Estaimation of kinetic papremeters using optimization

Hi,

I am trying to solve the pde system(stiff) for my kinetics experiments. We have around 100 experimental data points.

unknowns are: {k1,E1, k2,E2} are positive values

r=(k1*exp(-E1/T)*c2+k2*exp(-E2/T)*c5)c1*c2

equations are :

(1) dc1/dt=D*d^2(c1)/dx^2-r;  
(2) dc2/dt=D*d^2(c2)/dx^2-2*r;  
(3) dc3/dt=D*d^2(c3)/dx^2+r;  
(4) dc4/dt=D*d^2(c4)/dx^2+r;   
(5) dc5/dt=D*d^2(c5)/dx^2;

and i am using ode15s and collocation method for solving the equations. After getting the solution i need find the flux and compare with experimental flux values.

I need to minimize the error between experimental and modelled flux.

I tried to fminsearch but most of the times my objective function is not zero.

 objective function=(flux_exp_flux_model)^2/(flux_exp*flux_model)

I need to mention that for one complete run of all data points it takes around 300 seconds.

So pelase suggest me how can i get the optimized values.

[Matt J]

I tried to fminsearch but most of the times my objective function is not zero.

One doesn't expect a numerical minimization routine to reach zero exactly. Is there other evidence you see of a poor fit?