Build Model & Apply If-else Logic


In this chapter, we will create a model and apply if-else logic to it. Let us first collect blocks to create our model.

Now, open MATLAB Simulink (blank model) and the Simulink library browser as shown below −


Click on the Blank Model and open Simulink library browser as shown below −


The blocks we require to build the model with if-else logic is as follows −

Constant block from Commonly used blocks


Switch block from Signal Routing


Display block from Sinks


Let us now get all the blocks together to create a model as shown below −


Let us now connect the lines with each block. So you can see that the constant block has one output and the switch has three inputs and one output. We are going to connect them to the display block.

After connecting the lines, the model is as shown below −


Now, double click the switch block and add a threshold.

The threshold value will be compared with the block in the center. Based on the constant value of the middle block, the first block value will be displayed or the last constant block value will be displayed.

Let us add a threshold value to the switch as shown below −

Threshold Value

The threshold value given is 3. Click on OK to update the threshold. Now the threshold value is seen inside the switch block as shown below −

Switch Block

The middle constant block will be compared with the switch threshold and accordingly the display will be decided.

Let us now update the middle constant block with some value as shown below −


The value of the constant block is 1. Let us now change the first constant block and give it a value as 0.5 as shown below −


Let us now change the last constant with value as 2.5 as shown below −


Hence, the first constant value is 0.5, the middle constant value is 1 and the last one is 2.5. The middle constant value 1 will be compared to switch threshold value i.e. 3 as (1 >3). It will print the value as 2.5 the last constant value.

Click on the run button to get the output in the display block as shown below −

Middle Constant

Let us now change the middle constant to a higher value than the threshold of switch and see the output −


The value is changed from 1 to 3.5. Click on OK and run the model to see the output in the display −


Now, since the value of the middle constant is greater, the value from the first constant is printed in display. If it is less, then the value from the last constant will be printed.