Import matrix with y variables into ode45
Hi all,
I want to solve an ode45 equation for a multibody model. The matrixes I have to implement in the ode45 are very big. Now I am using the subs function to place the values for x into the matrixes. However because the fact that this is done inside the ode45 function running the function takes a while. Is there a way to already implement the x value in the matrixes as a variable outside the ode45 function?
In the code WT and w_bar are matrixes of 12x15 and12x1
The vector hulp_vec and hulp_vec_derivative contain both 15 syms variables
% Solve the equation
[t,x]=ode45(@(t,x)analytical_simplified(t,x,M,H,S,WT,w_bar,N,constr_eq,hulp_vec,hulp_vec_derivative),tspan,x0);
function [dx, lambda, constraint_eq]=analytical_simplified(t,x,M,H,S,WT,w_bar,N,constraint_eq,hulp_vec,hulp_vec_derivative)
tic
tau=[0;sin(t);0];
%make matrices afhankelijk van x and dx
% WT=subs(WT,hulp_vec',x(1:N));
WT=subs(WT,hulp_vec_derivative',x(N+1:2*N));
w_bar=subs(w_bar,hulp_vec',x(1:N));
w_bar=subs(w_bar,hulp_vec_derivative',x(N+1:2*N));
constraint_eq=subs(constraint_eq,hulp_vec',x(1:N));
toc
tic
Minv=inv(M);
% Stabilize the matrixes
wo=100;
alpha=wo/5; beta=1;
w_bar_stab = w_bar + 2*alpha*beta*WT*x(N+1:2*N) + alpha^2*constraint_eq;
% w_bar_stab=w_bar;
L1=(WT*Minv*WT');
L2=(WT*Minv*(H-S*tau)-w_bar_stab);
L1=double(L1); L2=double(L2);
lambda=L1\L2;
ddx=Minv*(S*tau-H+WT'*lambda);
dx(1:N)=x(N+1:2*N);
dx(N+1:2*N)=ddx;
dx=dx';
dx=double(dx);
toc
end
With kind regards,
Janne
2 Comments
Time Descending
Hi @Janne Daams, we have moved your question to MATLAB Answers here, where a wider support audience is available to help you:
You should move this into MATLAB Answers
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