Linear Quadratic Gaussian Control for a Liquid-Carrying Quadrotor

Abstract A quadrotor with a liquid tank may be used in various tasks such as spraying pesticides and firefighting. Therefore, motion of the quadrotor should be controlled such that liquid sloshing is suppressed. To tackle this issue, a LQG controller is proposed in this paper. The LQG controller is based on a linear equivalent mechanical model for liquid sloshing which is presented in this study. The proposed controller uses position and attitude feedback of quadrotor to estimate and control the liquid states. This is different than other controllers presented in the literature where they consider liquid sloshing as an external disturbance. LQG controller is simulated using system’s nonlinear equations and compared to a PID controller. The results depicted a 20% improvement in trajectory tracking performance for LQG controller while using 11% less energy than its PID counterpart. Also the LQG control scheme was able to compensate for a constant external disturbance whereas the PID controller was not able to stabilize the system while the constant disturbance is present.