| China is the country with the highest chestnut production in the world,accounting for 84%of the global chestnut production.As one of the main chestnut producing areas in southern China,Luotian County,Hubei Province has problems such as high planting cost,low economic benefit and labor shortage in its chestnut industry.The high labor cost of chestnut harvesting is the main reason for the high planting cost.In the planting cost per mu of chestnut in Luotian,the labor harvesting cost accounts for 57%of the total cost.Aiming at the problems of difficulty in harvesting chestnuts in Luotian,high cost and low level of mechanization,a chestnut multi-head flapping and fruit-dropping device based on the principle of crank-rocker mechanism was designed.The main research contents are as follows:(1)The planting agronomic investigation of Chestnut in Luotian was carried out,and the test on separating force of handle,diameter of fruit and width of result branch group of Chestnut were carried out,which provided practical basis for structural design of the device.(2)The whole machine design of fruit drop device.Based on the artificial harvesting method of Luotian chestnut,the fruit drop device based on crank-rocker mechanism was designed.Three schemes are designed,"yi" zigzag frame,adjustable frame and "ping" zigzag frame.Considering the overall quality and stability of the device,a zigzag rack structure is adopted.Based on the width measurement data of chestnut branch group,the width of the designed rack is 900mm.(3)Motion analysis of the mechanism.The movement of four-bar mechanism is analyzed theoretically using analytical method,and the angular velocity and acceleration of each lever at each moment are determined.Based on ADAMS,the kinematics and dynamics of the device are analyzed,and the stability of the mechanism motion is verified.According to the simulation,the flapping force provided by the device is obtained,and the speed of the working motor is determined to be more than 300r/min.(4)Finite element analysis of key components.Based on the finite element analysis software ANSYS,the frame and connecting frame of the device are analyzed statically.The results of static analysis show that the structure of the frame and connecting frame meets the requirements of strength and rigidity.The modal analysis of the frame shows that the frame will not resonate with the external excitation source.Through parameter optimization design of the connecting frame,the quality of the optimized connecting frame was reduced from 12.804kg to 9.1544kg,and the quality was reduced by 28.5%.(5)Processing technology was determined and prototype production of the device was completed.A bench test for flapping force measurement of the device was carried out to verify the flapping force performance of the device and to determine the working speed.The results show that the average flapping force provided by the device at 365 r/min and 456 r/min is 66.76N and 76.22N respectively,which can meet the requirements of chestnut harvesting.Field experiments on chestnut harvesting of the device were carried out.The results show that the rate of fruit drop on test branches is 84.0%and 89.7%respectively when the speed of the device is 365 r/min and 456 r/min within 15 s of harvesting time.In order to solve the sloshing problem of the device in the field test,the vibration source determination test is carried out for the device.The test results show that the main cause of the device vibration is the impact of the slapping rod movement on the frame.An optimum method for installing torsion spring on the rotating shaft of the tapping rod on the device is proposed and the parameters of the torsion spring are designed. |
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