Fabrizio Caccavale

This paper deals with the centroid and formation control problem of multi–agent robotic systems. The proposed solution is based on a leader–follower scheme, where only a subset of agents, i.e., the leaders, knows the desired trajectories for the centroid and the formation of the system, while the other agents, i.e., the followers, are required to estimate them through a dynamic consensus scheme. The leaders perform trajectory scaling in order to cope with velocity limits of the single robots. Once the trajectories for the centroid and the formation are estimated, each agent can compute its own reference trajectory and a local control loop is designed to track it. An approach to map the velocity constraints of each agent to the velocity limits at the task level is developed. Then, a trajectory scaling algorithm is adopted to ensure velocity constraints fulfillment. The stability and performance properties are rigorously analyzed under two different assumptions about the planned trajectories. Finally, both simulation and experiments are run on Robotarium platform to show the effectiveness of the approach and the effect of parameter tuning on the achieved performance.

This work proposes an Augmented Reality (AR) application designed for HoloLens 2 which allows human operators, without particular experience or knowledge of robotics, to easily interact with collaborative robots. Building on the application presented in a previous work of the authors, the novel contributions are focused on a bi-directional interaction that manages the exchange of data from the robot to the human operator and, in the meantime, the flow of commands in the opposite direction. More in detail, the application includes the reading of the robot state, in terms of joint positions, velocities and torques, the visualization of the workspace and the generation and manipulation of the end-effector trajectory by directly moving a set of way-points displayed in the AR environment. Finally, the trajectory feasibility is verified and notified to the user by taking into account the workspace limits. A usability study of the AR platform has been conducted involving 45 participants with different ages and expertise in robot programming and Extended Reality (XR) platforms, comparing two programming methods: a classical kinesthetic teaching interface, provided by the Franka Emika Panda cobot, and the presented AR platform. Participants have reported the effectiveness of the proposed platform, experiencing less physical demand and higher intuitiveness and usability.

This paper presents a motion control scheme for a new concept of omnidirectional aerial vehicle for transportation and manipulation tasks. The considered aerial platform is a novel quadrotor with the capability of providing multi-directional thrust by adding an actuated gimbal mechanism in charge of modifying the orientation of the frame on which the four rotors are mounted. The above mechanical design, differently from other omnidirectional unmanned aerial vehicles (UAVs) with tilted propellers, avoids internal forces and energy dissipation due to non-parallel propellers’ axes. The proposed motion controller is based on a hierarchical two-loop scheme. The external loop computes the force to be applied to the vehicle and the reference values for the additional joints, while the inner loop computes the joint torques and the moment to be applied to the multirotor. In order to make the system robust with respect to the external loads, a compensation of contact forces is introduced by exploiting the estimate provided by a momentum based observer. The stability of the motion control scheme is proven via Lyapunov arguments. Finally, two simulation case studies prove the capability of the omnidirectional UAV platform to track a 6-DoFs trajectory both in free motion and during a task involving grasping and transportation of an unknown object.