利用BP网络逼近对象y(k)=u(k)^3+y(k-1)/(1+y(k-1)^2)。采样时间取1ms。输入信号为u(k)=0.5sin(6*pi*t)。(Approximate object y (k), =u (k), ^3+y (k-1) / (1+y (k-1) ^2) using BP networks. Sampling time is 1ms. The input signal is u (k) =0.5sin (6*pi*t).)