Can anyone help to see what is wrong with this function to solve a DAE problem

dx(1)=x(2);
dx(2)=k1*(x(3)-x(1))-(knl_1*x(1)+knl_3*x(1)^3);
dx(3)=x(4);
dx(4)=(-c*x(4)-k1*(x(3)-x(1))+kAmp*cos(w*t)+theta_p*x(5))/m;
dx(5)=(-theta_p*(ks/(kp+ks))*(x(4)-x(2))*R_s-x(5))/R_s/C_p;

The mass matrix

M=diag([1 0 1 1 1]);
options = odeset('mass', M, 'RelTol',1.e-6);

I am trying to solve the equations below. The y values and V values are unknown and the rest of them are constant.

But, it gave out the error

"This DAE appears to be of index greater than 1."

Can anyone help to solve the problem?

Thank you very much.

[Zoé Cord'homme]

Hello ! I currently have a similar issue, did you find a way ?

[haohaoxuexi1]

I think ode15 works in some situations.

But for faster calculation, ode45 is better.