Noise-based underactuated mobile robot inspired by bacterial motion mechanism

Living organisms have various kinds of flexibility and robustness which are realized by ¿yuragi,¿ i.e. biological fluctuations or noises. Bacterial motion is a form of noise-based motion, since bacteria can move towards a higher concentration of some chemical which they prefer even though they have only a limited 1-DOF of flagella for mobility. Bacteria also have only a limited sensory device which cannot detect the spatial gradient of the chemical at a time. The simple strategies that bacteria take to realize chemotaxis are (1) to tumble (or turn) to change orientation randomly with unbundled flagella in various directions being hit by surrounding water molecules, and (2) to change the frequency of tumbling according as the time change of chemical concentration. In this paper, we describe a small and simple, 1-DOF swimming robot developed by mimicking the bacterial motion generation mechanism. The robot only has a single motor and a single sensor (a photo detector), however, by changing its orientation in response to various noises which exist in the environment, and by changing the frequency of turning, the robot can approach its goal. Experimental results indicate that the robot statistically approaches the goal (a light source) in two dimensional space with its 1-DOF actuator, which would be impossible for the robot to achieve without utilizing noises in the environment.