I run a dynamic model in MATLAB/Simulink and i have a error like below. that say me : 

Derivative input 1 of '....' at time 0.0149 is Inf or NaN. Stopping simulation. There may be a singularity in the solution. If not, try reducing the step size (either by reducing the fixed step size or by tightening the error tolerances)

any one can help me.

thanks alot