Design And Experimental Research Of A New Caudal-fin Propelled Robotic Fish

Compared with the traditional underwater propulsion,bionic robotic fish has the advantages of high propulsion efficiency,good maneuverability and small disturbance to the environment.The design and research of robotic fish has become an important subject in the field of underwater robot.The study shows that the efficiency of the mechanism is an important factor affecting the speed of the robotic fish for the Body and/or Caudal Fin(referred to BCF)movement mode of the robotic fish.The caudal-fin propeller with two-dimensional motion space can greatly simplify the mechanical structure and motion control of the robotic fish.This paper designed a biomimetic robotic fish based on the new two-degree-of-freedom caudal-fin propulsion mechanism.It avoids the low transmission efficiency of the frequent reversing of the motor in the propulsion mechanism,and realize the robotic fish's four basic sports only by its caudal fins,including straight parade,turning,floating.The results of underwater experiments of it show that the robotic fish has good speed and maneuverability,which could provide a new reference for the design of propulsion mechanism of robotic fish.The main research work is as follows:(1)This paper designs a new type of Two-DOF caudal-fin propulsion mechanism and completes the system design of the robotic fish.Firstly,the main problems that need to be solved in the design of robot fish and system components are introduced.Then,a design scheme of Two-DOF caudal-fin propulsion mechanism is proposed and a concrete structural design is given based on the comparative analysis of the existing propulsion mechanism.Large capacity lithium batteries and brushless DC motors are used as the power unit of the robotic fish.And it solves the designing of wireless communication and program of hardware equipment of the robotic fish.The sealing scheme of the robotic fish is optimized and the weight of the robotic fish is evaluated by means of Solid Works tools.Eventually,the principle prototype of the bionicrobotic fish propelled by the Two-DOF caudal-fin is completted.(2)The kinematic equations of the Two-DOF caudal-fin propulsion mechanism are established,and the virtual prototype simulation is carried out.This paper introduced the working principle of the novel propulsion mechanism.Use the motion consistency of the double slanting block and the universal joint as the starting point,it solves the kinematics equation of the propulsion mechanism,and deduces the positive and inverse kinematics of the propulsion mechanism.Two kinds of working modes of the propulsion mechanism are proposed,namely,the motor is moving in the same and opposite direction as the same speed.Two kinds of control modes of velocity and position are presented.In the Adams,the kinematics simulation of the linear swimming,turning,floating and diving movement of the robotic fish's virtual prototyping model is carried out.The variation curve of the caudal fins' angle under the corresponding motor input function verifies the feasibility of the novel Two-DOF caudal-fin propulsion mechanism for the robotic fish.(3)Swimming test and experimental results of the robotic fish are carried out,According to the results of kinematic simulation,this paper establishes control strategies in five swimming postures,and gives parameter-changing table of the corresponding motor control.And write the control program in Visual Studio environment.The task of debugging of each module,sealability test and counterweight correction has been completed before the experiment.Straight swimming and turning experiments of the robotic fish are carried out in the outdoor pond with the unmanned aerial vehicle(UAV)photographing.We get the experimental data by processing the acquired videoes to get the robotic fish's position coordinates.The results of the experiments show that the cruising speed of the robotic fish is about 0.69 m/s and its minimum turning radius is about 0.23m(0.16BL).