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Study on Dynamics Properties of Combine Soil Preparing Implement Based on the Virtual Technology

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Tutor: LiJianQiao
School: Jilin University
Course: Agricultural Mechanization Engineering
Keywords: soil preparing combine,dynamics properties,virtual measurement,virtual assembly,
CLC: S222
Type: PhD thesis
Year:  2007
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Abstract:
Saving energy and constructing friendly environment become main guidelines for many works in China nowaday and in the future. It was found from field survey that the non-matching phenomena between the mini- or medium-sized combines and power of the tractors are ubiquitous, combined the policy of developing the great project¡°Manufacture of Multifunctional Agricultural Equipments and Establishments¡±in the¡°eleventh five-year plan¡±, and analyzed the farming actuality based on individual farmer household in China nowadays. Supported by the Jilin provincial science and technology developing plan project¡°Research on the Bionic Soil-engaging Components of the Soil Preparing Combine¡±(No. 20050539), one mini-sized soil preparing combine was taken as the study object. The virtual measurement systems for agriculture engineering and virtual design and assembly were performed as study method. To manufacture a mini- or medium-sized combines with low energy-consuming was regarded as study goal, which provided new thoughts of research for the agricultural machine design.When soil is disturbed by terrain-machine, such as farming tool, bulldozer and vehicle, considered its complex constituent and many interferential factors, the mechanical properties changing of disturbed soil is unstable. Soil is a kind of discrete, multiphase compounds that is composed of soil particles, soil liquid and soil air, the constituent of it is very complex. If one kind of soil condition needs to be kept or soil need to be changed from one kind of condition to the required condition, and the mechanical forces need to be used effectively, the mechanical properties of soil subjected by external forces need to be understood except for external forces themselves. The dynamic process and the influencing factors of soil mechanical properties are relevant to many aspects directly, such as the working efficiency of terrain machines and farming tools, the cultivating quality of agriculture and so on. Because the mechanical properties changing of soil under the similar conditions are very complex, the results of soil experiment repeated badly,which bring a lot of difficulties to study the working status of agriculture tools. Firstly, the changing of soil water content and soil hardness is analyzed with the external factors (e.g. temperature, compaction load on soil, and compaction times) changing. Therefore, the quantificational results among the factors influencing the homogeneous feature of the soil mechanical properties were analyzed simply through soil-bin experiment. Based on the above quantificational results, the different results of soil preparing combine experiments, which were done in different phases, had relativity and repeated characteristic through scientific treatment of soil.Secondly, three sets of self-design virtual instruments were designed, which were used to measure and study the tractor performance parameters(e.g. :fuel oil consumption, engine speed and so on), the drag force of the tractor and the forces of soil-touching parts, when the soil-bin experiments of mini-sized soil preparing combine machine were done in the room under the different experiment conditions. The virtual instruments were as follows: (1)4-channel pulse signal virtual measuring system for tractor performance parameters ;( 2) 2-channel Stress-Strain portable virtual measuring system for the rotary cultivation torque and ridging resistance of soil preparing combine machine;(3) single channel high-speed virtual measuring system for the dragging force of tractor.Thirdly, based on the experimental optimization principle of design, the experiment projects of testing performance parameter and the dragging force of the tractor were designed by the law of augmentation of experiment. After analyzing the data of two above experiments using the method of range analysis, variance analysis and credibility analysis, the results of experiments shown that the two factors, such as working ways of soil preparing combine machine and working speed of tractor, had the remarkable influence to the above two experimental target. And what¡¯s more, the working ways of soil preparing combine machine have the decisive influence on the target of experiments in two factors. These results gave reference to study the improvement performance of the combine machine. In view of the measuring ridging resistance and the rotary cultivation torque of the combine machine, the experiment project was designed by selecting the orthogonal array L4(23). This experiment mainly provided the rotary cultivation torque and the ridging load foundation parameter for the following power simulation analysis. Finally, the 3 dimensional virtual assembly model of combine machine was built through the three dimensional CAD software Inventor,and then the parameters including materials behavior and rotation inertia of the key components can be acquired in this model, these parameters lay the foundation to design the simulation model of the combine machine for the dynamics analysis using software ADAMS accurately. Moreover, according to the optimized result after simulation analysis, auto-adapted design, the assembly connection design and the part size parameterization function which three dimensional software Inventor had, were fully used to update the dimension of correlative parts of combine machine during the course of design conveniently.After the virtual simulation model constructing, it was verified successfully. Through comparisons of the simulation results and the soil-bin test results, it is shown that the maximum error was 1.13%, min-error was 0.34%, and average error was 0.86% between them, so the simulation model was suitable.compaired with prototype soil preparing combine machine,, the results of simulation shown that the drag force of improved soil preparing combine machine was reduced about 6.953% after the loadings of bionic soil-touching parts on the simulation model.According to the above simulation result, the key components (e.g. gear box gear, mainly mechanical axis and key etc) were improved, and the strength of them were checked and approved. The results of checking shown that the improved parts were complied with the requirements of functions and technique. Based on the improved parameters of shape and size, the 3-D virtual assembly model designed by software Inventor was updated and virtual assembled again. And what¡¯s more, for preventing material waste or redesign in the later manufacture period, the kinematics simulation of interference detection was used to check the conflict and interference fit among the all parts after the virtual model assembling.The main parts, including cutting tool, frame, land wheel and ridging shovel, were checked the static interference among the important parts mutually, the results of above checking shown that the whole machine had no interference.In the three-dimensional virtual assembly model, as the main motion part, the rototilling blade accomplished its motion simulation by using the driving bonds. Therefore, the assembly confliction in the motion can be checked, and the interferential phenomena resulted from the changed design on the workability of the parts can be observed. No conflictions can be seen when the driving blade turned in the positive direction with the driving blade axis turning 3600.The checked results from the interferential examination and the dynamic confliction detection indicated that the structure and the sizes of the parts by the optimized design are logical, and the machinery parts can be manufactured based on the virtual prototype assembly model.The simulation platform of virtual prototype was improved and the new machine with the bionic soil-touching parts was manufactured according to the modified 3D virtual assembly of soil preparing combine model. The virtual performance tests with multi-work conditions have been done using the improved virtual prototype simulation platform, the results of tests showed that the simulation traction force for the stubble-removing and ridging was reduced 0.948% compared with the original design after optimization of the key partial dimensions; and the working traction force was also reduced 7.41% under the same multi-work conditions. The performance tests in the field have been done and the results showed that the working traction force of the new Soil preparing Combine was reduced 6.335% under the stubble removing and ridging conditions compared with the original machine.Virtual measurement, virtual tests, virtual assembly and the virtual prototype, used to study the dynamics of small Soil Preparing Combine, are the modernization digital experimental technology and design methodology. Meanwhile, these methods are the application of technology of computer for agricultural machine engineering. The results of the present research will provide new idea and methods for implements design in agricultural machinery engineering
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