No abstract

Recently, there is a rising interest on studying fish-like underwater robots because of real fish's great maneuverability and high energy efficiency. However, the researches about the fish-like underwater robots have not been done so much and there are still diverse problems in respect of using of the fish robot in the real environment such as in the river. For example, the fish robot has a short operating time and cannot move narrow passage such as swimming between aquatic plants. Therefore, this paper mainly describes a control method according to propulsion algorithm for improving energy efficiency and obstacle avoidance. The fish robot 'Ichthus' has a 3-DOF serial link-mechanism and is developed in KITECH. Also, we propose a dynamic equation of the fish robot to use the underwater environment. In the control portion, response characteristics of the fish robot were analyzed according to the input parameters of tail fin's amplitude and oscillation frequency. In consequence of this result, Control parameters of robot fish were found. These parameters are useful to increase energy efficiency and it can be used when the fish robot moves in the real environment.

Reference velocity is a performance index required to derive the efficient movement of each joint from pseudo-inverse which is a joint movement optimized based on the speed of front joint in a multi-body with hyper redundancy and has been applied in finding the optimal solution of each joint at kinematic level when creating the swimming motion of a bio-inspired robotic fish. The motion of each joint in creating the movement of a bio-inspired robotic fish has been programmed based on sinusoidal motion inspired by the swimming pattern of an actual fish and successful in creating a flexible movement up to this point, but it turns out that the actual movement of a bio-inspired robotic fish in the water is different from what is expected when the analyzed optimal solution of joint motion in a bio-inspired robotic fish's movement is applied since the thickness, length and width of the target fish affects the result of analysis. When the solution of joint motion based on reference velocity is applied, on the other hand, more flexible swimming movement than those in other existing researches has been observed even though there are still some differences between the movements of an actual fish and a bio-inspired robotic fish such as forward-speed, turning radius and so on.