@article {mellet:hal-05313710, title = {Evaluation of Human-Robot Interfaces based on 2D/3D Visual and Haptic Feedback for Aerial Manipulation}, journal = {Journal of Intelligent and Robotic Systems}, volume = {111}, year = {2025}, pages = {104}, keywords = {Aerial manipulation, aerial physical interaction, Haptic, Mixed Reality, Multimodal, Teleoperation}, doi = {10.1007/s10846-025-02284-7}, url = {https://hal.science/hal-05313710}, author = {Mellet, Julien and Allenspach, Mike and Cuniato, Eugenio and Pacchierotti, Claudio and Siegwart, Roland and Tognon, Marco} } @article {10558713, title = {Controlled Shaking of Trees With an Aerial Manipulator}, journal = {IEEE/ASME Transactions on Mechatronics}, year = {2024}, month = {2024/06}, pages = {1-12}, keywords = {aerial physical interaction, aerial robotics, autonomous aerial vehicles, control for manipulation, control of flexible elements, controlled shaking, Manipulators, Oscillators, Potential energy, Task analysis, Vegetation, Vibrations}, doi = {10.1109/TMECH.2024.3410167}, author = {Gonz{\'a}lez-Morgado, Antonio and Cuniato, Eugenio and Tognon, Marco and Heredia, Guillermo and Siegwart, Roland and Ollero, An{\'\i}bal} } @article {10428092, title = {Geranos: A Novel Tilted-Rotors Aerial Robot for the Transportation of Poles}, journal = {IEEE Robotics \& Automation Magazine}, volume = {31}, year = {2024}, month = {2024/02}, pages = {66-77}, keywords = {autonomous aerial vehicles, Autonomous robots, Grippers, Helicopters, Load management, Mechanical cables, Payloads, Task analysis, Transportation}, doi = {10.1109/MRA.2023.3348306}, author = {Bamert, Samuel and Cathomen, Rafael and Gorlo, Nicolas and K{\"a}ppeli, Gabriel and M{\"u}ller, Mario Sven and Reinhart, Tim and Stadler, Henriette and Shen, Hua and Cuniato, Eugenio and Tognon, Marco and Siegwart, Roland} } @article {2023-RosTogBalCarCorFraSch, title = {Coordinated multi-robot trajectory tracking control over sampled communication}, journal = {Automatica}, volume = {151}, year = {2023}, month = {2023/02}, pages = {110941}, author = {E. Rossi and M. Tognon and L. Ballotta and R. Carli and J. Cort{\'e}s and A. Franchi and L. Schenato} } @conference {cuniato2023design, title = {Design and Control of a Micro Overactuated Aerial Robot with an Origami Delta Manipulator}, booktitle = {2023 IEEE International Conference on Robotics and Automation (ICRA)}, year = {2023}, month = {2023/05}, author = {Eugenio Cuniato and Christian Geckeler and Maximilian Brunner and Dario Str{\"u}bin and Elia B{\"a}hler and Fabian Ospelt and Marco Tognon and Stefano Mintchev and Roland Siegwart} } @conference {10156426, title = {Design and Evaluation of a Mixed Reality-based Human-Robot Interface for Teleoperation of Omnidirectional Aerial Vehicles}, booktitle = {2023 International Conference on Unmanned Aircraft Systems (ICUAS)}, year = {2023}, month = {2023/06}, doi = {10.1109/ICUAS57906.2023.10156426}, author = {Allenspach, Mike and K{\"o}tter, Till and B{\"a}hnemann, Rik and Tognon, Marco and Siegwart, Roland} } @conference {10156414, title = {Design of PrisMAV: An Omnidirectional Aerial Manipulator based on a 3-PUU Parallel Mechanism}, booktitle = {2023 International Conference on Unmanned Aircraft Systems (ICUAS)}, year = {2023}, month = {2023/06}, doi = {10.1109/ICUAS57906.2023.10156414}, author = {Rubio, Matthias and N{\"a}f, Joshua and B{\"u}hlmann, Franz and Brigger, Philippe and H{\"u}sser, Moritz and Inauen, Martin and Ospelt, Nicole and Gisler, Daniel and Tognon, Marco and Siegwart, Roland} } @article {10149811, title = {Equilibria, Stability, and Sensitivity for the Aerial Suspended Beam Robotic System Subject to Parameter Uncertainty}, journal = {IEEE Transactions on Robotics}, year = {2023}, month = {2023/06}, pages = {1-17}, doi = {10.1109/TRO.2023.3279033}, author = {Gabellieri, Chiara and Tognon, Marco and Sanalitro, Dario and Franchi, Antonio} } @conference {172, title = {Force-based Pose Regulation of a Cable-Suspended Load Using UAVs with Force Bias}, booktitle = {2023 IEEE/RSJ International Conference on Intelligent Robots and Systems}, year = {2023}, month = {2023/10}, publisher = {IEEE}, organization = {IEEE}, address = {Michigan, USA}, author = {Chiara Gabellieri and Marco Tognon and Dario Sanalitro and Antonio Franchi} } @conference {cuniato2023learning, title = {Learning to Open Doors with an Aerial Manipulator}, booktitle = {2023 IEEE/RSJ International Conference on Intelligent Robots and Systems}, year = {2023}, month = {2023/10}, author = {Eugenio Cuniato and Ismail Geles and Weixuan Zhang and Olov Andersson and Marco Tognon and Roland Siegwart} } @conference {10156523, title = {Mixed Reality Human-Robot Interface to Generate and Visualize 6DoF Trajectories: Application to Omnidirectional Aerial Vehicles}, booktitle = {2023 International Conference on Unmanned Aircraft Systems (ICUAS)}, year = {2023}, month = {2023/06}, doi = {10.1109/ICUAS57906.2023.10156523}, author = {Allenspach, Mike and Laasch, Severin and Lawrance, Nicholas and Tognon, Marco and Siegwart, Roland} } @article {20.500.11850/627309, title = {Multi-directional Interaction Force Control with an Aerial Manipulator under External Disturbances}, journal = {Autonomous Robots}, year = {2023}, month = {2023/07}, type = {Journal Article}, abstract = {

To improve accuracy and robustness of interactive aerial robots, the knowledge of the forces acting on the platform is of uttermost importance. The robot should distinguish interaction forces from external disturbances in order to be compliant with the firsts and reject the seconds. This represents a challenge since disturbances might be of different nature (physical contact, aerodynamic, modeling errors) and be applied to different points of the robot. This work presents a new extended Kalman filter (EKF) based estimator for both external disturbance and interaction forces. The estimator fuses information coming from the system{\textquoteright}s dynamic model and it{\textquoteright}s state with wrench measurements coming from a Force-Torque (FT) sensor. This allows for robust interaction control at the tool{\textquoteright}s tip even in presence of external disturbance wrenches acting on the platform. We employ the filter estimates in a novel hybrid force/motion controller to perform force tracking not only along the tool direction, but from any platform{\textquoteright}s orientation, without losing the stability of the pose controller. The proposed framework is extensively tested on an omnidirectional aerial manipulator (AM) performing push and slide operations and transitioning between different interaction surfaces, while subject to external disturbances. The experiments are done equipping the aerial manipulator (AM) with two different tools: a rigid interaction stick and an actuated delta manipulator, showing the generality of the approach. Moreover, the estimation results are compared to a state-of-the-art momentum-based estimator, clearly showing the superiority of the extended Kalman filter (EKF) approach.

