Abstract:
A dynamic model and Lagrange equation of forced vibration of camellia oleifera were established for the fruit picking machine with a shaking branch mode according to the theory of forced vibration separation. The equation of inertia force for camellia oleifera fruit was also obtained by solving the governing equation. In dynamic analysis of the equation, main factors affecting the vibration of camellia oleifera can be obtained, including the vibration amplitude, frequency, action time and clamping position of the excitation force. A high speed camera was used to record the vibration shedding process of camellia oleifera fruit. The results showed that the average shedding time of fruit decreases with the increase of vibration frequency under the same amplitude. At the same frequency, the average time of fruit shedding decreased with the increase of amplitude. The picking efficiency was better when the frequency was about 6-10 Hz and the amplitude was about 20-40 mm. The average shedding time of fruit was about 4-12 s. An integrated electromechanical and hydraulic picking device of camellia oleifera fruit was designed with the frequency between 0 and 10 Hz, and the amplitude adjustable from 20 to 40 mm. A three-level orthogonal experiment for fruit picking was designed based on four factors: dynamic amplitude, frequency, action time and vibration position. According to the fact that most camellia oleifera fruits are concentrated at a distance of about 260 mm from the tree top, the height of 0-260 mm was selected as a factor level of clamping position, with an increase of 100 mm, and 260-360 and 360-460 mm were set as the other two test levels. According to the falling time of camellia oleifera fruits under different amplitudes and frequencies, the vibration frequency was selected as 6, 8 and 10 Hz, and the vibration amplitude was selected as 20, 30 and 40 mm. Since the average shedding time of camellia oleifera was between 4-12 s, the vibration time 4, 8 and 12 s were selected. The mature period of camellia oleifera fruit is generally in late October and early November. From October 30 to November 2, 2018, during the mature and suitable period of camellia oleifera fruit, 9 camellia oleifera trees of Xianglin No. 56 in the camellia oleifera forest of Qidong County, Hunan Province were selected, and 3 canopy branches with the same physical state and similar fruits amount and flower buds were selected as the picking objects, to mark and count the total fruits and flower buds on the branches. At the end of the experiment, the remaining number of camellia oleifera fruits and damaged buds were counted and recorded. The results showed that the holding lamping position of the end-effector had the greatest influence on the picking effect, while the vibration time has the least influence. The optimal picking parameters was that the clamping position was 0-260 mm from the treetop, the vibration frequency was 10 Hz, the amplitude was 20 mm, the vibration time was 8 s, under this condition, the leakage rate of fruits was the lowest (10.87%), the bud damage rate was 31.80%. Since the damage rate of flower bud was relatively large, the machine should be further improved.