说明：  duffing方程的混沌判别中使用到了庞加莱截面，即多维相空间中适当选取一截面 ，此截面不与轨线相切，不包含轨线，且便于观察系统的运动特征变化.
(use Poincare chaotic duffing equation discriminant, multi-dimensional phase space appropriate to select a cross-section, this section is not tangent to the trajectory does not contain the rail line, and easy motion characteristics of the observed system changes.)