| Chinese wolfberry is the most characteristic traditional industries in Ningxia.At present,in the process of Ningxia wolfberry industry development,harvesting has become a serious problem which is restricting the development of chinese wolfberry industry.In the period of harvesting,large amount of labor employment and labor supply are needed,which greatly increase in the cost of Chinese wolfberry.High efficiency and low damge of harvesting mechanization is needed to solve the technical problems.Based on the characteristics of wolfberry in Ningxia,design a vibration harvesting platform,complete the experiments,the main research contents and conclusions are as follows:(1)Study on the biomechanical properties of chinese wolfberry.Through the mechanical test of wolfberry,the separation force of mature fruits,immature fruit and leaves were obtained.The compressive limit of the lateral pressure and vertical pressure of wolfberry was studied by the manual test machine,which provided data support for controlling the damage rate of harvesting.The flexural elastic modulus of the branches of wolfberry was obtained by the universal tester,the characteristic is that as the diameter of the branches increases,its flexural elasticity model tends to increase linearly.(2)Study on the principle of fruit dropping and mode of vibration,the dynamic model of a single fruit and a tree system were constructed by numerical analysis and other theories.through the analysis and calculation of the model,get the different motion states and stress conditions of the wolfberry fruit at shedding moment.The main factors for the dropping of chinese wolfberry fruit are vibration frequency and vibration amplitude.The simulation and analysis of the branches of chinese wolfberry by ANSYS software.In modal analysis and harmonic response analysis,we can get the steady response of wolfberry branches under different excitation forces.During the simulation of vibration harvesting process,large acceleration response when harvesting frequency is 7.836 Hz,the optimal effect can be achieved by the optimized force size of 10.67 N and the three-point mode of excitation force.(3)Based on the principle of four-bar mechanism and the agronomic characteristics of chinese wolfberry,a scheme of vibratory harvesting—a vibration harvesting platform with no quick return characteristics is worked out.Its feature is using the four-bar mechanism to convert the rotation of the motor into a reciprocating motion of the nylon rod to complete harvesting.(4)Propose a test performance index evaluation system.Through the four-factor and three-level rotation orthogonal combination test,the significant order of factors performance index was obtained by multiple regression analysis and variance analysis.Using design-expert software to analyze the response surface,we can get the interaction between the vibration frequency and vibration amplitude and the interaction between vibration frequency and vibration time.The test results were optimized to obtain the best vibration harvesting combination which the vibration amplitude is 40 mm and the vibration frequency is 8.17.Hz,the vibration time is 15.95 s,and the number of vibration rods is 4.The test results show that the performance indexes meet the design requirements.(5)Based on the high speed camera technology,the actual movement of wolfberry in the process of vibration harvesting was studied.Through the frame-by-frame analysis and data processing of the fruit and branches,it was confirmed that there was compound movement in the vibration harvesting process.Under the conditions of same amplitude and frequency,the order of dropping at different positions on the same branch is different,and the fruits that were closer to the vibration source had preferential shedding.There is a time gap between the instantaneous speed of the branch and the fruit.The movement tendency of them is similar.When the relative speed of them reach the maximum,the acceleration of the fruit reach the maximum and the fruit separates from the branch. |
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