基于图像矩的四旋翼无人机视觉伺服方法

An Image Moment Based Visual Servo Method for Quadrotor UAVs

针对四旋翼无人机的欠驱动和强耦合特性造成像机固定于机体的视觉伺服效果不佳的问题,提出一种基于图像矩的视觉伺服方法。首先,构建虚拟像平面,选取图像矩为特征,进行图像动力学解耦,进一步结合四旋翼无人机动力学模型建立特征误差与速度之间的伺服关系;其次,根据四旋翼无人机动力学解耦关系,将系统解耦为位置控制和姿态控制;位置控制器根据伺服关系求取速度控制律,通过动力学扩展的方式直接求得期望的姿态;最后,由于系统非线性特性造成姿态扰动,设计滑模控制器进行姿态跟踪控制。跟踪移动目标的仿真实验结果证明所提方法的优越性和鲁棒性。

Due to the underactuation and strong coupling of quadrotor UAVs,the visual servo effect of the camera fixed on the UAV airframe is not good.To solve the problem,an image moment based visual servo method is proposed.Firstly,the virtual image plane is built to select image moments as features,and then image dynamics is decoupled.Furthermore,the servo relationship between image errors and velocity is established by using the quadrotor dynamics model.Secondly,according to the dynamic decoupling of the quadrotor,the system is decoupled into position controller and attitude controller.The velocity control law is obtained by the position controller according to the servo relationship,and the desired attitude is obtained directly by means of dynamic expansion.Finally,a sliding mode controller is designed for attitude tracking control aiming at the attitude disturbance caused by the nonlinearity of the system.Simulation results verify the superiority and robustness of the proposed method.