}, issn = {0929-5593}, doi = {10.3929/ethz-b-000627309}, author = {Malczyk, Grzegorz and Brunner, Maximilian and Cuniato, Eugenio and Tognon, Marco and Siegwart, Roland} } @article {klemm2023non, title = {Non-Smooth Trajectory Optimization for Wheeled Balancing Robots with Contact Switches and Impacts}, journal = {IEEE Transactions on Robotics}, year = {2023}, month = {2024/10}, author = {Klemm, Victor and de Viragh, Yvain and Rohr, David and Siegwart, Roland and Tognon, Marco} } @article {10026619, title = {Robust Sampling-Based Control of Mobile Manipulators for Interaction With Articulated Objects}, journal = {IEEE Transactions on Robotics}, year = {2023}, month = {2023/01}, pages = {1-18}, doi = {10.1109/TRO.2022.3233343}, author = {Rizzi, Giuseppe and Chung, Jen Jen and Gawel, Abel and Ott, Lionel and Tognon, Marco and Siegwart, Roland} } @conference {10155970, title = {State-Aware Path-Following with Humans Through Force-based Communication via Tethered Physical Aerial Human-Robot Interaction}, booktitle = {2023 International Conference on Unmanned Aircraft Systems (ICUAS)}, year = {2023}, month = {2023/06}, doi = {10.1109/ICUAS57906.2023.10155970}, author = {Hallworth, Ben and Allenspach, Mike and Siegwart, Roland and Tognon, Marco} } @article {9826901, title = {Adaptive Tank-based Control for Aerial Physical Interaction with Uncertain Dynamic Environments Using Energy-Task Estimation}, journal = {IEEE Robotics and Automation Letters}, volume = {7}, year = {2022}, month = {2022/07}, pages = {9129-9136}, doi = {10.1109/LRA.2022.3190074}, author = {Benzi, Federico and Brunner, Maximilian and Tognon, Marco and Secchi, Cristian and Siegwart, Roland} } @conference {143, title = {Aerial Layouting: Design and Control of a Compliant and Actuated End-Effector for Precise In-flight Marking on Ceilings}, booktitle = {Robotics: Science and System XVIII}, year = {2022}, month = {2022/06}, publisher = {Robotics: Science and Systems Foundation}, organization = {Robotics: Science and Systems Foundation}, address = { New York City (USA)}, doi = {10.3929/ethz-b-000551168}, author = {Lanegger, Christian and Ruggia, Marco and Tognon, Marco and Ott, Lionel and Siegwart, Roland} } @conference {137, title = {Energy Tank-Based Policies for Robust Aerial Physical Interaction with Moving Objects}, booktitle = {2022 IEEE Int. Conf. on Robotics and Automation}, year = {2022}, month = {2022/04}, author = {M. Brunner and L. Giacomini and R. Siegwart and M. Tognon} } @article {9684670, title = {Human-State-Aware Controller for a Tethered Aerial Robot Guiding a Human by Physical Interaction}, journal = {IEEE Robotics and Automation Letters}, volume = {7}, year = {2022}, month = {2022/01}, pages = {2827-2834}, doi = {10.1109/LRA.2022.3143574}, author = {Allenspach, Mike and Vyas, Yash and Rubio, Matthias and Siegwart, Roland and Tognon, Marco} } @article {9779498, title = {Indirect Force Control of a Cable-suspended Aerial Multi-Robot Manipulator}, journal = {IEEE Robotics and Automation Letters}, volume = {7}, year = {2022}, month = {2022/05}, pages = {2377-3766}, doi = {10.1109/LRA.2022.3176457}, author = {Sanalitro, Dario and Tognon, Marco and Jimenez-Cano, Antonio and Cortes, Juan and Franchi, Antonio} } @article {9842318, title = {Learning Variable Impedance Control for Aerial Sliding on Uneven Heterogeneous Surfaces by Proprioceptive and Tactile Sensing}, journal = {IEEE Robotics and Automation Letters}, year = {2022}, month = {2022/07}, pages = {1-8}, doi = {10.1109/LRA.2022.3194315}, author = {Zhang, Weixuan and Ott, Lionel and Tognon, Marco and Siegwart, Roland} } @conference {136, title = {Modeling and Control of an Omnidirectional Micro Aerial Vehicle Equipped with a Soft Robotic Arm}, booktitle = {2022 IEEE 5th International Conference on Soft Robotics (RoboSoft)}, year = {2022}, month = {2022/04}, author = {R. Sz{\'a}sz and M. Allenspach and M. Han and M. Tognon and R. K. Katzschmann} } @article {147, title = {A Planning-and-Control Framework for Aerial Manipulation of Articulated Objects}, journal = {IEEE Robotics and Automation Letters}, volume = {7}, year = {2022}, month = {2022/07}, pages = {10689-1069}, chapter = {10689}, doi = {10.1109/LRA.2022.3191178}, author = {Brunner, Maximilian and Rizzi, Giuseppe and Studiger, Matthias and Siegwart, Roland and Tognon, Marco} } @article {9780016, title = {Power-based Safety Layer for Aerial Vehicles in Physical Interaction using Lyapunov Exponents}, journal = {IEEE Robotics and Automation Letters}, volume = {7}, year = {2022}, month = {2022/05}, pages = {6774-6781}, doi = {10.1109/LRA.2022.3176959}, author = {Cuniato, Eugenio and Lawrance, Nicholas Robert Jonathon and Tognon, Marco and Siegwart, Roland} } @article {jimenez2022precise, title = {Precise Cable-Suspended Pick-and-Place with an Aerial Multi-robot System}, journal = {Journal of Intelligent \& Robotic Systems}, volume = {105}, year = {2022}, month = {2022/07}, pages = {1{\textendash}13}, author = {Jim{\'e}nez-Cano, AE and Sanalitro, D and Tognon, M and Franchi, A and Cort{\'e}s, J} } @conference {9981658, title = {Reactive Motion Planning for Rope Manipulation and Collision Avoidance using Aerial Robots}, booktitle = {2022 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)}, year = {2022}, month = {2022/10}, doi = {10.1109/IROS47612.2022.9981658}, author = {Shi, Liping and Pantic, Michael and Andersson, Olov and Tognon, Marco and Siegwart, Roland and Jacobsen, Rune Hylsberg} } @conference {138, title = {Towards 6DoF Bilateral Teleoperation of an Omnidirectional Aerial Vehicle for Aerial Physical Interaction}, booktitle = {2022 IEEE Int. Conf. on Robotics and Automation}, year = {2022}, month = {2022/04}, author = {M. Allenspach and N. Lawrance and M. Tognon and R. Siegwart} } @conference {126, title = {Active Model Learning using Informative Trajectories for Improved Closed-Loop Control on Real Robots}, booktitle = {2021 IEEE Int. Conf. on Robotics and Automation}, year = {2021}, month = {2021/04}, publisher = {IEEE}, organization = {IEEE}, address = {Xi{\textquoteright}an, China}, abstract = {

