This work addresses the interaction control problem of a fully actuated aerial vehicle considered as a flying end-effector. We tackle the problem using geometrically consistent variable-stiffness impedance control for safe wrench regulation using the concept of energy tanks, where both the modeling and the control are carried out in the port Hamiltonian framework. We exploit previous well-known results in the literature of ground manipulators and extend them to be applied for novel and challenging aerial physical interaction with a focus on quasi-static applications. The energy-awareness of the presented control method guarantees the stability of the aerial robot in both free-flight and in-contact scenarios together with a level of safety in the case of contact-loss with the unknown environment. Furthermore, by utilizing bond graphs we demonstrate how the closed-loop passivity can be graphically conducted. The validity of our proposed approach is shown via several experiments. We also provide several insights on how the proposed framework could be extended to a generic dynamic aerial physical interaction.

The integration of computer vision techniques for the accomplishment of autonomous interaction tasks represents a challenging research direction in the context of aerial robotics. In this paper, we consider the problem of contact-based inspection of a textured target of unknown geometry and pose. Exploiting state of the art techniques in computer graphics, tuned and improved for the task at hand, we designed a framework for the projection of a desired trajectory for the robot end-effector on a generically-shaped surface to be inspected. Combining these results with previous work on energy-based interaction control, we are laying the basis of what we call vision-based impedance control paradigm. To demonstrate the feasibility and the effectiveness of our methodology, we present the results of both realistic ROS/Gazebo simulations and preliminary experiments with a fully-actuated hexarotor interacting with heterogeneous curved surfaces whose geometric description is not available a priori, provided that enough visual features on the target are naturally or artificially available to allow the integration of localization and mapping algorithms.

In this work, we show how the interactive behavior of an aerial robot can be modeled and controlled effectively and elegantly in the port-Hamiltonian framework. We present an observer-based wrench/impedance controller for a fully-actuated hexarotor. The analysis and control are performed in a geometrically consistent manner on the configuration manifold of the special Euclidean group SE (3) such that the UAV's nonlinear geometric structure is exploited. The controller uses a wrench observer to estimate the interaction wrench without the use of a force/torque sensor. Moreover, the concept of energy tanks is used to guarantee the system's overall contact stability to arbitrary passive environments. The reliability and robustness of the proposed approach is validated through simulation and experiment.