A Trajectory-Optimization Framework for Transition-Phase Control of Small-Scale Thrust-Vectoring V/STOL Air Vehicles

Abstract

The controllability envelope of a vertical/short take-off and landing (V/STOL) air vehicle during transition is dictated chiefly by the orientation of the thrust-vectoring nozzle, whose time-history must be chosen so as to reconcile actuator saturation, stall limits, and mission-level performance indices. This paper advances a fully model-based pipeline in which the transition corridor is constructed directly from an attainable-equilibrium-set (AES) projection of the longitudinal dynamics, rather than by assembling piecewise envelope fragments. A scaled F-35B-class prototype equipped with a three-bearing swivel duct (3BSD) nozzle and a lift fan is adopted as the reference platform, and the coupling between the propulsive jet and the airframe flow field is embedded in the dynamic model through empirical jet-induced-loss closures. The redundancy inherent in the multi-actuator longitudinal channel is resolved by a mode-dependent control-principle map that exposes only four pilot handles and delegates actuator assignment to a regularised pseudo-inverse allocator. On top of this architecture, the full transition problem is recast as a continuous-time optimal-control problem with mission- and handling-quality constraints, then converted into a finite nonlinear programme via Hermite-Simpson collocation and solved with a sequential quadratic programming (SQP) method. Numerical experiments on four canonical missions demonstrate that the framework simultaneously respects the AES-derived corridor, produces pilot-compatible stick time-histories, and improves smoothness and energy metrics relative to heuristic schedules.