基于固定时间扰动观测器的四旋翼无人机轨迹跟踪控制

Trajectory tracking control of quad-rotor UAV based on fixed-time disturbance observer

摘要:

针对六自由度小型四旋翼无人机在轨迹跟踪控制过程中，单一控制器构成的控制系统存在外部未知干扰，系统的鲁棒性以及轨迹跟踪精度容易产生较大的波动问题，该文章提出了一种基于固定时间扰动观测器的全闭环控制方案，即针对位置与姿态的双闭环控制。首先利用固定时间理论设计了两个扰动观测器，在固定时间内对扰动做出估计并进行补偿；在此观测器对扰动值的精确估计基础之上，设计了两个具有扰动补偿能力的非线性跟踪控制器。李雅普诺夫稳定性理论证明了所述方法的有效性。仿真实验中，为对比所述控制方法的有效性，同时采用传统单一控制器构成的无人机控制系统进行对比分析。在无人机质量为m=1.44kg 、环境重力加速度为g=9.8m/s^2 以及其他模型参数一致的前提下，进行大量的仿真实验验证了所提出的基于固定时间扰动观测器的扰动补偿控制系统，能够保证小型四旋翼无人机六自由度受到复杂外部干扰时准确估计出外部干扰值，并实现无人机进行高精度轨迹跟踪控制，且轨迹跟踪精度与抗扰性能皆优于传统单一控制器构成的无人机控制系统。

Abstract:

In the trajectory tracking control process of a six-degree-of-freedom quadrotor UAV, the control system composed of a single controller has unknown external disturbance, and the robustness of the system and the tracking accuracy of the trajectory are prone to large fluctuations. The paper proposes a full-closed-loop control scheme based on a fixed-time disturbance observer, that is, double-closed-loop control for position and attitude. First, two disturbance observers are designed using the fixed-time theory to estimate and compensate for the disturbance within a fixed time; on the basis of the accurate estimation of the disturbance value by this observer. Two nonlinear tracking controllers with disturbance compensation capability are designed. The Lyapunov stability theory proves the effectiveness of the method. In the simulation experiment, in order to compare the effectiveness of the control method, at the same time, the UAV control system composed of a traditional single controller is used for comparative analysis. Under the premise that the UAV mass is m=1.44kg, the environmental acceleration of gravity is g=9.8m/s^2, and other model parameters are consistent, a large number of simulation experiments are carried out to verify the proposed disturbance compensation control system based on a fixed-time disturbance observer. The compensation control system can ensure that the six degrees of freedom of the quadrotor UAV can accurately estimate the external disturbance value when it is subjected to external disturbance, and realize the high-precision trajectory tracking control of the UAV, and the trajectory tracking accuracy and anti- disturbance performance are better than the UAV control system composed of a traditional single controller