Computer aided synthesis and design of PID controllers

Abstract

This thesis aims to cover some aspects of synthesis and design of Proportional- Integral-Derivative (PID) controllers. The topics include computer aided design of discrete time controllers, data-based design of discrete PID controllers and data- robust design of PID controllers. These topics are of paramount in control systems literature where a lot of stress is laid upon identification of plant and robust design. The computer aided design of discrete time controllers introduces a Graphical User Interface (GUI) based software. The controllers are: Proportional (P), Proportional-Derivative (PD),Proportional-Integral (PI) and Proportional-Integral- Derivative (PID) controllers. Different performance based design methods with these controllers have been introduced. The user can either explore the performance by interactively choosing controllers one by one from the entire set and visualizing its performance or specify some performance constraints and obtaining the resulting set. In data-based design, the thesis presents a way of designing PID controllers based on input-output data. Thus, the intermediate step of identification of model from data is removed, saving considerable effort. Moreover, the data required is step response data which is easier to obtain in case of discrete time system than frequency response data. Further, a GUI developed for interactive design is also described. In data-robust design, the problem of uncertainty in data is explored. The design method developed finds the stabilizing set which can robustly stabilize the plant with uncertainty. It has been put forward as an application to interval linear programming. The main results of this research include a new way of designing discrete time PID controllers directly from the data. The simulations further confirm the results. Robust design of PID controllers with data uncertainty has also been established. Additionally, as a part of this research, a GUI based software has been developed which is expected to be very beneficial to the designers in manufacturing, aerospace and petrochemical industries. PID controllers are widely used in the industry. Any progress in this field is well acknowledged both in the industry and the academia alike. This thesis attempts a small step further in this direction.