Research On Magnetism Enhanced Spherical Robot Driven By Omnidirectional Wheel

Spherical robot is a kind of mobile robot that drives the spherical shell to produce rolling motion through mechanism.Because of its simple and flexible movement characteristics,it can be used in life,military,industry and other fields.Aiming at the shortcomings of the current spherical robot mechanism,this paper proposes an omni-directional wheel driven magnetic enhanced spherical robot mechanism,and makes theoretical analysis,simulation and experimental research on its structural characteristics,kinematics and dynamics.Firstly,aiming at the structural defect of insufficient driving force in the existing spherical robot configuration,a new spherical robot configuration with omni-directional wheel driving and magnetic enhancement is proposed.The configuration is driven by four vertically distributed omni-directional wheels.The non-contact magnetic force is used to increase the positive pressure between the omni-directional wheel and the spherical shell to prevent the driving mechanism from overturning at a large swing angle,so as to make full use of the driving force of the motor.On this basis,the mechanism is designed and the three-dimensional model is established.The position and pose of the sphere on the plane is described by Euler angle,and the kinematic model is established according to the pure rolling constraints.Aiming at its dynamic characteristics,the dynamic model of spherical robot is established by using Newton Euler method and Lagrange dynamics method,and the expression of magnetic force required for linear motion is deduced.Secondly,the dynamic model of linear motion is modified considering air resistance and rolling friction.The motion state of the driving unit is controlled by trigonometric function and Gaussian function,and the uniform linear motion of the spherical robot is realized.The steering motion is studied by using the method of step and section.The dynamic models of climbing and jumping are established,and the expressions of magnetic force required for climbing and jumping are deduced respectively.The factors affecting the climbing and obstacle climbing performance of spherical robot are analyzed by using the method of classical mechanics.Then,the finite element simulation software Maxwell is used to analyze the magnetic force between the magnet and the spherical shell.Through parametric modeling,the variation law of the magnetic force with the spacing and the size of the magnet is obtained.Using Runge Kutta method,the dynamic equations of linear,climbing and jumping motion are numerically solved,and a series of theoretical curves of state variables such as displacement and speed of spherical robot with time are obtained.With the help of ADAMS software,the above motion is simulated for many times,and the theoretical curve is compared with the corresponding simulation curve.The error is no more than 1%,which verifies the correctness of the theoretical model.By observing the change of friction coefficient in the simulation,the rationality of the magnetic force expression required for the above motion is proved.When the motor input is constant torque,the maximum climbing angle of the spherical robot simulation model is 20 ° by using the climbing motion dynamics equation,which is verified by simulation.Finally,the prototype manufacture,installation and debugging are completed,and the experiments of straight line,steering and obstacle crossing are carried out.The experimental results show that the speed of the prototype can reach 1m/s when moving stably,and the basic steering action can be realized.At the same time,at a certain initial speed,the prototype can cross the obstacle with a height of 19 mm,which is close to the results of theoretical analysis,which verifies the feasibility of the design of omni-directional wheel driven magnetic enhanced spherical robot.Through the above research contents,it shows that the proposed omni-directional wheel driven magnetic enhanced spherical robot configuration has obtained a more concise implementation mechanism,and improved the driving ability and comprehensive motion performance.