  Human-robot collaborative tasks foresee interactions between humans and
robots with various degrees of complexity. Specifically, for tasks which
involve physical contact among the agents, challenges arise in the modelling
and control of such interaction. In this paper we propose a control
architecture capable of ensuring a flexible and robustly stable physical
human-robot interaction, focusing on a collaborative transportation task. The
architecture is deployed onto a mobile manipulator, modelled as a whole-body
structure, which aids the operator during the transportation of an unwieldy
load. Thanks to passivity techniques, the controller adapts its interaction
parameters online while preserving robust stability for the overall system,
thus experimentally validating the architecture.
