Human-Led Decentralized Constant-Spacing Robot Platoons Without Communication

Leader-follower-type platooning can aid human management of multiple robots through complex environments, where the human manages constraints and obstacle-avoidance of the lead robot and the other robots follow the same human-generated leader trajectory. However, the spacing error between robots in the platoon should be small to ensure that each robot in the platoon maintains visual contact with its predecessor during tight maneuvers around obstacles. The main challenge is that current decentralized constant-spacing platoons require robot-to-robot communication, to avoid string instability that would increase spacing error along the length of the platoon. Such communication is not always available when ad-hoc platoons are formed without communication infrastructure, or when such broadcast communication is not permissible due to security or jamming concerns. The primary contribution of this letter is the development of a novel string-stable platooning strategy, that enables arbitrarily small spacing error, provided the sensing rate is sufficiently high, using a Delayed Self-Reinforcement (DSR) method. This is the first algorithm that shows arbitrarily small spacing error for constant-spacing platoons without communication. Additionally, simulation results show that the DSR approach results in an 85% reduction in the longitudinal target spacing error for autonomous platoons when compared to the baseline without DSR, which aids in reducing task completion time by 44% in human-led ($N=10$) platoons.