| Wheeled mobile robots are widely used in various fields of social production and daily life because of their light weight,simple structure and convenient control.With the development of productivity and the continuous progress of science and technology,the wheeled mobile robot has higher and higher requirements,which often requires multiple robots to cooperate with each other to complete more complex tasks.Under this background,the formation control of wheeled mobile robot has become a research hotspot.Most of the current researches on formation control of wheeled mobile robots assume that the robot movement meets the conditions of ideal nonholonomic constraint,that is,there is no longitudinal slip and sideslip between the wheel and the ground.However,in the actual working environment,due to the factors such as wet ground and fast turning,this assumption is difficult to meet.Therefore,formation control of wheeled mobile robots under longitudinal sliding and sideslip conditions is studied in this thesis.The main research contents are as follows:(1)Considering the longitudinal slipping between wheels and the ground,sliding rate parameters are introduced and an adaptive formation controller is designed to realize formation control of wheeled mobile robots in the longitudinal slipping state.Firstly,the formation error model of the wheeled mobile robot under longitudinal slipping condition is derived by considering the longitudinal slipping between the wheel and the ground.Secondly,based on the adaptive control theory,the formation controller under the longitudinal slipping state of the wheel is designed,and the stability of the formation system is proved by the Lyapunov stability theory.Finally,the effectiveness of the proposed adaptive controller is verified by simulation.(2)Considering the sideslip between wheels and the ground,a fast terminal sliding mode formation controller based on sliding mode observer is designed to realize formation control of wheeled mobile robots under sideslip.Firstly,considering the sideslip of wheeled mobile robots in the formation system,the kinematic model of wheeled mobile robots in the sideslip state is established,and the formation error model of wheeled mobile robots is derived.Secondly,a sliding mode observer is designed for unknown sideslip interference in formation system,and a fast terminal sliding mode formation controller is designed based on the observer.The stability of the system is proved by the stability theorem of Lyapunov.Finally,the effectiveness of the fast terminal sliding mode formation controller is verified by simulation.(3)Considering the longitudinal slipping and sideslip of wheels and the ground,a formation controller is designed based on hierarchical sliding mode to realize formation control of wheeled mobile robots under longitudinal slipping and sideslip conditions.Firstly,the kinematic model of the wheeled mobile robot in polar coordinates is derived under both longitudinal slipping and sideslip,and the formation error model under longitudinal slipping and sideslip is established.Secondly,the formation controller is designed based on the hierarchical control method to realize attitude tracking while ensuring the formation stability.The stability of the formation system is proved by the Lyapunov stability theory and La Salle invariance principle.Finally,The effectiveness of the proposed formation controller is verified by simulation. |
PDF Full Text Request