Research On Position And Attitude Control Of Vision Based Mobile Robot With Nonholonomic Constrains

With the development of science and technology,mobile robot technology becomes mature,and mobile robots become more important in industrial production.In the field of logistics and warehouse management,wheeled mobile robot has great application potential.In order to shorten the development time,wheeled mobile robot is usually modified by electric forklift.The control problem of wheeled mobile robot is more complex.On the one hand,the wheel can only roll,but not slide along the axis,the motion of the mobile robot has nonholonomic constraints,which leads to the complexity of the position and heading control of mobile robots.On the other hand,the tracking precision of rudder angle control system is insufficient,which leads to a low control precision of the robot.In this paper,the position and attitude control algorithm of mobile robot has been designed.By establishing the kinematic model of the mobile robot in the polar coordinate system,the linear constant state feedback algorithm is designed to realize the position and attitude error convergence at the same time.Local stability is proved by constructing Lyapunov function,and the stability range is shown.In order to increase the stability range of the system,the controller parameters were optimized,if the initial condition of the mobile robot does not satisfy the local stability conditions,the controller will control the robot to move to the local stability range,to make sure the system finally can be asymptotically stable.The effectiveness of the algorithm is verified by simulation.The control precision of the rudder angle system also determines the control precision of the mobile robot.This paper presents a compound correction scheme for rudder angle control system,which improves the tracking precision of rudder angle control system.The tracking accuracy of the robot rudder angle control system is not enough,and the output has serious lag.If the robot is not corrected,the control error of the mobile robot can't fulfill he requirment.In order to improve the tracking precision of the rudder angle control system,the rudder angle system is corrected by the input compensation complex correction structure.In order to reasonably select the control parameters,the rudder angle control system is modeled.the amplitude frequency characteristic curve of the rudder control system and phase frequency characteristic curves are founded by frequency sweep method experiments.MATLAB was used to identify the model parameters.Due to the need of feeding forward signal,according to the analytical formula of the position and attitude controller of the mobile robot,the derivative signal of rudder angle command is given.Because it is not necessary to divide the instruction difference by time,the tracking precision of rudder angle control system is improved and the stability of the system is guaranteed.After the input compensation complex correction,the position control error of the mobile robot is less than 8 mm,and the attitude control error is less than 0.17 rad.