Research On Part-time Four Wheel Steering System Of Jujube Harvester

At the end of 2015,the planting area of Xinjiang jujube accounted for more than 1/3 of the national area,and jujube cultivation was mainly distributed in the southern region of Xinjiang.At present,the harvest of jujube depends mainly on manual,but mechanized harvesting is the inevitable trend of development.Aiming at the problem of large turning radius of the self-propelled and short-cut and close planting jujube harvester,this paper presented the research on part-time four wheel steering system of jujube harvester,which can realize the function of two wheel steering when the harvester is in harvesting operation and four wheel steering in turning around in the fields.Based on the analysis of the overall structure and working principle of jujube harvester,combined with the principle of Ackerman,full hydraulic steering and part-time control,a part-time four wheel steering system that enables switching of two steering modes was studied,which was accomplished by means of two sets of ladder mechanism and hydraulic system to control the hydraulic cylinder on the tie rod.The overall scheme of the part-time four wheel steering system composed of three parts of steering trapezoidal mechanism unit,hydraulic system unit and part-time control unit was determined.The trapezoidal mechanism of two wheel steering mode and four wheel steering mode was designed respectively,and the trapezoidal arm length of the two wheel steering trapezium mechanism was determined to be158.95 mm and the trapezoidal bottom angle was 65.43o.But the trapezoidal arm length of the four wheel steering trapezium mechanism was determined to be 241.02 mm and the trapezoidal bottom angle was 60.00o.And the study showed that the minimum turning radius in the two wheel steering mode and the four wheel steering mode was 7455 mm and 4303 mm respectively.The load sensing hydraulic system diagram of the part-time four wheel steering was designed,which included a steering drive subsystem and two modes of switching subsystem.The maximum steering resistance moment and load were calculated and determined,combining the structural parameters of the trapezoid mechanism,the driving cylinder model was selected as HSGK100-70×300E,the steering gear model was BZZ5-E1000,and the hydraulic pump model was CBF-E50.According to the kinematic position of the tie rod of the ladder mechanism and the working pressure of hydraulic system,the telescopic cylinder model was selected as CDL1M00(AL-phi 32×300).The MCU was used as the processor,and its P1.0,P1.1 and P1.7 as the input port of control signal.They corresponded to the two wheel switch button,the four wheel switch button and the photoelectric sensor(E18-D80NK)signal output port respectively.The I/O port of P0 was used as the output port,and they were respectively connected with six electromagnetic valves in the steering hydraulic system.By means of programmable control,the control of the input signal to the output signal was realized.