  We present an approach for the verification and validation (V&V) of robot
assistants in the context of human-robot interactions (HRI), to demonstrate
their trustworthiness through corroborative evidence of their safety and
functional correctness. Key challenges include the complex and unpredictable
nature of the real world in which assistant and service robots operate, the
limitations on available V&V techniques when used individually, and the
consequent lack of confidence in the V&V results. Our approach, called
corroborative V&V, addresses these challenges by combining several different
V&V techniques; in this paper we use formal verification (model checking),
simulation-based testing, and user validation in experiments with a real robot.
We demonstrate our corroborative V&V approach through a handover task, the most
critical part of a complex cooperative manufacturing scenario, for which we
propose some safety and liveness requirements to verify and validate. We
construct formal models, simulations and an experimental test rig for the HRI.
To capture requirements we use temporal logic properties, assertion checkers
and textual descriptions. This combination of approaches allows V&V of the HRI
task at different levels of modelling detail and thoroughness of exploration,
thus overcoming the individual limitations of each technique. Should the
resulting V&V evidence present discrepancies, an iterative process between the
different V&V techniques takes place until corroboration between the V&V
techniques is gained from refining and improving the assets (i.e., system and
requirement models) to represent the HRI task in a more truthful manner.
Therefore, corroborative V&V affords a systematic approach to 'meta-V&V,' in
which different V&V techniques can be used to corroborate and check one
another, increasing the level of certainty in the results of V&V.
