dsolve running too long
5 views (last 30 days)
Show older comments
Hey guys, I have an issue where I am trying to solve 7 ODEs with 7 initial conditions but it takes way to long to compute. I let it run for an hour and no solution. What can i do about it? Thanks in advance for help.
Heres the code:
eul_d=[pi/2 pi pi/3];
quat_d=eul2quat(eul_d);
eul_0=[0 0 0];
quat_0=eul2quat(eul_0);
eta_d=quat_d(1,1);
eta_0=quat_0(1,1);
epsilon_d=[quat_d(1,2); quat_d(1,3); quat_d(1,4)];
epsilon_0=[quat_0(1,2); quat_0(1,3); quat_0(1,4)];
I=[250000 0 0;0 100000 0;0 0 110000];
syms omega1(t) omega2(t) omega3(t) eta(t) epsilon1(t) epsilon2(t) epsilon3(t)
ode1 = diff(omega1,t) == (80000-2*epsilon1*eta_d-2*epsilon2*epsilon_d(3,1)+2*epsilon3*epsilon_d(2,1)+eta*epsilon_d(1,1)-1.5*omega1+3+I(2,2)*omega3*omega2-I(3,3)*omega2*omega3)/I(1,1);
ode2 = diff(omega2,t) == (155000-2*epsilon2*eta_d+2*epsilon_d(3,1)*epsilon1-epsilon1*epsilon_d(3,1)+epsilon_d(2,1)*eta-1.5*omega2+1.5-I(1,1)*omega3*omega1+omega1*I(3,3)*omega3)/I(2,2);
ode3 = diff(omega3,t) == (-292300-2*epsilon3*eta_d-2*epsilon1*epsilon_d(2,1)-epsilon_d(1,1)*epsilon2+eta*epsilon_d(3,1)-1.5*omega3+0.75+omega1*omega2*I(1,1)+omega1*omega2*I(2,2))/I(3,3);
ode4 = diff(epsilon1,t) == -0.5*(-omega2*epsilon2+omega2*epsilon3-eta*omega1);
ode5 = diff(epsilon2,t) == -0.5*(omega3*epsilon1-omega1*epsilon2-eta*omega2);
ode6 = diff(epsilon3,t) == -0.5*(-omega2*epsilon1+omega1*epsilon2-eta*omega3);
ode7 = diff(eta,t) == -0.5*(omega1*epsilon1+omega2*epsilon2+omega3*epsilon3);
odes = [ode1; ode2; ode3; ode4; ode5; ode6; ode7];
cond1 = omega1(0) == 1;
cond2 = omega2(0) == 0;
cond3 = omega3(0) == 0;
cond4 = epsilon1(0) == epsilon_0(1,1);
cond5 = epsilon2(0) == epsilon_0(2,1);
cond6 = epsilon3(0) == epsilon_0(3,1);
cond7 = eta(0) == eta_0;
conds = [cond1; cond2; cond3; cond4; cond5; cond6; cond7];
S=dsolve([odes, conds], 'MaxDegree',2);
2 Comments
Torsten
on 24 Apr 2022
Your system of ODEs is nonlinear.
I think you can cancel the symbolic computation and use ODE45 or ODE15S to solve the system numerically.
Answers (0)
See Also
Categories
Find more on Equation Solving in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!