| Simulation analysis,experimental study and dynamic response analysis of the key parts,such as groove opener,rope laying parts and soil covering device,of roped type rice direct seeding machine were carried out,and the rope laying mechanism was optimized to solve the existing problems of seed rope breaking,uneven depth of ditching,uneven thickness of soil covering,based on related researches and the actual situation of rice planting in China,especially in Liaoning province..A small roped type rice direct seeding machine was developed.The main research contents and achievements are as follows:1.The tensile and penetrating properties of wrinkled paper and polylactic acid nonwoven fabrics were studied,and the effect of twisting parameter on the tensile and penetrating properties of the two materials were obtained.The experimental study was carried out to reveal the effect of twisting parameter on growth of rice and the influence of twisting parameter on emergence rate,height and root growth index of rice were determined which may provide a reference for the selection of material for rice seed rope.2.Exponential,parabolic and circular shape cutting edge of groove opener were put forward in this paper and the effect of the cutting edge curve on resistance of furrow openers was analyzed.Simulation analysis and optimization of cutting edge curve were carried out based on discrete element method.The results of simulation showed the resistance of openers were as follows: exponential type was 16.82 N,the parabolic was 20.39 N and the circular was 22.40 N.The validity of simulation analysis was verified by experiments and the results may provide a theoretical basis for the design of the groove opening device of roped type rice direct seeding machine.3.The transfer function of rope laying system was established,the effect of system damping,moment of inertia and other parameters on rope laying process was revealed and the rope laying system was optimized.Rope laying simulation test was carried out based on Adams/Cable model,the effect of position of the guide roller on the tension of the seed rope was analyzed with objective of a minimum force on the rope and the results showed that the lowest rope tension occurred when the wrap angle of rope guiding roller is 45°,and the rope laying device was optimized.The transfer function of rope laying system was established by system dynamic simulation test and the effect of system damping,moment of inertia and other parameters on time constant,magnification factor were revealed.Performance test of roperelease system showed that error rate of rope laying was 0.6%,which means the rope laying system meet the design requirements.It provides the basis for the development of the seed roped type rice direct seeding machine.4.The mechanical model of soil particles on surface of the cover plate was established,and the structural factors affecting the covering thickness are as follows: the deflection of the cover,the spacing of the cover plate,the working width and the track overlap,and the structure parameters of the covering device were optimized.Based on optimization module of DesignExpert and experimental study,the regression equation of covering thickness was set up and the influence of each factor on the thickness was analyzed with response surface method.The structural parameters combination satisfies the thickness of soil cover is determined,that is,declination angle of covering plate is 34°,the pitch of covering plate edge in the forward direction is 70 mm,working width for covering plate is 90 mm,0 mm path overlap.Results of soil covering showed that the mean value of seed rope covering thickness is 23.09 mm,the standard deviation was 2.35 mm and the variation coefficient was 10.22%,the roller slip rate was 7.2%.The working performance meets the design requirements.5.A kind of small roped type rice direct seeding machine was developed and the MIMO model of “Soil – Direct seeding machine” was established which revealed the dynamic response characteristics of ditching depth and covering thickness on initial surface roughness,vibration of the prototype and operator’s operation.System dynamic response analysis was carried out,and the input-output signal was analyzed in time domain and frequency domain according to theory of automatic control system and error recognition method,then the MIMO model of the “Soil – Direct seeding machine” was established.The results showed that the dynamic performance of the machine system can meet the design requirements.The model established can well respond to the system response characteristics which can predicted the seeding effect of this direct seeding machine under different soil and force conditions.The results may provide a reference for the design of similar mechanical systems. |
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