Integration of a vector inside function for ode45

4 次查看（过去 30 天）
SM
SM 2022-9-7
评论： SM 2022-9-10
I am trying to solve a set of differential equations using ode45 command. The problem is I want to integrate one of the variables of the differential equations. For that I need to save the values/solution of that variable in a vector inside the function. I am unable to store x(1) as a vector. In the code, I need to integrate x(1) for which I have used cumtrapz but its not helping . My differential equations arre x1dot=x2 ;x2dot=-9.81*sin(x1)+u where dot means diffeentiation with respect to time. For u, e, ei and de are as defined in the code. Kindly help.
function dxdt=slmc(t,x)
dx1dt=x(2);
e=-x(1);
de=-x(2);
ei=0.01*cumtrapz(e);
u=75*e+5*ei+25*de;
dx2dt=-9.81*sin(x(1,:))+u;
dxdt=[dx1dt;dx2dt];
end
t=0:0.01:10;
in=pi/2;
indxdt=0;
[t,x]= ode45(@(t,x) slmc(t,x),t,[in indxdt]);
plot(t,x(:,1))

请先登录，再回答此问题。

采纳的回答

Torsten
Torsten 2022-9-7
Ran in:
In the code below, x(3) = integral_{tau=0}^{tau=t} -0.01*x(1) dtau
t=0:0.01:10;
in=pi/2;
indxdt=0;
[t,x]= ode45(@(t,x) slmc(t,x),t,[in indxdt 0]);
plot(t,x(:,3))
function dxdt=slmc(t,x)
dx1dt=x(2);
e=-x(1);
de=-x(2);
ei = x(3);
u=75*e+5*ei+25*de;
dx2dt=-9.81*sin(x(1,:))+u;
dxdt=[dx1dt;dx2dt;-0.01*x(1)];
end
  11 个评论
显示 9更早的评论
Paul
Paul 2022-9-9
The initial() command is plotting the IC response of the plant, not the closed loop system.
The closed loop system formed by G and c1 is not the same as that implemented in test_pid2. In the latter, the control input is
u=50*e+30*ei+16*de = -(50*x1 + 30*intx1 + 16*x2) % that 16*x2 was probably meant to be 16*x1dot
whereas in the former the control is
u = -(50*y + 30*inty + 16*ydot) = -(50*x2 + 30*intx2 + 16*x2dot)

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Ordinary Differential Equations 的更多信息

标签

产品


版本

R2018b

Community Treasure Hunt

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

Start Hunting!

Translated by