Stability, Transparency, and User Experience with Grounded, Wearable, and No Force-Feedback Tele-Operation

Usability is one of the most important aspects of tele-operation. Ideally, the operator's experience should be one of complete command over the remote environment, but also be as close as possible to what s/he would have if physically present at the remote end - in terms of both action and perception. These two aspects may coincide in favorable conditions, where classic approaches such as the four-channel architecture assure transparency of the control framework, creating than a condition of so-called perfect telepresence. In presence of substantial delays between the user and the slave, however, the inherent stability-performance trade-off of bilateral tele-operation deteriorates not only transparency, but also command. The used haptic interface influences the possibility to experience perfect telepresence as well. Grounded interfaces are the ideal choice for high quality feedback but they are generally heavy and barely movable, while wearable interfaces are preferable for their portability. Among the latter there is then a trade-off between agility/freedom of movements (maximized with small devices, e.g., hand exoskeletons) and feedback effectiveness (better results using full arm exoskeletons). There are then cases in which the lightest user’s interface is desirable, removing any possible haptic feedback in favor of immediacy of use. As unilateral tele-operation does not include force feedback, it is absolutely robust to delays, while the operator’s ability to fine control and regulate the remote interaction is obviously strongly restricted, as well as her/his possibly to compensate for any control inaccuracy. An augmented, unilateral approach is given by tele-impedance, which controls the slave-environment interaction by measuring and remotely replicating the user’s limb endpoint position and impedance. With this control paradigm the user's control of the remote interaction is better than classic unilateral approach, but with performance still not comparable to the ones of bilateral solutions. In an attempt to improve the tele-operation state-of-the-art and user's experience in the above different areas, this thesis addresses all the three previous problems, i.e., usability and effectiveness of tele-operation with no, wearable and grounded haptic feedback. In unilateral tele-operation scenarios, it introduces a novel shared-autonomy framework applied to a bimanual setup. This solution facilitates the accomplishment of complex and composed tasks, leaving to the user the choice between the classic direct unilateral approach and the new shared-autonomy one on the need. In the field of wearable haptic interfaces, this thesis introduces a new wearable device that involves only the last two arm links (i.e., forearm and hand) and renders a force at the hand palm center, settling it between the two extremes above, and better balancing the trade-off between portability and capability to provide an effective force feedback. The design of a prototype will be followed by its characterization, psychometric assessment and experimental section, that will validate this new solution. Finally, dealing with full-transparency controls for perfect telepresence applications, it defines a novel control framework which integrates a new, fully transparent, two-channel bilateral architecture with the tele-impedance paradigm, so as to provide a maximum degree of both transparency and command in all delay conditions and, consequently, a better operator’s experience in spite of time inconsistencies. Furthermore, to evaluate and compare the usability of the new method with the state-of-art, an extensive campaign of multi-subject dynamic experiments, with different communication delay profiles, is performed.