Another Way to Use Lookup Table in Simscape Custom Models

Hello,

I am using a lookup table for one of my components. The thing is I want to have the ability to select a point from two parameters with set of values that I set as a parameter to be used later on in a lookup table function. I tried to do a lookup table to select the point, but I found out that lookup table requires a monometric parameter.

  parameters
    G_op = { 1e-7 , 'S' };
    G_ct = {[0.5144e3,0.4629e3,0.3861e3,0.3636e3,0.31904e3,0.2899e3,0.2578e3,0.2012e3],'S'} %Cl Con
    T_ra= {[0,25,50,75,100,125,150,175],'degC'} %Temp ref
    Time_unitary = {(0:0.01:1),'1'};
    Ton = {2e-6, 's'};
    Toff = {1e-7, 's'};
  end
  
  variables
    G = {1e4, 'S'};
    G_closed = {1e4,'S'};
    Opening_instant = {0,'s'};
  end
  
  equations
    G_cl ==(tablelookup(T_rate,G_ctable,Temp, interpolation=linear, extrapolation=nearest));
    G == (tablelookup(Time_unitary*Toff,(Switch_Dynamic.^log(G_op/G_cl))*G_cl/Con, time-Opening_instant, interpolation=linear, extrapolation=nearest)+1e-9)*Con;
  end
    

These are some of the code that has the parameters related to the lookup table that I want to create.

I was thinking of using a polynomial approach for the G_cl value but in the end it was not working as it was also read as a parametric value by the lookup table of the variable G.

Is there any other way to have the data set for G_ct and T_ra to have one point to be use for the table lookup without detected as parametric?

Thank you beforehand.

Answer 1

[Shreshth]

Hello Anugerah,

In the context of your code provided, I could see that you are trying to use two parameters’G_ct’ and ‘T_ra’ to determine a single point for use in a lookup table ‘G_cl’.Currently you are using the 1D lookup table function which will only allow you to have a single dimensional lookup. To solve your issue it is recommended to use a 2D Lookup table that maps combinations of ‘G_ct’ and ‘T_ra’ to ‘G_cl’ values. You would then use a 2D interpolation method to find the value of ‘G_cl’ for any given ‘G_ct’, ‘T_ra’ pair.

To grab an understanding of the use of 2D lookup table, you can also refer to the documentation provided by MathWorks.

https://www.mathworks.com/help/simulink/slref/2dlookuptable.html

Additionally, if you do not want to use 2D lookup table, you can also create a mapping function if the relationship between ‘G_ct’, ‘T_ra’, and ‘G_cl’ can be described by a mathematical function, you could define this function explicitly in your code. This function would take ‘G_ct’ and ‘T_ra’ as inputs and output the corresponding ‘G_cl’ value.

Hope it helps.

Thank you,

Shubham Shreshth.