Coordinated collective behavior through contact interactions and adaptive oscillators

The collective behavior of animals and robots, such as flocking and schooling, often involves long-range sensing within low-density groups. However, when collectives are in high density configurations their vision and communication capabilities may be compromised. Instead of vision and communication, individuals in high density collectives may leverage physical interactions to coordinate their movements. In this talk we present design principles for high density collectives to achieve phase synchronized motion through contact interactions. This approach relies on appropriately chosen adaptive oscillators that govern each individual's movement, and that can synchronize through contact interactions between robots. We demonstrate these capabilities through two sets of experiments: 1) worm-inspired collective undulatory movement in which undulatory gaits synchronize through contact, and 2) ant-inspired collective manipulation in which pushing robots synchronize their collective pushing phases. To study the stability of these collective behaviors we introduce the contact return-map, which examines the evolution of phases through contact to next contact. The contact return-map provides the ability to design oscillator feedback rules that enable optimal synchronization and collective movement. We lastly discuss how these principles may apply to biological collectives that operate in close-proximity.