对液位先建模，然后对其进行P、PI、PD、PID算法，观察模型变化

PID tuning by using Gravitational Search Algorithm (GSA). GSA is new algorithm which is believed can produce a better result compare to other optimization technique

pid-算法 The values of Process point,Set point, P gain, I gain, D gain(PID algorithm The values of Process point,Set point, P gain, I gain, D gain)