Circumventing Unstable Zero Dynamics in Input-Output Linearization of Longitudinal Flight Dynamics

TL;DR

This paper addresses the challenge of unstable zero dynamics in input-output linearization of longitudinal flight dynamics by introducing an additional output, leveraging geometric properties to achieve linearization.

Contribution

The paper proposes a novel method to circumvent unstable zero dynamics in longitudinal flight control by adding an output and exploiting geometric properties.

Findings

Zero dynamics can be stabilized using an additional output.

Linearization is achievable due to specific geometric properties.

The approach improves control design for flight dynamics.

Abstract

In this paper, we consider the problem of input-output linearization of the longitudinal flight dynamics. In longitudinal flight dynamics, inputs are typically thrust and elevator deflection whereas the outputs are the velocity and the flight path angle. An input-output linearization-based controller can be designed to render the multi-input, multi-output system linear; however, the resulting zero dynamics turns out to be unstable. In this work, we remove the zero dynamics from the closed-loop dynamics by considering an additional output. Although the additional output makes the system tall, which, in general, means that the input-to-output dynamics can not be linearized, we show that in the case of longitudinal flight dynamics, linearization is possible due to special geometric properties of the nonlinear terms.