Research On Ascent Stage Trajectory Optimization And Guidance For Air-breathing Hypersonic Vehicle

Among hypersonic weapons,the air-breathing hypersonic vehicle using scramjet has become the key development at home and abroad.Because the vehicle has advantages in propulsion efficiency,near space penetration and long time hypersonic cruise.The scramjet ignites and works within a certain dynamic pressure window and angle of attack.The demonstration tests show that a solid rocket boosting is an important prerequisite for the normal ignition of the scramjet.As a result,the design of the ascent stage is related to the success or failure of the entire flight test.The two core issues to be solved in the design of the ascent stage are trajectory optimization and guidance.The trajectory optimization guarantees that the aircraft can achieve the dynamic pressure and attitude conditions required for engine ignition under ideal conditions.And the guidance ensures that the aircraft can still operate on the specified trajectory and ignite successfully through feedback correction in actual environment with drastic changes.In this paper,the trajectory optimization and guidance problems of the boost stage of a certain type of air-breathing hypersonic vehicle are studied.Before dealing with the probelems directly,the scope was determined according to the mission profile of the aircraft.And the simplified longitudinal trajectory optimization particle model and the longitudinal guidance small disturbance linearization model were established.Then,based on the multiple constraints and nonlinearity characteristics of the boost stage,the trajectory optimization methods based on particle swarm optimization and hp-adaptive pseudospectral method are studied.The process of trajectory design and optimization is started from some engineering method.Then the particle swarm optimization algorithm is adopted to optimize the initial launch angle and the angle of attack gradually.Considering that the boost rocket energy is not abundant enough,the hp-adaptive pseudospectral method is implented to optimize the adjust time to avoid the big speed loss when adjusting the attitude.The method is able to get high precision results when the model is simple.Finally,an adaptive dynamic inversion guidance strategy based on modern control theory is mainly studied in the guidance problem.The closed-loop guidance law is designed.And the guidance law based on PID controller is given to verify the effectiveness of the algorithm.The results show that for the trajectory optimization,the particle swarm optimization algorithm used in this paper can meet the end state requirements and the heat flow and overload constraints during flight.Meanwhile,the algorithm results have advantages over the empirical formula optimization results both in the terminal speed and path of angle.The hp-adaptive pseudospectral method based on the optimized trajectory can shorten the passive attitude adjustment time by a quarter and strictly meet the given boundary conditions.For the boost stage guidance,the adaptive dynamic inversion guidance law is easy to adjust for its simple parameters.And the guidance law can achieve the effect of the multi feature points designed PID controller in the boundary condition simulation.What's more,it has better adaptability in Monte Carlo simulation.