Design Of Propulsion Mechanism Of Bionic Robot Fish With Flexible Mechanism

As one of the underwater vehicles,the bionic robotic fish has the advantages of great maneuverability,fast motion response,high propulsion efficiency and little noise.It has been widely used in many fields such as marine biological observation,marine water quality monitoring,submarine pipeline inspection and military exploration.The bionic robotic fish is a new high-tech equipment in the current marine field.The propulsion mechanism of the bionic robotic fish determines its swimming features.The bionic robotic fish with rigid components cannot adapt to underwater movement,and there are problems such as low efficiency and inability to imitate the flexible oscillation of the fish.Therefore,the research trend is the bionic robot fish that can swing flexibly with higher swimming efficiency.Since the existing methods cannot establish analytical models for closed-loop elastic structures with large deformations,it is difficult to establish kinematic models for existing bionic robotic fish propulsion mechanisms of elastic components,which makes it unavailable to structural dimensional optimize.In this paper,we propose an equivalent modeling method for the closed-loop slender thin plate large deformation problem,which leads to the establishment of a coordinated deformation analysis model for the elastic thin plate parallel mechanism.Moreover,we complete the design of the bionic fish’s tail propulsion mechanism and build an experimental prototype to verify the effectiveness and correctness of the proposed method.The specific contents of this thesis are as follows.(1)The deformation model of the thin plate is proposed with the principal axis decomposition of the structural stiffness matrix method.By discretizing the variable elastic plate into several elastic series structures with 6-DOF elastic joints,the relationship between force and deflection is constructed.The objective function of the deformation is constructed and the deformation results are obtained.Then which are verified by the simulation calculation and experiments can verify it is accurate.Comparing with traditional calculation method,this method can solve the approximate deformation more quickly and easily.Then established a closed-loop elastic large deformation calculation model.(2)Complete the propulsion mechanism design with the established trajectory movement process.The motor-driven cylindrical cam mechanism has the advantages of realizing fast movement,fast speed regulation and one-way drive of the motor in a small space.Establish the inverse kinematics model of the closed-loop configuration equivalent multi-rigid system,which makes the cylindrical cam contour design completed.Therefore,the tail of the propulsion mechanism can swing according to the fish motion curve.(3)Build the prototype of the propulsion mechanism and the bionic robotic fish for experiments to verify the design.After completing the overall design and detailed design of the bionic robotic fish,the corresponding prototype was built and the experiment was conducted.The experiment was divided into two parts: the tail motion accuracy experiment of the propulsion mechanism and the underwater propulsion experiment of the bionic robotic fish.The first experiment is motion accuracy experiment of the propulsion mechanism.During first experiment,the tail motion curves are measured.It find that the experimental measurements are consistent with the expected motion target and the model calculation results,which indicates the design is reasonable and the model is correct.For the underwater propulsion experiment of the bionic robotic fish,when placed underwater the swimming speed of the bionic robotic fish is measured by the rotate phase difference between the cylindrical cams and the swing frequency of tail.The experimental results indicate that swimming velocity increases and then goes down;the initial phase difference between cylindrical cams can increase the maximum speed of the robotic fish.Conclusions can be drawn that this design is feasible and and introduces novel design for bionic robotic fish.