Tracking control for air-breathing hypersonic vehicles based on active disturbance rejection control technique

In order to deal with the inherent characteristics of an air-breathing hypersonic vehicle (AHV) including high nonlinearity, strong coupling, fast-time variability, under-actuation, parameter perturbations as well as uncertainties, the cascade decoupling technique based on the active disturbance rejection control (ADRC) is applied to design a tracking controller during cruise. The tracking strategy designed in this way does not need to ignore the inner-to-outer-loop couplings when the tracking task is performed on the basis of dividing the control system into the inner and outer loops. By using the ADRC, the summation of the parameter perturbations and external disturbances can be estimated on line thus compensated for in the feedback loop, therefore, it is easier to achieve the real-time dynamic feedback linearization. The longitudinal motion dynamics of an AHV is partitioned into two parts, the velocity and rotational (flight-path-angel, angle of attack, and pitch rate) subsystems and, the rotational subsystem is rewritten as the cascade form. Then the rotational subsystem is regarded as the combination of the inner loop (flight-path-angel), middle loop (pitch angle), and outer loop (pitch rate). The ADRC is employed in the velocity subsystem and the three loops of the rotational subsystem to arrive the tracking controller. Numerical simulations show that the designed controller has good robustness and adaptability for the parameter perturbations and external disturbances.