@article {2020a-NavSabTogPucFra,
	title = {Direct Force Feedback Control and Online Multi-task Optimization for Aerial Manipulators},
	journal = {IEEE Robotics and Automation Letters},
	volume = {5},
	year = {2020},
	month = {04/2020},
	pages = {331-338},
	abstract = {In this paper, we present an optimization-based method for controlling aerial manipulators in physical contact with the environment. The multi-task control problem, which includes hybrid force-motion tasks, energetic tasks, and position/postural tasks, is recast as a quadratic programming problem with equality and inequality constraints, which is solved online. Thanks to this method, the aerial platform can be exploited at its best to perform the multi-objective tasks, with tunable priorities, while hard constraints such as contact maintenance, friction cones, joint limits, maximum and minimum propeller speeds are all respected. An on-board force/torque sensor mounted at the end effector is used in the feedback loop in order to cope with model inaccuracies and reject external disturbances. Real experiments with a multi-rotor platform and a multi-DoF lightweight manipulator demonstrate the applicability and effectiveness of the proposed approach in the real world.},
	keywords = {Aerial Physical Interaction, Aerial Robotics},
	doi = {10.1109/LRA.2019.2958473},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020a-NavSabTogPucFra.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020a-NavSabTogPucFra.mp4},
	author = {Gabriele Nava and Quentin Sabl{\'e} and Marco Tognon and Daniele Pucci and Antonio Franchi}
}
@article {2016c-TogDasFra,
	title = {Observer-based Control of Position and Tension  for an Aerial Robot Tethered to a Moving Platform},
	journal = {IEEE Robotics and Automation Letters},
	volume = {1},
	year = {2016},
	note = {Also selected for presentation at the 2016 IEEE Int. Conf. on Robotics and Automation, Stockholm , Sweden},
	month = {01/2016},
	pages = {732-737},
	abstract = {In this paper we address a challenging version of the problem of controlling tethered aerial vehicles (also known as UAV, MAV, and UAS) by considering the aerial robot linked to a generic and independently moving platform. We solve the exact tracking control problem for both the 3D position of the robot (either absolute or with respect to the platform) and the tension along the link. To achieve this goal we prove some fundamental system properties, useful to design a nonlinear controller, such as differential flatness and dynamic feedback linearizability. To close the control loop a set of minimal and standard sensors is proposed. Then we show that it is possible to retrieve the full system state from those sensors by means of nonlinear measurements transformations and a bank of low-dimension estimators based on the nonlinear high gain observer. The ability of the proposed observer-controller method is tested by extensive numerical simulations spanning many non-ideal conditions.},
	keywords = {Aerial Physical Interaction, Aerial Robotics},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016c-TogDasFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016c-TogDasFra..mp4},
	author = {Marco Tognon and Sanket S. Dash and Antonio Franchi}
}
@conference {2015j-TogFra,
	title = {Nonlinear Observer for the Control of Bi-Tethered Multi Aerial Robots},
	booktitle = {2015 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2015},
	month = {09/2015},
	pages = {1852-1857},
	address = {Hamburg, Germany},
	abstract = {We consider the problem of state-observation and control for a bi-tethered aerial system composed by a physical chain of two underactuated aerial robots, also called UAVs.  The controlled outputs are the Cartesian position of the last robot and the internal forces along the links. We aim at a minimal use of sensors in order to retrieve the full state. For this goal we propose an output transformation method whose applicability implies the system observability.  When this is the case we prove that it is possible to design a nonlinear state estimator based on the  high gain- and Luenberger-  observers that is able to retrieve the state from any dynamic condition. We also demonstrate how this estimator can be employed with a nonlinear controller for the Cartesian position and the link stresses while ensuring the stability in  closed-loop. We show the validity of the method for sensorial configurations composed only by two accelerometers (no gyros) and just two encoders, or two accelerometers (no gyros) and just two inclinometers. A realistic simulative validation concludes the paper.},
	keywords = {Aerial Physical Interaction, Aerial Robotics},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015j-TogFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015j-TogFra.mp4},
	author = {Marco Tognon and Antonio Franchi}
}
