Design of Longitudinal Control for Reduced-Gravity Atmospheric Flights

Reduced-gravity environments created by airplanes have a wide range of potential applications, such as astronaut training and scientific research in zero- or partial- gravity levels.Reduced-gravity flights, casually called parabolic flights, can be achieved by making aircraft follow specific trajectories. This work describes the physics behind reduced-gravity flights and develops a flight control framework for a zero-gravity flight using a proof-mass-tracking approach. During the zero-gravity parabola phase, aircraft has a zero local (non-gravitational)acceleration and be in a state of free-fall, thus causing the sensation of weightlessness. Hence,the control objective is to simultaneously compensate for aerodynamic drag using thrust control and to make lift force zero by regulating the aircraft with the elevator. A triple-integral control structure is adopted to overcome the unknown drag that is expected to grow quadratically with time. Moreover, the position deviation from the reference object is measured in the cockpit to enable a better control performance. Flight simulations are performed and visualized to illustrate the proposed control strategy.

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