| As a modern cultivation technique,vegetable seedling transplanting can improve the utilization rate of land,increase crop growth period and raise crop yield effectively.The cultivation of vegetables has the disadvantages of great labor intensity and low working efficiency with the method of manual and semi-automatic transplanting operation,which limits the rapid development of industrialization of vegetable in China.While the mechanization of automatic transplanting,with the comprehensive advantages of high working efficiency,consistent standardization,and convenient field management in later period,is the inevitable trend in scale development of vegetable transplanting."Research and Development on High-speed and Automatic Transplanting Technology and Equipment for Vegetables"(project No.2017YFD0700803)is among the National Key Research and Development Program of the thirteenth Five-Year plan.Based on that,the push-stab method of picking seedlings has been put forward for the first time with analysis and reference on the advanced picking seedlings technology at home and abroad.Basing on previous research experience,a set of pick-up mechanism with picking in one whole row and feeding in two parts was designed,and then the research of automatic picking seedlings system got conducted further.The automatic pick-up device was developed after analyzing and synthesizing the research results,and testing of the picking seedlings system was carried out to evaluate the mechanical performance.The specific research contents are as follows:1.After comparing and analyzing the characteristics of existing picking seedlings scheme,a new seedlings picking method of push combining with side stab was presented,and the work program of picking in one whole row and feeding in two parts was carried out,which would realize the requirements of high efficiency and low loss.According to working program of the pick-up device,the movement of picking seedlings,demand of the movement,and the driving scheme of each working mechanism were protocolled.By far,the design of the overall structure and the work process of the pick-up device for vegetable seedlings were finished.2.Lettuce seedlings cultivated by transformable potted tray with 128(8×16)cells were selected as the research object in this paper.The compression test and push-out test of pot seedlings were implemented based on different proportion of matrix media,matrix moisture,and mandril diameter.The experiment results showed that the compression resistance and the push-out performance of the seedling matrix were best with the matrix components being MT1(peat,vermiculite,pearlite being mixed in percentage proportion of 3:1:1 by volume),matrix moisture content being around 55%and the mandril diameter being 8 mm,which was appropriate for mechanical operation.Under this condition,the lifting force needed by the pot seedling substrate to separate from the tray cell was not less than 7.43N,and the displacement of the mandril was not less than 5.12mm,which would provide data support for the design of pick-up mechanism and push-out mechanism.3.According to the design requirements of the overall scheme of the seedling device,the research of pick-up mechanism,sending seedlings parts,and tray push-out mechanism were conducted.The structure parameters of the picking manipulator were optimized with the methods of combination of theoretical analysis and experimental study.As the result,a set of optimal parameter combination was obtained to create a better performance for picking seedlings,which were the length of pick-up needle(S0)being 120mm,the depth of stabbing matrix(S1,being 30mm,the stabbing position(h)being about 5mm from the top of matrix,the two needles fixed position(k0)being at a distance of 26mm,the space of two holes controlling the needles change(k1)being 18mm,the diameter of picking needles(d)being 2mm,and the stabbing angle(a3)being 45°.Parametric modeling of push-out mechanism was established by using the mathematical method.Based on MATLAB-SQP(sequential quadratic programming)algorithm,the optimal structure parameters meeting the demands of push-out mechanism were obtained.The parameter combination was L0=125 mm,L1=88 mm,L2=125 mm,L3=92 mm,L5=168 mm,θ-5π6,the coordinate of C being(-86mm,198mm),and the initial length of push-out cylinder(L4)being 171mm.The precise stepping control system of sending seedlings was established based on Fuzzy-PID algorithm,and the performance test of positioning for the stepping system was designed.The experiment results were that the maximum value of the accumulative stepping error in sending seedlings was 1.07mm,and the accuracy of stepping displacement was above 97.03%,the results showed that the sending mechanism could satisfy the actual working requirements in a good manner.4.Combined with the requirement of the operation process,research of the sequence control and logic algorithm of the automatic picking system was conducted,and a set of human-machine interactive automatic transplant control system was designed and developed based on FPGA and Lab VIEW.With core functions such as automatic sending/picking/conveying seedlings,tray specifications setting,single step debugging simulation,and automatic planting number calculating and recording,this system can effectively control the automatic seedling picking process.5.A test for the automatic pick-up device was arranged to verify the performance of picking seedlings after this pick-up device was trial-manufactured and debugged integrally.The test results indicated that the process of the pick-up device,including sending,picking,dividing,and casting seedlings,could realize the automatic,sequential and accurate operation.When the frequency of picking seedlings was not more than 220 plants per minute(110 plants per row and minute),the success rate of picking seedlings reached above 97%,and the loss rate of matrix was below 7.5%.The system could properly meet the performance requirements,and the structure designed was verified to be reasonable. |
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