Design And Motion Control Of 4WID High-clearance Sprayer

The current situation of large farming area and insufficient rural labor force in China has made the farmland management mode gradually change to mechanization and intellectualization,and the modern agriculture has been transformed into "continuous,low-consumption and high-efficiency" fine agriculture.High-clearance sprayers are widely used for their high efficiency.But at present,the high-clearance sprayer mainly adopts the mechanical transmission structure with complex structure.In complex environments such as soft and muddy paddy fields,it is easy to cause failure,slip and subsidence of driving wheels of high-clearance sprayer,affecting the maneuverability and stability of sprayers.In this paper,hub motor drive is used to break through the original mechanical transmission structure and realize four-wheel independent drive control.A new self-steering structure is designed,and the kinematics and dynamics model of the four-wheel independently driven high-clearance sprayer is established to realize 4WID speed coordinated control and improve the controllability and adaptability of the system.The main research contents are as follows:(1)Design and optimization of four-wheel independent drive chassis mechanism.In order to improve the speed and stability of sprayer when steering,a four-wheel independent electric drive self-steering chassis is designed,including the walking system and the power system.Then,UG was used to build the simulation platform for the high-clearance sprayer.The fault and fault-tolerant operation of the four-wheel independent chassis is analyzed,and the chassis structure is optimized through hydraulic push rods and connecting rods: When only one hub motor fails,the hydraulic push rod assists the steering mechanism to turn,the design of the connecting rod ensures that the track between the inner wheel and the outer wheel fully coincides;and when wheel hub motors failure occur at present and afterwards,high-clearance sprayer cannot steering automatically,the hydraulic push rod provides active steering.The unique steering structure design improves the fault tolerant operation ability when the hub motor failures,ensures the same rotation angles of the front and rear steering mechanisms,which reduces crop damage.(2)Model study of 4WID high-clearance sprayer.According to the AckermannJeantand steering model,the front wheel steering and all-wheel steering model of the four-wheel independently driven high-clearance sprayer is established.The ideal steering radius of all-wheel steering is half of the radius of front wheel steering.Due to the need to balance the force of the wheels in the process of steering control,the dynamic model of the four-wheel independent driving highland gap sprayer and the components in the steering is analyzed and studied.The five degree of freedom dynamic model of the high-clearance sprayer is simplified to a four degree of freedom dynamic model,leads to reduce the controlled volume,which making the high-clearance sprayer easier to control in actual operation.(3)Research on motion control of 4WID high-clearance sprayer.In order to meet the needs of low speed and high torque,the hub motor is optimized and the mathematical model is established.On the basis of the "all-wheel steering model" of the independent electric drive high-clearance sprayer,the overall control strategy of the 4WID high-clearance sprayer is established.The simulation of differential steering coordinated control and the fault-tolerant control experiment under single motor failure are carried out.The test results show that the wheels of designed 4WID high-clearance sprayer is rolling forward,which reducing energy consumption.It can turn better in paddy fields with deep mud feet,and has certain self-rescue ability when wheels fall into mud.The hub motors at both ends of the chassis connecting rod bear the output of each other’s torque.The fault-tolerant control strategy is effective to ensure the normal operation of the whole vehicle.