Model-based controllers on real robots require accurate knowledge of the system dynamics to perform optimally. For complex dynamics, first-principles modeling is not sufficiently precise, and data-driven approaches can be leveraged to learn a statistical model from real experiments. However, the efficient and effective data collection for such a data-driven system on real robots is still an open challenge. This paper introduces an optimization problem formulation to find an informative trajectory that allows for efficient data collection and model learning. We present a sampling-based method that computes an approximation of the trajectory that minimizes the prediction uncertainty of the dynamics model. This trajectory is then executed, collecting the data to update the learned model. In experiments we demonstrate the capabilities of our proposed framework when applied to a complex omnidirectional flying vehicle with tiltable rotors. Using our informative trajectories results in models which outperform models obtained from noninformative trajectory by 13.3\% with the same amount of training data. Furthermore, we show that the model learned from informative trajectories generalizes better than the one learned from non-informative trajectories, achieving better tracking performance on different tasks.

}, author = {Weixuan Zhang and Marco Tognon and Lionel Ott and Roland Siegwart and Juan Nieto} } @article {128, title = {Design of Multirotor Aerial Vehicles: a Taxonomy Based on Input Allocation}, journal = {International Journal of Robotics Research}, volume = {40}, year = {2021}, month = {2021/05}, pages = {1015-1044}, chapter = {1015}, doi = {10.1177/02783649211025998}, author = {Mahmoud Hamandi and Federico Usai and Quentin Sabl{\'e} and Nicolas Staub and Marco Tognon and Antonio Franchi} } @conference {125, title = {Direct Force and Pose NMPC with Multiple Interaction Modes for Aerial Push-and-Slide Operations}, booktitle = {2021 IEEE Int. Conf. on Robotics and Automation}, year = {2021}, month = {2021/04}, publisher = {IEEE}, organization = {IEEE}, address = {Xi{\textquoteright}an, China}, abstract = {

In this paper, we present a model predictive controller for a fully actuated aerial manipulator to track a hybrid force and pose trajectory at the end-effector in an aerial interaction task. A force sensor at the end-effector is used to detect contact and to directly control the interaction force. We propose an approach for automatic transition between three operation modes which reflect the state of contact constraints, including free flight and two modes for force control based on static or dynamic friction at the end-effector. For each mode, desired performance is defined with mode-specific weight matrices in the optimization problem, and through a practical implementation of contact constraints in the system dynamics formulation. Results from flight experiments, which combine force, position, and attitude tracking, show the performance of the controller in terms of accuracy and precision. The performance is further benchmarked against a hybrid force/impedance controller.

}, author = {Lazar Peric and Maximilian Brunner and Karen Bodie and Marco Tognon and Roland Siegwart} } @article {130, title = {Dynamic End Effector Tracking with an Omnidirectional Parallel Aerial Manipulator}, journal = {IEEE Robotics and Automation Letters}, volume = {6}, year = {2021}, month = {2021/08}, pages = {8165-8172}, url = {https://ieeexplore.ieee.org/document/9507086}, author = {Karen Bodie and Marco Tognon and Roland Siegwart} } @conference {9571032, title = {Modelling and Estimation of Human Walking Gait for Physical Human-Robot Interaction}, booktitle = {2021 Aerial Robotic Systems Physically Interacting with the Environment (AIRPHARO)}, year = {2021}, month = {2021/10}, doi = {10.1109/AIRPHARO52252.2021.9571032}, author = {Vyas, Yash and Allenspach, Mike and Lanegger, Christian and Siegwart, Roland and Tognon, Marco} } @article {127, title = {Past, Present, and Future of Aerial Robotic Manipulators}, journal = {IEEE Transactions on Robotics}, volume = {38}, year = {2021}, month = {2021/05}, chapter = {626}, doi = {10.1109/TRO.2021.3084395}, url = {https://ieeexplore.ieee.org/document/9462539}, author = {Anibal Ollero and Marco Tognon and Alejandro Suarez and Dongjun Lee and Antonio Franchi} } @article {103, title = {Physical Human-Robot Interaction with a Tethered Aerial Vehicle: Application to a Force-based Human Guiding Problem}, journal = {Transactions on Robotics}, volume = {37}, year = {2021}, month = {2021/02}, pages = {723-734}, chapter = {723}, abstract = {

Today, physical Human-Robot Interaction (pHRI) is a very popular topic in the field of ground manipulation. At the same time, Aerial Physical Interaction (APhI) is also developing very fast. Nevertheless, pHRI with aerial vehicles has not been addressed so far. In this work, we present the study of one of the first systems in which a human is physically connected to an aerial vehicle by a cable. We want the robot to be able to pull the human toward a desired position (or along a path) only using forces as an indirect communication-channel. We propose an admittance-based approach that makes pHRI safe. A controller, inspired by the literature on flexible manipulators, computes the desired interaction forces that properly guide the human. The stability of the system is formally proved with a Lyapunov-based argument. The system is also shown to be passive, and thus robust to non-idealities like additional human forces, time-varying inputs, and other external disturbances. We also design a maneuver regulation policy to simplify the path following problem. The global method has been experimentally validated on a group of four subjects, showing a reliable and safe pHRI.

