Design And Trajectory Control Of A Friction Type Internal Drive Sphere Robot

The spherical robot has the maneuverability and carrying capacity of the wheeled robot,and combines the advantages of the legged robot in adapting to different environments.It has the characteristics of compactness,lightness,flexibility,etc.It is a kind of rolling robot mechanism that can walk freely in all directions.This paper designs a friction-type inner-driven spherical robot mechanism composed of omnidirectional wheel,inner and outer spherical shells.The paper takes the friction-type inner-driven spherical robot as the research object,and focuses on the two aspects of dynamic modeling and trajectory control.It has mainly done the following work:At first,a new type of spherical robot mechanism consisting of three omnidirectional wheels,inner and outer spherical shells are designed.This mechanism uses omnidirectional wheel,cow eye wheel and other structural components to design the supporting driving device.It is symmetrically installed inside the shell.The center of the omnidirectional wheel is located on three orthogonal axes from the center of the sphere.The axis of the omnidirectional wheel intersects at one point which is located directly above the center of the sphere.Secondly,according to the structural characteristics of the friction-type inner-driven spherical robot,the kinematics and dynamic analysis of the spherical robot is carried out.And two versions of the dynamic model of the spherical robot are established based on the Chaplygin equation.The dynamic model of the first version facilitates the control of the attitude of the inner and outer spherical shells.The dynamic model of the second version facilitates the trajectory control research of the spherical robot.The correctness of derivation process of the two versions by numerical simulation is verified.Thirdly,based on non-holonomic constraint analysis of the system,physical prototyping test is used to verify the established non-holonomic constraint relationship between the omnidirectional wheel and the spherical shell.The results show that the measured values of the constrained relation can track the calculated value well both when the motor is driven or the manipulator toggles the spherical shell.It verifies effectively the effectiveness of the omnidirectional wheel drive and the correctness of the nonholonomic constraint relationship between the omnidirectional wheel and the spherical shell.Fourthly,the physical prototype of a friction-type inter-driven spherical robot is designed and built,which includes the spherical robot mechanical mechanism and the friction-type internally-driven spherical robot measurement and control system based on an industrial computer and a digital signal processor(DSP).And the PC software control interface of spherical robot is developed.Fifthly,the controllers of positioning motion,S-curve motion,circular motion,rotation motion and posture motion are designed by using partial feedback linearization method.The feasibility and the correctness of the designed control strategy are verified by Matlab numerical simulation.The influence of omnidirectional wheel's radius on the S-curve motion control is analyzed.Finally,based on the kinematics analysis of the spherical robot's rotation motion,a prototype experiment of the spherical robot's rotation movement is completed.The results show that,when the spherical robot moves on the ground,the spherical robot with the omnidirectional wheel speed changing by sine law performs a better rotation movement effect comparing with which has a constant omnidirectional wheel speed.