说明：  求三阶传递函数的阶跃响应 其中对象采样时间为1ms。 采用专家PID设计控制器。在仿真过程中， 取0.001，程序中的五条规则与控制算法的五种情况相对应。
(Seeking third-order transfer function of the step response in which the object sampling time 1ms. PID controller is designed by experts. In the simulation process, taking 0.001, five rules and procedures in the control algorithm corresponding to the five conditions.)