Robust adaptive control of hypersonic vehicles via Backstepping method

A robust adaptive Backstepping control approach is proposed for a hypersonic vehicle. The vehicle model is nonlinear, multivariable, and unstable and includes uncertain parameters. The command filtered approach is used to generate the tracking commands and their first derivatives of inner loop, so that the tedious analytic computation of virtual control signal derivatives is avoided. The uncertain parameters are adapted online by Lyapunov-based update laws. With the design of assistant filters and the use of a modified definition of tracking errors in the update laws, where the effect on tracking errors due to the implementing limits of desired control signals is removed, a stable parameter estimation process is ensured even when constraints on the control signals are in effect. Simulation results show that the proposed approach is not only simple to apply, but also achieves the closed-loop stability in the presence of uncertain parameters as well as good tracking performance.