@article {2021e-RylBicGiuLovFra,
	title = {FAST-Hex - A Morphing Hexarotor: Design, Mechanical Implementation, Control and Experimental Validation},
	journal = {IEEE/ASME Transactions on Mechatronics},
	year = {2021},
	doi = {10.1109/TMECH.2021.3099197},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021e-RylBicGiuLovFra.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021e-RylBicGiuLovFra.mp4},
	author = {Markus Ryll and Davide Bicego and Mattia Giurato and Marco Lovera and Antonio Franchi}
}
@article {2019h-RylMusPieCatAntCacFra,
	title = {6D Interaction Control with Aerial Robots: The Flying End-Effector Paradigm},
	journal = {The International Journal of Robotics Research},
	volume = {38},
	year = {2019},
	pages = {1045-1062},
	doi = {10.1177/0278364919856694},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-1.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-2.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-3.mp4},
	author = {Markus Ryll and Giuseppe Muscio and Francesco Pierri and Elisabetta Cataldi and Gianluca Antonelli and Fabrizio Caccavale and Davide Bicego and Antonio Franchi}
}
@conference {2018r-MorBicRylFra,
	title = {Energy-Efficient Trajectory Generation for a Hexarotor with Dual-Tilting Propellers},
	booktitle = {2018 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2018},
	month = {10/2018},
	address = {Madrid, Spain},
	abstract = {In this paper, we consider a non-conventional hexarotor whose propellers can be simultaneously tilted about two orthogonal axes: in this way, its underactuation degree can be easily adapted to the task at hand. For a given tilt profile, the minimum-energy trajectory between two prescribed boundary states is explicitly determined by solving an optimal control problem with respect to the angular accelerations of the six brushless motors. We also perform, for the first time, a systematic study of the singularities of the control allocation matrix of the hexarotor, showing the presence of subtle singular configurations that should be carefully avoided in the design phase. Numerical experiments conducted with the FAST-Hex platform illustrate the theory and delineate the pros and cons of dual-tilting paradigm in terms of maneuverability and energy efficiency.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018r-MorBicRylFra-preprint.pdf},
	author = {Fabio Morbidi and Davide Bicego and Markus Ryll and Antonio Franchi}
}
@article {2018d-FraCarBicRyl,
	title = {Full-Pose Tracking Control for Aerial Robotic Systems with Laterally-Bounded Input Force},
	journal = {IEEE Trans. on Robotics},
	volume = {34},
	year = {2018},
	month = {04/2018},
	pages = {534-541},
	abstract = {A class of abstract aerial robotic systems is introduced, the Laterally Bounded Force (LBF) vehicles, in which most of the control authority is expressed along a principal thrust direction, while in the lateral directions a (smaller and possibly null) force may be exploited to achieve full-pose tracking. This class approximates platforms endowed with non-collinear rotors that can modify the orientation of the total thrust in body frame. The proposed SE(3)-based control strategy achieves, if made possible by the force constraints, the independent tracking of position-plus-orientation trajectories. The method, which is proven using a Lyapunov technique, deals seamlessly with both under- and fully-actuated platforms, and guarantees at least the position tracking in the case of an unfeasible full-pose reference trajectory. Several experimental tests are presented, that clearly shown the approach practicability and the sharp improvement with respect to state of-the-art.},
	doi = {10.1109/TRO.2017.2786734},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018d-FraCarBicRyl.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018d-FraCarBicRyl-1.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018d-FraCarBicRyl-2.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018d-FraCarBicRyl-3.mp4},
	author = {Antonio Franchi and Ruggero Carli and Davide Bicego and Markus Ryll}
}
@article {2018a-MicRylFra,
	title = {Fundamental Actuation Properties of Multi-rotors: Force-Moment Decoupling and Fail-safe Robustness},
	journal = {IEEE Trans. on Robotics},
	volume = {34},
	year = {2018},
	month = {06/2018},
	doi = {10.1109/TRO.2018.2821155},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018a-MicRylFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/video1_explaination.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/video2_triggered_failures.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/video3_hitting_failures.mp4},
	author = {Giulia Michieletto and Markus Ryll and Antonio Franchi}
}
@conference {2018n-RylBicFra,
	title = {A Truly Redundant Aerial Manipulator exploiting a Multi-directional Thrust Base},
	booktitle = {12th IFAC Symposium on Robot Control},
	year = {2018},
	month = {08/2018},
	address = {Budapest, Hungary},
	abstract = {We present a novel aerial manipulator concept composed of a fully actuated hexarotor aerial vehicle and an n degree of freedom manipulator. Aiming at interaction tasks, we present a trajectory following control framework for the end-effector of the manipulator. The system is modeled in Euler-Lagrangian formalism and in Denavit-Hartenberg form. Benefiting from the redundancy of the system, we present several cost function strategies based on the projected gradient method to optimize the aerial manipulator behavior. The control framework is based on exact feedback linearization. In an advanced simulation section, we thoroughly present the robustness of the system and its limits in two typical configuration constituted by an 8 and a 10 degrees of freedom redundant aerial manipulator.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018n-RylBicFra-preprint.pdf},
	author = {Markus Ryll and Davide Bicego and Antonio Franchi}
