Experimental design of robust decentralized PI controller for TRMS through polytopic modeling

Abstract

This paper presents a new approach to deal with the nonlinear dynamics present in a Twin Rotor MIMO System (TRMS) without any approximation of the system model. Conventionally, there are two approaches/options for adopting linear control design methods for a nonlinear system. The first one is to linearize the model around an operating point, neglecting the higher order dynamics. This could result in drastic changes in the transient behavior of the model for which the controller fails to ensure robustness and a good tracking response. The second approach is to consider the exact model and represent the nonlinear terms involved, in the form of structural or model uncertainties. The design technique adopted in this paper is based on the second approach. The nonlinear model of TRMS is represented in the form of a linear parameter-varying system, thereby facilitating the design of a linear robust controller, with a better tracking control of the desired states. Additionally, a robust Linear Matrix Inequality (LMI) based decentralized Proportional Integral (PI) controller is designed along with locating closed-loop poles in a desired region. A comparative study is done for experimental results of various existing designs and the proposed method. © 2020 IEEE.