说明：  This paper analyses the Proportional-Integral-Derivative (PID) controller’s performance for quadruple tank process. The selection of controlling the flow ratios in quadruple tank process act as Minimum and Non-minimum phase system. Its performance can be affected when system is shifted minimum to non-minimum phase configuration and vice versa. This paper mainly focuses on searching the optimal controller structure by increasing the controllers’ performance criteria. A comparative study on different controllers’ structures responses are in the presence of peak overshoot. A simulation study of PID controller and Modified PID controller structures have been designed and to analyzed the different controllers’ performance for the minimum and non-minimum phase system