  Systems for relative localization in multi-robot systems based on
ultra-wideband (UWB) ranging have recently emerged as robust solutions for
GNSS-denied environments. Scalability remains one of the key challenges,
particularly in ad-hoc deployments. Recent solutions include dynamic allocation
of active and passive localization modes for different robots or nodes in the
system. With larger-scale systems becoming more distributed, key research
questions arise in the areas of security and trustability of such localization
systems. This paper studies the potential integration of collaborative-decision
making processes with distributed ledger technologies. Specifically, we
investigate the design and implementation of a methodology for running an UWB
role allocation algorithm within smart contracts in a blockchain. In previous
works, we have separately studied the integration of ROS2 with the Hyperledger
Fabric blockchain, and introduced a new algorithm for scalable UWB-based
localization. In this paper, we extend these works by (i) running experiments
with larger number of mobile robots switching between different spatial
configurations and (ii) integrating the dynamic UWB role allocation algorithm
into Fabric smart contracts for distributed decision-making in a system of
multiple mobile robots. This enables us to deliver the same functionality
within a secure and trustable process, with enhanced identity and data access
management. Our results show the effectiveness of the UWB role allocation for
continuously varying spatial formations of six autonomous mobile robots, while
demonstrating a low impact on latency and computational resources of adding the
blockchain layer that does not affect the localization process.
