K. Hirata and D. Aoki, January 24, 2003

In order to investigate the up-down motion of a small fish robot, we designed and built the Prototype Fish Robot, PF-200. We discussed about various the up-down motion mechanisms. As the result, the PF-200 was adopted 'movement of weight' mechanism. The mechanism brings inclinations of the fish robot, and it has the up-down motion with the thrust force of a tail fin.

The figure to the right shows the structure of the PF-200. A weight is located in a head, and it moves to the front and the rear. A servomotor for the tail fin and another servomotor for the weight are located in a body. A microcomputer drives the servomotor with a given pattern repeatedly.

Structure of the PF-200

The follows figures shows the inclinations of stationary situation with the movement of the weight. The inclinated angle of the fish robot is affected by the movement of the weight and the height between the center of gravity and the floating point.

Down Motion

Up Motion

To get the up-down motion of the PF-200 suitably, we must adjust the floating force carefully. The follows figures shows the experimental results with thin balsa floats (40x10x2 mm) for the adjustment. The PF-200 has 543.4 gf of weight on air. The adjustment of a balsa is only 0.6 gf. The PF-200 swims with up-down motion after the adjustment.

PF-200の上下運動ビデオ（MPEG1，7.8MB）

(a) Float: 16 sheets (-9.6 gf)

(b) Float: 17 sheets (-10.2 gf)

(c) Float: 18 sheets (-10.8 gf)

(d) Float: 19 sheets (-11.4 gf)

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CAD Data of the PF-200 (Underconstructing...)
Microcomputer and Program of the PF-200 (Underconstructing...)

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