Enhanced trajectory linearization control based advanced guidance and control for hypersonic reentry vehicle with multiple disturbances

In this paper, the guidance and control problem for hypersonic reentry vehicle (HRV) in the presence of control constraints and multiple disturbances is handled based on unified enhanced trajectory linearization control (TLC) framework under reference-tracking methodology. First, based on the nominal trajectory and open-loop command generated by Gauss pseudo-spectral method (GPM), a time-varying feedback guidance law with integral action is synthesized to stabilize the tracking error dynamics along the nominal trajectory under the framework of TLC. Second, to improve the robustness of attitude and angular rate loop, variations of various aerodynamic coefficients and external disturbances are considered as lumped uncertainties, reduced-order linear extended state observers (LESO) with given model information are constructed to estimate the lumped uncertainties in each loop, respectively. In addition, comparisons between the estimation efficiency of LESO and reduced-order LESO are carried out. Then augmented with the disturbance estimates and TLC control law, tracking errors of the rotational dynamics can be actively rejected without sacrificing nominal performances. More importantly, fewer control consumption and smooth transient performances are achieved by using nonlinear tracking differentiator (TD) in attitude loop. The stability of the resulting closed-loop system is well established based on Lyapunov stability theory. Finally, the effectiveness of the proposed advanced guidance and control strategy is verified through extensive simulations on the six-degree-of-freedom reentry flight.