Contact Sensing Enables Tunable Ratcheting of a Robotic Collective*

Robotic collectives provide a convenient testbed for the study of stimuli-responsive self-propelled particles, and the generated knowledge, in turn, enables new control schemes for the collective. Here we study a simulated robotic collective, with individuals performing run-and-tumble behavior. In the presence of an asymmetric barrier, the collective exhibits flow towards a preferred side of the barrier, which is known as a ratchet effect [1]. The robots implement contact sensing modeled after our recently developed physical sensor mechanism [2]. We employ various rules in response to detected contact – either passive dynamics, alignment with the wall, or a 90/180-degree turn. For both 90 and 180 degree turns we observe an inverse ratchet effect, where the robots preferentially flow towards the direction opposite to the passive run-and-tumble behavior. The employed rule is tunable instantaneously, which allows the robots to modulate their behavior in real-time. We demonstrate how a sensing-control feedback loop on the individual leads to synchronized collective fluctuations in the presence of an asymmetric barrier.
[1] C.J. Olson Reichhardt and C. Reichhardt, Ann. Rev. Cond. Mat. Phys. 2017
[2] S. Li et al., arXiv:2009.05710