Aeroelasticity Modeling And Robust Gain-Scheduling Control Of Hypersonic Vehicle

With windely application in civil and military fields, hypersonic vehicles have drawn attention from military powers allover the world, leading to a main research direction of aerospace flight technology. The large Mach number of hypersonic vehicle brings great advantages over conventional aircrafts, together with many technical challenges at the same time. From the perspective of control science, these challenges mainly include:the coupling among aerodynamic, elasticity, and control system; the coupling between air-frame and engine; the violent change of system parameters owing to large span flying; the low efficiency of control surface; the condition that the closed loop system is always in critical stable state. This paper mainly focuses on the aeroelastic problem of hypersonic vehicle, and aims at the existing problems in aeroelastic analysis and control-oriented models. According to the research approach of problem analysis, model establishment, problem posing, control method, controller design and synthesis, the aerodynamic force and elastic deformation are analyzed, together with the relationships between them. By in-troducing new variables, the nonlinear dynamic model of the vehicle is established. Aim-ing at the uncertainty and parameter varying problem, related control algorithms are pro-posed respectively. A complete controller design and synthesis method is provided. The attitude stabilization in the process of cruising and large span flying is guaranteed.The airframe surface’s airflow partition characteristic of conformation X-43 A hy-personic vehicle in hypersonic flow is analyzed, and the relationships are given with air-flow characteristics of different airframe surfaces, height, velocity and attack angle. The unsteady aerodynamic forces of different airframe surfaces and upper and lower control surfaces are analyzed by using local flow piston theory, and the resultant of forces and torques that the vehicle gets when in flying process are given, which makes a foundation for subsequent works of analysis of relationships between aerodynamics and elasticity; model establishment of hypersonic vehicle; flight control system design.The free oscillation and static elastic deformation of hypersonic vehicle are ana-lyzed, and the airframe front end deflection equations are given when vehicle is under aerodynamic forces on different surfaces of airframe. Based on the inherent connections between aerodynamics and elasticity, the concept of induced attack angle is proposed that the dynamics of induced attack angle has a concise form of expression and it is able to describe the characteristics and relationships between unsteady aerodynamic force and elastic deformation. The flight dynamic model of hypersonic vehicle is established by using Lagrange equations. By analyzing the relationships between induced attack angle and different variables of rigid body motion, the rigid body model is modified, and the nonlinear dynamic equation of hypersonic vehicle is given which contains aeroelasticity information. The given aeroelastic model of hypersonic vehicle is a foundation for sub-sequent work of control system design.Aiming at the problems that hypersonic vehicle has model uncertainty and parameter uncertainty, gusty wind disturbance and violent changes of system parameters due to large span maneuver flight, the problems come down to standard H∞ problem under the frame-work of LPV systems. Based on the characteristics of polynomial systems, LPV robust gain-scheduling control algorithm is given by using affine parameter dependent Lyapunov method. By utilizing the thought of mixed sensitivity, the synthesis method of robust gain-scheduling is given. Subsequently, LPV system model is established by treating height and velocity as scheduled variables, and then transform the model into polynomial LPV system form. By choosing appropriate weight function and solving LMI problem, the H∞ robust gain-scheduling controller is synthesized. The designed controller is applied to solve the problem of attitude stabilization when hypersonic vehicle is in cruise phase and maneuver phase. Simulation results show the controller can effectively guarantee sys-tem’s stability under the existence of disturbance and uncertainty. As a comparison, the control effect of a single point controller is given which is based on LTI system design and under a corresponding flight condition. The comparison result shows that LPV robust gain-scheduling controller has better performance in maneuver phase.According to the flight task requirements of hypersonic vehicle, trajectory tracking control system is designed. Based on the frequency band separation principle, the con-trolled object is divided into high frequency circuit and low frequency circuit. By adopting multi-loop control structure, an LPV attitude stabilization controller and trajectory track-ing controller are synthesized separately. The obtained controllers are applied to track the universal periodic decay trajectory and X43-A climb test flight trajectory. Simulation re-sults show that the controllers can effectively guarantee that the vehicle follows the given trajectory instruction.