How can i select 1 of the 2 outputs on the basis of conditions?

I am designing a controller. I have certain logical conditions on which one of the two controllers i.e. Main controller and sub controller is to be selected . I am using an "if block" with two "if action" sub blocks for selection. The output of both the controllers is a 3x1 vector. Now "if block" will select the controller based on certain conditions. But how to select one of two outputs from the controllers is my problem!! Kindly see the attached Simulink model for more clear idea of my problem. I have already tried merge and mux blocks but both of these cannot select one of the outputs.

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Answer 1

[Astik Sachan]

Merge Block will work fine here as 1 output at a time will be enabled by IfElse Block.

Goto: https://in.mathworks.com/help/simulink/slref/merge.html for more details.

[Mati]

Thanks Astik. I tried using merge.my output is a 3x1 vector. But "merge" selects the first entry of the 3x1 vector and the others are Nan. Please see image attached. Is there any mistake in using merge?

[Astik Sachan]

Firstly, You can use Scope Block instead of Display as it will give you only last sample time results.

Secondly, Can you tell me the Dimension of the Out1 coming from "If Action for MainController" subsystem and "If Action for Sub Controller" subsystem.

And that "Nan" you are getting is maybe due to the output of If action blocks. Check inside those If action subsystems for the Root Cause of "nan".

Note: Please Check dimension of both the input of Merge Block are they same?

[Mati]

Thanks astik for replying,

I have used scope block too but the result is a zero graph. The output of Out1 is a 3x1 vector.

I have checked earlier, and i ran my sub blocks separately and they works. The figure i uploaded in the first question shows that both the inputs of Merge block are 3x1 vector.

[Mati]

Dear Astik, One thing else I want to discuss which is related to this question. I also tried using switch(as shown in the attached figure). I used Out1 of the if action sub controller as control input of switch. It worked, some how, but the switch only passes the last entry of the vector which is at its input.

Is this approach right for solving this problem??

Why switch do not passes the whole vector??

[Astik Sachan]

No, Switch Block is not at all encouraged for combining two inputs from If action Subsystems.Merge block is what MathWorks also suggest.

Please enable signal Dimension and Port data type so that I will be able to see what is coming from If Action Subsystem.

1. Goto: Display>>signal Dimension
2. Goto: Display>>Port data type

and if possible attach the model here I will look into it. or reach me on mail [e-mail]

[Mati]

Thanks Alot Astik. The Merge block is working and there was a problem in my model in if else block. Thanks for your support.