Site: The University of Tokyo
Department of Mechano-Informatics
7-3-1 Hongo, Bunkyo-Ku
Tokyo 113, Japan
Date Visited: September 29, 1993
Report Author: L. Salmon
Hirobumi Miura Professor
Professor Hirobumi Miura began by describing his previous work on macroscale robotics. He showed a film showing motion of macroscale biped and quadruped robots he had made. He also demonstrated a robot that completed the more complicated action of throwing a top. His goal was to make an intelligent robot, but he was disappointed with the results of his work. He had to use extensive external computer control to enable his robots to move. Although he used neural network and fuzzy logic control algorithms, the robots are still not intelligent.
The limitations caused by the control problems for his macrorobots led him to focus his attention on smaller robots that used physical properties of their construction to control motion. Professor Miura uses insects as models in his pursuit of simple control of robots. Insects such as the locust use the mechanical construction of their bodies to provide and control actuation. For example, Dr. Miura uses the locomotion mechanisms of insects as models for his microrobots. He showed us two types of microrobots: the microant and the micromosquito. Each of the microrobots uses a different physical mechanism for actuation.
The microant is actuated using the coupling of vibration from the base underneath the robot into its limbs. The base is vibrated at or near the resonant frequency of the microrobot. Direction of motion is determined through differences in the resonance frequencies of the limbs. Changes in the frequency of the table vibration then increase coupling into one limb or the other, and the microant turns. The micromosquito is made of a ferromagnetic material and is actuated by an external magnetic field. Professor Miura indicated that he believes that magnetic actuation is the most promising actuation approach for his microrobotic efforts. The limitation is the need for a large external magnetic field.
Several frequently used fabrication concepts are common to the microrobots described by Professor Miura. The microrobots have rigid, external structures based upon insect exoskeletons. Locomotion is based upon flexible hinges made by connecting rigid members with polyimide. Finally, all of the microrobots are assembled using an assembly process based on origami. The origami-like structure is evident in the microant shown in Figure Mechano.1. Another common theme of Professor Miura is to use milliscale robots to test out microrobot concepts. He showed us a millirobot constructed using shaped memory alloys that his students constructed to test out locomotion similar to that of an insect. Millisize models permit researchers to evaluate concepts without the complications introduced by microfabrication.
Professor Miura showed the JTEC team the laboratory used to fabricate and test microrobots. The laboratory contains the equipment needed to fabricate micromachines and utilizes clean fume hoods that serve a set of multiple processing tools. One hood has a spinner and a CVD system mounted into a common unit. The laboratory is not a clean room, but is sufficient to fabricate the simple structures Professor Miura is studying. Assembly and test equipment are also contained in the laboratory.
Figure Mechano.1. Origami-like structure evident in microant.