Research On Autonomous Navigation Control Of The Agricultural Machinery For Delay And Disturbances Attenuation

In this paper,the control technologies and methods of the autonomous navigation for agricultural machinery are discussed and researched.Kinematic models of the agricultural vehicle are specific objects of the study.In the framework of kinematic model,tracking accuracy and anti-interference capability of the autonomous navigation control system for agricultural machinery are seriously and technically observed.For the above purpose,the integer order PID,fractional order PID and Disturbance Observer Controller(DOBC)are applied to suppress and eliminate the delay and disturbances during the control of the autonomous navigation of the agricultural machinery to achieve real-time optimization control.ITAE performance index is used as evaluation standard to comprehensively and effectively evaluate the experimental results in this paper.The above methods and technology for autonomous navigation of the agricultural machinery is mainly discussed in this paper.Research contents and results are summarized as below:(1)Two-wheel model of path tracking control system of autonomous navigation for agricultural machinery is selected as the Kinematic model of the system.Based on two-wheel kinematic model of agricultural vehicle,the parameters of autonomous navigation control system for agricultural vehicle are seriously and significantly designed.The impacts of uncertain delay and disturbances for the control system of autonomous navigation for agricultural machinery are analyzed and discussed.(2)Delay rejection method of the path tracking control system of autonomous navigation for agricultural machinery is technically given.As we all know,in the control process,the uncertain delay often affects dynamic quality of the system,even makes the control system unstable.According to the advanced experience of the control field,some advanced delay link processing method has been effectively developed and researched.The adverse effects of the delay for the control system has been analyzed and at the same time,based on the IATE criterion,integer order PD controller and the fractional order PD controller have been designed to tune the control system.Simulation results show that more effective control mechanisms are given.(3)The impact of the internal disturbance based on the model error for the control system is analyzed.Firstly the outer loop control should be introduced.It is assumed that farmland is relatively flat and the speed of the tractor is constant.Besides,the lateral slip of the tire and the ground need to be ignored.According to the above conditions,the kinematic model of agricultural vehicle has been simplified to analyze and design the control system.Because of the nonlinearity of the kinematic model of agricultural vehicle,it is difficult to directly design the controller for the control system.Besides,the controller designed for nonlinear system is also difficult to achieve.Therefore,it is assumed that the lateral deviation error and steering angle are small and in the vicinity of the equilibrium point,the kinematic model of agricultural vehicle is linearized regardless of the high order and remainder term of the nonlinear system.Based on the above linearized system,pole placement method of modern control theory is applied to design linear feedback controller.Under the action of the feedback controller,the dynamic performance and steady performance of the system is satisfactory.However,the nonlinear system with the above feedback controller can’t get satisfactory performance.During the modeling process of the autonomous navigation control system for agricultural machinery,the system will produce static error and at the same time the model parameters and the sensor parameters of the system could be easily influenced by some factors.The above disturbance can be regarded as internal disturbance.The linear feedback control can be regarded as the outer loop control.Simulation results show that the simple outer loop control can’t sufficiently eliminate the uncertainty of the model of the system.(4)The influence of the external disturbance for the control system is discussed.According to the above description of(3),the linear feedback controller can’t guarantee that the system with uncertain disturbances has satisfactory performance.Besides,this passive control method compensating and eliminating the disturbances is uneconomical and unreliable.Thence based on the idea of interference active control,the disturbance observer is skillfully applied to observe and estimate uncertain disturbances and compensate them in the paper.The effects of agricultural operation environment for vehicle navigation can be regarded as the external disturbance of the control system.For example,the external disturbances include ups and downs of the road,vibration of the vehicle,random external noise and so on.Based on the description of the internal and external disturbance,the disturbance observer is used to design the inner loop control structure which actively estimates and compensates the uncertain disturbances to eliminate the influence of disturbance to the control system.Simulation results show that introducing the disturbance observer can effectively observe and estimate the uncertainty of the system and enhance the capability of actively compensating the disturbance and robust stability of the control system to further improve the path tracking precision of the system.(5)The method of active suppression and compensation for the uncertain disturbances of the path tracking control system of the autonomous navigation for agricultural machinery is established.The inner loop and outer loop design of the control system is successfully realized.The state-space method and pole-placement method is used to design the linear feedback controller of the outer loop and DOBC is applied to design the disturbance observer of the inner loop in this paper.Simulation results show that Aiming at the uncertainties of the control system,the inner loop and outer loop design is put forward to effectively restrain the effects of uncertainty on the control system in this paper.Based on the described control method,the path tracking control system of autonomous navigation for agricultural machinery could be further researched and discussed to improve the performance of the system.