Porblem with ode 45 solver
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hi I am trying to solve nonlinear state space int the form
xdot= Ax+R(x,u)
y= S(x,u)
i have written a function given below
function xdot = system(t,x,u)
Tab=sqrt(2/3)*[cos(x(1)) cos(x(1)-2*pi/3) cos(x(1)+2*pi/3)
-sin(x(1)) -sin(x(1)-2*pi/3) -sin(x(1)+2*pi/3)
1/sqrt(2) 1/sqrt(2) 1/sqrt(2)]
wc=2*pi*50;
L=1.35e-3;
R=.056;
C=50e-6;
Rc=.131;
Lc=0.96e-3;
P=10e3;
Q=5e3;
KpllI=5000;
KpPPL=2.1;
Kid2=460;
Kpd2=1;
Kiq2=460;
Kpq2=1;
udq= Tab*u;
A=[0 KpllI 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 -sqrt(2)*wc 0 wc*wc 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 -sqrt(2)*wc 0 wc*wc 0 0 0 0 0 0 0 0 0 0 0
0 0 -1 0 0 0 0 0 1 0 0 0 0 0 -1 0 0
0 0 0 -1 0 0 0 0 0 1 0 0 0 0 0 -1 0
0 0 0 0 0 0 0 0 -1 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 -1 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 -R/L 0 0 -1/L 0 0 0 0 0
0 0 0 0 0 0 0 0 0 -R/L 0 0 -1/L 0 0 0 0
0 0 0 0 0 0 0 0 0 0 -R/L 0 0 -1/L 0 0 0
0 0 0 0 0 0 0 0 1/C 0 0 0 0 0 -1/C 0 0
0 0 0 0 0 0 0 0 0 1/C 0 0 0 0 0 -1/C 0
0 0 0 0 0 0 0 0 0 0 1/C 0 0 0 0 0 -1/C
0 0 0 0 0 0 0 0 0 0 0 1/Lc 0 0 -Rc/Lc 0 0
0 0 0 0 0 0 0 0 0 0 0 0 1/Lc 0 0 -Rc/Lc 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -Rc/Lc];
w= KpllI*x(2)+KpPPL*udq(2);
vld=Kid2*x(7)+Kpd2*(x(3)-x(9))+udq(1)-w*L*x(10);
vlq=Kiq2*x(8)+Kpq2*(x(4)-x(10))+udq(2)-w*L*x(9);
;
R=[KpPPL*udq(2) % u(2)= voq
udq(2)
0
0
(udq(1)*P-udq(2)*Q)/((udq(2).^2)+(udq(1).^2))
(udq(1)*P+udq(2)*Q)/((udq(2).^2)+(udq(1).^2))
0
0
(vld*1/L)+w*x(10)
(vlq*1/L)-w*x(9)
0
w*x(13)
-w*x(12)
0
(-udq(1)*1/Lc)+w*x(16)
(-udq(2)*1/Lc)+w*x(15)
0];
xdot=A*x+R;
and the main file with
t=0:100e-5:5;
wc=50;
u= [240*sqrt(2)*sin(wc*t+pi/2)
240*sqrt(2)*sin(wc*t-2*pi/3+pi/2)
240*sqrt(2)*sin(wc*t+2*pi/3+pi/2)];
x0=zeros(17,1);
odeOptions = odeset('RelTol',1e-6);
[t,y] = ode45(@system,t,x0,odeOptions,u);
Tab=sqrt(2/3)*[cos(y(:,1)) cos(y(:,1)-2*pi/3) cos(y(:,1)+2*pi/3)
-sin(y(:,1)) -sin(y(:,1)-2*pi/3) -sin(y(:,1)+2*pi/3)
1/sqrt(2) 1/sqrt(2) 1/sqrt(2)];
udq= Tab*u;
The problem i am facing is that multiplication in the last line of code is giving error while in function file it gives no error but do not save the result. Kindly any body suggest me what i am doing wrong. Thanks
0 Comments
Accepted Answer
Torsten
on 30 Oct 2015
y(:,1), y(:,2) and y(:,3) are vectors of length numel(t).
So your matrix Tab is no longer 3x3.
Best wishes
Torsten.
2 Comments
Torsten
on 2 Nov 2015
so then what do you suggest i have to use a for loop to compute Tab at each time step using a for loop
That's exactly what I suggest you should do.
Best wishes
Torsten.
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