This article investigates a noncooperative game of multiagent systems in incomplete information scenarios. To cooperatively seek the Nash equilibrium (NE), each agent aims to minimize its own cost function by interacting with its neighbors over undirected communication networks. While existing distributed NE seeking methods alleviate the computational burden, they also entail higher communication costs. To reduce communication frequency and bandwidth, we propose a class of distributed edge-based NE seeking methods by leveraging the advantages of event-triggered mechanisms and quantization techniques. In the proposed framework, a buffer is equipped on every communication channel, thereby reducing the workload of both agents at either end. It is shown that the convergence error can be made arbitrarily small by tuning a constant threshold, and it can asymptotically converge to zero by setting an exponentially decaying threshold or a dynamic threshold. Moreover, in the case of unawareness of any global information, we further provide a fully distributed event-triggered quantized algorithm, by which the convergence error is ultimately uniformly bounded. Finally, two numerical examples are utilized to illustrate the effectiveness of the proposed algorithms.

This paper addresses the problem to simulate ARVA sensors using ROS and Gazebo. ARVA is a French acronym which stands for Appareil de Recherche de Victims en Avalanche and represents the forefront technology adopted in Search & Rescue operations to localize victims of avalanches buried under the snow. The aim of this paper is to describe the mathematical and theoretical background of the transceiver, discussing its implementation and integration with ROS allowing researchers to develop faster and smarter Search &Rescue strategies based on ARVA receiver data. To assess the effectiveness of the proposed sensor model, We present a simulation scenario in which an Unmanned Aerial Vehicle equipped with the transceiver sensor performs a basic S&R pattern using the output of ARVA system.

This paper introduces a new approach for victim localization in avalanches that will be exploited by UAVs using the ARVA sensor. We show that the nominal ARVA measurement can be linearly related to a quantity that is sufficient to reconstruct the victim position. We explicitly deal with a robust scenario in which the measurement is actually perturbed by a noise that grows with the distance to the victim and we propose an adaptive control scheme made of a least-square identifier and a trajectory generator whose role is both to guarantee the persistence of excitation for the identifier and to steer the ARVA receiver towards the victim. We show that the system succeeds in localizing the victim in a domain where the ARVA output is sufficiently informative and illustrate its performance in simulation. This new approach could significantly reduce the searching time by providing an exploitable estimate before having reached the victim. The work is framed within the EU project AirBorne whose goals is to develop at TRL8 a drone for quick localization of victims in avalanche scenarios.

This paper presents the autonomous battery exchange operation for small scale UAVs, using a mobile ground base that carries a robotic arm and a service station containing the battery exchange mechanism. The goal of this work is to demonstrate the means to increase the autonomy and persistence of robotic systems without requiring human intervention. The design and control of the system and its components are presented in detail, as well as the collaborative software framework used to plan and execute complex missions. Finally, the results of autonomous outdoor experiments are presented, in which the ground rover successfully localizes, retrieves, services, and deploys the landed UAV, proving its capacity to extend and enhance autonomous operations.

This paper deals with the problem of modelling and controlling an innovative aerial manipulator, i.e. a vertical take-off and landing aircraft equipped with a fully-actuated robotic arm. This system is able to perform complex operations that require the physical interaction with the surrounding environment while remaining airborne. Once a detailed dynamical model in the planar case is provided, a control law able to govern all the degrees of freedom of the system is discussed. Beside the methodological contribution that is easily extendable to different combinations of UAVs and robotic arms, the effectiveness and main properties of the proposed control algorithm are illustrated with the help of an experiment that takes into account the case in which the manipulator is in contact with the surrounding environment.

This video presents experiments conducted within the final review meeting demonstration session of the AIRobots project. AIRobots started at 2010 and the final review meeting took place on 22 of March, 2013. The presented experiments cover a wide area of the challenges related with aerial industrial inspection. In particular, multiple test-cases related with both vision-based and contact-based inspection and in general physical interaction are shown. It is highlighted that these experiments were recorded live during the project demonstration and evaluation process.

This paper provides an architectural description from the software point of view of the simulator environment developed for the AIRobots project. The scope of the project is the realization of an aerial service robotic prototype, a sort of robotic hand to be employed in inspection-by-contact tasks. The simulator is then crucial in both the training of the human operator, and as a support tool for the development and validation of low- and high-level control algorithms. The tasks that can be performed are not limited to free-flight missions, but include also to the cases in which the robot has to actively interact with the environment. The simulator relies on Simulink and Blender, and has been designed with a modular structure that makes software-in-the-loop and hardware-in-the-loop simulations possible by simply replacing the different control modules with the real controllers on the prototypes.

