Research On Longitudinal Guidance And Control Technology Of Unpowered Dropping For Reusable Launch Vehicle

Unpowered dropping experiment is the key and difficulty of reusable launch vehicle unpoweredlanding. It includes not only the issues of landing, but also the dropping. This paper studies the keytechnical issues of the RLV characteristics, trajectory, longitudinal guidance and control.In the characterization of RLV, the aerodynamic layout and rudder allocation are given at first.Then, this paper analyzed the longitudinal aerodynamic characteristics and longitudinal static stability,given the result of linearization, and analyzed longitudinal modal on the basis of the trim. The objectcharacteristics analysis provides the basis to trajectory design, guidance and control law design.Unpowered dropping trajectory shapes and mathematical descriptions are given in this paper.Unpowered dropping trajectory is designed using the trajectory design method based on height profile,and the trajectory robustness is assessed. The design approach of unpowered dropping area isprovided to solve the problem caused by uncertainty of dropping location and velocity.Longitudinal guidance is divided into four phases. According to the task and particularity of eachphase, guidance strategies of the various phases and results of simulation are given.Because the Shortcoming of basic guidance strategy, this paper proposes a new guidance strategy,called capture phase safety guidance strategy based on airspeed protection. Simulation results showthat the safety guidance strategy can expand the dropping area effectively, tolerate greater uncertaintyand lower dropping speed.According to the longitudinal control strategy, attitude control law, height control law, and speedcontrol law are designed. Through expression alteration uniting the control and guidance, and makingthe guidance results can be used to control. Simulate the control law in different trim point.Finally, this paper has set up a simulation platform base on M language. The simulation uses themethod of Monte Carlo, and involves environmental uncertainty, pneumatic uncertainty and droppinguncertainty. Results show that guidance and control system are correct and robust.