I have a virtual subsystem with a bunch of parameters. I would like to use those parameters to calculate other properties of the block. This needs to be done before the simulation starts, but after the block has been initialized.
I created a script that would do the calculations, and tried to get it to run from the StartFcn block callback. But the script cannot access the parameters (which are input by the user through the mask) in the callback. I'm guessing this is because those parameters aren't available in the Matlab workspace, only within the block.
Is there any way to access those parameters through StartFcn? Failing that, is there another way, instead of the StartFcn, through which I can perform some calculations BEFORE simulation starts?
To clarify, I cannot use the Initialization tab in the block's mask because the script requires data from other blocks too (which are available in the workspace at the start of the simulation).
Your guess is correct, block callbacks are evaluated in the base workspace, but mask parameters are part of the mask's private workspace. To access them use get_param and gcb within your callback function.
value = get_param(gcb, 'my_param_name');
Related
I am using Simulink to model a waste recycling plant out of a number of masked blocks that I created, representing sorting steps, buffers etc. Each module (that is, a masked block) has a failure probability, modeled using Discrete Events. If a failure event occurs, a triggered subsystem calls an Interpreted Matlab Function ("outside" of simulink). This function is supposed to set a parameter status of the masked block representing the module that failed as well as the upstream modules' status to 0 (because obviously, everything upstream has to stop as well or the material will just pile up).
`set_param(gcb, 'status', num2str(status));
PortConnectivity = get_param(gcb,'PortConnectivity');
sources = PortConnectivity.SrcBlock;`
Basically, this will be looped until I reach a block with no own Source Block.
This all works quite well, except for one problem: The gcb command gives me the block path to the last block I highlighted manually, and not to the block that called the Interpreted Matlab function. Is there any way to get the calling block's handle (which I would use with it's Parents parameter to access the Mask's status)? (A similar question has been asked here, with no results...)
I hope you get my problem - I'll be happy to elaborate if anything's unclear; I am not claiming to be a Simulink expert, so sorry for maybe using wrong terminology.
Ok, for everyone stumbling upon this:
For the mask that contains the caller of the Matlab Interpreted Function, in the mask editor I define a parameter 'this_block' (turn visibility off), that I initialize in the Initialisation pane using
parent = get_param(gcb,'Parent');
set_param(gcb, 'this_block','Parent')
Since this masked block (responsible for modelling the failure and its upstream communication) is itself used in another masked block also present in the library (responsible for modeling the module's behaviour), I also had to check "Allow library blocks to modify it's contents" in the mask editor Inititlization pane of the parent's mask. The parameter 'this_block' is then handed over as one of the input arguments of the called function (in my case, status_communication(u, this_block)).
I'm trying to figure out how to set a callback for for every instance of a specific MATLAB object type and not a single instance. In my case the object type is either a SimuLink Block, Subsystem, or ModelReference.
After having read
http://se.mathworks.com/help/matlab/creating_plots/callback-definition.html
I tried
function openCallback(src, evt)
disp('here');
end
set(groot, 'defaultBlockOpenFcn', #openCallback);
but it fails as
Error using matlab.ui.Root/set
blockopenfcn is an invalid class name
Is this possible, somehow?
Simulink block callbacks are set using set_param function on a block handle. You would need to set it for a single instance of the block. I do not think it is possible to set it for every instance of a block. If you have a model you can find all the blocks of a type and set their callbacks in a loop.
You can see help for block callbacks at http://www.mathworks.com/help/simulink/ug/block-callbacks.html. You would call set_param as
set_param(gcb, 'OpenFcn', 'disp(''open fcn'')')
where gcb is a function that returns currently selected block in a model.
I have a GUI callback that includes a for loop but compared to running the same code in a script, the data/variable being retrieved within the loop after the loop ends is not being recognized and instead MATLAB says that the variable is undefined. The script runs fine with the same inputs. I am well aware that scripts and functions have different workspaces, but does this mean that the recent data in a function after ending a loop is forgotten?
The callback belongs to a push button while the data I am handling in that callback is symbolic.
I would like to know what is causing this problem
There is difference between functions and scripts.
functions have their local variables. These variables are defined within the scope of that function only. Inside of a function is isolated from the caller scope. The only way to exchange data is input and output parameters of the function.
When the flow of program reaches to a function, all variables are stored in stack, and the execution of function starts without any variables except the input parameter. On the exit from function, all local variable defined in the function are deleted, and the stored variable on the stack will be returned back to the scope.
To circumvent this mechanism, you can use
global variables
assignin and evalin functions
But this is not considered as a procedural programming.
I've been having a lot of trouble getting simulink's block callbacks to run, and the documentation is woefully inadequate and disorganized. It seems that I'm misunderstanding multiple points of how Simulink compiles models, but since StackOverflow dislikes multi-part questions, I will post them one at a time.
The situation: I have a library of components, each of which is a virtual subsystem whose parameters are defined through the masks. Block A has Parameter a which is sent to the base workspace using the 'assignin' command.
Next, the block B has a parameter b which is initialized in the Initialization tab of the mask.
Finally, the StartFcn callback of the block B runs a script which needs to reference both a and b to calculate c. In the script, I reference a simply as a because it's in the 'base' workspace, and I reference b using get_param(gcb,'b').
Now, this last command works when the parameter b is a user input (so it's a constant value). But in my case, this b is calculated using other parameters in the Initialization tab. And for some reason, in the script, this parameter is always zero.
I added a display within the block B to see what these values are, and they are clearly non-zero.
Can someone please explain why the script cannot seem to get the real value of the areas out of the block?
You can get the masked workspace variable using getworkspacevariable
The Gain block and continuous block in Simulink require the user to specify a gain. This can be a workspace variable. But I want to vary this gain during runtime. I can't seem to get a solution for this. This idea is simple but I can't believe it is so difficult to implement.
I have tried using another block to write to workspace, but found out that the 'to workspace' block only writes to the workspace after the simulation ends or pauses.
I can store the variable in a data memory block, but I don't know how to specify the gain value(s) for the gain/PID block in this case.
If you have Inline Parameters turned off (it's on the Optimization page of the Configuration Set), you can just open the gain block dialog and change the value. If you want to use a workspace variable, then you can change the value of the workspace variable and do an Update Diagram (^D) while the simulation is running.
There's also a block called the Slider Gain which allows you to change the gain value using a slider UI.
May be it'd be helpful at some point: try using the MATLAB Function Block (Matlab user-defined function that can be used directly in Simulink).
As a command-line alternative, you can use the SET_PARAM function to change the Gain value of the block during model simulation.
For example, the following code would change the Gain value of a block named "My Gain" at the top level of a model called "my_model.mdl" to a value of 20:
set_param('my_model/My Gain','Gain','20');
Note, however, that only Tunable Parameters can be changed with SET_PARAM at runtime.