Design Of Pick-up End-effector And Optimization Of Seedling Cultivation Based On Seeding-bowl-root Multiple Properties

With the promotion of factory nursery and plug breeding,China has stepped up the concern of transplanting machinery,but,no domestic automatic vegetable transplanter goes into production currently.The main problem of restricting its development is the existing transplanting machinery lacks adaptability to the working object because of unclear mechanism of pick-up end-effector and plug seedlings,which causes the institution design and the nursery technology incompatible.In view of this problem,the root structure,mechanical properties and growth characteristics of the working object were studied,a pick-up end-effector was designed and the nursery technology was optimized in this paper.The main contents include the following aspects:(1)With tomato plug seedlings as the research objectives,method of threedimensional reconstruction for seeding bowl and root system was explored,and the structural parameters were measured and verified.The micro-CT scanning parameters for the tomato bowl were as follows: scanning voltage,scanning current and scanning voxels were 55 kVp,72?A and 45?m,respectively.Comparing spatial position of CT pot model with real models',it was found that the maximum relative error was 12.105%,while the minimum relative error was 4.419%.And the average error of root length and root angle was about 1.91%,8.35% respectively.Statistically,for main parameters of roots,root volume,root length and root diameter were tested at the relative errors of 3.85%,3.34% and 3.05% respectively,which two independent sample t test(?= 0.05)were conducted by p(bilateral)of all being higher than the significant level of 0.05,indicating that no significant difference of mean root volume,root length and root diameter between CT model's and real model's.(2)Based on the CT root system model,in order to explore the spatial distribution of the root system,the root distribution characteristics of seedlings under different nursery parameters were analyzed.The results show that in the vertical direction,the distribution of root volume and root layerd density both present quadratic parabolic law,while the volume of the root system also has a tendency of quadratic parabolic,with four polynomials regularity of root density in the horizontal direction.Furthermore,the orthogonal experiment was used to analyze the effect of substrate ratio(peat,vermiculite,perlite volume),compaction(filling substrate volume: plug volume),fertilization times on the vertical distribution,the horizontal distribution the plug seedlings' root system and the mechanical properties of seeding bowl to consider multiple indicators of plug seedlings for gripping synthetically.The result showed that the ratio of substrate was peat: vermiculite: perlite for 3: 1: 1,the number of fertilization was 3 times,and the compaction degree was 1.(3)Pick-up end-effector was designed and optimized based on the spatial distribution of tomato root and mechanical properties of seeding bowl.According to the working principle of the pick-up mechanism,the root distribution characteristics of the tomato plug seedling,the mechanism of the different gripping methods on the bowl body,the way to pick seedlings was determined.Also,the structure parameters of the end-effector are optimized by taking the structural characteristics,the root distribution of plug seedlings,the relationship between pulling force F and clamping deformation x into account.(4)Nursery technology was optimized by considering the spatial distribution of root system,mechanical properties,growth quality and seedling quality synthetically.Under different effective accumulated temperature,growth quality and picking quality of plug seedlings were statistically analyzed by conducting orthogonal experiment with the ratio of substrate,compaction and fertilization times of plug seedlings.The results showed that when the effective temperature was 707.82 ?,the seedling index of plug seedlings was the highest,and the picking quality was the best.Aiming at the multi-index(root spatial distribution,mechanical properties,strong seedling index and seedling success rate)of the plug seedlings under different nursery parameters,the optimal nursery parameters were determined for both transplanting performance and seedling quality.It is A3C3B1(peat: vermiculite: perlite = 3: 1: 1,fertilization times 3 times,compaction degree 1).