中文说明：基于非线性系统的阶跃响应数据，采用最小二乘方法用状态空间模型去拟合其响应曲线，进而获得状态变量模型参数。代码段有详细说明。
English Description：
Based on the step response data of the nonlinear system, the least square method is used to fit the response curve with the state space model, and then the parameters of the state variable model are obtained. The code snippet is detailed.