| Amphibians with perfect environmental suitability have the ability to move on land,under water and in the transition zone.The application of their movement performance to the research on bionic robot has great significance and practical value for the exploration of marine unknown environment and the development of propulsion technology of the underwater robot.The shoal environment is affected by flow erosion and sedimentation for a long time,in which many benthic and plankton multiply.So the application of traditional underwater robot is restricted due to the special amphibious environment.However,the reciprocating motion of fin or hydrofoil can get rid of the winding of plants.Their excellent propulsion performance can provide the reference for the research on amphibious bionic robot.In this paper,the development status of underwater bionic robot,and the simulation and experimental research on self-propelled swimming of aquatic organism are introduced.The prototype of shoal crab robot is developed by choosing the typical amphibious creature sea crab as the research object.Then the hydrodynamic modeling of swimming paddle is established and the swimming gaits of double paddles are planned.On this basis,the dynamic performance of each gait is analyzed.After that,the self-propelled swimming simulation of the robot is carried out based on the CFD method.And the corresponding experimental research is performed so as to improve the propulsion technology of swimming paddle.The structure and control system of the robot are designed.By observing the biological structure of sea crab and extracting the major joints from swimming leg and walking leg,the five-bar linkages walking leg and 3DOF swimming paddle are designed,and the aspect ratio of the robot is determined.Then the workspace of double paddles is analyzed based on the kinematic model.The layout of control system is planned and the three-dimensional model of the robot is established to solve the centroid position and moment of inertia.The dynamic modeling and analysis of the robot are carried out.First,the motion law of swimming paddle's joints are planned.Based on the theory of slice,this paper establishes the dynamic model of single paddle.Next,the parameters of synergetic sculling gait and alternate sculling gait in lift-based mode,and synergy gait in drag-based mode are all planned from the view of the angle of attack and wingtip trajectory.Then,due to the motion periodicity of the paddle,the dynamic analysis is carried out in stages for the three gaits.At last,the dynamic equations for self-propelled swimming of the robot are built up to lay the foundation for simulation.The self-propelled swimming simulation of the robot is carried out.Firstly,the basin and mesh type are determined to verify the mesh convergence.The study on the hydrodynamic performance of direct swimming is investigated by Fluent.By changing the amplitude and frequency of swimming paddle,the influence on velocity,acceleration,thrust,efficiency and Strouhal number are analyzed,and different approaches are discussed for the robot arriving at a predetermined velocity.Secondly,the flow field structure and motion performance of direct swimming about the above three gaits are analyzed.Thirdly,the turning motion based on amplitude differential is simulated to analyze the influence of amplitude difference on turning radius,angular velocity and efficiency.The experimental study on self-propelled swimming of the robot is conducted.According to the simulation model,the prototype of shoal crab robot is developed and the hardware configuration of control system is set up.The direct and turning swimming test are completed by building the experimental platform,and the results validate the correctness of theory and simulation analysis.Moreover,the optimal motion parameters of swimming paddle are obtained and the motion characteristics of the robot in each gait are analyzed,which realizes the self-propelled swimming with high efficiency and high maneuverability. |
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