Why " The boundary condition function BCFUN should return a column vector of length 5" error message is came?

13 次查看（过去 30 天）
Tu
Tu 2022-11-14
评论： Tu 2022-11-17
Ran in:
% function Y6
solinit = bvpinit(linspace(0,1),[0;3;1;1],2);
sol = bvp4c(@ode, @bc, solinit);
Error using bvparguments
Error in calling BVP4C(ODEFUN,BCFUN,SOLINIT):
The boundary condition function BCFUN should return a column vector of length 5.

Error in bvp4c (line 122)
bvparguments(solver_name,ode,bc,solinit,options,varargin);
y = sol.y;
time = sol.parameters*sol.x;
ut = -y(4,:);
figure(1);
plot(time,y([1 2],:)','-'); hold on;
plot(time, ut, 'k:');
axis([0 time(1,end) -1.5 3]);
text(1.3,2.5,'x_1(t)');
text(1.3,.9,'x_2(t)');
text(1.3,-.5,'u(t)');
xlabel('time');
ylabel('states');
title('Numerical solution');
hold off;
% -------------------------------------------------------------------------
% ODE's of augmented states
function dydt = ode(t,y,T)
dydt = T*[2*y(2);4*y(4);0;-2*y(3)];
end
% -------------------------------------------------------------------------
% boundary conditions: x1(0)=11;p2(0)=2; x2(tf)=3; 3*p1(tf)+p2(2)^2=0
function res = bc(ya,yb,T)
res = [ ya(1) - 11; ya(4); yb(2) - 3; 3*yb(3)+yb(4)^2];
end

请先登录，再回答此问题。

采纳的回答

Jan
Jan 2022-11-14
You provide an extra parameter:
solinit = bvpinit(linspace(0,1),[0;3;1;1],2);
% ^ here
But there is no condition for this parameter in bc().
  4 个评论
显示 2更早的评论
Tu
Tu 2022-11-16
编辑：Tu 2022-11-16
yes, i want to find U_optimal through numerical method of this problem. but i don''t know how to find it! can you help me please. U is a function of variable t u=u(t)
Jan
Jan 2022-11-16
This not trivial. If you do not know, which function u is, there is an infinite number of possible solutions. This is an optimization problem and not a simple BVP.

请先登录，再进行评论。

更多回答（1 个）

Torsten
Torsten 2022-11-16
编辑：Torsten 2022-11-16
Choose a grid
0=t0 < t1 < ... < tn = tf
With each grid point, associate a value ui of your control function u (the ui are your solution variables for the optimization problem).
Call fmincon with initial values for the ui.
Within the objective function for fmincon, solve the boundary value problem from above with the given vector u (e.g. using bvp4c or your own ODE solver for this simple boundary value problem) and return the value for J to the optimizer. The integral can be approximated by the trapezoidal rule, e.g.
Maybe the YouTube video is of help:
https://www.youtube.com/watch?v=60xX4R708Iw
  3 个评论
显示 1更早的评论
Torsten
Torsten 2022-11-16
I described the steps you have to follow and even gave a link to a video where everything is described in detail. This is all I can do for you - the task is not a "one-liner".

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Boundary Value Problems 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by