Research On Longitudinal Control Methods For Cruise Phase Of Hypersonic Vehicle

Hypersonic vehicle, which has extremely rapid response and attack ability, is theresearch focus among spacecrafts for most countries in the new century. However, thenonlinearity, uncertainty and strong coupling in dynamics of the vehicle make a lot ofchallenges for the design of the control system. In this paper, the control methods for thelongitudinal model of hypersonic vehicle during its cruise process are mainly studied.Firstly, according to the flight environment and its own characteristics, a full-statemodel and a longitudinal model of hypersonic vehicle are established. Referring to thedata of Winged-Cone test vehicle by NASA, the model of sub parts such as force,moments and etc are presented, which will lay the foundation for the subsequentcontroller design.In the next place, dealing with the small perturbation linearization method, thelongitudinal model is reduced to an approximate linear model. After that, two linearcontrol laws are designed for the system. One of them is asymptotic tracking control lawbased on pole assignment solving the tracking task of speed and height. The other isdynamic decoupling control law with compensator, which separates speed loop fromheight loop so that a PID controller can be added to each loop independently. In addition,considering about the overall robustness of the system, we will expand the concept oftraditional SISO stability margin to give an algorithm to analyze the stability margin ofthe designed hypersonic flight control system.Finally, two nonlinear control algorithms are designed directly with the nonlinearlongitudinal model of the vehicle in presence of parameter and disturbance uncertainties.In the whole process, an exact linearization model that is equivalent to the origin systemmodel is obtained based on differential geometry theory at first. Then, with respect todifferent kinds of uncertainties, an sliding mode control law and an backstepping controllaw are designed with robustness to realize the tracking of speed and height during cruiseprocess.