}
@conference {2017e-RylMusPieCatAntCacFra,
	title = {6D Physical Interaction with a Fully Actuated Aerial Robot},
	booktitle = {2017 IEEE Int. Conf. on Robotics and Automation},
	year = {2017},
	month = {05/2017},
	pages = {5190-5195},
	address = {Singapore},
	abstract = {This paper presents the design, control, and experimental validation of a novel fully{\textendash}actuated aerial robot for physically interactive tasks, named Tilt-Hex. We show how the Tilt-Hex, a tilted-propeller hexarotor is able to control the full pose (position and orientation independently) using a geometric control, and to exert a full-wrench (force and torque independently) with a rigidly attached end-effector using an admittance control paradigm. An outer loop control governs the desired admittance behavior and an inner loop based on geometric control ensures pose tracking. The interaction forces are estimated by a momentum based observer. Control and observation are made possible by a precise control and measurement of the speed of each propeller. An extensive experimental campaign shows that the Tilt-Hex is able to outperform the classical underactuated multi-rotors in terms of stability, accuracy and dexterity and represent one of the best choice at date for tasks requiring aerial physical interaction.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017e-RylMusPieCatAntCacFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017e-RylMusPieCatAntCacFra.mp4},
	author = {Markus Ryll and Giuseppe Muscio and Francesco Pierri and Elisabetta Cataldi and Gianluca Antonelli and Fabrizio Caccavale and Antonio Franchi}
}
@conference {2017f-MicRylFra,
	title = {Control of Statically Hoverable Multi-Rotor Aerial Vehicles and Application to Rotor-Failure Robustness for Hexarotors},
	booktitle = {2017 IEEE Int. Conf. on Robotics and Automation},
	year = {2017},
	month = {05/2017},
	address = {Singapore},
	abstract = {Standard hexarotors are often mistakenly considered {\textquoteleft}by definition{\textquoteright} fail-safe multi-rotor platforms because of the two additional propellers when compared to quadrotors. However this is not true, in fact, a standard hexarotor cannot statically hover with {\textquoteleft}only{\textquoteright} five propellers. In this paper we provide a set of new general algebraic conditions to ensure static hover for any multi-rotor platform with any number of generically oriented rotors. These are elegantly formulated as the full-rankness of the control moment input matrix, and the non-orthogonality between its null-space and the row space of the control force input matrix. Input saturations and safety margins are also taken into account with an additional condition on the null-space of control moment input matrix. A deep analysis on the hoverability properties is then carried out focusing on the propeller loss in a hexarotor platform. Leveraging our general results we explain why a standard hexarotor is not robust and how it can be made robust thanks to a particular tilt of the rotors. We finally propose a novel cascaded controller based on a preferential direction in the null-space of the control moment input matrix for the large class of statically hoverable multi-rotors, which goes far beyond standard platforms, and we apply this controller to the case of failed tilted hexarotor.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017f-MicRylFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017f-MicRylFra.mp4},
	author = {Giulia Michieletto and Markus Ryll and Antonio Franchi}
}
@conference {2016j-RylBicFra,
	title = {Modeling and Control of FAST-Hex: a Fully-Actuated by Synchronized-Tilting Hexarotor},
	booktitle = {2016 IEEE/RSJ Int. Conf. on Intelligent Robots and System},
	year = {2016},
	month = {10/2016},
	pages = {1689-1694},
	address = {Daejeon, South Korea},
	abstract = {We present FAST-Hex, a novel UAV concept which is able to smoothly change its configuration from underactuated to fully actuated by using only one additional motor that tilts all propellers at the same time. FAST-Hex can adapt to the task at hand by finely tuning its configuration from the efficient (but underactuated) flight (typical of coplanar multi{\textendash} rotor platforms) to the full-pose-tracking (but less efficient) flight, which is attainable by non-coplanar multi-rotors. We also introduce a novel full-pose geometric controller for generic multi-rotors (not only the FAST-Hex) that outperforms classical inverse dynamics approaches. The controller receives as input any reference pose in R^3{\texttimes}SO(3) (3D position + 3D orientation). Exact tracking is achieved if the reference pose is feasible with respect to the propeller spinning rate saturations. In case of unfeasibility a new feasible desired trajectory is generated online giving priority to the positional part. The new controller is tested with the FAST-Hex but can be used for many other multi-rotor platforms: underactuated, slightly fully-actuated and completely fully-actuated.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016j-RylBicFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016j-RylBicFra.mp4},
	author = {Markus Ryll and Davide Bicego and Antonio Franchi}
}
@conference {2015e-RajRylBueFra,
	title = {Modeling, Control and Design Optimization for a Fully-actuated Hexarotor Aerial Vehicle with Tilted Propellers},
	booktitle = {2015 IEEE Int. Conf. on Robotics and Automation},
	year = {2015},
	month = {05/2015},
	pages = {4006-4013},
	address = {Seattle, WA},
	keywords = {Aerial Robotics, UAV hardware platforms},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015e-RajRylBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015e-RajRylBueFra.mp4},
	author = {Sujit Rajappa and Markus Ryll and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@booklet {2014l-GioSalFraMalSchMelRylBuePra,
