Research On Trajectory Tracking Control Of Wheeled Agricultural Mobile Robot

Agricultural robot,as important research field of agricultural engineering,is the major product of automation technology and robot technology applied in the field of agriculture,which plays an irreplaceable role in the process of agricultural modernization.In harsh environment,people can be replaced by it for agricultural production so that the labor intensity can be decreased and the production efficiency can be increased.With the development of agricultural robot,the requirements of its motion control performance can not be met through the traditional control methods,so it is necessary to further develop advanced control algorithms to achieve higher motion control performance.Therefore,in this study,the mathematical models are established for wheeled agricultural mobile robot,and its trajectory tracking control algorithms are emphatically studied.The main work is listed as follows.(1)The kinematic model,dynamic model and actuator model of wheeled agricultural mobile robot are established respectively.Meanwhile,the stability theory,backstepping,adaptive control theory and three common fuzzy logic systems are introduced.(2)Based on the kinematic model of robot,velocity controller is designed to achieve asymptotic stabilization and tracking.Firstly,the unknown physical parameters of kinematic model are estimated by projection algorithm and the adaptive velocity controller is designed.Besides,using Lyapunov stability theory,it can be proved that stabilization errors and trajectory tracking errors of the system converge to zero asymptotically.Finally,the effectiveness of proposed control algorithm is demonstrated by MATLAB simulations.(3)Based on the dynamic model of the robot,torque controller is proposed to achieve asymptotic stabilization and tracking.Firstly,the interior damping,parameter uncertainties and external disturbances are considered.The fuzzy logic systems are used to approximate the uncertainties of the system and the adaptation laws are utilized to estimate the unknown parameters consist of upper bounds of external disturbances,as well as the upper bounds of approximation errors and the norms of the optimal weight matrices of the fuzzy logic systems.Furthermore,the dynamic surface control technique is adopted to design the adaptive fuzzy controller,which ensures that the stabilization errors and tracking errors of the system are uniformly bounded.Finally,the performance of proposed control algorithm is demonstrated by MATLAB simulations.(4)Based on the actuator model of the robot,voltage controller is designed to realize the trajectory tracking control of the robot.Firstly,the suitable velocity controller is selected.In addition,the unknown parameters in the actuator model are estimated by the adaptation law and the voltage controller is designed by using backstepping design method.Finally,the effectiveness of proposed control algorithm is proved by MATLAB simulations.