四旋翼无人机的偏航抗饱和与多模式PID控制

Anti-windup and Multi-Mode PID Control of Yaw Movement for a Quad-Rotor UAV

四旋翼无人机偏航运动能力比俯仰、滚转运动能力弱,因此在偏航运动上更容易出现执行器饱和.特别在外界干扰下,偏航常常出现饱和现象,对此从实际工程出发提出了一种多模式PID(MMPID)控制器,抑制偏航饱和,并保证在外界干扰情况下具有较好的偏航控制性能.首先,根据四旋翼无人机的动力学模型,设计了基于MMPID的偏航控制器.MMPID算法具有多模式特性,在满足一定条件时采取退饱和控制策略.其次,利用李亚普诺夫稳定理论证明了基于MMPID的偏航控制系统的稳定性.最后,通过四旋翼无人机偏航仿真实验比较了MMPID与变结构PID算法的抗饱和性能与偏航控制性能,结果表明MMPID算法具有明显的控制性能优越性.并且,通过四旋翼原型机实验验证了MMPID偏航控制器的有效性和鲁棒性.实验结果表明:在室内无干扰情况下,基于MMPID的偏航系统基本无执行器饱和现象,最终偏航角误差收敛到±0.05 rad;在室内加入干扰情况下,执行器退出饱和时间约10 s,偏航角误差收敛到±0.08 rad;在室外,偏航退饱和时间约5 s,偏航误差收敛到±0.13 rad.MMPID控制器有效地抑制了四旋翼无人机偏航运动上的执行器饱和,并可实现准确的偏航姿态控制和强鲁棒性.

The actuator saturation tends to occur in the yaw movement of a quad-rotor UAV （unmanned air vehicle）, espe- cially in the presence of disturbances, which results from the fact that yaw movement is much weaker than pitch movement and roll movement. In order to address this problem, a multi-mode proportional-intergral-differential （MMPID） anti-windup controller is proposed from the view point of practical engineering, to prevent actuator saturation in the yaw movement, and the favorable yaw control performance can be guaranteed in the case of external disturbances. Firstly, MMPID method as yaw controller is designed based on the dynamic model of the quad-rotor. MMPID controller has multi-mode characteristic and carries out desaturation strategy under certain conditions. Then, the yaw control system based on MMPID method is proved to be stable using Lyapunov theory. Finally, comparative experiments based on quad-rotor simulation show that MMPID method has significant advantages than variable-structure PID method with respect to the anti-windup performance and yaw control performance. In additon, the validity and robustness of MMPID yaw controller are verified via quad-rotor prototype experiments. Experimental results indicate that the yaw control system based on MMP1D method has nearly no saturation with yaw angle error limited to ±0.05 rad indoors without disturbances. It spends 10 s to exit saturation with yaw angle error limited to ±0.08 rad indoors with disturbances. It spends 5 s to exit saturation with yaw angle error limited to ±0.13 rad outdoors. MMPID controller can effectively prevent actuator saturation in the yaw movement with accurate yaw control and strong robustness for a quad-rotor UAV.