Study On The Key Technology Of Special Wheel-tracked Mobile Robot With Movement Transformation Function

Mobile robot is a critically important branch in robotics field,which can be widely employed to replace people in natural disaster relief,fighting against terrorism and violence,military reconnaissance,and war etc.Therefore,researches on key technologies of robotics have become a hot and difficult issue.The fundamental issues that determine whether the robot can be maturely applied are its mobile flexibility,obstacle climbing capability and stability.Supported by both the NSFC(National Science Foundation of China)and the robotics state key laboratory fund,a special mobile robot with wheel-track coupling structure is proposed.Then,a detailed analysis is carried out on the robot mobility,obstacle climbing capability,stability during movement,statics and dynamics.Moreover,the stability of the typical terrain and the location of multi-sensor information fusion are further studied.In this paper,a method to realize the coupling mechanism of mobile robot is firstly presented.That is to say,to make the robot wheel body structure switch between its wheel and track structure through four-link principle,the essential idea of which is to take full advantage of the high mobility of wheeled robot and the high trafficability of tracked robot.When the robot meets the steps,stairs and other obstacles,it will rely on the driving wheel body deformation structure to realize the switch of robot body motions.In order to enhance the robot capability of crossing obstacles,the tail rod structure is involved on the basis of the robot body structure.Through the change of the movement attitude of the tail rod mechanism,the adjustment of the center of mass is achieved,which can effectively improve the obstacle crossing capability and stability of the robot.Aiming at the problem of the steering of the wheel-track mobile robot,this paper mainly analyzes the nonlinear distribution of the forces acting on the ground during the steering process of the robot.Comparing with the linear distribution,it is found that the traction force calculated by the traction force model based on the stress theory of nonlinear distribution is closer to the reality than that obtained by the linear distribution.In addition,on the basis of the interaction between wheel and ground,the relationship between the interaction between track and ground of wheeled tracked robot under the action of elastic track is proposed and simulated.For obstacle crossing processes of the wheeled mobile robot in different attitudes,the dynamic models adopted in wheeled type,tail rod and wheeled type,and tracked type during the obstacle crossing process are seperately built up,which carry out motion planning analysis for tail rod and tracked mobile robot in two kinds of obstacle crossing motions;The dynamics modeling and analysis of forward obstacle-crossing are carried out,and the driving torque of the robot is obtained by virtual equivalent moment distribution.The obstacle-crossing mode of the robot in different states is analyzed,and the maximum obstacle height of the robot is obtained.In addition,the center of mass of the wheel-track mobile robot can be changed as a result of the different motion situations during the robot swinging and crossing the obstacles,which leads to the instability of the robot movements.In this case,an analysis is made on the stability of the robot on both flat ground and slope environment.Take the stair terrain as the research object,the dynamic models during the robot climb up the stairs in the two conditions that with the tail rod and without the tail rod are established respectively;also,a dynamic stability distinguished method is analyzed when the robot contacts the stairs in different situations with the tail rod.On the basis of establishing the robot odometer and ultrasonic ranging sensor model,the extended kalman filter location method is proposed,comparing with which there is a dead reckoning method,and combining the advantages of these two a self-adaptive method is put forward.Besides,considering the surrounding environment an self-adaptive fuzzy kalman filter method is introduced,which helps reduce the impact of environmental noise.Furthermore,as for non-uniform motion positioning problem,Multi-model kalman filter method is raised,making sure that the robot can be precisely located.Eventually,experiments of the wheel-track robot on different terrains are carried out in order to test its trafficability,obstacle crossing stability and complex ground adaptability.The experiments results show that the theoretical analysis,technical methods and means are correct.