}, doi = {10.1109/TRO.2020.3038700}, url = {https://ieeexplore.ieee.org/document/9353246?source=authoralert}, author = {Marco Tognon and Rachid Alami and Bruno Siciliano} } @conference {9571051, title = {Understanding the omnidirectional capability of a generic multi-rotor aerial vehicle}, booktitle = {2021 Aerial Robotic Systems Physically Interacting with the Environment (AIRPHARO)}, year = {2021}, month = {2021/10}, doi = {10.1109/AIRPHARO52252.2021.9571051}, author = {Hamandi, Mahmoud and Sable, Quentin and Tognon, Marco and Franchi, Antonio} } @conference {95, title = {Communication-based and Communication-less approaches for Robust Cooperative Planning in Construction with a Team of UAVs}, booktitle = {2020 International Conference on Unmanned Aircraft Systems (ICUAS)}, year = {2020}, month = {2020/09}, publisher = {IEEE}, organization = {IEEE}, address = {Athens, Greece}, abstract = {

In this paper, we analyze the coordination problem of groups of aerial robots for assembly applications. With the enhancement of aerial physical interaction, construction applications are becoming more and more popular. In this domain, the multi-robot solution is very interesting to reduce the execution time. However, new methods to coordinate teams of aerial robots for the construction of complex structures are required. In this work, we propose an assembly planner that considers both assembly and geometric constraints imposed by the particular desired structure and employed robots, respectively. An efficient graph representation of the task dependencies is employed. Based on this framework, we design two assembly planning algorithms that are robust to robot failures. The first is centralized and communication-based. The second is distributed and communication-less. The latter is a solution for scenarios in which the communication network is not reliable. Both methods are validated by numerical simulations based on the assembly scenario of Challenge 2 of the robotic competition MBZIRC2020.

}, keywords = {aerial vehicles application, multi-robot systems, task planning}, author = {Elena Umili and Marco Tognon and Dario Sanalitro and Giuseppe Oriolo and Antonio Franchi} } @conference {76, title = {Direct Acceleration Feedback Control of Quadrotor Aerial Vehicles}, booktitle = {2020 IEEE Int. Conf. on Robotics and Automation}, year = {2020}, month = {2020/06}, publisher = {IEEE}, organization = {IEEE}, address = {Paris, France}, abstract = {

\ In this paper we propose to control a quadrotor through direct acceleration feedback. The proposed method, while simple in form, alleviates the need for accurate estimation of platform parameters such as mass and propeller effectiveness. In order to use efficaciously the noisy acceleration measurements in direct feedback, we propose a novel regressionbased filter that exploits the knowledge on the commanded propeller speeds, and extracts smooth platform acceleration with minimal delay. Our tests show that the controller exhibits a few millimeter error when performing real world tasks with fast changing mass and effectiveness, e.g., in pick and place operation and in turbulent conditions. Finally, we benchmark the direct acceleration controller against the PID strategy and show the clear advantage of using high-frequency and low-latency acceleration measurements directly in the control feedback, especially in the case of low frequency position measurements that are typical for real outdoor conditions.

}, author = {Mahmoud Hamandi and Marco Tognon and Antonio Franchi} } @article {74, title = {Direct Force Feedback Control and Online Multi-Task Optimization for Aerial Manipulators}, journal = {IEEE Robotics and Automation Letters}, volume = {5}, year = {2020}, month = {2019/12}, pages = {331-338}, abstract = {

In this letter 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 systems: mechanics and control, force control, force feedback, hybrid force-motion tasks, multitask control problem, position control, quadratic programming}, issn = {2377-3766}, doi = {10.1109/LRA.2019.2958473}, author = {Gabriele Nava and Quentin Sabl{\'e} and Marco Tognon and Daniele Pucci and Antonio Franchi} } @article {75, title = {Full-Pose Manipulation Control of a Cable-Suspended Load With Multiple UAVs Under Uncertainties}, journal = {IEEE Robotics and Automation Letters}, volume = {5}, year = {2020}, month = {2020/01}, pages = {2185-2191}, abstract = {

In this work we propose an uncertainty-aware controller for the Fly-crane system, a statically rigid cable-suspended aerial manipulator using the minimum number of aerial robots and cables. The force closure property of the Fly-crane makes it ideal for applications where high precision is required and external disturbances should be compensated. The proposed control requires the knowledge of the nominal values of a minimum number of uncertain kinematic parameters, thus simplifying the identification process and the controller implementation. We propose an optimization-based tuning method of the control gains that ensures stability despite parameter uncertainty and maximizes the H$\infty$ performance. The validity of the proposed framework is shown through real experiments.

}, keywords = {aerial robotic manipulation, cable-suspended aerial manipulator, cable-suspended load, fly-crane system, full-pose manipulation control, multi-robot systems, uncertainty-aware controller}, issn = {2377-3766}, doi = {10.1109/LRA.2020.2969930}, author = {Dario Sanalitro and Heitor J. Savino and Marco Tognon and Juan Cort{\'e}s and Antonio Franchi} } @article {94, title = {Human Physical Guidance by a Tethered Aerial Vehicle}, year = {2020}, month = {06/2020}, publisher = {ICRA 2020, workshop on Shared Autonomy: Learning and Control}, address = {Paris, France}, abstract = {

Today, physical Human-Robot Interaction (pHRI) is a very popular topic in the field of ground manipulation. At the same time, Aerial Physical Interaction (APhI) is also developing very fast. Nevertheless, pHRI with aerial vehicles has not been addressed so far. In this work, we present the study of one of the first systems in which a human is physically connected to an aerial vehicle by a cable. We want the robot to be able to pull the human toward a desired position (or along a path) only using forces as an indirect communication-channel. We propose an admittance-based approach that makes pHRI safe. A controller, inspired by the literature on flexible manipulators, computes the desired interaction forces that properly guide the human. The stability of the system is formally proved with a Lyapunov-based argument. external disturbances. The global method has been experimentally validated showing a reliable and safe pHRI.

