| Strawberry is the small berry with most cultivation,high economic value and nutritional value in the world,it has the advantages of easy reproduction,short growth cycle and convenient management.At present,China has become the largest strawberry producing country in the world,but strawberry production in our country is still stuck in the manual operation,and the manual transplanting process is the largest part of strawberry production operation time.Meanwhile,strawberry transplanting is time-consuming,laborious and difficult.According to the planting mode of "transplanting strawberry potted seedlings" put forward by agronomy experts,it can not only cultivate strong seedlings,improve the survival rate and yield of seedlings after transplanting,but also facilitate the realization of mechanized transplanting of strawberries and imp rove the efficiency of transplanting.Today,there are few reports and most company and scholars are in development on open field or greenhouse strawberry potted seedlings transplanting equipment at home and abroad.There are only a few semi-automatic potted seedling transplanting machines in the market which can be used for strawberry potted seedling transplanting after being improved.Meanwhile,it is necessary to pick and feed seedlings manually,and the planting mechanism should complete the planting.The mechanization degree is not high,the structure is complex and the price is expensive,so it is difficult to popularize and apply in China.In order to promote the development of automatic transplanting equipment for strawberry potted seedlings with high efficiency,light simplification and low cost,which is in line with China’s national conditions,the strawberry potted seedling transplanting mechanism designed by using fitted Hermite curves as the non-circular gear pitch curve is proposed,which based on Agronomy requirements of strawberry cultivation.Using the rotary non-circular gear planetary gear system mechanism and CAM multi-link mechanism combination of a pure mechanical transplanting mechanism,a replacement for Europe,America and Japan and other countries by using mechanical and electrical integration of liquid,transplanting mechanism eliminates many institutions cooperate with homework when planted the coherence error of the separation problem,implements a set of institutions in order to complete pick seedlings,transportation,dig a hole and planting.According to the above analysis,the main research contents and conclusions of dissertation are as follows:(1)Agronomic requirements and measurement of physical characteristics for strawberry potted seedling transplantingStrawberry potted seedling transplanting is a systematic project,involving seedling ratio of soil matrix,strawberry potted seedlings and mechanical structure,In order to design the strawberry potted seedlings transplanting mechanism more scientifically,the basic physical and mechanical characteristics of strawberry potted seedlings transplanting were tested and measured based on the idea of combining agricultural machinery and agronomy.Taking the plug size,soil matrix rati o and soil moisture content as experimental factors,the single factor test on the way to remove potted seedlings was carried by the WDZ-200 tensile strength testing machine,YZC tension pressure sensor and multi-channel tension pressure measuring instrument.It was concluded that a seedling taken out by picking soil is the best transplanting condition,it is beneficial to improve the success rate of seedling harvesting and less damage to stem and root system.Meanwhile,the above basic experiments will provide a theoretical basis for the design of follow-up strawberry transplanting mechanism and the transplanting of other upland field potted seedlings.(2)The theoretical modeling and mechanism analysis of strawberry potted seedling transplanting mechanismIn order to solve the problems of joint failure and complex structure of the existing transplanting machines in foreign countries,such as removal and separation of multiple sets of mechanisms or devices,this dissertation puts forward a strawberry potted seedling transplanting mechanism based on the Hermite interpolation gear.The movement of this mechanism was used to complete potted seedling transplanting operations such as picking seedlings,transporting seedlings,digging holes and planting seedlings,specially,the rotary non-circular gear planetary gear system mechanism completes the complex "hawk" trajectory and posture required for seedling collection,transportation and planting,and the CAM multi-link mechanism completes the complex "heart" trajectory and posture required for digging hole,so as to achieve the precise coordination between the seedlings picking and the holes dug.The mathematical model and kinematics analysis of the seedling picking and digging hole mechanism were carried out respective ly.At the same time,the Hermite interpolation method was applied to the pitch curve construction of non-circular gear,and the Hermite interpolation non-circular gear tooth profile forming design software was developed based on Visual Basic 6.0 programming language platform,to solve the difficulties in the high-precision tooth profile forming of non-circular gear.