How do i transfer big symbolic equations into Simulink

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Sed
Sed 2016-4-18
评论： Walter Roberson 2022-6-25
Hello everyone,
I am trying to solve the dynamics of a serial manipulator with 6DOF, and I want to transfer the result of an m file (vector of symbolic Torques) into a Simulink block and replace the symbolic variables with a vector of input to have the final numeric result as an output of the block.
I tried a Matlab function block but it does not support symbolic variables.
I tried to call the function as an extrinsic function but Simulink crashes every time I run it.
"from workspace" and "from m file" blocks are not what I need since I have an input to the block.
Any suggestions?
Thanks in advance.
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Sed
Sed 2016-4-19
hello Stefan,
I cannot use a constant block because it only has an output, no input.
I have this huge symbolic vector, I want to put it in a simulink block with an input and output, so that the input replaces all the symbols in the vector and displays a numeric one in the output.
let's say I have the following:
syms q1
syms q2
syms dq1
syms dq2
T=[cos(q1)+sin(q2)*dq1 ; son(q2)*dq2]
I want symbolic T to be in a block and the vector [q1;q2;dq1;dq2] to be an input to this block. matlab function would do it but it doesn't support symbols.
I also can't not use symbols because I have some derivations in the code.
I tried to copy the massive symbolic T vector in a matlab function but it's so big that simulink crashes every time I run it.
Negin Borna
Negin Borna 2022-6-20
Hello sed, I have same problem,can you explain how you fixed it?

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Ced
Ced 2016-4-19
What do you mean by "matlab function does not support symbols"? Maybe I misunderstood your problem, but there is a function called matlabFunction, and it is specifically made to take symbolic expressions and turn them into "numerical functions".
Here is a small example for a 3DOF robot arm:
% Given: symbolic EoM dx = f(....)
syms q1 q2 q3 dq1 dq2 dq3 T1 T2 T3 real
q = [q1 q2 q3]'; % generalized coordinates
dq = [dq1 dq2 dq3]'; % derivative of generalized coordinates
T = [T1 T2 T3]'; % torque vector
% ... HERE: computation of EoM, returning symbolic dx = f(q,dq,T)
% now generate function
matlabFunction(dx,'file','f_dyn','vars',{[q;dq],T});
This will generate a file f_dyn.m with function
function dx = f_dyn(in1,in2)
where in1 = [ q ; dq ] and in2 = T
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Negin Borna
Negin Borna 2022-6-25
Hello Every one.. I do this method and use matlab function block to call matlabFunction and run simulink but one error shows “ output argument ‘matrix name’ is not assigned on some execution paths. What should I do and write in this block to fixed this error?

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