Research On Slip-Ratio Control Method For High Clearance Self-Propelled Sprayer Over All Operating Conditions

The high clearance self-propelled sprayer is a kind of large and high-end agricultural machinery that can be used for plant protection operations of almost all crops and cash crops,especially high-stalked crops.It operates with large area,high efficiency and precision,thus can greatly reduce labor intensify of farmers,provide best protection of workers and improve economic efficiency significantly.At present,most of the high clearance self-propelled sprayers are imported from abroad at a high price in China,while the homemade ones have poor overall performance and cannot meet the requirements.The drive system,as one of the main components of the vehicle chassis,has an important impact on the performance of a sprayer.As an important means to ensure the performance of the drive system,the wheel slip-ratio control system directly affects the operating efficiency,driving stability and safety of a sprayer.Therefore,thorough research on the technologies and methods of wheel slip-ratio control of high clearance self-propelled sprayer has been conducted,which specifically includes the following aspects:(1)Six kinds of anti-slip driving schemes,commonly used in exsiting high clearance self-propelled sparyers,have been compared and analyzed,including the structural composition,application range and the advantages and disadvantages of the anti-slip control method.Based on this,two kinds of the driving control system schemes are proposed for the slip control of the high clearance self-propelled sprayers with small and medium power,high power respectively over all operating conditions.Meanwhile,according to the functional requirements,a kind of active electric proportional anti-slip control valve(ie,ASC valve)is proposed and the hydraulic schematic diagram of the chassis drive system is prezented.Based on the theory of fluid mechanics,the mathematical models of the ordinary dividing-combining valve(ie,HIC valve)and the ASC valve are built based on the boundary conditions.And the mathematical models of the four kinds of sprayer hydraulic drive systems mentioned above are established based on the HIC valve and the ASC valve.Using Matlab/Simulink,the characteristics of the HIC valve and the ASC valve are simulated.Then,the effects of the anti-slip control of the four kinds of schemes mentioned above and the energy loss of the anti-slip valves are simulated and analyzed.(2)According to the unique structure and function of high clearance self-propelled sprayer,the vehicle kinetic model of fifteen degrees of freedom is established,including 6 degrees of freedom of the body,the rotational and vertical runaway movements of the four wheels,and the wheel corner.The vehicle model is mainly composed of the body model,the wheel module,the corner calculation module,the suspension system model,the tire mdoel and the drive system model,so it can fully reflect the dynamic characteristics of the vehicle in all directions.Then,the simulation model of the sprayers with high power,small and medium power are constructed respectively by using Matlab/Simulink and the simulation analysis and vehicle tests are carried out under several typical working conditions.(3)The causes of the slip of the sprayer,the basic principal of wheel slip and the anti-slip control methods are analyzed.In view of the fact that the actual speed of the wheel center is not easy to obtain directly,the judgment criterions of wheel slip are developed,that is,using the relative slip ratio to judge under the straight driving condition and using the relative rotational speed ratio difference to judge under the steering condition.Aming at the problem of the acquisition of the sprayer wheel steering angle,the system scheme for both two-wheel and four-wheel steering is designed and the mathematical model of the full-hydraulic steering system is established.Based on the principle of the ASC valve electro-proportional control,the sprayer slip-ratio control system,including external input module,vehicle kinetics module,steering system module,driving system module and the control system module is constructed.Then,the PID and fuzzy control strategies are developed respectively,and the simulation and comparison are carried out by using Matlab/Simulink.Aming at the problem of throttling loss in ASC valve control,this paper proposes a slip rate control strategy of sprayer based on all conditions,which can be used to determinate the opening and closing of the ASC valve according to the specific operating conditions and energy consumption analysis.(4)The anti-slip controller is developed and the test platform for the slip rate control system of the high clearance self-propelled sprayer is bulit based on the hardware-in-the-loop simulation technology.Then,simulation tests about anti-slip control are conducted to testify the controller.