Control of a Micro-Organism as a Prototype Micro-Robot

Mobile devices built on a sub-millimeter scale working in a fluid medium could be useful for manipulation and testing of small biological or electrical components. Complete self-powered mobile systems on this scale already exist, in the form of simple single-celled animals. By applying external control signals, trajectories of these animals can be specified. Protozooans such as Paramecium provide a good example mechanism to begin exploring issues of control, sensing and planning for this environment and size. Path planning using an electric potential has been used to allow these mobile devices to solve a simple maze, using only intrinsic behavior. Using visual sensing of device position, primitive closed-loop trajectory following in the plane has been shown. Based on simple mechanical models [Roberts, 1970], force and velocity limitations for these devices can be estimated.

paramecia circle tracking
circle tracking #1 (movie)
paramecia circle tracking
circle tracking #2 (movie)

Trajectory following for a square path using proportional steering control

Since only the paramecium direction but not the velocity is controllable, the typical oscillatory response of a non-holonomic system using smooth controls is seen. Coordinates in pixel units: 1 pixel = 50 microns. Start location is at about (225, 160). Commanded velocity: 400 micron per second. Position gain : 1.2 V per mm. Electrode spacing 13 mm.

A brief excerpt of closed loop control. click here. (MPEG, 6288K)


R.S. Fearing, ``Control of a Micro-Organism as a Prototype Micro-Robot'', 2nd Int. Symp. on Micromachines and Human Sciences, Nagoya, Japan, Oct. 8-9, 1991. 4.8 MB scanned pdf
Please also see the recent work of Prof. A. Itoh on control of paramecia. Prof. Itoh
A. Itoh, ``Motion control of protozoa for bio MEMS,'' IEEE/ASME Trans. on Mechatronics, vol. 5, no. 2, pp. 181, June 2000.