Decoupled integral lqr controller with anti-windup compensator for MIMO two rotor aerodynamical system (TRAS)

Abstract

This paper employs a design of two sub-controllers based on a Linear Quadratic Regulator (LQR) for Two Rotor Aero-dynamical System (TRAS) in two Degree of Freedom (2-DOF) motion. TRAS is a nonlinear Multi-Input Multi-Output (MIMO) system that resembles the behaviour of a helicopter in certain aspects. The main focus of the research work is to control and stabilize the TRAS system in 2-DOF so that the desired trajectory is tracked quickly and accurately even in the presence of disturbances. However, this not always possible due to some reasons such as the strong cross couplings, poorly tuned control parameters and integral windup phenomena that significantly deteriorate the transient response. In this work, TRAS is decoupled into two subsystems (horizontal and vertical) with the cross couplings considered as disturbances. The derivation of the linear model of each subsystem is developed using Jacobean linearisation matrix. An optimal LQR controller is designed and tuned using Particle Swarm Optimisation (PSO) algorithm for each subsystem. To get full state information, provide asymptotic tracking for the reference signal and alleviate integral windup phenomena each sub-LQR controller has been combined with full state observer, integral action gain and anti-windup compensator based on back-calculation technique, respectively to ensure fast and reliable control of TRAS system without degrading the transient response. Experimental results show that the Decoupled Integral LQR Controller (DILQRC) exhibits a better performance in terms of transient and steady state responses with significant reduction of settling time, overshoot percentage and error index it also produces less aggressive and smooth control signals as compared to the Cross Coupled PID Controller (CCPIDC) tuned by the manufacturer.