LQR Controller with Kalman Estimator Applied to UAV Longitudinal Dynamics

Abstract

The aim of this study is designing an optimal controller with linear quadratic regulator (LQR) method for a small un-manned air vehicle (UAV). To better evaluate the effect of disturbances on the obtained measurements, a Kalman filter is also used in the system. For this purpose a small UAV that is normally used as a radio controlled plane is chosen. The linearized equations for a wings level flight condition and the state space matrices are obtained. An optimal controller using LQR method to control the altitude level is then designed. The effect of the disturbances on the measurements are taken into account and the effectiveness of the Kalman filter in obtaining the correct measurements and achieving the desired control level are shown using the controller designed for the system. The small UAV is commanded to the de-sired altitude using the LQR controller through the control inputs elevator deflection and thrust rate. The LQR effec-tiveness matrices are chosen to find the gains necessary to build an effective altitude controller. Firstly the controller is tested under the situation where disturbances are absent. Then a Kalman filter is designed and the system under distur-bances is tested with the designed controller and the filter. The results reveal the effectiveness of the Kalman filter and the LQR controller.