Hi !
For a project, I am currently needing to solve a second degree (or of index 2, I am not too familiar with those) DAE.
The equations are :
d²x/dt² = 1/m * (- f2(x-x1, dx/dt - dx1/dt))
0 = f2(x-x1, dx/dt - dx1/dt) - f1(x1,dx1/dt)
Where m is a scalar and f1 and f2 are functions looking like this :
function force=f1(x-x1, dx/dt - dx1/dt)
p1 = 1.4347e+07;
p2 = 1.9757e+06;
p3 = 3.1841e+05;
if vrel<=0
force = p1*(x-x1)^2 + p2*(x-x1) + p3;
else
force = p1*(x-x1)^2 + p2*(x-x1) + p3 - 260000;
end
So far, I have coded this :
m_materiel= ...
M=[1 0 0 0
0 1 0 0
0 0 0 0
0 0 0 1];
V0 =...
y0=[0 0 V0 V0];
dt=0.01;
tf=2;
tspan=0:dt:tf;
options = odeset('Mass',M,'Vectorized','on');
[t,Y]=ode15s(@(t,Y) f(t,Y,m_materiel),tspan,y0,options);
function out=f(t,Y,m_materiel)
out =[Y(3,:);
Y(4,:);
f_MI7984(Y(1,:),Y(3,:),data1,data2)-fQS_continue_MI20(Y(2,:)-Y(1,:),Y(4,:)-Y(3,:));
1/m*(fQS_continue_MI20(Y(2,:)-Y(1,:),Y(4,:)-Y(3,:)))];
I have used a similar technique than with classical second order differential equations,
Here "out" is dY where Y = [x1; x; dx1/dt; dx/dt]
When I run the code, I get multiple errors :
Error using vertcat
Dimensions of matrices being concatenated are not consistent.
Error in interp1q (line 31)
[~, j] = sort([x;xxi]);
Error in f (line 2)
out =[Y(3,:);
Error in @(t,Y)f(t,Y,m_materiel)
Error in odenumjac (line 143)
Fdel = feval(F,Fargs_expanded{:});
Error in daeic12 (line 37)
[DfDy,Joptions.fac,nF] = odenumjac(fun, {t0,y,args{:}}, f, Joptions);
Error in ode15s (line 310)
[y,yp,f0,dfdy,nFE,nPD,Jfac] = daeic12(odeFcn,odeArgs,t,ICtype,Mt,y,yp0,f0,...
Error in attelageeqVSmur (line 24)
[t,Y]=ode15s(@(t,Y) f(t,Y,m_materiel),tspan,y0,options);
Can you help me out ? Do you know how to solve this kind of equation ? Thank you :)
