Aerial manipulation of deformable objects

MSc assignment


Robotic aerial manipulation systems have met ceaseless growth in the past decade. Aerial robots have been endowed with manipulation capabilities through a variety of tools, including grippers, rigid tools, multi-dof arms, and cables. However, modeling and control of deformable aerial manipulation systems remain challenging. Even capturing the behavior of a deformable cable is not trivial, and cables have been often approximated as inextensible linear elements. Sometimes, the cable connected to the aerial robot has been modeled as an elastic spring [1], or a series of rigid links interconnected by passive spherical joints [2] [3] [4].

The objective of this assignment is to compute the model and design the control law of a complex system composed of multiple aerial robots physically connected through a net of cables. The student will be required to

  • Study the literature on cable-connected aerial robotic systems and find a class of systems that still need to be explored or for which certain control laws still needs to be tested, e.g., multiple point masses connected to UAVs through cables (representing nets manipulated by aerial robots), UAVs connected with flexible (and elastic?) cables, etc.
       - compute the dynamic equations of such systems
       - (possibly) investigate the properties of a general class of systems, e.g., controllability or differentially flat outputs of interest;
  • Consider then a simple system of that class that is tractable and, for that,
      - plan an offline trajectory for the controllable outputs
      - design a model-based control law that steers the controllable outputs along a trajectory in the presence of external disturbances;
      - simulate the robotic system using a dynamic simulator at choice, e.g., Matlab Simulink or Gazebo, to numerically validate the performance of the controller.
      - (possibly) analytically prove the stability of the closed-loop system;
      - (possibly) compare with a standard control law

The main related research questions are:

What can we say about the fundamental properties of previously unstudied systems composed of aerial robots connected to deformable objects, e.g., to nets or flexible cables?
Which control law can be used to control a system of the aforementioned class in the presence of external disturbances?

This MSc thesis will take place within the scope of the H2020 Aerial-Core European project.

[1]: Tognon, M., Gabellieri, C., Pallottino, L., and Franchi, A. "Aerial co-manipulation with cables: The role of internal force for equilibria, stability, and passivity." IEEE Robotics and Automation Letters 3.3 (2018): 2577-2583.
[2]: Kotaru, P., and Sreenath, K. "Multiple quadrotors carrying a flexible hose: dynamics, differential flatness and control." IFAC-PapersOnLine 53.2 (2020): 8832-8839.
[3]: Kotaru, P., Wu, G., and Sreenath, K. "Differential-flatness and control of quadrotor (s) with a payload suspended through flexible cable (s)." 2018 Indian Control Conference (ICC). IEEE, 2018.
[4]: Goodarzi, F. A., Lee, D., and Lee, T. "Geometric stabilization of a quadrotor UAV with a payload connected by flexible cable." 2014 American Control Conference. IEEE, 2014.