Using ODE45 to solve quarter model of suspension with input function (an endless obstacle)

Hi, i tried solve a quarter model of suspension. I want input function, there function is road (an endless obstacle)

I tried solve differential equation, but i can´t input the obstacle.

t=0:0.01:3;  
u1(t<=0.25)=0;
u1(t>0.25)=0.077;
U=zeros(4,301);
U(3,:)=u1;
[t,y]=ode45(@(t,y) fce(t,y,U),t,[0 0 0 0]);

with funciton

function dz=fce(t,z,u)

global b k10 k12 m1 m2

dz=zeros(4,1);
dz(1) = z(3);
dz(2) = z(4);
dz(3) = -((k10+k12)/m1)*z(1)+k12/m1*z(2)-b/m1*z(3)+b/m1*z(4);+k10/m1*u(3);
dz(4) = k12/m2*z(1)-k12/m2*z(2)+b/m2*z(3)-b/m2*z(4);

The program works, but the solution is matrix zero (so the program not working with input function (U)). Can you help me to solve this problem?

Answer 1

[Torsten]

t = 0:0.01:0.25; 
phase = 1;
y0 = [0 0 0 0];
[t1, y1] = ode45(@(t,y) fce(t,y,phase),t,y0);
t = 0.25:0.01:3; 
phase = 2;
y0 = y1(end,:);
[t2, y2] = ode45(@(t,y) fce(t,y,phase),t,y0);
T = [t1; t2];
Y = [y1; y2];
plot(T,Y)

function dz=fce(t,z,phase)
  global b k10 k12 m1 m2
  if phase == 1
    u = 0;
  else
    u = 0.077;
  end
  dz = zeros(4,1);
  dz(1) = z(3);
  dz(2) = z(4);
  dz(3) = -((k10+k12)/m1)*z(1)+k12/m1*z(2)-b/m1*z(3)+b/m1*z(4);+k10/m1*u;
  dz(4) = k12/m2*z(1)-k12/m2*z(2)+b/m2*z(3)-b/m2*z(4);

[faruk özalp]

this code gave this error

All functions in a script must be closed with an 'end'.

[Torsten]

Then do what MATLAB tells you to do:

function main
t = 0:0.01:0.25; 
phase = 1;
y0 = [0 0 0 0];
[t1, y1] = ode45(@(t,y) fce(t,y,phase),t,y0);
t = 0.25:0.01:3; 
phase = 2;
y0 = y1(end,:);
[t2, y2] = ode45(@(t,y) fce(t,y,phase),t,y0);
T = [t1; t2];
Y = [y1; y2];
plot(T,Y)
end

function dz=fce(t,z,phase)
global b k10 k12 m1 m2
if phase == 1
    u = 0;
else
    u = 0.077;
end
dz = zeros(4,1);
dz(1) = z(3);
dz(2) = z(4);
dz(3) = -((k10+k12)/m1)*z(1)+k12/m1*z(2)-b/m1*z(3)+b/m1*z(4);+k10/m1*u;
dz(4) = k12/m2*z(1)-k12/m2*z(2)+b/m2*z(3)-b/m2*z(4);
end

But don't forget to give values to the missing variables b, k10, k12, m1 and m2.