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Mathematical Problems in Engineering
Volume 2014 (2014), Article ID 471352, 12 pages
http://dx.doi.org/10.1155/2014/471352
Research Article

Designing a Robust Nonlinear Dynamic Inversion Controller for Spacecraft Formation Flying

1Center for ICT and Automobile Convergence, Kyungpook National University, Daegu 702-701, Republic of Korea
2School of Electronics Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea

Received 18 April 2014; Accepted 1 July 2014; Published 17 July 2014

Academic Editor: Vivian Martins Gomes

Copyright © 2014 Inseok Yang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The robust nonlinear dynamic inversion (RNDI) control technique is proposed to keep the relative position of spacecrafts while formation flying. The proposed RNDI control method is based on nonlinear dynamic inversion (NDI). NDI is nonlinear control method that replaces the original dynamics into the user-selected desired dynamics. Because NDI removes nonlinearities in the model by inverting the original dynamics directly, it also eliminates the need of designing suitable controllers for each equilibrium point; that is, NDI works as self-scheduled controller. Removing the original model also provides advantages of ease to satisfy the specific requirements by simply handling desired dynamics. Therefore, NDI is simple and has many similarities to classical control. In real applications, however, it is difficult to achieve perfect cancellation of the original dynamics due to uncertainties that lead to performance degradation and even make the system unstable. This paper proposes robustness assurance method for NDI. The proposed RNDI is designed by combining NDI and sliding mode control (SMC). SMC is inherently robust using high-speed switching inputs. This paper verifies similarities of NDI and SMC, firstly. And then RNDI control method is proposed. The performance of the proposed method is evaluated by simulations applied to spacecraft formation flying problem.