Dynamics, control, and estimation for aerial robots tethered by cables or bars

Marco Tognon*, Antonio Franchi

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

51 Citations (Scopus)


In this paper, we consider the problem of controlling an aerial robot connected to the ground by a passive cable or a passive rigid link. We provide a thorough characterization of this nonlinear dynamical robotic system in terms of fundamental properties such as differential flatness, controllability, and observability. We prove that the robotic system is differentially flat with respect to two output pairs: Elevation of the link and attitude of the vehicle; elevation of the link and longitudinal link force (e.g., cable tension, or bar compression). We show the design of an almost globally convergent nonlinear observer of the full state that resorts only to an onboard accelerometer and a gyroscope. We also design two almost globally convergent nonlinear controllers to track any sufficiently smooth time-varying trajectory of the two output pairs. Finally, we numerically test the robustness of the proposed method in several far-from-nominal conditions: nonlinear cross-coupling effects, parameter deviations, measurements noise, and nonideal actuators.

Original languageEnglish
Article number7892030
Pages (from-to)834-845
Number of pages12
JournalIEEE transactions on robotics
Issue number4
Publication statusPublished - Aug 2017
Externally publishedYes


  • Nonlinear control systems
  • Nonlinear dynamical systems
  • Robot control
  • Unmanned Aerial Vehicles (UAVs)


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