks palette. The CSCOPE block is placed after the transfer function block. The red input port in CSCOPE denotes that this block is an “event driven” block. It needs an event input for execution. An event generator block is available in event handling palette. The name of this block is clock underscore c Drag and place this block above the CSCOPE block. We have collected all the required blocks to do the simulation. Let us now connect the blocks together Select the output port of step function block and connect it to the input port of the transfer function block. Notice that the selected input port gets highlighted in green colour. Similarly, connect the remaining blocks as shown |
| Changing the parameter of step block | Now we will set the parameters of each block.
First, go to the step block and double click on it. A pop up window appears asking for the value of step time, initial value and final value Step time is the time at which the step change will occur We will keep it as 1 which is the default value Initial value is the initial output value of the step function We will keep it as 0 which is the default value Final value is the output of the step function after the step time is lapsed We will change it to 2 Click on OK. |
| Changing the parameter of Transfer function block | Follow the similar procedure to configure any other block.
For transfer function block, the following configuration is required. Numerator value in laplace domain has to be entered. We will keep it as 1 which is the default value Denominator value in laplace domain has to entered. We will change it to 2 asteric s plus 1 Click on OK. |
| Changing the parameter of scope | Double click on CSCOPE to configure for the following parameters
The value of y min and y max should be set depending on the range of the value of the variable to be plotted Set the value of Ymin to 0 Since I have given step input as 2, to display the output on graph I should change the y max to any higher value. We will change it to 3. Make a mental note of the default value of the refresh period The default vlaue is 30 We will keep the other parameters unchanged Click on OK |
| Changing the set up parameters | Now go to the simulation in menu bar and click on setup.
A pop up window appears. We will change the value of final integration time Final integration time decides how long the simulation will run Recall the value of refresh period of the CSCOPE block I will keep the value of final integration time equal to the value of refresh period of CSCOPE block So, I will change it to 30. Keep the other parameters unchanged. Click on OK. |
| saving the Xcos file | Now press control s to save the file with a suitable file name.
I will save it as firstorder.xcos |
| simulation | To start the simulation, click on the start button available on the menu bar of xcos window
A Graphic window will open showing the step response of the first order transfer function We can save this plot as an image file To save the graph, go to the file menu and click on “Export to” option I will name it as firstorder.png and click on Ok There are certain parameters which we chose to keep as the default value. These can be changed. For example In the Clock_c block, the period which means the sampling period and initial time can be set In the CSCOPE block, the output window number, position, size, buffer size , graph color etc can also be set |
| Slide | Pause the video here and solve the exercise given with the video.
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| Slide | Simulate a second order transfer function with damping ratio of 0.5 and angular frequency equal to 1.
Try changing the color of output graph. Using the first exercise, plot the Step input and the output in a single plot window. |
| Slide | Now let us summarize.
In this tutorial we have learnt to: Create xcos simulation diagrams using the palette browser Configure each block as per the simulation requirements Setup the simulation parameters Save the output plot. |
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Watch the video available at the following link
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The Spoken Tutorial Project Team
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Spoken Tutorial Project is a part of the Talk to a Teacher project
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| Hope you found this tutorial useful.
This is Rupak Rokade from IIT Bombay signing off.
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