基于LADRC的无人直升机轨迹跟踪

无人直升机轨迹控制系统是对多输入/多输出强耦合非线性系统进行解耦控制的系统。为解决无人直升机轨迹控制效果依赖于直升机物理参数的测量和辨识精度以及外部扰动大小问题,提出了一种基于线性自抗扰控制(LADRC)的多回路无人直升机轨迹控制系统。首先建立无人直升机X-Cell的飞行动力学模型,并引入风切变、大气紊流和突风模型以更加准确模拟真实飞行环境;然后对X-Cell进行配平计算以验证动力学模型和配平算法的准确性,并选取一组配平值作为轨迹控制仿真的初始状态和操纵量;随后根据被控量的动力学方程阶次选取对应的一阶和二阶LADRC基本控制器,并结合时间尺度原理,自内向外依次构建无人直升机的姿态、速度和位置控制回路,将三回路串联从而建立了无人直升机轨迹控制系统;而后进行了稳定性分析,特征根计算结果表明轨迹控制系统镇定了X-Cell开环系统不稳定的动态特性;最后将该控制系统应用于各种扰动下直升机轨迹跟踪仿真,结果表明本文无人直升机轨迹控制系统能很好地实现带爬升率的"8"字形轨迹跟踪,且相比于基于比例积分和微分(PID)控制的轨迹控制系统,该控制系统具有更优的鲁棒性和抗扰性。

LADRC-based trajectory tracking for unmanned helicopter

Trajectory tracking control system is used for decoupling the control unmanned helicopter, which is a nonlinear system with multi-input/multi-output and strong coupling effects. In order to avoid the dependence on accuracy of unmanned helicopter physical parameters measurement and identification and to reduce external disturbance impact, a multi-loop controller based on linear active disturbance rejection control (LADRC) is proposed. At first, the flight dynamics model is built for unmanned helicopter X-Cell. The atmospheric disturbance model, which contains wind shear, turbulence and gust model, is also set up for accurate simulation of real flight environment. Secondly, X-Cell is trimmed for verifying the accuracy of dynamic model and trim algorithm. A set of calculation values is selected as the initial state and input of the subsequent simulation. Then attitude, velocity and position control loop are built based on the first-order and second-order LADRC controllers which are selected according to system order. Combined with the time-scale separation principle, the whole trajectory control system is constructed from inner loop to outer loop. After that, the stability of the system is analyzed. The characteristic roots show that the whole system becomes stable with the trajectory controller. Finally, flight simulation experiments under various disturbance conditions are performed. The results show that the established control system can achieve a good climbing figure-eight trajectory tracking. Compared with controller based on proportion integration differentiation(PID), the controller based on LADRC has better robustness and capability of anti-disturbance.