This work presents the design and experimental validation of a control strategy for an innovative modular aerial vehicle characterized by redundant actuation. For this class of aircraft, the distinguishing feature of the proposed design - which sets it apart from standard vertical take-off and landing (VTOL) underactuated configurations such as helicopters, ducted-fan tail-sitters or multi-rotors - is that the input redundancy can be employed to improve the dynamical properties of the system. In particular, the vehicle performance can be enhanced in certain applications that benefit from a larger number of degrees of freedom being simultaneously controlled. A control strategy is proposed which is capable of globally stabilizing the dynamics of this class of vehicles along a desired trajectory. The methodology is validated by means of experiments carried out on a special prototype obtained by rigidly connecting two ducted-fan tail-sitter UAVs.

This video shows an innovative over-actuated aerial vehicle specifically designed for tasks requiring high maneuverability such as aerial inspection of infrastructure and aerial manipulation. The main feature of the system is the fact that the redundancy of actuators allows to obtain maneuvers otherwise impossible for other aerial systems such helicopters or quadrotors. The experiments proposed in the video demonstrate how this improved maneuverability can be exploited both during free-flight operations or when physical interaction with the environment is required.

Variable stiffness actuators realize highly dynamic systems, whose inherent mechanical compliance can be properly exploited to obtain a robust and energy-efficient behavior. The paper presents a control strategy for variable stiffness actuators with the primarily goal of tracking a limit cycle trajectory and a desired stiffness, which is a function of the output position of the actuator. The proposed controller guarantees that the load, attached at the output of the actuation system, asymptotically tracks the desired cyclic motion and the desired stiffness even in presence of external disturbances. Experimental tests on the rotational variable stiffness actuator vsaUT-II validate the control strategy.

This paper focuses on the modeling and control of a flying robot. The complete system, composed of a quadrotor unmanned aerial vehicle and a custom-made manipulator, has been designed for remote inspection by contact of industrial plants. The goal of this paper is to show the dynamical characteristics of the flying robot during tasks that require physical interaction, and to determine a control strategy that allows to safely interact with unknown environments. The methodology has been implemented on a real prototype and tested in an indoor area. Experimental results validate the proposed controller and show its effectiveness.

This video shows a special prototype of miniature aerial robot, the aerial manipulator, able to accomplish operations requiring the physical interaction with the surrounding environment while remaining completely airborne. The robot arises from the combination of a vertical take-off and landing aircraft, in particular a ducted-fan configuration, and a miniature robotic arm. The physical interaction relies on impedance control considerations. The control law is able to govern all the degrees of freedom of the system both in free-flight and during the interaction with the surrounding environment. In the latter case, the stability of the contact is robustly preserved. The video shows the robotic setup and the effectiveness of the proposed control algorithm in a real-world scenario.

This paper addresses the problem of robust take-off of a quadrotor unmanned aerial vehicle (UAV) in critical scenarios, such as in the presence of sloped terrains and surrounding obstacles. Throughout the maneuver, the vehicle is modeled as a hybrid automaton whose states reflect the different dynamic behaviors exhibited by the UAV. The original take-off problem is then addressed as the problem of tracking suitable reference signals in order to achieve the desired transitions between different hybrid states of the automaton. Reference trajectories and feedback control laws are derived to explicitly account for uncertainties in both the environment and the vehicle dynamics. Simulation results demonstrate the effectiveness of the proposed solution and highlight the advantages with respect to more standard open-loop strategies, especially for cases in which the slope of the terrain renders the take-off maneuver more critical to achieve.

This paper addresses the problem of robust takeoff and landing control of a quadrotor UAV (Unmanned Aerial Vehicle). During the critical flight phases of takeoff and landing the vehicle dynamics change according to the possible existence of contact with the ground. To model the vehicle during the overall maneuver a hybrid automaton is used where each state corresponds to a different dynamic behavior exhibited by the UAV. The original takeoff and landing problems are then addressed as a problem of tracking suitable reference signals in order to achieve the desired transitions between different hybrid states of the automaton. Both reference trajectories and feedback control laws are derived to explicitly account for measurement noise and uncertainties, in both the environment and in the vehicle dynamics. Simulation results demonstrate the effectiveness of the proposed solution.

Two techniques for slip detection with a rubber-based tactile matrix sensor are presented. The described results have been obtained within a common research activity between the Robotics and Automation Laboratory of the University of Bologna and the Control Laboratory of the Delft University of Technology. The first technique is based on a frequency analysis of the position of the center of force distribution. The main idea is that before a slip situation actually occurs, it is possible to detect a micro movement of the object due to the elasticity of the rubber. By implementing a FFT of the center of distribution and by testing the frequency components, the slip is identified before it practically occurs. The second approach is based on the principle that the normal forces measured by the tactile sensor fluctuate with a certain frequency during slip because of the rubber elasticity. This fluctuation is due to a 'catch and snap back' effect, which is present when an object is slipping over the sensor's surface. By testing the frequency domain of the normal force a slip condition can be detected. A comparison of the two approaches is presented and discussed on the basis of experimental results obtained in both laboratories.