说明：  基于LQ的二级倒立摆设计，可实现LQ校正，能画出原系统的阶跃响应，及加入LQ校正后的系统阶跃响应曲线。
(LQ-based design of double inverted pendulum, can be realized LQ correction, can draw the step response of the original system, and adding LQ corrected step response curve.)