四旋翼飞行器非线性轨迹跟踪控制

Nonlinear trajectory tracking control for a quadrotor

针对四旋翼飞行器在复杂飞行条件下速度不可测的轨迹跟踪控制问题,考虑系统存在外界未知干扰和模型参数不确定的情况,提出了一种基于扩张观测器的轨迹跟踪控制方法。该方法设计了积分型反步法跟踪控制器,以降低系统的稳态误差,并引入了状态扩张观测器,来估计系统未知速度信息,同时对干扰和模型参数不确定因素进行实时估计并给予补偿;最后,选取李雅普诺夫函数证明了该控制系统的稳定性。以Quanser公司的Qball2四旋翼飞行器为研究对象和飞行实验平台,对所设计的控制器进行验证。实验结果表明,本文所设计的基于扩张观测器的轨迹跟踪控制器,能够有效地估计轨迹跟踪控制过程中的未知速度信息,解决外界未知干扰和模型参数不确定的问题,增强对环境的适应能力,有效提高了飞行器对未知干扰的鲁棒性和轨迹跟踪控制的精确性。

Under complex flight conditions, it is hard to realize the trajectory tracking control of the quadrotor with unmeasurable speed. Considering the existence of unknown external disturbance and uncertain model parameters, the trajectory tracking control method based on an extended state observer is proposed. Firstly, the integral backstepping tracking controller is designed to reduce the steady state error of the system, and the state extended observer is introduced to estimate the unknown speed of the system. Then, the disturbance and the uncertainty of model parameters are estimated in real time and compensated accordingly. Finally, the Lyapunov function is utilized to prove the stability of the control system. Experiments are implemented on the Qball2 platform of Quanser′s quadrotor. Results show that the trajectory tracking controller based on the extended state observer can estimate the unknown speed in the trajectory tracking control process effectively. It can also solve the problem of unknown external disturbance and model parameter uncertainty. The adaptability to the environment can be enhanced. The robustness of the quadrotor to unknown disturbances and the accuracy of trajectory tracking control are improved effectively.