Control Design and Analysis for Reduced Gravity Atmospheric Flights

Abstract

Microgravity environments have a wide range of potential applications, such as astronaut training and scientific research in weightlessness or at partial-$g$ levels, which helps humans move toward space exploration. Parabolic flights are one way to simulate microgravity on Earth, which can be achieved by making aircraft follow specific flight trajectories. This work describes a kinematic and dynamic analysis of general partial gravity cases and develops a flight control framework for a zero-gravity flight using a proof-mass-tracking approach. During the zero-gravity parabola phase, aircraft will have 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 minimize lift force by regulating the elevator.

A triple-integral control structure is adopted to overcome unknown, quadratically increasing drag, based on an internal model principle. Furthermore, to avoid the non-minimum phase characteristics of aircraft longitudinal dynamics, the position deviation from the inertial reference is redefined such that the closed-loop system is minimum phase. Flight simulations are demonstrated to validate the proposed control strategy and are visualized in the open-source flight simulator FlightGear.