Embedded Matlab Array Bounds Error

[aspiers]

Hi,

I keep running into the same problem using the embedded MATLAB blocks of simulink. Once the equations to be solved in my blocks reach a certain length I get an array out of bounds error.

I know Simulink can handle this size of calculation in a timestep as I have much larger equations running in S-Functions in similar models.

Does anyone have any ideas how I can get around this array out of bound problem? (I've already switched to a variable step solver and have tried splitting the equation up into more bite-size chunks).

function [p1_out,p2_out] = fcn(theta1,theta2)

pq1 = 2*a1*g*cos(theta2)*M2-2*a1*g*cos(theta1)^2*cos(theta2)*M2+a2*g*cos(theta2)^2*M2-2*a2*g*cos(theta1)^2*cos(theta2)^2*M2+M1*a1*g*cos(theta2)-M1*a1*g*cos(theta1)^2*cos(theta2)+sin(theta1)*M1*a1*g*sin(theta2)*cos(theta1)+2*sin(theta1)*a1*g*sin(theta2)*cos(theta1)*M2-sin(theta1)*a1*M2(g*(sin(theta1)*cos(theta2)+cos(theta1)*sin(theta2)))-sin(theta1)*a2*M2(g*(sin(theta1)*cos(theta2)+cos(theta1)*sin(theta2)))*cos(theta2)+2*sin(theta1)*a2*g*sin(theta2)*cos(theta1)*cos(theta2)*M2-a2*M2(g*(sin(theta1)*cos(theta2)+cos(theta1)*sin(theta2)))*sin(theta2)*cos(theta1)+a2*g*cos(theta1)^2*M2

pq2 = 1; % this will be changed to an equation later

p1_out = pq1;
p2_out = pq2;

I know the obvious answer in that the equation is large so no need to remind me of that one ;-)

Many Thanks,

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[mmwave]

riana

Hi Adriana,

Thank you for reaching out with your problem. It sounds like you have already tried some potential solutions, such as using a variable step solver and splitting the equation into smaller chunks. These are good approaches, but there may be some other factors at play here as well.

Firstly, it's important to check if there are any errors in your equations themselves. It's possible that there is a mistake or typo that is causing the array out of bounds error. Double check your calculations and make sure everything is correct.

Another potential issue could be with the data types you are using. Make sure that your variables are large enough to handle the calculations you are doing. If you are using double precision, try switching to single precision to see if that helps.

If these steps don't solve the issue, it may be worth reaching out to the Simulink support team for further assistance. They may be able to provide more specific guidance based on your model and equations.

Best of luck with your simulations!




Scientist at [Your Institution]

 

[oswaler]

rian

Dear Adrian,

I can understand your frustration with encountering an array out of bounds error while using the embedded MATLAB blocks in Simulink. This error occurs when the index used to access an element in an array is outside the allowed range.

There could be several reasons for this error, such as incorrect indexing, incorrect dimensions of the array, or insufficient memory allocation for the array. In your case, it seems like the equations you are trying to solve are too large for the embedded MATLAB blocks to handle. As you have mentioned, the same equations can be solved in S-Functions in similar models, which suggests that the issue may lie with the limitations of the embedded MATLAB blocks.

One possible solution could be to try using a different solver in Simulink, such as the ODE45 solver, which is known to handle larger equations. Another option could be to break down your equations into smaller parts and solve them separately, as you have already tried. You could also try increasing the memory allocation for your arrays, if possible.

If none of these solutions work, you may need to consider using a different software or programming language that can handle larger equations. I hope this helps and wish you the best of luck in finding a solution to your problem.

Sincerely,