TS-110
Development of Experimental Fish Robot
Koichi HIRATA*
ABSTRACT
Underwater robots are widely used in the fields of ocean development, ocean investigation and marine environmental protection. They need higher efficient of propulsive performance. In order to get an underwater robot with high propulsion efficiency, we have studied on a fishlike swimming mechanism and developed a prototype fish robot. It has about 600 mm body length, and three joints of a tail moved by two servomotors with an original link mechanism. It can simulate various moving patterns optionally. In this paper, experimental results of swimming speed measurements using two types of a tail fin are reported. Also, research areas needed for getting higher performance fish robots are discussed.
Key Words: Fish Robot, Propulsion System, Robotics, and Underwater Technology
1. INTRODUCTION
Underwater robots are widely used in the fields of ocean development, ocean investigation and marine environmental protection [1], [2]. As the request that the underwater operation should be carried out more efficiently becomes strong, autonomous underwater robots are planned, and several robots have been already developed. They need higher efficiency of propulsive performance.
The author has taken much interest in high efficient propulsion of fish, and attempts to apply it to the underwater robot for fishlike swimming mechanism, In order to develop a high-performance and intelligent underwater robot, a study on fish robot has been started since 1999 at Ship Research Institute.
Purposes of this study are as follows.
(1) Development of a high efficient propulsion device,
(2) Development of a fish robot which has high propulsive performance,
(3) Development of an intelligent fish robot which learns optimal swimming pattern itself,
(4) Discussion of a suitable power source for a fish robot.
2. PROTOTYPE FISH ROBOT
In order to clarify characteristics of a fishlike swimming mechanism, and discuss high efficient propulsion of a fish robot, a prototype fish robot that has about 600 mm body length is developed.
2.1 DESIGN CONCEPT
Swimming methods of fish are various; i.e., an eel swims waving the whole of body, and a flat fish swims waving long fins. In this study, the focus is on swimming method of the fishes such as a pike or a tuna, which waves a tail fm and a tail peduncle to right and left. Figure 1 shows a shape of the pike and the tuna that is referred to the prototype fish robot. They have different shapes of the tail fin. The pike has a triangle tail fin, and it has high acceleration performance. The tuna has a crescent tail fin, and it can swim with high speed and high efficiency. In order to clarify their fundamental characteristics, the prototype fish robot is developed. The author expects that their results contribute to a development of higher performance fish robots in the next step.
Several model fish robots were manufactured before designing the prototype fish robot. [4], [5]. From their test results and discussions, it is considered that a rotating electric motor is suitable as a power source for high speed and high efficiency. However, the prototype fish robot needs to simulate complex and various moving patterns of the tail, because it is necessary to clarify the relationship between the moving pattern and propulsive performance. Therefore, two servomotors for a radio control model (R/C) are adopted. They can easily control various moving patterns.
Fig. 1 Shape of a pike and a tuna [3]
Fig. 2 Structure of the prototype fish robot
