Method for Analytically Obtaining Reset Ratio in Non-Minimum Phase Systems with PI+CI Controller in order to Improve Performance

The non-minimum phase systems are systems with dead time that are found in many processes in industry, they decrease system phase and give rise to a non-rational transfer function for the system, making them more difficult to be analyzed and controlled. In this paper a design method is proposed to improvement closed-loop performance. For this purpose, reset ratio required to obtain suitable output response for non-minimum phase plant must be calculated analytically. We also conducted a survey on reset control system response to investigate the influence of reset controller on linear time-invariant (LTI) systems. Using such controller may overcome the inherent design limitations such as right half plane zeros, delays or plant integrators. At the beginning, general first and second order non-minimum phase plants are considered and reset PI controller is tuned for some values of plants parameters. Then, PI+CI is compared with its base PI controller. The preferences of reset controller with other types of PI controllers are shown in fundamental properties of the closed loop step response such as overshoot, rise time, settling time and control effort.

Keywords:

Reset ratio , Clegg integrator , non-minimum phase , PI+CI controller