二阶系统的最小二乘一次完成算法辨识程序，图形的横坐标是采样时刻i, 纵坐标是输出观测值z, 图形格式为连续曲线-second-order system of least-squares algorithm for a complete identification procedures, graphics abscissa is the sampling time i, longitudinal coordinates of the output value of observation z, graphical format for continuous curve