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CEAS EuroGNC 2026

Robustness Analysis and Comparison of Linear and Nonlinear Control Approaches: an Application to Launch Vehicles
João T. Diz PhD Candidate/GNC Engineer, TU Delft/Indra Deimos, Control & Simulation/GNC Team, 2628 CD/1070-061, Delft/Lisbon, The Netherlands/Portugal.
Paulo Rosa Head of Flight Segment, Indra Deimos, Avenida Columbano Bordalo Pinheiro 85, 1070-061 Lisbon, Portugal.
Spilios Theodoulis Associate Professor, Technical University of Delft, 2628 CD Delft, Netherlands.
Pedro Simplício GNC Engineer, European Space Agency, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands.
Paul Acquatella GNC Engineer, European Space Agency, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands.
Abstract:
This paper presents a robustness assessment and a comparison of three control techniques: Nonlinear Dynamic Inversion (NDI), Incremental Nonlinear Dynamic Inversion (INDI), and H-infinity Loop Shaping (LS). The methods are evaluated in the context of launch vehicle (LV) attitude control, making use of linear analysis tools to assess performance and robustness. The study proceeds in two stages. First, the linear versions of NDI and INDI are used to invert the launch vehicle system. The input-output singular values of four systems are then compared: the two inverted systems, a shaped plant from an H-infty LS controller, and the open-loop system. The results show that the inversion strategies naturally achieve singular value patterns similar to the H-infinity design with minimal designer intervention, although inherent limitations are identified. Second, an outer-loop controller is added to the linear INDI system and tuned by shaping the closed-loop singular values. The resulting controller is compared, in terms of performance and robustness, to an H-infinity LS controller and to a controller employing the LV state-of-the-art architecture. The analyses confirm the superiority of the H-infinity LS controller, and that the limitations inherent to the inversion strategies cannot be fully mitigated by outer-loop control. Nevertheless, the tuned inversion-based controller meets all design requirements and surpasses the performance of the state-of-the-art approach. Overall, this paper illustrates that NDI and INDI, when applied to LV attitude control, can achieve most — though not all — of the performance and robustness of linear robust control approaches. This is achieved with lower design complexity, highlighting the practical use of these techniques for flight control system design.
Keywords: Nonlinear Dynamic Inversion; Incremental Nonlinear Dynamic Inversion; Launch Vehicle; Robust Control; Nonlinear Control
 View PDF CEAS-GNC-2026-018 doi: 10.82124/CEAS-GNC-2026-018


João T. Diz, Paulo Rosa, Spilios Theodoulis, Pedro Simplício, Paul Acquatella: Robustness Analysis and Comparison of Linear and Nonlinear Control Approaches: an Application to Launch Vehicles. Proceedings of the 2026 CEAS EuroGNC conference. Madrid, Spain. May 2026. doi: 10.82124/CEAS-GNC-2026-018.
BibTeX entry (UTF-8):

@Incollection{CEAS-GNC-2026-018,
    author = {Diz, João T. and Rosa, Paulo and Theodoulis, Spilios and Simplício, Pedro and Acquatella, Paul},
    title = {Robustness Analysis and Comparison of Linear and Nonlinear Control Approaches: an Application to Launch Vehicles},
    booktitle = {Proceedings of the 2026 {CEAS EuroGNC} conference},
    address = {Madrid, Spain},
    month = may,
    year = {2026},
    doi = {10.82124/CEAS-GNC-2026-018}
}