}, author = {Marco Tognon and Rachid Alami and Bruno Siciliano} } @conference {97, title = {Inertial Estimation and Energy-Efficient Control of a Cable-suspended Load with a Team of UAVs}, booktitle = {2020 International Conference on Unmanned Aircraft Systems (ICUAS)}, year = {2020}, month = {2020/09}, publisher = {IEEE}, organization = {IEEE}, address = {Athens, Greece}, abstract = {

The Fly-Crane is a multi-robot aerial manipulator system composed of three aerial vehicles towed to a platform by means of six cables. This paper presents a method to estimate the mass and the position of the center of mass of a loaded platform (i.e. the Fly-Crane platform including a transported load). The precise knowledge of these parameters allows to sensibly minimize the total effort exerted during a full-pose manipulation task The estimation is based on the measure of the forces applied by the aerial vehicles to the platform in different static configurations. We demonstrate that only two different configurations are sufficient to estimate the inertial parameters. Far-from-ideal numerical simulations show the effectiveness of the estimation method. Once the parameters are estimated, we show the enhancement of the system performances by minimizing the total exerted effort. The validity of the proposed algorithm in non-ideal conditions is presented through simulations based on the Gazebo simulator.

}, author = {Aantonio Petitti and Dario Sanalitro and Marco Tognon and Annalisa Milella and Juan Cort{\'e}s and Antonio Franchi} } @conference {96, title = {Omni-Plus-Seven (O 7 + ): An Omnidirectional Aerial Prototype with Minimal Uni-directional Thrusters}, booktitle = {2020 International Conference on Unmanned Aircraft Systems (ICUAS)}, year = {2020}, month = {2020/09}, publisher = {IEEE}, organization = {IEEE}, address = {Athens, Greece}, abstract = {

The aim of this paper is to present the design of a novel omnidirectional Unmanned Aerial Vehicle (UAV) with seven uni-directional thrusters, O 7 +. The paper formally defines the O + design for a generic number of propellers and presents its necessary conditions; then it illustrates a method to optimize the placement and orientation of the platform{\textquoteright}s propellers to achieve a balanced O + design. The paper then details the choice of the parameters of the O 7 + UAV, and highlights the required mechanical and electrical components. The resultant platform is tested in simulation, before being implemented as a prototype. The prototype is firstly static-bench tested to match its nominal and physical models, followed by hovering tests in multiple orientations. The presented prototype shows the ability to fly horizontally, upside down and at a tilted angle.

}, author = {Mahmoud Hamandi and Kapil Sawant and Marco Tognon and Antonio Franchi} } @book {2020g-TogFra, title = {Theory and Applications for Control of Aerial Robots in Physical Interaction Through Tethers}, series = {Springer Tracts in Advanced Robotics}, volume = {140}, year = {2020}, month = {2020/07}, publisher = {Springer, Springer Tracts in Advanced Robotics}, organization = {Springer, Springer Tracts in Advanced Robotics}, abstract = {

This book focuses on the study of autonomous aerial robots interacting with the surrounding environment, and in particular on the design of new control and motion planning methods for such systems. Nowadays, autonomous aerial vehicles are extensively employed in many fields of application but mostly as autonomously moving sensors used only to sense the environment. On the other hand, in the recent field of aerial physical interaction, the goal is to go beyond sensing-only applications and to fully exploit aerial robots capabilities in order to interact with the environment, exchanging forces for pushing/pulling/sliding, and manipulating objects. However, due to the different nature of the problems, new control methods are needed. These methods have to preserve the system stability during the interaction and to be robust against external disturbances, finally enabling the robot to perform a given task. Moreover, researchers and engineers need to face other challenges generated by the high complexity of aerial manipulators, e.g., a large number of degrees of freedom, strong nonlinearities, and actuation limits. Furthermore, trajectories of the aerial robots have to be carefully computed using motion planning techniques. To perform the sough task in a safe way, the planned trajectory must avoid obstacles and has to be suitable for the dynamics of the system and its actuation limits. With the aim of achieving the previously mentioned general goals, this book considers the analysis of a particular class of aerial robots interacting with the environment: tethered aerial vehicles. The study of particular systems, still encapsulating all the challenges of the general problem, helps on acquiring the knowledge and the expertise for a subsequent development of more general methods applicable to aerial physical interaction. This work focuses on the thorough formal analysis of tethered aerial vehicles ranging from control and state estimation to motion planning. In particular, the differential flatness property of the system is investigated, finding two possible sets of flat outputs that reveal new capabilities of such a system. One contains the position of the vehicle and the link internal force (equivalently the interaction force with the environment), while the second contains the position and a variable linked to the attitude of the vehicle. This shows new control and physical interaction capabilities different from standard aerial robots in contact-free flight. In particular, the first set of flat outputs allows realizing one of the first {\textquotedblleft}free-floating{\textquotedblright} versions of the classical hybrid force-motion control for standard grounded manipulators. Based on these results we designed two types of controllers. The first is an easy-to-implement controller based on a hierarchical approach. Although it shows good performance in quasi-static conditions, actually the tracking error increases when tracking a dynamic trajectory. Thus, a second controller more suited for tracking problems has been designed based on the dynamic feedback linearization technique. Two observers, for the 3D and 2D environments, respectively, have been designed in order to close the control loop using a minimal sensorial setup. We showed that the tether makes possible to retrieve an estimation of the full state from only an IMU plus three encoders for the 3D case, while from just an IMU for the 2D case. Parts of those results were extended to a novel and original multi-robots case as well. We considered a multi-tethered system composed of two aerial robots linked to the ground and to each other by two links. The theoretical results on generic tethered aerial vehicles were finally employed to solve the practical and challenging problem of landing and takeoff on/from a sloped surface, enhancing the robustness and reliability of the maneuvers with respect to the contact-free flight solution.

}, isbn = {978-3-030-48659-4}, doi = {10.1007/978-3-030-48659-4}, author = {Marco Tognon and Antonio Franchi} } @article {72, title = {Cooperative Aerial Load Transportation via Sampled Communication}, journal = {IEEE Control Systems Letters}, volume = {4}, year = {2019}, note = {

Also selected for presentation at the 2019\ IEEE Conf. on Decision and Control, Nice, France.

}, month = {06/2019}, pages = {277-282}, abstract = {

In this letter, we propose a feedback-based motion planner for a class of multi-agent manipulation systems with a sparse kinematics structure. In other words, the agents are coupled together only by the transported object. The goal is to steer the load into a desired configuration. We suppose that a global motion planner generates a sequence of desired configurations that satisfy constraints as obstacles and singularities avoidance. Then, a local planner receives these references and generates the desired agents velocities, which are converted into force inputs for the vehicles. We focus on the local planner design both in the case of continuously available measurements and when they are transmitted to the agents via sampled communication. For the latter problem, we propose two strategies. The first is the discretization of the continuous-time strategy that preserves stability and guarantees exponential convergence regardless of the sampling period. In this case, the planner gain is static and computed off-line. The second strategy requires to collect the measurements from all sensors and to solve online a set of differential equations at each sampling period. However, it has the advantage to provide doubly exponential convergence. Numerical simulations of these strategies are provided for the cooperative aerial manipulation of a cable-suspended load.