	title = {The Flying Hand: a Teleoperation Framework for Cooperative Aerial Grasping and Transportation},
	howpublished = {Automatica.it 2014, Convegno Annuale dei Docenti e Ricercatori Italiani in Automatica},
	year = {2014},
	month = {09/2014},
	address = {Bergamo, Italy},
	keywords = {workshop},
	author = {Guido Gioioso and Gionata Salvietti and Antonio Franchi and Monica Malvezzi and Stefano Scheggi and L. Meli and Markus Ryll and Heinrich H. B{\"u}lthoff and Domenico Prattichizzo}
}
@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}
}
@conference {2013o-SpiRobRylBueFra,
	title = {An Open-Source Hardware/Software Architecture for Quadrotor UAVs},
	booktitle = {2nd IFAC Workshop on Research, Education and Development of Unmanned Aerial Systems},
	year = {2013},
	month = {11/2013},
	address = {Compiegne, France},
	abstract = {In this paper, we illustrate an open-source ready-to-use hardware/software architecture for a quadrotor UAV. The presented platform is price effective, highly customizable, and easily exploitable by other researchers involved in high-level UAV control tasks and for educational purposes as well. The use of object-oriented programming and full support of Robot Operating System (ROS) and Matlab Simulink allows for an efficient customization, code reuse, functionality expansion and rapid prototyping of new algorithms. We provide an extensive illustration of the various UAV components and a thorough description of the main basic algorithms and calibration procedures. Finally, we present some experimental case studies aimed at showing the effectiveness of the proposed architecture.},
	keywords = {Aerial Robotics, UAV hardware platforms},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013o-SpiRobRylBueFra-preprint.pdf},
	author = {Riccardo Spica and Paolo Robuffo Giordano and Markus Ryll and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@article {2012q-FraMasGraRylBueRob,
	title = {Modeling and Control of UAV Bearing-Formations with Bilateral High-Level Steering},
	journal = {The International Journal of Robotics Research, Special Issue on 3D Exploration, Mapping, and Surveillance},
	volume = {31},
	year = {2012},
	month = {10/2012},
	pages = {1504-1525},
	abstract = {In this paper we address the problem of controlling the motion of a group of UAVs bound to keep a formation defined in terms of only relative angles (i.e., a bearing-formation). This problem can naturally arise within the context of several multi-robot applications such as, e.g., exploration, coverage, and surveillance. First, we introduce and thoroughly analyze the concept and properties of bearing-formations, and provide a class of minimally linear sets of bearings sufficient to uniquely define such formations. We then propose a bearing-only formation controller requiring only bearing measurements, converging almost globally, and maintaining bounded inter-agent distances despite the lack of direct metric information. The controller still leaves the possibility to impose group motions tangent to the current bearing-formation. These can be either autonomously chosen by the robots because of any additional task (e.g., exploration), or exploited by an assisting human co-operator. For this latter {\textquoteleft}human-in-the-loop{\textquoteright} case, we propose a multi-master/multi-slave bilateral shared control system providing the co-operator with some suitable force cues informative of the UAV performance. The proposed theoretical framework is extensively validated by means of simulations
and experiments with quadrotor UAVs equipped with onboard cameras. Practical limitations, e.g., limited field-of-view, are also considered.},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012q-FraMasGraRylBueRob-preprint.pdf},
	author = {Antonio Franchi and Carlo Masone and Volker Grabe and Markus Ryll and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@article {2012f-FraSecRylBueRob,
	title = {Shared Control: Balancing Autonomy and Human Assistance with a Group of Quadrotor UAVs.},
	journal = {IEEE Robotics and Automation Magazine, Special Issue on Aerial Robotics and the Quadrotor Platform},
	volume = {19},
	year = {2012},
	month = {09/2012},
	pages = {57-68},
	abstract = {In this paper, we present a complete control framework and associated experimental testbed for the bilateral shared control of a group of quadrotor UAVs. This control architecture is applicable to any task and allows to integrate: i) a decentralized topological motion control (responsible for the mutual interactions in the UAV formation), ii) a human assistance module (allowing human intervention, whenever needed, on some aspects of the UAV group behavior), and iii) a force-feedback possibility (increasing the telepresence of the human assistants by providing suitable haptic cues informative of the UAV behavior). 
We will show, as worked-out case studies, how to specialize the topological motion controller to the relevant cases of constant, unconstrained and connected group topologies, and how to let a human operator intervening at the level of single UAVs or of the whole group dynamics.
A detailed description of the experimental testbed is also provided with emphasis on the quadrotor UAV hardware and software architectures. Finally, the versatility of the proposed framework is demonstrated by means of experiments with real UAVs. Although quadrotors are used as actual robotic platforms, the proposed framework can be straightforwardly extended to many different kinds of UAVs with similar motion characteristics.},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Middleware for robotics, Motion control of multiple robots, Multi-robot systems, UAV hardware platforms},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012f-FraSecRylBueRob-preprint.pdf},
	author = {Antonio Franchi and Cristian Secchi and Markus Ryll and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
