离散RCS的PWPF调制方式改进及混合控制逻辑设计

可重复使用飞行器(RLV)再入控制常涉及离散的反推力控制系统(RCS)和连续的气动舵面的混合控制,其中避免离散RCS出现极限环振荡和混合控制的逻辑是设计的关键问题。为此,对应用脉宽脉频(PWPF)调制的离散RCS进行极限环振荡行为的离散描述函数法预测,推导极限环出现条件,设计了一种前置非对称死区环节规避极限环而不损失性能,在此基础上提出便于工程应用的RCS与气动舵面混合控制逻辑。通过对典型飞行器的控制仿真验证表明,改进的离散RCS的PWPF调制方式及设计的混合控制逻辑能够获得良好的控制效果,满足控制要求。

An Improvement on PWPF Modulation of Discrete RCS and Design of the Blended Control Logic

The re-entry control of reusable launch vehicles(RLV) often involves both discrete reaction control system(RCS) and continuous aerodynamic controls,in which the avoidance of limit cycles and the blended control logic are the key issues of design.In this paper the limit cycle oscillation behavior of the discrete pulse-width and pulse-frequency(PWPF) modulation is predicted by application of the discrete describing function analysis technique,the appearance conditions are then derived,and an asymmetric dead zone is further constructed and used in the forward path to eliminate the limit cycle oscillations,without performance loss.Based on the improved PWPF modulation,a RCS and aerodynamic surfaces blended control logic is designed with concern on implementation.Simulations on the control of a typical RLV show that the improved discrete PWPF modulation and the blended logic work satisfactorily to the requirements of control.