ESO based nonlinear dynamic inversion control for hypersonic flight vehicle

In the presence of parametric uncertainties and external disturbance for the longitudinal model of a Hypersonic Flight Vehicle (HFV), a scheme of Extended State Observer (ESO) based Nonlinear Dynamic Inversion (NDI) control is exploited in this paper. The decoupling of velocity and altitude is realized by adopting Exact Feedback Linearization (EFL) technique, and then the NDI controller is designed. In order to estimate the equivalent disturbance precisely, a second-order ESO is designed for the velocity subsystem and altitude subsystem. The estimated equivalent disturbances values are used as a compensation in NDI controller. Hence, the precise reference command tracking of velocity and altitude is achieved, which enormously improves the ability of disturbance rejection while the control accuracy is ensured. The simulation results and their analysis demonstrate that, comparing with Sliding Mode Control, the proposed methodology in this paper has better response speed and tracking accuracy which indicates good control performance and robustness of the method.