Passivity-based Teleoperation of Multi-Robot Systems with Time-Varying Topology

This talk addresses the problem of establishing a bilateral teleoperation system for remotely controlling the motion of groups of (possibly heterogeneous) mobile robots in a decentralized way. Instead of being focused on a particular class of robot, an approach general enough to allow for a straightforward application to any kind of mobile robot, such as aerial, ground, space, naval, or underwater vehicles, is discussed. Indeed, the fundamental problem addressed in this work consists of establishing a bilateral teleoperation channel for remote navigation purposes, i.e., a necessary premise for any other specific objective, such as tele-exploration, transport, or-manipulation. In the presented teleoperation system, the remote mobile robots, namely the slave-side, should possess some minimum level of local autonomy and act as a group, e.g., by maintaining some desired inter-distances and avoiding collisions by means of decentralized controllers. At the same time, the human operator, acting on the master device, should be in control of the overall group motion and receive, through haptic feedback, suitable cues informative enough of the remote robot/environment state. On top of this remote navigation layer, the group should still be allowed to perform additional local tasks by exploiting the internal slave side redundancy with respect to the master device commands. Bilateral teleoperation of (multiple) mobile robots presents several differences with respect to conventional teleoperation systems: first, there exists a structural kinematic dissimilarity between master and slave sides, i.e., the master possesses a limited workspace while the slave an unbounded one. Second, in a typical scenario, there is no physical contact with the environment since this would represent a dangerous situation (e.g., a crash) for the robots. Therefore, the interaction forces with the external world, such as contact forces, must be fabricated and, to some extent, a redefinition of standard concepts related to telepresence is required to properly assess the human operator immersiveness. Lastly, the slave side possesses large motion redundancy w.r.t. the master side because of the mismatch between the degrees of freedom (DOFs) of the master (usually in the range of 3V6), and the DOFs of the slave (in the range of 6N for N robots, when considered as rigid bodies). In addition to these issues, a proper design of a multi-robot slave-side must also cope with the typical requirements of decentralized sensing and control for guaranteeing robustness to failures, achieving actual feasibility, and ensuring low computational