In this paper, a longitudinal dynamic model of a variable-sweep-wing morphing aircraft is proposed based on the Firebee unmanned aerial vehicle (UAV), accounting for changes in aerodynamic and inertial properties. Wing geometries and aerodynamic performance are also analyzed in six morphing configurations. The eigenvalues, damping, and frequency are investigated within short-period and phugoid modes. In addition, a classic proportional–integral–derivative (PID) controller is designed with different gains according to six morphing configurations. In three degrees of freedom (DOF) nonlinear simulations, the morphing aircraft maintains a straight and level flight in dash configuration at first and then changes to a loiter configuration at a fast and slow morphing rate. Except for the morphing moment caused by wing gravity, other morphing forces and moments can be ignored. Simulation results show that the designed controller works well with good trajectory-tracking performance, and a larger morphing rate leads to greater magnitudes in attitude, velocity, and altitude variations.

With the fast development in aeronautical technology, aircraft are evolving towards a wider speed ranging from subsonic, transonic, and supersonic to hypersonic speeds. The variable-sweep-wing morphing waverider provides an effective way to meet the demanding wide-speed and long-range flight requirements. However, the special morphing mechanism, variable stability margin, and the aero-thermal heating of the morphing waverider, altogether impose difficulties and challenges on its flight tracking control problem, especially under parameter uncertainties, input saturation, and state constraints. To handle this issue, a six-degrees-of-freedom (6DOF) Barrier-Lyapunov-Function (BLF) based nonlinear model predictive controller (NMPC) consisting of two loops is proposed in this paper based on the control-oriented model of a symmetric-sweep-wing morphing waverider. Specifically, a virtual control signal of three-axis angular rates is provided by the BLF based outer-loop NMPC to not violate the flight constraints, combined with an auxiliary system according to the desired angle of attack, sideslip angle, and bank angle. Then, the desired virtual control signal is modified by a saturation function and a first-order command filter, and the control commands are generated by the BLF based inner-loop NMPC to deal with the input saturation by an auxiliary system. Meanwhile, a nonlinear disturbance observer is applied to estimate the morphing moments considering parameter uncertainties. The stability of the overall closed-loop system is analyzed by the Lyapunov stability theory. Finally, the performance of the controller is investigated via extensive and comparative numerical simulations.