| Tiger-nut has extremely high economic value and is a new type of oil crop,with an oil content of 38.7% and an oil yield of 7～10 times that of rapeseed.It is praised by agricultural experts around the world as the "King of Oil Crops" and can be promoted as an alternative oil crop in China,which is of great significance for ensuring the safe supply of edible oil in China,improving the rural ecological environment,and increasing the income of rural residents.However,due to the complexity of the field environment and the undulation and variation of the ridge surface,it is easy to cause problems such as walking deviation,frequent speed regulation,high power consumption,and low operating efficiency,which can also lead to high loss rates and serious damage,high technical requirements for manual operation,and a serious lag in mechanized harvesting of tiger-nuts,which is still in the experimental research stage.Starting from the growth characteristics and planting patterns of Tiger-nuts in the Huanghuaihai region,this paper conducts research on the design of the walking device and drive system of a self-propelled tiger-nut harvester through mechanical design and theoretical analysis,three-dimensional modeling design,comprehensive comparative analysis,simulation test analysis,and field test verification,with the aim of designing a walking device and drive walking system suitable for a self-propelled tiger-nut harvester,Ensure that the harvester can stably walk in the field while protecting the underground tiger-nuts from being damaged.When driving and walking,it can achieve two-way stepless speed regulation,improve the driver’s operating environment,effectively improving operating efficiency,harvesting quality,and the environmental adaptability of the entire machine.Based on the national key research and development plan "R&D and Demonstration of Tiger-nut Production and Drying Equipment(2019YFD1002602)",the following main contents were studied in this paper:(1)Design of the traveling device of a crawler type tiger-nut harvester.Firstly,the overall layout of the tiger-nut harvester was analyzed,and the three-dimensional modeling design was completed based on the overall layout plan of the engine transverse arrangement,the driving device and the oil tank front and rear arrangement,the operation transmission and the traveling transmission left and right arrangement,and the cab and the material box front and rear arrangement.Then,based on the layout structure of the entire machine,the planting mode of tiger-nuts,and the design principles of the walking device,the performance of the crawler type walking device and the wheel type walking device,as well as the characteristics of different structural forms of the rubber track,are compared and analyzed,and the walking device of the tiger-nut harvester is determined to be an inverted trapezoidal rubber track type structural form.Then,based on the theoretical basis of mechanical design and mechanical principles,and using theoretical analysis and structural design as the research method,the parameter design of the rubber track,driving wheel,supporting wheel,supporting pulley,tensioning device,and guide wheel of the crawler walking device was completed.The overall parameter of the walking device is that the track is a rubber track with a pitch of 100 mm,with a track gauge of 1400 mm,a track grounding length of 2300 mm,and a track width of 400 mm,The tracks on both sides are evenly distributed with nine supporting rollers and two supporting rollers,and are fully loaded walking gear frames.Finally,a finite element static analysis was performed on the designed crawler traveling device,and the maximum stress and displacement were 1.242×10~8 N/m~2 and 1.073 mm,meeting the strength and stiffness requirements.(2)Design of the driving and walking system of the crawler type tiger-nut harvester.Firstly,based on the design requirements of the drive walking system,the hydraulic drive mode is determined through comparative analysis of different drive systems,such as mechanical drive,electric drive,and hydraulic drive.Then,the hydraulic system circuit,hydraulic system speed regulation form,and motor drive scheme are determined for the hydraulic drive walking system,and the schematic diagram of the hydraulic drive walking system is designed.Then,the tractive performance of the crawler type oilseed bean harvester when walking in the field was studied.The results showed that the rotational speed of the driving wheel was 24 r/min and the driving torque was 8000 N·m.Then,the main hydraulic components of the hydraulic drive walking system are selected and designed.The displacement of the hydraulic motor is 44.65 m L/r,and the displacement of the hydraulic pump is 44.58 m L/r.Finally,an integrated hydrostatic drive system with a displacement of 46 m L/r and a system pressure of 16 MPa is determined.Finally,the hydraulic pump,hydraulic motor,and working pressure of the hydraulic drive traveling system were checked.The design parameters were within the maximum conditions of the hydraulic components,indicating that the reliability and service life of the system met the requirements.(3)The simulation of hydraulic drive walking system based on AMESim.This chapter first introduces the AMESim software and its operation process,establishes a simulation model of the system in AMESim based on the designed hydraulic drive walking system,and completes the setting of working parameters.Then,the simulation analysis of the field operation system was completed,and the input flow rate of the hydraulic motor was about 106.1 L/min when it was stable,consistent with the output flow rate of the hydraulic pump.The rotational speed of the hydraulic motor was about2282 r/min,meeting the rotational speed requirements of the hydraulic motor.Then,the simulation analysis of the system response performance was completed.The acceleration time of the system under different loads was within 1.3 s,and the stability time was around 1.5 s,indicating that the system had good responsiveness and stability.Finally,the simulation verifies the stepless speed regulation performance of the system.The output speed of the hydraulic motor varies with the output flow of the hydraulic pump,and there is no jumping condition.The bidirectional stepless speed regulation performance is good.(4)Manufacturing and testing of a prototype crawler type tiger-nut harvester.Firstly,during the internship in the factory,complete the processing and manufacturing of components,procurement,and prototype assembly based on the three-dimensional model of the entire machine and the design of the walking device and its hydraulic drive system.Then,field tests were conducted on the passing capacity,walking straightness,walking speed and stability,starting and braking performance,and ramp parking braking performance of the test prototype.The minimum passing height of the prototype was 262 mm,the overall linear walking deviation rate was between 0.090%and 0.180%,the maximum walking speed was 1.080 m/s,the standard deviation of speed stability was 0.030,and the variance was 0.000962.The starting performance,braking performance,and ramp parking performance were good.Then,a field walking test was conducted on the prototype.The linear walking performance of the entire machine is good,and it can complete field steering.When walking,there is no damage to the non harvested underground tiger-nuts.The field operating speed is 0.331 m/s,and the operating efficiency is 0.216 hm~2/h,both of which are better than the required values. |
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