Fixed-time controller of visual quadrotor for tracking a moving target

Abstract

In order to eliminate the dependence of finite-time control on the initial state of the system in the image-based visual servoing (IBVS) of a quadrotor UAV (QUAV) for the moving target, we propose a control scheme for the moving target of a QUAV based on fixed-time stability. We select the image moments of the virtual camera plane as features and establish an image moment dynamics model that includes target motion parameters based on them. Then, we use the backstepping method to design the fixed-time controller for the system. The design steps of the controller mainly consist of two parts. Firstly, we designed a fixed-time stable linear velocity observer to address the unmeasurable linear velocity and unmeasurable monocular camera depth issues of QUAV. Then, using a high-order tracking differentiator to estimate the target linear velocity as a feedforward, combined with the fixed-time linear velocity observer estimated QUAV linear velocity, we designed a fixed-time controller for the system using the backstepping method. We demonstrated the fixed-time stability of the controller using the Lyapunov theory. The effectiveness and robustness of the proposed method are demonstrated by numerical simulation. At the same time, the comparative simulation shows that the method can guarantee the rate of convergence of the system and has high control accuracy.