Adptive Entry Guidance And Control Method For RLV

Significantly more safe,reliable and autonomous is the goal of next generation reusable launch vehicles(RLVs).However,conventional guidance system and control system is designed seperately,which cost more time and hard to handle unexpected circumstances such as actuator failures.With poor adaptability and task autonomy,RLV cannot guarantee its safety reentry and return.This paper summed up RLV and its advanced guidance & control technology development,studies the adaptive guidance & control(AGC)system,and applies it to the reentry phase for RLV.The study contents mainly include the following aspects.Firstly,a three-loop AGC system is proposed based on online trajectory planning,adaptive guidance and reconfigurable control.According to the reentry flight mission characteristics of RLV and the features of the vehicle shape and structure,this paper analyzes the possible actuator failure mode in the reentry process,shows the basic frame of the AGC system,and gives a brief description of its subsystems.Secondly,a reconfigurable control algorithm via adaptive PID control is investigated,it has a good ability of anti-interference and strong adaptive.Through the linearization transformation of original entry control problem,a two-loop controller with inner and outer loop is designed.The outer loop tracks attack angle,sideslip angle and bank angle,while inner loop follows roll,pitch and yaw angular velocity.Considering all possible actuator failures,this paper designed a reconfigurable controller based on adaptive PID controller and pesudo-inverse control allocator.Simulation results show the availability and validly of reconfigurable control.Thirdly,an adaptive guidance algorithm is present which combines trajectory tracking guidance,trajectory linearization control and backstepping guidance.Trajectory planning model considers all constraints and provides a flyable trajectory for guidance to track.Based on trajectory linearization control,this paper proposes a trajectory tracking guidance structure with altitude loop and velocity loop,and then gives the parameter setting method for closed loop dynamic matrix.An adapting for guidance algorithm above based on backstepping is set out,this promotes guidance system and control system to work together so that it finally realise the attitude control and states track under actuator failures.Simulation results show that this algorithm can adapt to different missions and has a high guidance precision,and trajectory tracking can be re alised in failure mode with control system work together.Meanwhile,the application of memory-based optimization for online RLV trajectory planning is studied.The algorithm consists of memory model,stimulus type,search strategies,fogetting and memory updating module.The stimulus-type judgment module determines the quality of the alternative solutions according to the change of the objective function value.The search strategy module gives five flexible search strategies,which assures the global optim ality and fast convergence.The forgetting and memory update model calculates the residual value of the total memory,and finally chooses the alternative solutions with the largest residual memory value as optimum solutions.The simulation results show tha t the algorithm has some advantages in convergence speed,convergence precision and global optimality.It also proves that it is feasible to apply the memory optimization algorithm to the online trajectory planning for RLV.Finally,the specific workflow of the AGC system for RLV in reentry phase is studied.A single actuator jammed failure is simulated and analyzed to preliminarily grasp the usable range of actuators that ensures the safe return of the RLV.Considering all kinds of interference,a Monte Ca rlo simulation is carried out when multiple actuators fails at the same time,and the success rate of reentry of RLV after using the conventional guidance & control system and the AGC system is compared and analyzed.Monte Carlo results show that the AGC system can meet the design requirements of RLV,and it has well reliability,autonomy and safety,and can adapt to various flight environment and most of the actuator failures.