(3)Establishment of optimization objective and objective function of strawberry potted seedling transplanting mechanismBased on the kinematic analysis model established by the strawberry potted seedling transplanting mechanism,the concepts of multi-objective,multi-parameter and strong coupling of the mechanism parameter optimization are expounded in detail.Meanwhile,the design requirements and optimization characteristics of the transplanting mechanism of strawberry pot ted seedlings based on Hermite interpolation are analyzed.Then the optimization objectives of strawberry potted seedling transplanting mechanism were divided into 5 categories,and 21 optimization objectives were formulated.Additionally,the mathematical relationship between the parameters of the transplanting mechanism and the optimization objectives was analyzed by using the intersection of mathematics and mechanism,and the corresponding objective function is established,which lays a theoretical foundation for the development of the optimization software of transplanting mechanism.(4)Optimization design software development and parameter analysis of strawberry potted seedling transplanting mechanismAccording to the kinematics model analysis of the transplanting mechanism,the optimization parameters and the established optimization objective functions,and based on Visual Basic 6.0programming language platform,developed the computer aided analysis and optimization design software for strawberry potted seedling transplanting mechanism.At the same time,the functions of the optimized design software developed are introduced in detail.The software can simulate the structure size,position and motion state of the mechanism in real time.Through human-computer interaction,to display a bar to identify the pros and cons of the target,and optimize the target of transplanting mechanism by adjusting parameters,meanwhile,observe and summarize the influence law of parameters on transplanting trajectory,and combined with the trajectory,attitude change trend and design experience,a set of non-inferior solution parameters satisfying the transplanting objectives and structural design requirements are finally optimized.(5)Structure design and virtual prototype kinematics simulation of strawberry potted seedling transplanting mechanismAccording to the parameters of the mechanism obtained by the optimization design software,the CAXA electronic drawing software was used to complete the design of the two-dimensional drawing and the overall assembly drawing of the strawberry potted seedling transplanting mechanism with Hermite interpolation.In combination with NX 10.0 software,the 3d modeli ng of all parts was completed.Then,the 3d model and ADAMS are co-simulated.Finally,the relative motion and absolute motion simulation tests of virtual prototype were completed.At the same time,the track of picking seedlings,digging holes,relative m ovement velocity curve and absolute movement velocity curve corresponding to the point of seedling tip and the point of digging shovel were compared with the theoretical track and theoretical velocity curve obtained by the optimization software.Which indicates the theoretical analysis is consistent with the theoretical velocity curve and the theoretical,and the correctness,rationality and accuracy of transplanting mechanism and structural design is verified.(6)Development of physical prototype of strawberry potted seedling transplanting mechanismUsing high-performance,industrial-grade,rapid prototyping 3D printing technology,combined with the established 3D digital model file of transplanting mechanism,based on SLA solid laser rapid prototyping equipment and photosensitive resin material,the rapid prototyping of core parts of transplanting mechanism physical prototype was completed.It can be seen the cost and risk of die development for complex parts are reduced and the development cycle is shortened.The physical assembly of the physical prototype of the transplanting mechanism was completed and the physical prototype machine was assembled.The design of the planting arm components and camshaft was modified and improved.Additionally,the parts with high fracture strength requirements,metal manufacturing and processing were adopted.(7)Performance experiment of strawberry potted seedling transplanting mechanismBased on the experiment of determining the physical characteristics of strawberry potted seedlings,the optimum value of plug size,soil matrix ratio and soil moisture content for suitable transplanting of strawberry potted seedlings was obtained.T he seedling cultivation of strawberry potted seedlings was completed in the plant factory laboratory,and the seedlings is used in the performance experiment of strawberry potted seedling transplanting mechanism.Firstly,the physical prototype of the transplanting mechanism was installed on the established strawberry potted seedling transplanting test bench,then the transplanting trajectory and posture of strawberry potted seedling transplanting mechanism were verified based on the high speed camera technology,the above results indicate the theoretical trajectory,virtual simulation trajectory and bench test trajectory are basically the same,which verifies the correctness of the mechanism design.Moreover,the results of performance experiment show that the success rate of seedling picking was 92%,the success rate of planting was 85%,and the average p lanting distance was 172.9mm,the depth,length and width of the digging holes is all better,and the experiment shows that the designed transplanting mechanism is feasible and practical to meet the transplanting requirements of strawberry potted seedlings. |
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