Research On Reaction Control System Of Reentry For Reusable Launch Vehicle

The Reusable Launch Vehicle(RLV)has two sets of executive mechanism: Reaction Control System(RCS)and aero-surfaces.Along with the increase of dynamic pressure,the reentry control can be divided into three stages: the RCS control,the compound control of RCS and aerodynamic and the aerodynamic control.This paper mainly focus on the research of RCS control and compound control of reentry for RLV.RLV reentry modeling is the precondition of reentry control problem.Firstly,the mechanical model of RCS and aerodynamic is established.Then,the kinetic equation is linearized with small deviation,and the linear control model of RCS can be obtained.By analyzing the characteristics of RCS control,the RCS control problem can be divided into three sub-problems: the design of RCS control law,Jet Select Logic(JSL)of RCS and Pulse-Width Modulation(PWM)algorithm.The three channel RCS control law based on attitude deviation is designed by using the classical PD control method.Three kinds of JSL are studies in this paper: axis-based selection,level-based selection and selection based on linear programming,on this basis,RCS flow and RCS fault analysis are carried out.For the PWM problem,the impulse equivalence principle of PWM is introduced in detail,then the meanings of three control dead zones are analyzed.Through the nonlinear simulation,the feasibility of RCS control law,JSL and PWM is verified,so the RCS control problem is solved preferably.The compound control problem also can be divided into three sub-problems: determination of switching time of compound control,the design of compound control law and the study on compound allocation strategy.Firstly,the timing of the RCS quit are determined by analyzing the efficiency of the aero-surfaces.After that,considering that the compound control law in this paper is composed of two parts: RCS and aerodynamic,so,after the design of the RCS control law,the conventional aerodynamic control law is designed according to the analysis of the aerodynamic characteristics and the lateral deviation characteristics.Finally,a compound allocation strategy based on the allocation of attitude angle deviation is proposed,then the compound allocation problem can be transformed into optimization problem,so the particle swarm optimization(PSO)algorithm can be used to optimize the weight coefficient.The compound allocation strategy based on PSO algorithm can achieve more smooth control effects.