Flat singularities of chained systems, illustrated with an aircraft model

Yirmeyahu Kaminski, François Ollivier

Research output: Contribution to journalArticlepeer-review


We consider flat differential control systems for which there exist flat outputs that are part of the state variables and study them using Jacobi bound. We introduce a notion of saddle Jacobi bound for an ordinary differential system of n equations in n+m variables. Systems with saddle Jacobi number equal to 0 generalize various notions of chained and diagonal systems and form the widest class of systems admitting subsets of state variables as flat output, for which flat parametrization may be computed without differentiating the initial equations. We investigate apparent and intrinsic flat singularities of such systems. As an illustration, we consider the case of a simplified aircraft model, providing new flat outputs and showing that it is flat at all points except possibly in stalling conditions. Finally, we present numerical simulations showing that a feedback using those flat outputs is robust to perturbations and can also compensate model errors, when using a more realistic aerodynamic model.

Original languageEnglish
Article number135
JournalComputational and Applied Mathematics
Issue number3
StatePublished - Apr 2024
Externally publishedYes

Bibliographical note

Publisher Copyright:
© The Author(s) under exclusive licence to Sociedade Brasileira de Matemática Aplicada e Computacional 2024.


  • 12H05
  • 68W30
  • 90C27
  • 93-10
  • 93B27
  • 93D15
  • Aircraft aerodynamics models
  • Differential thrust
  • Differentially flat systems
  • Engine failure
  • Flat outputs
  • Flat singularities
  • Forward slip landing
  • Gravity-free flight
  • Hungarian method
  • Jacobi’s bound
  • Rudder jam


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