Design And Control Research On Hydraulic System Of Cotton Picker

Cotton is one of the important economic crops in my country.Cotton farmers in China need to recruit many workers to harvest cotton every year,which increases the cost of cotton harvesting.In recent years,the problem of "difficulties in employment" has become increasingly prominent,so it is inevitable to transform the cotton picking process from manual to mechanical automation.The research and development of cotton picker started early in foreign.The John Deere Company and Case Company of the United States have dominated in in the cotton picker market.At present,the development of our country’s cotton picker is still in the stage of independent innovation on the basis of imitation,so it is particularly important to develop our country’s independent cotton picker technology.Firstly,This paper introduced the development status of cotton pickers and the application status of hydraulic technology in cotton pickers at home and abroad,and analyzed the composition and working principle of the cotton picker,creatively proposed a double-column and three-row picking method to increase the net picking rate of cotton picker.Secondly,the hydraulic system of the cotton picker is designed by step of design process,the hydraulic schematic of cotton picker is drawn,and the hydraulic components are designed and selected through calculation and analysis.The speed control circuits of the cotton picker mainly contained pump-control-motor closed-circuit,exit throttle orifice speed-regulating circuit,and single-pump multi-actuator load-sensing circuit.Then the AMESim simulation software was used to establish the simulation models of hydraulic systems of the cotton picker,and the curves of speed characteristic,pressure characteristic and flow characteristic will be compared to exactly match the hydraulic system design requirements,and verified the feasibility and stability of the hydraulic system of the cotton picker.This paper reserched the speed control of the exit throttle orifice circuit and load-sensing circuit applying in the hydraulic system of the cotton picker.The results showed that as for the exit throttle orifice circuit working in constant pressure condition,the outlet pressure of the actuator can be controlled by adjusting the opening of the throttle valve,and then the speed of the actuator can be adjusted.As for the variable hydraulic source load-sensing circuit,when the actuator is hydraulic motors or hydraulic cylinders bearing a positive load,the speed of the actuator can be stably controlled by the load-sensing directional valves and the pressure compensaters.When the actuator is a hydraulic cylinder bearing a negative load,the speed of cylinder will be controlled stably during lifting but vary with load during descending.In order to solve this problem,an overcenter valve was added to the lowering chamber of the hydraulic cylinder.Through theoretical analysis,it is found that the setting pressure and the control ratio of overcenter valves are important to affect the system stability.And through AMESim simulation analysis,it is known that a higher control ratio will lead to greater oscillations.Finally the parameters suitable for the profiling system of the cotton picker were obtained.In this paper,the synchronization control loop of synchro-valve is studied.The mathematical model of the synchro-valve is used to analyze the factors that affect the synchronization accuracy,and a complete simulation model of the diverting and gathering conditions is established to model the Synchronous control of inner-cotton-box system.The simulation results showed that increasing the diameter of the spool,reducing the diameter of the fixed orifice,and reducing the opening length of the spool are all conducive to increasing the synchronization accuracy of the synchro-valve,and the synchronization accuracy of the gathering condition is lower than that of the diverging condition.Finally,the profiling system of the cotton picking is tested,and the measured hydraulic cylinder flow and pressure data are basically consistent with the simulation results.