2nd order differential equation

Hi everyone

I'm modeling the cardiac valves and one of the equations used is a second order differential equation, which corresponds to the 14th expression mentioned in the pdf from this link: http://www.sciencedirect.com/science/article/pii/S0021929005002927

I tried to implement it in this way, however the values of teta_ao variable have to be between 5 degrees and 75 degrees. How can I put this condition when solving the equation with the ode45 command?

      {function acelerteta_ao=f(t,w,Plv,Psas,Qao)

global Kp_ao Kf_ao Kb_ao Kv_ao; %Parameters related with the aortic valve opening

      for j=1:klokmax 

          D=zeros(1,klokmax);

      if(Qao>=0)

          D(j)=(Plv-Psas)*Kp_ao*cos(teta_ao)-Kf_ao*w(2)+Kb_ao*Qao*cos(teta_ao)-Kv_ao*Qao*sin(teta_ao)

      else

          D(j)=(Plv-Psas)*Kp_ao*cos(teta_ao)-Kf_ao*w(2)+Kb_ao*Qao*cos(teta_ao)

      end

      acelerteta_ao=[w(2);D(j)]

      end

end
}

{main.m

clear all

klokmax=180000;
       t=[0 klokmax]
       initialvalues=[5 0];     
       [t,w]=ode45(@f,t,initialvalues)

}

Thanks in advanced for any suggestion.

Carla

Answer 1

[Walter Roberson]

I am still fairly weak with the ode* solvers, but I wonder if perhaps using an "event" would be suitable for your purpose? See http://www.mathworks.com/help/techdoc/ref/odeset.html