}, keywords = {cable-suspended load, cooperative aerial manipulation, decentralized controller, motion control, multi-robot systems, sampled measurements}, issn = {2475-1456}, doi = {10.1109/LCSYS.2019.2924413}, author = {Enrica Rossi and Marco Tognon and Ruggero Carli and Luca Schenato and Juan Cort{\'e}s and Antonio Franchi} } @article {73, title = {A Study on Force-based Collaboration in Swarms}, journal = {Swarm Intelligence}, volume = {14}, year = {2019}, month = {11/2019}, pages = {57 - 82}, abstract = {

Cooperative manipulation is a basic skill in groups of humans, animals and in many robotic applications. Besides being an interesting challenge, communication-less approaches have been applied to groups of robots in order to achieve higher scalability and simpler hardware and software design. We present a generic model and control law for robots cooperatively manipulating an object, for both ground and floating systems. The control method exploits a leader{\textendash}follower scheme and is based only on implicit communication (i.e., the sensing of contact forces). The control objective mainly consists of steering the object manipulated by the swarm of robots to a desired position and orientation in a cooperative way. For a system with just one leader, we present analytical results on the equilibrium configurations and their stability that are then validated by numerical simulations. The role of object internal forces (induced by the robots through contact forces) is discussed in terms of convergence of the object position and orientation to the desired values. We also present a discussion on additional properties of the controlled system that were investigated using thorough numerical analysis, namely the robustness of the system when the object is subject to external disturbances in non-ideal conditions, and how the number of leaders in the swarm can affect the aforementioned convergence and robustness.

}, isbn = {1935-3820}, url = {https://doi.org/10.1007/s11721-019-00178-7}, author = {Chiara Gabellieri and Marco Tognon and Dario Sanalitro and Lucia Pallottino and Antonio Franchi} } @article {71, title = {A Truly-Redundant Aerial Manipulator System With Application to Push-and-Slide Inspection in Industrial Plants}, journal = {IEEE Robotics and Automation Letters}, volume = {4}, year = {2019}, month = {01/2019}, pages = {1846-1851}, abstract = {

We present the design, motion planning, and control of an aerial manipulator for non-trivial physical interaction tasks, such as pushing while sliding on curved surfaces-a task which is motivated by the increasing interest in autonomous non-destructive tests for industrial plants. The proposed aerial manipulator consists of a multidirectional-thrust aerial vehicle-to enhance physical interaction capabilities-endowed with a 2-DoFs lightweight arm-to enlarge its workspace. This combination makes it a trulyredundant manipulator going beyond standard aerial manipulators based on collinear multirotor platforms. The controller is based on a PID method with a {\textquotedblleft}displaced{\textquotedblright} positional part that ensures asymptotic stability despite the arm elasticity. A kinodynamic task-constrained and control-aware global motion planner is used. Experiments show that the proposed aerial manipulator system, equipped with an Eddy current probe, is able to scan a metallic pipe sliding the sensor over its surface and preserving the contact. From the measures, a weld on the pipe is successfully detected and mapped.

}, keywords = {aerial manipulator, contact-based inspection, dexterous manipulators, motion control, motion planning}, issn = {2377-3766}, doi = {10.1109/LRA.2019.2895880}, author = {Marco Tognon and Hermes A. Tello-Chavez and Enrico Gasparin and Quentin Sabl{\'e} and Davide Bicego and Anthony Mallet and Marc Lany and Gilles Santi and Bernard Revaz and Juan Cort{\'e}s and Antonio Franchi} } @article {69, title = {Aerial Co-Manipulation With Cables: The Role of Internal Force for Equilibria, Stability, and Passivity}, journal = {IEEE Robotics and Automation Letters, Special Issue on Aerial Manipulation}, volume = {3}, year = {2018}, month = {07/2018}, pages = {2577-2583}, abstract = {

This letter considers the cooperative manipulation of a cable-suspended load with two generic aerial robots without the need of explicit communication. The role of the internal force for the asymptotic stability of the beam position-and-attitude equilibria is analyzed in depth. Using a nonlinear Lyapunov-based approach, we prove that if a nonzero internal force is chosen, then the asymptotic stabilization of any desired beam attitude can be achieved with a decentralized and communicationless master-slave admittance controller. If, conversely, a zero internal force is chosen, as done in the majority of the state-of-the-art algorithms, the attitude of the beam is not controllable without communication. Furthermore, we formally proof the output-strictly passivity of the system with respect to an energy-like storage function and a certain input-output pair. This proves the stability and the robustness of the method during motion and in nonideal. The theoretical findings are validated through extensive simulations.

}, keywords = {admittance controller, aerial co-manipulation, asymptotic stability, cable-suspended load, communication-less, decentralised control, Lyapunov-based approach, passivity}, issn = {2377-3766}, doi = {10.1109/LRA.2018.2803811}, author = {Marco Tognon and Chiara Gabellieri and Lucia Pallottino and Antonio Franchi} } @article {70, title = {Control-Aware Motion Planning for Task-Constrained Aerial Manipulation}, journal = {IEEE Robotics and Automation Letters, Special Issue on Aerial Manipulation}, volume = {3}, year = {2018}, note = {

Also selected for presentation at the 2018 IEEE Int. Conf. on Robotics and Automation, Brisbane , Australia

}, month = {07/2018}, pages = {2478-2484}, abstract = {

This letter presents a new method to address the problem of task-constrained motion planning for aerial manipulators. We propose a control-aware planner based on the paradigm of tight coupling between planning and control. Such paradigm is especially useful in aerial manipulation, where the separation between planning and control is not advisable. The proposed sampling based motion planner uses a controller composed of a second-order inverse kinematics algorithm and a dynamic tracker, as a local planner, thus allowing a more natural consideration of the closed-loop system dynamics. For task-constrained motions, this method let us to sample directly in the reduced and more relevant task space, predict the behavior of the controller avoiding motions that bring to singularities or large tracking errors, and guarantee the correct execution of the maneuver. The method is tested in simulation for a multidirectional-thrust vehicle endowed with a 2-DoF manipulator. The proposed approach is very general, and could be applied to ground and underwater robotic systems to perform manipulation or inspection tasks.

