说明：  通过对PID控制器中的参数（微分时间常数Td）的研究，并绘制出不同的微分时间常数Td下的单位阶跃响应图，比较得出微分时间常数Td对控制的控制性能的影响。
(Through the study of the parameter (differential time constant Td) in the PID controller, the unit step response diagram with different differential time constant Td is drawn, and the influence of the differential time constant Td on the control performance is compared.)