Dynamic Modeling And Swimming Stability Analysis Of Beaver-Like Underwater Robot

With the continuous development and utilization of marine resources as well as various military needs.Robots adapted to various underwater environments have received great attention in marine resource exploration and military reconnaissance.The underwater biomimetic robot can realize the complex underwater detection and exploration by simulating the movement mode of organisms.Biologically,beavers have strong hind legs and powerful tails,and their hind legs have wide webbed feet.In underwater motion,the fins play the main role of propulsion,the tail mainly plays the role of stabilizing the body,and then plays the role of auxiliary propulsion.With webbed hind legs and tails,beavers are able to swim well in underwater environments.At present,the research of beaver-like underwater robot is relatively limited,and the dynamics and stability of the robot is even less.Dynamics research of beaver-like underwater robot is the basis of good motion control.The beaver-like underwater robot moves mainly through its hind legs and tail.In order to explore the hydrodynamic dynamics of the hind leg composed of two legs with webbed feet,this paper proposes a rigid-liquid fusion dynamic model combining the rigid body dynamics and hydrodynamics of the robot.The modeling method is based on the Newton-Euler formula,the leg kinematics of the hind leg of the robot is extrapolated,and the hydrodynamic model on the webbed foot is established based on the hydrodynamics.Combined with Newton-Euler’s formula,the force of hip joint was calculated and verified by simulation and experiment.This modeling method integrates the rigid body dynamics and hydrodynamics,which has good reference value for the dynamics modeling of the robot with multi-joint webbed propulsion.The tail of the beaver-like robot is flat and wide,with only one joint,and the force cannot be calculated by the common hydrodynamic theory.In this paper,a piecewise dynamic modeling method for the tail of the beaver-like underwater robot is proposed,which combines the theory of hydrodynamics and deflection deformation.The dynamic characteristics of the tail in the swinging process can be effectively analyzed,and the correctness of the model can be analyzed by comparison simulation and experiment.Combining propulsion efficiency and motion stability,an index was proposed to measure the motion performance of the robot’s tail,and its motion performance was quantitatively evaluated.Finally,based on the hydrodynamic simulation results of the hind legs and tail of the beaver-like underwater robot,the experimental data and the hydrodynamic simulation results of the shell,the overall attitude angle of the robot is analyzed and calculated by the simulation software Adams.Combined with the model of changing center of gravity and changing center of buoyancy(because the center of gravity and center of buoyancy of the beaver-like underwater robot will change with the movement of the hind legs and tail),The recovery moment and interference moment are obtained from the calculation,and the stability index is obtained.Through the comparison and analysis of the experimental data and the simulation data under different gaits,the foundation is laid for the underwater motion control and optimization of the beaver-like underwater robot.