}, keywords = {aerial manipulator, control-aware motion planning, task-constrained motions}, issn = {2377-3766}, doi = {10.1109/LRA.2018.2803206}, author = {Marco Tognon and Elisabetta Cataldi and Hermes A. Tello-Chavez and Gianluca Antonelli and Juan Cort{\'e}s and Antonio Franchi} } @article {68, title = {Omnidirectional Aerial Vehicles With Unidirectional Thrusters: Theory, Optimal Design, and Control}, journal = {IEEE Robotics and Automation Letters}, volume = {3}, year = {2018}, month = {07/2018}, pages = {2277-2282}, abstract = {

This letter presents a theoretical study on omnidirectional aerial vehicles with body-frame fixed unidirectional thrusters. Omniplus multirotor designs are defined as the ones that allow to exert a total wrench in any direction using positive-only lift force and drag moment (i.e., positive rotational speed) for each rotor blade. Algebraic conditions for a design to be omniplus are derived, a simple necessary condition being the fact that at least seven propellers have to be used. An energy optimal design strategy is then defined as the one minimizing the maximum norm of the input set needed to span a certain wrench ellipsoid for the adopted input allocation strategy. Two corresponding major design criteria are then introduced: first, a minimum allocation-matrix condition number aims at an equal sharing of the effort needed to generate wrenches in any direction; second, imposing a balanced design guarantees an equal sharing of the extra effort needed to keep the input in the nonnegative orthant. We propose a numerical algorithm to solve such optimal design problem and a control algorithm to control any omnidirectional platform. The work is concluded with informative simulation results in nonideal conditions.

}, keywords = {aerial systems: mechanics and control, algebraic conditions, design, motion control, omnidirectional aerial vehicles}, issn = {2377-3766}, doi = {10.1109/LRA.2018.2802544}, author = {Marco Tognon and Antonio Franchi} } @conference {66, title = {A Study on Force-Based Collaboration in Flying Swarms}, booktitle = {International Conference on Swarm Intelligence}, year = {2018}, month = {10/2018}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, address = {Rome, Italy}, abstract = {

This work investigates collaborative aerial transportation by swarms of agents based only on implicit information, enabled by the physical interaction among the agents and the environment. Such a coordinating mechanism in collaborative transportation is a basic skill in groups of social animals. We consider cable-suspended objects transported by a swarm of flying robots and we formulate several hypothesis on the behavior of the overall system which are validated thorough numerical study. In particular, we show that a nonzero internal force reduces to one the number of asymptotically stable equilibria and that the internal force intensity is directly connected to the convergence rate. As such, the internal force represents the cornerstone of a communication-less cooperative manipulation paradigm in swarms of flying robots. We also show how a swarm can achieve a stable transportation despite the imprecise knowledge of the system parameters.

}, isbn = {978-3-030-00533-7}, author = {Chiara Gabellieri and Marco Tognon and Lucia Pallottino and Antonio Franchi} } @mastersthesis {tognon:tel-02003048, title = {Theory and Applications for Control and Motion Planning of Aerial Robots in Physical Interaction with particular focus on Tethered Aerial Vehicles}, volume = {PhD}, year = {2018}, school = {Institut national des sciences appliqu{\'e}es de Toulouse}, type = {phdTheses}, address = {Toulouse}, keywords = {Aerial manipulation, Aerial manipulation by cables, aerial physical interaction, Aerial robots, Commande, Control, Interaction physique a{\'e}rienne, Manipulation a{\'e}rienne, Manipulation a{\'e}rienne via des c{\^a}bles, motion planning, Multidirectional- thrust aerial vehicles, Planification du mouvement, Robots a{\'e}riens, tethered aerial vehicles, V{\'e}hicules a{\'e}riens {\`a} pouss{\'e}e multidirectionnelle, V{\'e}hicules a{\'e}riens attach{\'e}s par des c{\^a}bles}, url = {https://hal.laas.fr/tel-02003048}, author = {Marco Tognon} } @conference {62, title = {Dynamic decentralized control for protocentric aerial manipulators}, booktitle = {2017 IEEE International Conference on Robotics and Automation (ICRA)}, year = {2017}, month = {05/2017}, address = {Singapore, Singapore}, abstract = {

We present a control methodology for underactuated aerial manipulators that is both easy to implement on real systems and able to achieve highly dynamic behaviors. The method is composed by two parts: i) a nominal input/state trajectory generator that takes into account the full-body dynamics of the system exploiting its differential flatness property; ii) a decentralized feedback controller acting on the actuated degrees of freedom that confers the needed robustness to the closed-loop system. We demonstrate that the proposed controller is able to precisely track dynamic trajectories when implemented on a standard hardware. Comparative experiments clearly show the benefit of using the nominal input/state generator.

}, keywords = {aerial manipulator, decentralised control, differential flatness, motion control, protocentric aerial manipulators}, doi = {10.1109/ICRA.2017.7989753}, author = {Marco Tognon and Burak Y{\"u}ksel and Gabriele Buondonno and Antonio Franchi} } @article {56, title = {Dynamics, Control, and Estimation for Aerial Robots Tethered by Cables or Bars}, journal = {IEEE Transactions on Robotics}, volume = {33}, year = {2017}, month = {04/2017}, pages = {834 - 845}, chapter = {834}, keywords = {Nonlinear control systems, nonlinear dynamical systems, robot control, unmanned aerial vehicles}, doi = {10.1109/TRO.2017.2677915}, url = {https://ieeexplore.ieee.org/abstract/document/7892030}, author = {Marco Tognon and Antonio Franchi} } @conference {65, title = {Landing and Take-off on/from Sloped and Non-planar Surfaces with more than 50 Degrees of Inclination}, booktitle = {9th International Micro Air Vehicles Conference}, year = {2017}, month = {09/2017}, address = {Toulouse, France}, abstract = {

This technical paper summarizes the recent experimental results concerning the challenging problem of landing and take-off on/from a sloped surface with an aerial vehicle exploiting the force provided by an anchored taut tether. A special regard is given to the practical aspects concerning the experimental part. In this manuscript we show extreme landing and take-off maneuvers on slopes with at least 50{\textopenbullet} inclination and non flat surfaces, such as, e.g., on industrial pipes.

