Difference between revisions of "Scilab/C2/Xcos-Introduction/English"

Xcos is a Scilab package for modeling and simulation of dynamical systems.

It includes both continuous and discrete systems.

• What is XCOS.
• What is palette.
• Build block diagrams in Xcos
• Setup the parameters of blocks.
• Setup the simulation parameters.
• Simulate the constructed block diagram.

I am using Ubuntu Linux 12.04 and Scilab version 5.3.3 for demonstration

Go to applications and select Xcos or type “xcos” in your scilab console window and press enter

The two windows are

1. Palette browser and
2. Untitled-Xcos window

In palette browser you will find different types of blocks

• Commonly Used Blocks
• Continuous time system blocks
• Discrete time systems blocks and many more.

The other window, Untitled-Xcos is blank with grids

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

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.

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.

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

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.

I will save it as firstorder.xcos

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

Try changing the color of output graph.

Using the first exercise, plot the Step input and the output in a single plot window.

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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This is Rupak Rokade from IIT Bombay signing off.

Thank You.