| Vegetable cultivation is an essential part of the vegetable industry, and planting methods include both direct seeding and seedling transplanting. There are more than 60 percent of vegetable varieties grown using the method of seedling transplanting. However, the transplanting work is mainly finished manually in our country, which is not only labor-intensive and inefficient, but also difficult to guarantee the qualities after planting. Thus a main problem needed to be solved is to achieve mechanical transplanting in vegetable industry. According to summary and analysis of the planting mechanism, physical and mechanical properties of seedling pots, the study about parameters’optimization and performance test of the dibble-type transplanter was carried out. The paper made the following results:1. According to the requirements for mechanized transplanting of tomato seedlings, a test-bed for dropping loss of seedling pots has been designed in this study to obtain the dropping loss rates. The single factor experiment was carried out with the index of the loss rate of tomato seedling pots, which included the factors of volume of seedling pot, substrate material volume proportion, moisture content and seedling age. The result of single factor experiment showed that volume of seedling pot was with significant effect to the loss rate of tomato seedling pots. As cell size of plug tray changed with 72,128 and 200 holes in turn, the loss rate of tomato seedling pots decreased to a minimum value and then increased with the reduction of volume of seedling pot, and the loss rate of tomato seedling pots got the minimum value when volume of seedling pot was medium(128 holes plate). The volume proportion of substrate material was made up of peat moss, vermiculite and perlite with volume proportion 1(2:2:1), volume proportion 2(6:3:1) and volume proportion 3(7:2:1). By using of medium volume of seedling pot(128 holes plate) to cultivate seedlings, it concluded that substrate material volume proportion was with significant effect to the loss rate of tomato seedling pots, and the loss rate of tomato seedling pots got the minimum value when volume proportion of substrate material was volume proportion 2(6:3:1). When come to moisture content, there was two polynomial function correlation between the loss rate of tomato seedling pots and moisture content. Through range in average moisture content from 55% to 88%, the loss rate of tomato seedling pots decreased to a minimum value and then increased with the rise of moisture content, and the loss rate of tomato seedling pots got the minimum value when moisture content was 80.6%. However, there was significantly negative exponential function correlation between the loss rate of tomato seedling pots and seedling age. Within the seedling age scope during 23 to 43 d, the loss rate of tomato seedling pots continuously decreased with the increase of seedling age, while the loss rate of tomato seedling pots got an insignificant decrease when seedling age was more than 38d. Factors and levels of the orthogonal experiment were selected based on the single factor experiment. Substrate material volume proportion, moisture content and seedling age were selected to perform the orthogonal experiment with the loss rate of tomato seedling pots as the experimental index. The result of orthogonal experiment showed that the optimal combined parameters were as follows: substrate material volume proportion of 6:3:1, moisture content of 80% and seedling age of 38d.2. A test-bed for dibble-type planting apparatus of eccentric disk that could adjust the parameters was designed and a soil trough experiment was conducted for seedling transplanting. A central composite design method of second order regression orthogonal rotation was carried out with transplanting speed, characteristic parameter and oblique angle of dibble as experimental factors and with qualification ratio of perpendicularity, variation coefficient of planting spacing and qualification ratio of planting depth as response values. By using SAS 9.1 regression analysis method and response surface method, both single factor and interactive factor on response values were analyzed. Combined with nonlinear optimization calculation method, the structural parameters and working parameters were calculated optimally. The results obtained in the condition of high transplanting speed (90 seedlings per minute) indicated that, in terms of significant degree, the influence factors of qualification ratio of perpendicularity were oblique angle of dibble, characteristic parameter and transplanting speed; the influence factors of variation coefficient of planting spacing were transplanting speed, characteristic parameter and oblique angle of dibble; the influence factors of qualification ratio of planting depth were transplanting speed, oblique angle of dibble and characteristic parameter. The optimum parameter condition of the dibble-type planting apparatus of eccentric disk after optimizing was 0.47m/s of transplanting speed,1.18 of characteristic parameter and 87° of oblique angle of dibble. At this time, qualification ratio of perpendicularity achieved theoretical optimum value of 98.01%, variation coefficient of planting spacing was 5.93%, and qualification ratio of planting depth was 89.25%. Through verification by an experiment in optimum condition, the experimental value of qualification ratio of perpendicularity was 96.6%, variation coefficient of planting spacing was 6.1%, and qualification ratio of planting depth was 87.8%, which indicated that the experimental results and predicted results were consistent, and regression models established by the experiment were appropriate. According to comparison of transplanting performance before and after parameters optimization, qualification ratio of perpendicularity and qualification ratio of planting depth increased by 5.8% and 3.6% respectively, and transplanting performance was superior to the technique indexes of national and industry standards as well.3. In order to satisfy the requirements in automatic transplanting, a chain driven dibble-type planting apparatus was put forward. Firstly, the kinematics model was established and the trajectory of planting point was analyzed. Then, the structures of overall and key mechanisms were designed. Finally, a test-bed was designed and manufactured for seedling transplanting to complete performance test of the new planting apparatus in the condition of different seedling characteristics and transplanting frequency. The results indicated that, as cell size of plug tray was 72 or 128 holes, the qualification ratio of planting increased to a maximum value and then decreased with the increase of moisture content from 55% to 88%, and the qualification ratio of planting got the maximum value when moisture content ranged from 75% to 80%,80% to 88% with 72 and 128 holes plug tray respectively. Within the seedling age scope during 23 to 43d, the qualification ratio of planting increased to a maximum value and then decreased with the increase of seedling age, and the qualification ratio of planting got the maximum value when seedling age ranged from 33 to 38d with both 72 and 128 holes plug tray. When transplanting frequency varied from 50 to 90 seedlings per minute, the qualification ratio of planting was more than 90%. The qualification ratio of planting got the maximum value when transplanting frequency ranged from 60 to 80,70 to 90 seedlings per minute with 72 and 128 holes plug tray respectively, so the new planting apparatus had a good stability for seedling transplanting in common speed. |
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