Research On Ascent Guidance Technology Of Hypersonic Vehicle

In this dissertation,for the ascent hypersonic vehicle,the research work is carried out around the research of ascent trajectory design and ascent guidance technology and how to meet the window constraint and the general constraint in the case of uncertain affect for the characteristics such as the harsh of working condition of ramjet engine,general constraint,the strong influence of thrust on trajectory and the strong influence of uncertain factors on flight state.In order to describe the moving state of the hypersonic vehicle in the ascent accurately,A three degrees of freedom motion model is built.The effects of thrust,pitch angle,lift,drag and atmospheric density on trajectory are analyzed,which provides the basis for the design of trajectory and guidance law.The nominal trajectory's design is based on flight corridor,and the flight corridor is described in different digital forms according to the different constraints of power section and unpowered section In the power section,the altitude-velocity flight corridor is design which satisfies all the constraints by calculating the elevation angle-velocity corridor.And then design the appropriate pitch angle nominal profile in the pitch angle-velocity corridor.And then the nominal altitude-velocity is calculated by trajectory parameter algorithm.In the unpowered section,the rate-of-change-in-altitude-altitude flight corridor is design which satisfies all the constraints by calculating the elevation alphaaltitude corridor.And then design the appropriate pitch angle nominal profile in the pitch alphaaltitude corridor.And then the nominal rate-of-change-in-altitude-altitude is calculated by trajectory parameter algorithm.According to the mission of the ascent,the ascent can be divided into the initial ascent,power section and unpowered section.The initial ascent is defined as the stage from takeoff of the vehicle to the speed of 100m/s,the guidance law is not designed in the section because of the low speed and the strong of influence of uncertain factors.The power section is defined from the end of the initial ascent to the shutdown of engine,the altitude tracking guidance scheme is adopted by controlling the value of the pitching angle.The unpowered section is defined from the shutdown of engine to the highest point,the rate-of-change-in-altitude tracking guidance scheme is adopted by controlling the value of the alpha.Finally,simulation environment of six degrees of freedom is constructed to verify the reentry guidance strategy.The simulation results show that the guidance scheme proposed in this dissertationcan meet the window constraint and the general constraint under these uncertainties.