可重复使用运载器预测制导与鲁棒容错控制

为实现可重复使用运载器(Reusable launch vehicle, RLV)的再入段准确制导与鲁棒容错控制,提出了一种基于改进预测校正制导律和鲁棒容错姿态控制联合的方法.首先,设计改进倾侧角幅值模型和航迹方位角走廊的预测校正制导律,结合标称迎角剖面,在线计算得出姿态系统的输入指令;然后,针对控制系统的不确定/干扰及舵面部分失效问题,提出一种改进跟踪微分干扰观测器来估计不确定/干扰和舵面失效作用,通过在观测器中增加前馈项进一步提高了复合干扰的估计精度;最后,针对舵面饱和问题设计辅助抗饱和系统,并应用sigmoid饱和函数来改善姿态系统中角速率回路反步法的控制性能.制导与控制系统的六自由度联合仿真实验表明,在考虑姿态回路复合干扰、舵面部分失效及饱和的情况下,RLV准确跟踪了姿态角指令,其飞行轨迹能够到达再入终端落点区域并满足约束条件,因此提出的方法实现了再入段准确制导,较好解决了姿态回路不确定、舵面部分失效及饱和问题,具备良好的鲁棒容错控制性能.

Predictive guidance and robust fault-tolerant control for RLVs

A joint design based on improved predictor-corrector guidance and robust fault-tolerant attitude control was proposed to realize the re-entry accurate guidance and robust fault-tolerant control for reusable launch vehicles (RLVs). First, an improved predictive guidance law with modified magnitude model of bank angle and corridor function of track angle was designed. Combined with the nominal profile of the angle of attack, the input command of the attitude system was calculated online. Then, a modified tracking differential disturbance observer was presented to estimate the system uncertainty/disturbance and the actuator faults. The estimation accuracy of compound disturbance was further improved by adding feed-forward term to the observer. Finally, an auxiliary anti-saturation system was designed to tackle the problem of the saturation of control surfaces, and a sigmoid saturation function was utilized to enhance the control performance of the backstepping method in the angular rate loop. Simulation test on 6 degree-of-freedom (DOF) guidance control system shows that the RLV was capable of tracking attitude angle commands precisely in the presence of the compound disturbance of attitude system, the actuator faults and saturation, and the RLV trajectory reached the re-entry terminal area with satisfying constraints. Thus, the proposed method can realize the re-entry guidance accurately and solve the problems of attitude system uncertainty, actuator faults and saturation, indicating its satisfactory robustness and fault-tolerant capability.