In this paper, study about an optimization method to find the design parameters of fish robot. First, we analyze the dynamic model of the 3-joint Carangiform fish robot by using Lagrange method. Then the Genetic Algorithm (GA) is used to find the optimal lengths’ values of fish robot’s links. | TAÏP CHÍ PHAÙT TRIEÅN KH&CN, TAÄP 18, SOÁ K1- 2015 An application of genetic algorithm to optimize the 3-Joint carangiform fish robot’ s links to get the desired straight velocity Phu Duc Huynh Tuong Quan Vo University of Technology, VNU – HCM ABSTRACT: Biomimetic robot is a new branch of researched field which is developing quickly in recent years. Some of the popular biomimetic robots are fish robot, snake robot, dog robot, dragonfly robot, etc. Among the biomimetic underwater robots, fish robot and snake robot are mostly concerned. In this paper, we study about an optimization method to find the design parameters of fish robot. First, we analyze the dynamic model of the 3-joint Carangiform fish robot by using Lagrange method. Then the Genetic Algorithm (GA) is used to find the optimal lengths’ values of fish robot’s links. The constraint of this optimization problem is that the values of fish robot’s links are chosen that they can make fish robot swim with the desired straight velocity. Finally, some simulation results are presented to prove the effectiveness of the proposed method. Keywords: Biomimetic robot, Carangiform, Fish robot, Lagrange, Genetic Algorithm (GA), Singular Value Decomposition (SVD), Straight velocity, Links. 1. INTRODUCTION Fish has been passing over millions years of evolution throughout many generations to adapt to the harsh of underwater environment. So more and more types of fish with diversity movements were born to be able to exist in natural environment. Many kinds of fish move by using the change of their body shape for generating the movement. This changing shape generates propulsion force to make fish moves forward effectively. Carangiform fish type also uses this changing shape to move itself in the underwater environment. Based on the motion mechanism of Carangiform fish, there are some researches about this type of motion. Koichi Hirata et al. discussed turning modes for the fish robot that uses tail swing [1]. Qin .