| The omnidirectional wheeled mobile robot is widely used in industrial production,service and people's daily life due to its light weight,large carrying capacity,simple structure,relatively convenient drive control and movement in any direction.For example,the self-service food delivery robot,the sorting robot of logistics and distribution,and the sweeping robot of family life generally adopt wheeled mobile chassis,which can realize specific tasks in indoor environment,reduce labor costs and improve people's living standards.In some complicated operations and dangerous work environments,the role of wheeled mobile robots is irreplaceable.Therefore,wheeled mobile robots have good academic research significance and application value.The paper takes three-wheel omnidirectional mobile robot as the research object,and mainly studies the indoor path track control problem of mobile robot.Because structural and non-structural factors such as parameter disturbance and external disturbance will affect the motion performance of the three-wheel omnidirectional mobile robot,there will be problems such as low accuracy of the path tracking motion control of the mobile robot,large tracking error and long tracking time.In order to solve these problems and make the mobile robot accurately track the set path and the planned path,this paper studies the path tracking control method of indoor mobile robot.Based on the analysis and drawing on similar literature and research existing at home and abroad,the following research is made:(1)This paper summarizes the research status of mobile robot and path tracking control methods at home and abroad.The existing mobile robot structure and control methods are compared and analyzed,and highlights the characteristics of the research object and research algorithm.(2)By analyzing the motion characteristics and mathematical model of the three-wheel omnidirectional mobile robot,the control scheme based on the kinematics model of the three-wheel omnidirectional mobile robot system is selected,and the path tracking control system is described.The A* path planning algorithm is discussed initially,and A* algorithm is used to for the simulation experiment of mobile robot path planning.Two collision-free optimal paths are planned and used as the reference path.(3)The sliding path tracking control algorithm for indoor mobile robots is studied.Based on the simulation study of the index sliding mode variable structure control method(ESMC)path tracking control.In order to effectively solve the problem that the approach coefficient and rate in the exponential approach law are not easy to adjust,and the approach rate is too large will leads to chattering and insufficient exponential approximation rate.An improved approach law of sliding mode control algorithm(ISMC)is proposed.The combination function is used to replace the approach rate of the exponential approach law.The improved approach law is used to design the sliding mode controller,so that the controller output is relatively stable.And the appropriate Lyapunov function is selected to prove the stability of this control method.(4)In the real indoor environment,the improved sliding mode tracking control law is applied to the mobile robot platform for tracking ellipse and actual path experiments with the established three-wheeled omnidirectional mobile robot system.The results show that the tracking error gradually convergent to 0 within 18 s,and the maximum tracking error is less than 50 mm,which effectively weakened the inherent chattering problem of sliding mode,better realized the path tracking control of the mobile robot,and verified the effectiveness and feasibility of the improved sliding mode controller. |
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