MATLAB: How to set the initial state of a Simulink block programatically

block stateinitial statesimulink

I am trying to set the initial state for selected blocks in my Simulink model (not for the whole model). According to MATLAB manual, you can use getBlockSimState & setBlockSimState to access and modify SimState of individual blocks.

However, this is not very well documented and I always get an error when trying to use those functions. Is there an example of the correct syntax or is there another recommended way of setting the state?

Best Answer

The easiest way to set the initial state of a block from MATLAB code is to use the "set_param" command. This is essentially the programmatic way to populate a block's dialog. The command uses the following format:

set_param( 'model_name/system_name/block_name', 'parameter_name', 'new_parameter_value' )

The "parameter_name" will vary from block-type to block-type, but you can find out the name of a give block's state (It is usually close to the text in the dialog) in the help under "Block-Specific Parameters". The "new_parameter_value" is usually a string that represents the text that you would have typed in the dialog fields.

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MATLAB: Change “current block”/gcb/gcbh programmatically

Is it not possible to change the code to use block path (string such as 'myModel/Gain') instead of gcb or gcbh? This would be the most straightforward thing to try. If you cannot do this for various reasons:

How do you get the value of hBlock? If you are hard coding it as a variable (by specifying a number) there could be two issues with this:

As this documentation says, You can use the block handle in subsequent calls to get_param or set_param. If you examine the handle, you can see that it contains a double. Do not try to use the number of a handle alone (e.g., 5.007) because you usually need to specify many more digits than MATLAB displays. Instead, assign the handle to a variable and use that variable name to specify a block. Use getSimulinkBlockHandle to get the handle to a block.
Using hard coded values might result in breaking of logic since Simulink can change the handle to the block every time the model is loaded/opened. For e.g it could be 16.0001 now. If I close and open the model again, it maybe different.
I am guessing the equality test might fail because you are trying to compare two floating point numbers.

For e.g. if I do this, it seems to work:

%Open demo model
vdp
%Set Mu block as selected
set_param('vdp/Mu','Selected','on')
%Get Handle to the block
hBlock = getSimulinkBlockHandle(gcb)
%Compare handle value to gcbh
isequal(hBlock,gcbh)

If you run this code mutliple times (each time clearing workspace and closing the open vdp model), you can see the value of hBlock keeps changing.

MATLAB: How to obtain the parameters of more than one mask at the same time

Use the following command to get the list of mask parameters of a block:

get_param('model/sub_block', 'DialogParameters')

To get the values of the masked parameters, you may write as folllows:

dialogPrms = get_param('model/sub_block', 'DialogParameters'); 
dialogPrmNames = fieldnames(dialogPrms); % Parameter names 
for idx = 1:numel(dialogPrmNames) 
   dialogPrmValue = get_param('model/sub_block', dialogPrmNames{idx}) % Parameter values 
end

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MATLAB: Change “current block”/gcb/gcbh programmatically

MATLAB: How to obtain the parameters of more than one mask at the same time

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