Cultivated Microorganisms Control a Real Robot: A Model of Dynamical Coupling between Internal Growth and Robot Movement

Abstract

In biological systems, internal microorganisms adaptively survive but often serve necessary functions to the host, such as energy production by mitochondria as symbiosis. On the other hand, malignant germs have a parasitic relationship with the host and provide no benefit. A significant property that distinguishes healthy symbioses and malignant parasites is reproduction speed, or pace. For example, the rapid reproduction of influenza viruses destructs the host system, resulting in death. This study explored the necessary temporal property to establish a healthy relationship with the host under conditions where internal organisms have individual life spans. We propose a simple model of microorganisms, which are distributed spatially as colonial organizations undergoing temporal evolution and hypothesize that a self-consistent rhythm generated in collective behavior that is functionally coupled with the temporal global property of the host system is critical. To investigate the real-time coordination capability, an experimental framework with a mobile robot moving in the real world was used. As the on-line system, the microorganism model controls this robot. In this model, microorganisms expanded spatially and had colonial and power law distributions through time evolution. The neighboring distances, which are crucial for reproduction speed and are globally modulated by the size of the whole living area, are plastically changed to exhibit a rhythmic modulation. In the real-environmental experiment, the robot’s navigation was successfully demonstrated by producing a temporal adaptability of microorganisms with the living area reshaped according to the current sensory information of the mobile robot. This is a first step of the microorganism-based framework to investigate the real-time coordination mechanism between internal and external timescales. The result may further groundbreaking research of bio-morphological robots.