Obstacle Avoidance Control Method For Multiple Wheeled Mobile Robots Formation

With the advantages of high efficiency,less energy consumption and low individual risk,multi-agent system has attracted more and more attention,and has been widely used in military and people's livelihood.In the practical application,formation often needs to work in the obstacle environment,and the ability of avoiding obstacles is the basis and key issue for the system to work effectively.Therefore,this paper takes the navigation following formation system composed of wheeled mobile robots as the research object,and studies the obstacle avoidance problem of robot formation in obstacle environment.Firstly,in order to describe the motion coupling relationship between the individual robot and the robot in formation,the kinematics model of the individual robot,the distance-angle-based pilot-following formation model and the distance-distance-based pilot-following formation model are established respectively.The coupling relationship between the key parameters in the system is clarified,which lays a model foundation for the subsequent research.Secondly,combining the dynamic characteristics of formation movement,the model predictive control(MPC)method is introduced into formation control,which realizes the formation control of distance-distance model and distance-angle model,respectively.Furthermore,considering the topological switching of formation between different models,the switching mechanism of the two models in formation motion is discussed.Then,the differences and connections of communication protocols between multiple robots under different topological connections are clarified,and the formation can be switched to other topological modes in time when the current topology is out of synchronization,so as to improve the robustness of the formation movement.Thirdly,aiming at the obstacle avoidance problem of formation in dynamic obstacle environment,two kinds of obstacle avoidance methods,homogeneous and heterogeneous,are provided.In addition,considering the safety of formation in the process of obstacle avoidance,the concept of inner safety constraint and outer safety constraint is introduced to ensure the safety of formation in the process of deformation.Furthermore,in order to quickly determine the optimal heterogeneous obstacle avoidance formation,this paper establishes a formation bank and introduces deformation and energy consumption indicators which can reflect the performance of formation during the obstacle avoidance process to quantitatively evaluate the performance of formation obstacle avoidance.By combining the above restraint system with the evaluation criteria,the formation can quickly determine the optimal obstacle avoidance formation in the obstacle environment,and the adaptability of the formation to the obstacle environment is enhanced.Finally,in order to improve the individual obstacle avoidance ability of formation,the artificial potential field(APF)method is applied to the formation obstacle avoidance.For the Leader robot,the obstacle potential field is established,and trajectory tracking and obstacle avoidance are realized simultaneously through APF control at the speed level;for the follower robots,a composite vector field including obstacle potential field and individual safety field is established,and the formation tracking and individual obstacle avoidance/collision avoidance of the follower are realized by the composite control of MPC and APF.Through the combined control of MPC and APF,the formation individual can avoid obstacles independently without affecting other robots,thus improving the obstacle avoidance ability of robot individuals.In this paper,obstacle avoidance in formation of robots is studied.The simulation results verified on the platform of Matlab/Simulink show that the proposed control strategy can effectively solve the problem of obstacle avoidance in formation.