Try using the "Concatenate" block to form one matrix of dimension [5x3]. Then you could use the "Selector" block with input dimension 2. Select index options "Starting and Ending indices (port)" for the first dimension and "Select all" for the second dimension. Now you can wire an [1x2] array to the index port to select the matrix you want (i.e. [1,3] for Matrix 1 or [4,5] for Matrix 2). Since this array of starting and ending indices has a constant size it could be routed through a multi port switch with fixed output size.

Hope this solution with the selector block is compatible with PLC hardware target you plan to use.

Regards,

Rouven 

Dear Rouven, thanks a lot for your answer. This definitely works in Simulink. However, this too seems to have an issue with PLC compatibility. I tried forming a subsystem with your suggested solution and checked for PLC compatibility. I got an error message regarding the output matrix variable size (attached in the PLC check 1 and PLC check 2 images). Please find the Simulink file with subsystem 'solution_selection_PLCcheck' attached as well.

Do you have any ideas on how to move past the variable size error (or is this a necessary curse of the chosen problem ?)

Regards,

Aditya

Would the attached workaround fit your need?  It maintains fixed variable size, but requires you to know when to ignore variable rows.   

Hi Joel,

Could you please send me the file in Simulink R2015B compliant version. I do not have the R2016 version.

Regards,

Aditya

Hi Aditya,  R2015b version attached.  -Joel

Hi Joel, thanks for your email. This approach is PLC compatible, but as I mentioned in the original post, the issue is I cannot add zeros to make the matrices of the same size, because this will affect a part of my Simulink block downstream. Think this issue is a limitation of the PLC environment and there may not be a clear workaround.

Hi Aditya,  I should have read your original post more closely.  Sorry about that.  However, I suspect with a little effort the workaround could address downstream dependencies.  I also suspect that in the worst scenario, some function block logic would be required that interfaces to the compiled Simulink function block.  I cannot say for certain without knowing what your system contains downstream, but I would be happy to look at something small and representative if you think there is that possibility.

Hi Joel,

Thanks for your quick reply. In fact, I am using the information from the output of this block as input information to a block that calculates the impedance of the power system . It would be complex and tedious to share the code for this. 

However, the main issue I have is that the algorithm in the impedance calculation block generates an output of dimension nxn, where n is the number of non-zero rows in the input matrix. Since can vary between 2 or 3, depending on input, the matrix varies in size. I have highlighted this in the figure attached. I am unable to generate this in a way that passes PLC compatibility, and would love to hear if you have any workarounds for this.  If this matrix can be generated while complying with PLC compatibility requirement, the impedance calculation will be a straight forward process.

Thanks for your suggestions, in advance

Regards,

Aditya

Hi Aditya,  I understand that providing a simplified view of a complex system is easier said than done, but the figure does not help me pose a workaround.  Shooting from the hip here, would two Function Blocks work in the PLC ladder logic that are selected by a switch (i.e., Selector number) where one outputs 2x2 array and the other 3x3)?