Analysis And Experimental Study On Swimming Performance Of Crab-like Robot With Meshless Method

With the increasing importance of marine resources for human survival,it is necessary to detect the oceans.However,the marine environment has many unknown dangers for human beings,which requires a kind of equipment that can detect and move in its complex environment.Through observation,it is found that the underwater swimming and land-moving organisms can help us solve this problem.Bionic robots emerge as the times require.The motion characteristics of amphibians are applied to the robots,so the bionic robots can be perfectly integrated into the surrounding environment.However,the way of swimming in water with fins as propulsion can not be disturbed by the complex underwater environment.SPH(Smooth Particle hydrodynamics)method is a meshless numerical method to solve hydrodynamic problems.Compared with the method based on grid technology,it can better solve complex boundary conditions.In this paper,the typical amphibious shoal crab is complex,so SPH numerical method is chosen.The hydrodynamic model of the swimming paddle and the gait planning of the two-paddle swimming are established in the research of the crab-like robot.Analyzing the dynamic performances of each gait,In order to verify that the SPH method can simulate the robot correctly,a swimming experiment is designed to optimize the propulsion performance of the robot.Firstly,modeling and analyzing the dynamic of the crab-like robot.Planning the joint motion law of the swimming propeller,establishing the single-propeller dynamic model based on slice theory.Aiming at the periodicity of the paddle beating,the synchronization of the two modes(lift mode and drag mode)was analyzed by stages,and the motion effects of each gait were compared.Finally,the whole machine swimming dynamics equation is established to provide the programming basis for autonomous swimming simulation.Secondly,meshless SPH method is applied to the simulation of robot swimming.Firstly,the size of the watershed and the size of particles are determined.The underwater swimming simulation of the robot is carried out by using AUTODYN,and the parameters of the robot’s swimming paddle are constantly changed to study the curves of various forces generated by the robot and the swimming time to make it swim in the best state.After that,the flow state ofwater around the paddle and the pressure distribution on the paddle surface were compared between the " 8 " and the " ? ".Finally,the autonomous swimming experiment of the crab-like robot is carried out.Through the structure of crab body and swimming paddle,the robot model is made.The control system is designed to make the robot move.The pool is built to make the robot swim in water.The equipment to control the robot motion is designed so that it can change the swimming motion freely.The data obtained are compared with the simulation data,so that the robot’s swimming can achieve the best effect.