Fu Wei, Zhang Zhiyuan, Liu Yudong, Pan Junbing, Cui Jian, Ding Kai, Zhang Huiming. Simulation experiment in lab on force transfer effect of jujube under vibration excitation[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2017, 33(17): 65-72. DOI: 10.11975/j.issn.1002-6819.2017.17.009
    Citation: Fu Wei, Zhang Zhiyuan, Liu Yudong, Pan Junbing, Cui Jian, Ding Kai, Zhang Huiming. Simulation experiment in lab on force transfer effect of jujube under vibration excitation[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2017, 33(17): 65-72. DOI: 10.11975/j.issn.1002-6819.2017.17.009

    Simulation experiment in lab on force transfer effect of jujube under vibration excitation

    • Abstract: In recent years, jujube planting area in Xinjiang has been increasing, and jujube harvest depends entirely on manual work that is characterized by low efficiency and high cost, which has become the bottleneck of the sustainable development of Xinjiang jujube industry. Therefore, mechanized operation is in urgent need. In order to improve the efficiency of vibration harvesting for fruits to reduce power consumption in excitation, the effect of force transfer in vibration harvesting was studied based on the changes in instantaneous acceleration of fruits in vibration,. Aimed to vibration harvesting of jujube, the preset study analyzed natural frequencies in system vibration through simplifying "branch-stalk-fruit" of jujube to a double-pendulum vibration model firstly, and then constructed Lagrange's double-pendulum multi-degree-of-freedom vibration equation, and the natural vibration frequencies of the system were obtained (14.69 and 17.26 Hz respectively). Based on electrodynamic vibration test stands, experiment of frequencies scanning was conducted for the whole jujube tree. In the resonance, with the gradual increase of the distance to excitation source, resonance frequency increased gradually. The resonant frequency of 3 test points in each path ranged from 12 to 24 Hz, which provided reference for constant frequency test. In order to investigate the effect of vibration frequency and amplitude on instantaneous acceleration of each branch of the sample tree, vibration test for constant frequency of jujube was carried out at the amplitude of 3, 5 and 7 mm, respectively, and the frequency of 12-24 Hz. DHDAS analysis showed a correlation between vibration frequency and instantaneous acceleration of jujube. The longer the distance to excitation source, the greater the change of instantaneous acceleration in resonance. Instantaneous acceleration showed no obvious changes with the increase of amplitude. The bifurcation point and diameter of the tree had great influence on the resonance amplitude; and the more the bifurcation points of the path, the smaller the change of instantaneous acceleration. The motion of jujube under forced vibration was analyzed using 3D (three-dimensional) high-speed camera technology to reveal the maximum instantaneous acceleration value of jujube in space. Statistical analysis demonstrated that the maximum instantaneous inertia force of jujube was greater than the maximum breaking load of fruit stalk (6 N). With the increase of amplitude, the maximum instantaneous acceleration of jujube increased gradually, and its variation coefficient did not change obviously. That was, within the range of the amplitude of the sample jujube tree, the maximum acceleration value of each jujube was relatively large and jujube was more likely to fall with the increase of amplitude. With the same amplitude and different paths, the larger the mass of jujube, the larger the instantaneous acceleration of jujube vibration, suggesting that large mass of jujube is correlated with easy falling in vibration. With different amplitudes and the same path, the smaller the trunk diameter of each path of the sample tree, the larger the average value of vibration acceleration of jujube, which suggested that trunk diameter was also one of the main factors affecting jujube vibration harvest. This study can provide a theoretical basis and technical reference for the design of the excitation system for jujube harvest.
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