help with lqr control of DIPC

hello, i need help with the LQR control of a double inverted pendulum on a cart, the thing is when i simulate the model,everything goes ok, but when i try to calculate the gain K a problem occurs,pls help me i need it desperetly here is the problem message: Warning: Discontinuity detected at A(4,3) Error using lqr (line 45) The value of the "a" property must be a numeric array without any Inf's or NaN's.

Error in pendattempt (line 15) K = lqr(A,B,Q,R);

if the file pnd2 didnt open change the extansion to .mdl and it should be enough for it to work thanks in advance