Research On Kinetic Modeling And Control Of Omnidirectional Mobile Robot

Omni-wheel is an omnidirectional mobile mechanism with special structure,excellent performance and wide application.The omnidirectional mobile robot equipped with omni-wheels can realize three degrees of freedom(horizontal,vertical and rotational)movement in any plane.Moreover,in-depth study of the motion control problem of mobile robots can explore its motion potential to a large extent,exert its sports advantages,and satisfy people's needs for high-precision,high-degree of freedom of omnidirectional mobile robots.Therefore,as a product of rapid development of science and technology in the new era,omnidirectional mobile robots have extremely high academic research significance and practical application value.Omnidirectional mobile robot is a complex system with typical nonholonomic constraints and many uncertain factors.The errors of the mechanical structure,the roughness of the contact surface,and the uncertainties of the outside will affect the motion characteristics of the omnidirectional mobile robot.This thesis takes the four-wheeled omnidirectional mobile robot as the research object,and focuses on the influence of the friction force caused by the omni-wheel contact with the ground on the precise motion of the mobile robot.It is based on the reference and analysis of relevant literature and research in the world,the thesis makes the following research:Firstly,the thesis introduces the different types of omni-wheels,compares the advantages and disadvantages of various existing omni-wheels,and highlights the characteristics of the omni-wheels used in this study.Secondly,the force of the omnidirectional wheel in the course of rotation is analyzed in detail,based on its special structure and layout.The problems that the ground friction caused by the driving wheel and the driven wheel affects the precise movement of the mobile robot is mainly studied.Then,according to the logical order of the first part and the whole,based on Newton Euler kinetic equation,the kinetic model of the single omni-wheel and the whole robot's all friction force is established in turn.After that,simple PD control is used to verify the effect of friction on mobile robot.In order to reduce the influence of friction and improve the precision of mobile robotmotion control,a new sliding mode control method is proposed according to the relationship between physical matrix in robot system.A new adaptive control rate is designed to reduce the shaking of sliding mode control,and the stability of the control method is proved by Lyapunov function.Then,MATLAB/Simulink and S-Function are used to simulate the omnidirectional mobile robot,the results of trajectory tracking under different paths are analyzed and the simulation results of PD controller under the same conditions are compared.The validity and accuracy of adaptive sliding mode control method are further verified.Finally,the viewpoint of thesis is proved by the practical operation of the simulation path,combined with the experimental equipment available in the laboratory.Finally,the conclusion of thesis is summarized,the innovation point and the main research results of this subject are expounded,and the practical significance of the research is studied,as well as,the shortcomings of the research and the need to be improved are put forwarded.