A novel passively coupled VTOL aircraft for arbitrary flying attitude

Abstract

In this paper we present a novel VTOL aircraft design which evolves from our previous work on passively coupled systems. This can be seen as an improvement over our previous drone topology since the present one allows the main hub of the drone to assume any arbitrary orientation, while the center of mass of the main hub is stabilized at a desired point. This design manages to decouple the movement of the center of mass by the movement of the orientation. Therefore the reference for the center of mass of the main hub is independent by the reference for the orientation of the main hub at any point of the trajectory. We derive in detail the full nonlinear model using D’Alembert’s principle and propose a fully nonlinear control techniques composed of two cascaded controllers. The inner loop controller performs an additional optimization step to assign commands to eight rotors such that six variables are fully controlled. The outer loop controller upon solving a nonlinear algebraic equation provides the required references to the inner loop controller such that a six degrees of freedom reference (trajectory of the c.o.m and attitude of main body) is followed with vanishing error. Simulations of the mathematical model as well the proposed control law for different types of trajectories are also presented.