Investigation On Control Technology For Hypersonic Vehicle During Cruise Phase

Air-breathing hypersonic vehicle has characteristics of fast velocity, high cruisealtitude and maneuvers, etc, and it is of special strategic significant in both the themilitary and commercial areas. Therefore, it attacks an ever increasing attentionworldwide. However, there is a strong inherent coupling among the aerodynamics,propulsion, structure and control dynamics due to the adoption of the scramjet engine,airframe/engine integrated design and other advanced technologies, and this leads to ahigh nonlinear dynamic model and serious uncertain. At the same time, a series ofdifficulties are encountered by the control system design because of control systemparameters and engine thrust both being extremely sensitive to changes in flightconditions.In this dissertation, the control problem in the cruising phase of the air-breathinghypersonic vehicle is studied, in particular on the longitudinal control and bank-to-turn(BTT) control. Additionally, the longitudinal control include angle of attack control atsteady-state and longitudinal maneuver control, and the BTT control performs theinvestigation on the attitude control problem.First of all, a six degree-of-freedom (6DOF) simulation model of a conceptualair-breathing hypersonic vehicle is presented, according to the available literatures andits flying characteristics during the cruising phase, and it includes the whole of kineticequations and motion equations. Aerodynamic and engine thrust coefficients are givenas functions of angle of attack, mach number, height and control surface deflections.Subsequently the longitudinal control and BTT control models are established.Open-loop dynamics and stability characteristics analysis demonstrates that theproposed model can reflect complex the nonlinear, coupling and fast time-varyingcharacteristics of the hypersonic vehicle, and it can provide a platform for the design ofnonlinear decoupling and robust performance of a controller.In the angle of attack control at steady-state, the control/stability characteristics areanalyzed, and three kinds of control law based on fuzzy PID, adaptive sliding modewith reference model and adaptive global sliding mode are designed respectively. Thecontrol scheme emphasises on the output of the system tracking the anticipant signalsfast and accurately with uncertain parameters and serious disturbance.In the longitudinal nonlinear uncertain model control, the non-linear feedbacklinearization control is employed as an inner loop to convert the complex nonlinearmathematic model into equivalent linear model accurately for control design, match andmismatched uncertainties control problems respectively, and then a sliding mode and abackstepping sliding mode are proposed as outer loops for the controllers, the globalstability and robustness of the closed-loop is guaranteed. In the decoupling control for linear model of BTT hypersonic vehicle, a robustcontrol approach for roll channel based on adaptive global integral sliding mode isproposed, and a decoupling autopilot is designed for pitch/yaw channel usingmultivariable frequency domain approach based on the Nyquist array method. Thecross-coupling is decreased with a proportional-integral (PI) model percompensatormatrix, which has much better affect than the ordinary first-order precompensationmatrix. A main-controller is then designed for the approximately decoupled system tomeet the requirement of the desired dynamic performance and stable accuracy throughpole placement design method for an independent system.In the decoupling design for nonlinear uncertain model of BTT hypersonic vehicle,an adaptive global integral sliding mode control approach is proposed to solve theuncertainties, which satisfy the generalized matching conditions. This methodguarantees the system robustness during the whole control process and eliminates thecross-coupling at the reaching phase. The sliding mode error caused by disturbance andperturbation is weakened with feedback, and the efficient decoupling and robustnessduring the whole control process is achieved. For the condition of the uncertaintiesdissatisfying the generalized matching conditions, a backstepping sliding modecontroller is designed, and a global integral sliding mode is introduced at each step ofthe backstepping design, which makes the initial state of the system locate on the slidingmode. The dummy control is obtained based on the Lyapunov stability theorem step bystep, and all the state is balanced and the output is traced progressively.