@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 {2015f-YueMahSecBueFra,
	title = {Design, Identification and Experimental Testing of a Light-Weight Flexible-joint Arm for Aerial Physical Interaction},
	booktitle = {2015 IEEE Int. Conf. on Robotics and Automation},
	year = {2015},
	month = {05/2015},
	pages = {870-876},
	address = {Seattle, WA},
	abstract = {In this paper we introduce the design of a light- weight novel flexible-joint arm for light-weight unmanned aerial vehicles (UAVs), which can be used both for safe physical interaction with the environment and it represents also a preliminary step in the direction of performing quick motions for tasks such as hammering or throwing. The actuator consists of an active pulley driven by a rotational servo motor, a passive pulley which is attached to a rigid link, and the elastic connections (springs) between these two pulleys. We identify the physical parameters of the system, and use an optimal control strategy to maximize its velocity by taking advantage of elastic components. The prototype can be extended to a light-weight variable stiffness actuator. The flexible-joint arm is applied on a quadrotor, to be used in aerial physical interaction tasks, which implies that the elastic components can also be used for stable interaction absorbing the interactive disturbances which might damage the flying system and its hardware. The design is validated through several experiments, and future developments are discussed in the paper.},
	keywords = {Aerial Physical Interaction, Aerial Robotics},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015f-YueMahSecBueFra-preprint_0.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015f-YueMahSecBueFra.mp4},
	author = {Burak Y{\"u}ksel and Saber Mahboubi and Cristian Secchi and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@conference {2015c-GioMohFraPra,
	title = {A Force-based Bilateral Teleoperation Framework for Aerial Robots in Contact with the Environment},
	booktitle = {2015 IEEE Int. Conf. on Robotics and Automation},
	year = {2015},
	month = {05/2015},
	pages = {318-324},
	address = {Seattle, WA},
	keywords = {Aerial Physical Interaction, Aerial Robotics, Bilateral Shared Control of Mobile Robots},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015c-GioMohFraPra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015c-GioMohFraPra.mp4},
	author = {Guido Gioioso and Mostafa Mohammadi and Antonio Franchi and Domenico Prattichizzo}
}
@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}
}
@conference {2014a-GioFraSalSchPra,
	title = {The Flying Hand: a Formation of UAVs for Cooperative Aerial Tele-Manipulation},
	booktitle = {2014 IEEE Int. Conf. on Robotics and Automation},
	year = {2014},
	month = {05/2014},
	pages = {4335-4341},
	address = {Hong Kong, China},
	abstract = {The flying hand is a robotic hand consisting of a swarm of UAVs able to grasp an object where each UAV contributes to the grasping task with a single contact point at the tooltip. The swarm of robots is teleoperated by a human hand whose fingertip motions are tracked, e.g., using an RGB-D camera. We solve the kinematic dissimilarity of this unique master-slave system using a multi-layered approach that includes: a hand interpreter that translates the fingertip motion in a desired motion for the object to be manipulated; a mapping algorithm that transforms the desired object motions into a suitable set of virtual points deviating from the planned contact points; a compliant force control for the case of quadrotor UAVs that allows to use them as indirect 3D force effectors. Visual feedback is also used as sensory substitution technique to provide a hint on the internal forces exerted on the object. We validate the approach with several human-in-the-loop simulations including the full physical model of the object, contact points and UAVs.},
	keywords = {Aerial Physical Interaction, Aerial Robotics, Bilateral Shared Control of Mobile Robots, Motion control of multiple robots},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014a-GioFraSalSchPra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014a-GioFraSalSchPra.mp4},
	author = {Guido Gioioso and Antonio Franchi and Gionata Salvietti and Stefano Scheggi and Domenico Prattichizzo}
}
@conference {2014d-YueSecBueFra,
	title = {Reshaping the Physical Properties of a Quadrotor through IDA-PBC and its Application to Aerial Physical Interaction},
	booktitle = {2014 IEEE Int. Conf. on Robotics and Automation},
	year = {2014},
	month = {05/2014},
	pages = {6258-6265},
	address = {Hong Kong, China},
	abstract = {In this paper we propose a controller, based on an extension of Interconnection and Damping Assignment Passivity Based Control (IDA-PBC) framework, for shaping the whole physical characteristics of a quadrotor and for obtaining a desired interactive behavior between the robot and the environment. In the control design, we shape the total energy (kinetic and potential) of the undamped original system by first excluding external effects. In this way we can assign a new dynamics to the system. Then we apply damping injection to the new system for achieving a desired damped behavior. Then we show how to connect a high-level control input to such system by taking advantage of the new desired physics. We support the theory with extensive simulations by changing the overall behavior of the UAV for different desired dynamics, and show the advantage of this method for sliding on a surface tasks, such as ceiling painting, cleaning or surface inspection.},
	keywords = {Aerial Physical Interaction, Aerial Robotics},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014d-YueSecBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014d-YueSecBueFra.mp4},
	author = {Burak Y{\"u}ksel and Cristian Secchi and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@conference {2014b-GioRylPraBueFra,
	title = {Turning a Near-hovering Controlled Quadrotor into a 3D Force Effector},
	booktitle = {2014 IEEE Int. Conf. on Robotics and Automation},
	year = {2014},
	month = {05/2014},
	pages = {6278-6284},
	address = {Hong Kong, China},
	abstract = {In this paper the problem of a quadrotor that physically interacts with the surrounding environment through a rigid tool is considered. We present a theoretical design that allows to exert an arbitrary 3D force by using a standard near-hovering controller that was originally developed for contact-free flight control. This is achieved by analytically solving the nonlinear system that relates the quadrotor state, the force exerted by the rigid tool on the environment, and the near-hovering controller action at the equilibrium points, during any generic contact. Stability of the equilibria for the most relevant actions (pushing, releasing, lifting, dropping, and left-right shifting) are proven by means of numerical analysis using the indirect Lyapunov method. An experimental platform, including a suitable tool design, has been developed and used to validate the theory with preliminary experiments.},
	keywords = {Aerial Physical Interaction, Aerial Robotics, UAV hardware platforms},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014b-GioRylPraBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014b-GioRylPraBueFra.mp4},
	author = {Guido Gioioso and Markus Ryll and Domenico Prattichizzo and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@booklet {2013m-GioFraSalSchPra,
	title = {Hand Driven UAV Formation for Cooperative Grasping and Transportation: the Flying Hand},
	howpublished = {RSS 2013 Work. on Aerial Mobile Manipulation},
	year = {2013},
	month = {06/2013},
	address = {Berlin, Germany},
	keywords = {Aerial Physical Interaction, Motion control of multiple robots},
	author = {Guido Gioioso and Antonio Franchi and Gionata Salvietti and Stefano Scheggi and Domenico Prattichizzo}
}
@conference {2013r-Fra,
	title = {Towards Autonomous-collaborative and Haptic-tele-operated UAVs with Fully-onboard State Estimation and Physical Interaction Capabilities},
	booktitle = {2013 IROS Work. on From Remotely-Controlled to Autonomous-Collaborative Robots},
	year = {2013},
	month = {11/2013},
	address = {Tokyo, Japan},
	keywords = {Aerial Physical Interaction, Aerial Robotics, UAV hardware platforms},
	author = {Antonio Franchi}
}