}, keywords = {take-off and landing, tethered aerial vehicle}, author = {Marco Tognon and Antonio Franchi} } @conference {64, title = {Position Tracking Control for an Aerial Robot Passively Tethered to an Independently Moving Platform}, booktitle = {20th World Congress of the International Federation of Automatic Control}, year = {2017}, month = {07/2017}, address = {Toulouse, France}, abstract = {

We study the control problem of an aerial vehicle moving in the 3D space and connected to an independently moving platform through a physical link (e.g., a cable, a chain or a rope). The link is attached to the moving platform by means of a passive winch. The latter differs from an active winch by producing only a constant uncontrollable torque. We solve the problem of exact tracking of the 3D position of the aerial vehicle, either absolute or with respect to the moving platform, while the platform is independently moving. We prove two intrinsic properties of the system, namely, the dynamic feedback linearizability and the differential flatness with respect to the output of interest. Exploiting this properties we design a nonlinear controller able to exponentially steer the position of the aerial robot along any sufficiently smooth time-varying trajectory. The proposed method is tested through numerical simulations in several non-ideal cases.

}, keywords = {Aerial robot control, nonlinear control, tethered aerial vehicles}, author = {Marco Tognon and Antonio Franchi} } @conference {63, title = {Visual Marker based Multi-Sensor Fusion State Estimation}, booktitle = {20th World Congress of the International Federation of Automatic Control}, year = {2017}, month = {10/2017}, address = {Toulouse, France}, abstract = {

This paper presents the description and experimental results of a versatile Visual Marker based Multi-Sensor Fusion State Estimation that allows to combine a variable optional number of sensors and positioning algorithms in a loosely-coupling fashion, incorporating visual markers to increase its performances. This technique allows an aerial robot to navigate in different environments and carrying out different missions with the same state estimation architecture, exploiting the best from every sensor. The state estimation algorithm has been successfully tested controlling a quadrotor equipped with an extra IMU and a RGB camera used only to detect visual markers. The entire framework runs on an onboard computer, including the controllers and the proposed state estimator. The whole software is made publicly available to the scientific community through an open source implementation.

}, keywords = {Autonomous Mobile Robots, Image Sensors, Inertial Sensors, Position Estimation, Sensor Fusion, State Estimation}, doi = {https://doi.org/10.1016/j.ifacol.2017.08.1911}, url = {http://www.sciencedirect.com/science/article/pii/S2405896317325387}, author = {Jose L. Sanchez-Lopez and Victor Arellano-Quintana and Marco Tognon and Pascual Campoy and Antonio Franchi} } @article {67, 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}, month = {07/2016}, pages = {732-737}, abstract = {

In this letter, 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 3-D 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 nonideal conditions.

}, keywords = {aerial robot, differential flatness, dynamic feedback linearization, force control, non-liner observers, Nonlinear control systems, observer-based control, position control, tethered aerial vehicle}, issn = {2377-3766}, doi = {10.1109/LRA.2016.2523599}, author = {Marco Tognon and Sanket S. Dash and Antonio Franchi} } @conference {61, title = {Takeoff and landing on slopes via inclined hovering with a tethered aerial robot}, booktitle = {2016 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)}, year = {2016}, month = {10/2016}, address = {Daejeon, South Korea}, abstract = {

In this paper we face the challenging problem of takeoff and landing on sloped surfaces for a VTOL aerial vehicle. We define the general conditions for a safe and robust maneuver and we analyze and compare two classes of methods to fulfill these conditions: free-flight vs. passively-tethered. Focusing on the less studied tethered method, we show its advantages w.r.t. the free-flight method thanks to the possibility of inclined hovering equilibria. We prove that the tether configuration and the inclination of the aerial vehicle w.r.t. the slope are flat outputs of the system and we design a hierarchical nonlinear controller based on this property. We then show how this controller can be used to land and takeoff in a robust way without the need of either a planner or a perfect tracking. The validity and applicability of the method in the real world is shown by experiments with a quadrotor that is able to perform a safe landing and takeoff on a sloped surface.

}, keywords = {hierarchical nonlinear controller, inclined hovering, tethered aerial robot, unmanned aerial vehicle}, doi = {10.1109/IROS.2016.7759273}, author = {Marco Tognon and Andrea Testa and Enrica Rossi and Antonio Franchi} } @conference {59, title = {Control of Motion and Internal Stresses for a Chain of Two Underactuated Aerial Robots}, booktitle = { IEEE/EUCA 2015 European Control Conference}, year = {2015}, month = {07/2015}, publisher = {IEEE}, organization = {IEEE}, address = { Linz, Austria}, abstract = {

Given the tethered aerial robot problem, in this paper we investigate a multi-agent extension considering a chain of two underactuated flying robots. Our goal is to independently control the elevations (angles) of the two links (or, equivalently, the Cartesian position of the last robot) and their internal stress. For this purpose we theoretically prove the dynamic feedback linearizability of the system and we exploit this property to design a nonlinear controller that exactly linearizes the system. The controller is able to steer the outputs of interest along any trajectory s.t. the desired elevations and stresses are functions of time of class C 3 and C 1 , respectively. The controller is able to track independently both positive and negative stresses, i.e., both tension and compression. Resorting to an equivalence argument we then also show the differential flatness of the system. Finally we also demonstrate some of the abilities of the proposed method through numerical examples.

}, keywords = {differential flatness, dynamic feedback linearization, force control, motion control, multi-robot systems, nonlinear controller design, tethered aerial vehicles}, doi = {10.1109/ECC.2015.7330769}, url = {https://ieeexplore.ieee.org/abstract/document/7330769}, author = {Marco Tognon and Antonio Franchi} } @conference {60, title = {Nonlinear observer for the control of bi-tethered multi aerial robots}, booktitle = {2015 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)}, year = {2015}, month = {09/2015}, 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 = {autonomous aerial vehicles, bitethered, closed loop systems, high gain-observer, multi-robot systems, multiaerial robots, Nonlinear control systems, nonlinear observer, nonlinear state estimator, position control}, doi = {10.1109/IROS.2015.7353619}, url = {https://ieeexplore.ieee.org/document/7353619}, author = {Marco Tognon and Antonio Franchi} } @conference {57, title = {Nonlinear Observer-based Tracking Control of Link Stress and Elevation for a Tethered Aerial Robot using Inertial-only Measurements}, booktitle = { 2015 IEEE International Conference on Robotics and Automation (ICRA)}, year = {2015}, month = {05/2015}, publisher = {IEEE}, organization = {IEEE}, address = {Seattle, WA}, keywords = {nonlinear dynamical systems, Observability, Observers, Stress, Trajectory, Vehicle dynamics, Vehicles}, doi = {10.1109/ICRA.2015.7139757}, url = {https://ieeexplore.ieee.org/abstract/document/7139757}, author = {Marco Tognon and Antonio Franchi} }