Abstract
A hypersonic vehicle uses the airbreathing scramjet engine and the airframe and engine integrated design. Therefore, there is a strong cross-coupling effect among its aerodynamic force, thrust, structure, and control. The nonlinearity and uncertainty of the model cause difficulties in control system design. Considering the nonlinearity, coupling characteristics, and aerodynamic parametric uncertainty of its longitudinal dynamic model, we design the control law for its altitude system and velocity system based on the adaptive backstepping control method. Because of the feedback linearization method, we introduce the constraints of the flight vehicle’s actuator into the design, obtaining the robust adaptive control system constrained by the actuator of the flight vehicle. To avoid the high-order derivation problem of the feedback linearization method and the derivation of the virtual control volume in adaptive backstepping control method, we use the arbitrary-order robust exact differentiator to solve the high-order derivatives in feedback linearization and utilize the command filter to obtain the virtual control volume and its derivatives. The simulation results show that the robust adaptive control system we designed can achieve the error-free tracking of altitude and velocity command. It can well overcome the influence of structural parameters, aerodynamic parametric uncertainty, and disturbances; meanwhile, the control command can satisfy the constraints of the actuator.
Highlights
A hypersonic vehicle flies fast and has a large altitude range, and its parameters vary with time greatly
Taking into account the input coupling and modeling uncertainty problems that exist in the application of the feedback linearization method, Rehman et al [6, 7] proposed the robust feedback linearization and minimax linear quadratic regulator (LQR) hybrid control method
The deflection comparison results show that the backstepping control method can well suppress the uncertainties of structural parameters and aerodynamic parameters in the model of hypersonic vehicle and track its velocity and altitude, tracking errors being within the tolerable range, and that eventually all the state variables can reach their steady-state values
Summary
A hypersonic vehicle flies fast and has a large altitude range, and its parameters vary with time greatly. Jianfei et al [13] proposed the adaptive backstepping terminal sliding mode control method for an uncertain nonlinear system with a class of strict feedback parameters, which enabled the last state of the hypersonic vehicle to converge within a limited time; the hypersonic vehicle was robust to both matching and nonmatching uncertainties. To solve velocity and altitude tracking control problem of a hypersonic vehicle, we combine the feedback linearization method with the backstepping control method and introduce the actuator constraints into the control law design. This method can decouple the altitude and velocity of the hypersonic vehicle and enhance the control system’s robustness to parametric uncertainty and its commandtracking speed, within a reasonable control command scope
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