The Stability Analysis Of An Amphibious Spherical Robot System

With the continuous progress of human society,the robotic technology has already established a close relationship with our life.As a kind of robot,the amphibious spherical robot has many excellent properties in environment adaptability and flexibility,because of its symmetrical structure.It has been applied in many kinds of fields.So the amphibious spherical robot has become a hot topic in the field of robotic research.First of all,in this paper,we proposed a novel amphibious spherical robot system.The robot has dynamic stability,small environmental disturbance and flexible movement due to the global symmetry.The driving unit of the mechanical leg with a DC jet propulsion system can not only complete the multiple movements on land,but also realize the movement and operation under water.Secondly,in order to analyze the stability of the spherical amphibious robot on land and under water,we analyzed the stability theory of spherical amphibious robot,then we analyzed stability of amphibious robots on land by using the theory of the fluid structure interaction,we also obtained the figure of overall deformation for the spherical amphibious robots,the distribution of elastic strain and the distribution of equivalent stress.The pressure between copper column and motor is 5 Pa.But the pressure is far less than the yield strength of material.It is mean that the pressure satisfies the requirement of stability.At last,we carried out some experiment;we analyzed the experimental result and verified the validity of the structure.By compared different swing angle and movement cycle of the joints,we got the best swing angle is 30°and the best movement cycle of the robot is 0.2 s.Finally,this paper briefly introduced the theory of fluid mechanics analysis,and then the paper draw the simplified model of robots,the fluid mechanics analysis was carried out on the water jet propulsion.At last,we divided the grid to the spherical amphibious robots under water,we also exert the corresponding constraints to the robot and used ANSYS software for simulation of robot,when the robot had the upward movement underwater,the pressure of the top in spherical shell is 16 N,the pressure far less than the structural strength of acrylic materials,it is also satisfied the requirement of stability.After this,we got the pressure contours and the velocity vector diagram of the robot.At the same time,we analyzed the simulation results.When the input voltage of the robot propeller is 6 V,the yaw angle of the robot in the forward motion is about 10 °.It is the most stable voltage of the robot underwater.Then we carried out the stability experiment of the robot,when the robot in the underwater,the maximum displacement deviation is 0.1 m,the result shows that the robot has a horizontal plane operation stability;Finally,the trajectory tracking experiment of robot was carried out to verify the trajectory tracking ability of the robot is well.