there is something wrong with the model，when i run the model,it turns up the summary:"At time 0.0005159318861234992, simulation hits (1000) consecutive zero crossings. Consecutive zero crossings will slow down the simulation or cause the simulation to hang. To continue the simulation, you may 1) Try using Adaptive zero-crossing detection algorithm or 2) Disable the zero crossing of the blocks shown in the following table." I don't know why,could you tell me the reason.thanks! My matlab version is R2010a.