Research On Mechanism And Parameter Optimization Of Rapeseed Mat Seedling Cutting And Transplantation

The currently underdeveloped rapeseed production mechanization technic and low performance of machines are the critical problems that hindered the development of rapeseed production in China. To coup with the problems of mat seedling shattering and poor planting performance that occur on current rapeseed mat seedling transplanters, following work has been done in this paper:A test on soil moisture and penetration force was carried out during a time period which ranged from one day before rice harvesting to two days after. The average soil moisture content in 0-100 mm depth range and soil penetration force at different depth in 0-160 mm depth range are measured. Tillage experiments were carried out under different soil moisture conditions to find its effect on soil pulverization in rotary tillage and the resulting difference in soil flowability. Clod fineness of tilled soil was fond out by sieving with 10 mm and 25 mm spacing sieves. Soil flowability was determined by piling the tilled soil and measuring the repose angle. Analysis of variation and regression analysis of the data were performed with Excel2010 software. Result shows that the moisture content of rice paddy soil saw no significant change during a short period of time that ranged before and after harvesting and stayed around 26%, but rose significantly after precipitation to about 30%. Quadratic regression relationship could be established between soil penetration force and penetration depth while linear regression relationship could be established between soil penetration force and soil moisture content. Analysis of variation indicated that test time and test spot location both have significant effect on soil moisture content, as well as their interaction. Tillage experiments proved that rotary tillage in wet condition could result in a higher proportion in large clods and a lower proportion in small ones, and vice versa. However, no significant effect of soil moisture content was fond on the repose angle of soil piles.Direct shear test of rapeseed mat seedling was done with TJ soil shear meter and elastic, compress, shear and piecing test were done with Instron 3343 material tester. Result showed that the rapeseed mat seedling had inner friction coefficient f=0.37, cohesive stress c=0.08 MPa, average elastic modulus of 0.07 MPa, average elastic strength 5.4kPa and average compress modulus of 3.15 MPa. The sample showed plasticity in compress test and no compress strength could be found out. Quadratic regression relationship could be established between elastic modulus and material proportion as well as between elastic modulus and material proportion. The peak resistance during piecing is about 15 N. The less soil there is in the mat material, the less it is likely to break.The effect of the four factors of needle width, rotational speed, longitudinal clearance and shifts per cycle on the three indexes of seedling damage rate, qualified cutting rate and cutting uniformity are investigated with orthogonal experiment. The best combination of factor levels derived from the experiment was needle width 13.4mm, rotational speed 170 rpm, longitudinal clearance 2mm and 12 shifts per cycle.A hydrostatic transmission is designed for the trenching blades. The first program used a throttle speed control circuit with a gear pump of 7.8ml/r and a cycloid motor of 160ml/r. Nominal pressure was 10 MPa, nominal flow was 17.4L/min, and nominal power was 2.4kW. Field test showed that the system functioned with a output speed of 100 rpm, but is subject to overloading. Analysis of the mechanical property, stiffness, speed control performance, variable condition performance and efficiency was carried out. Result showed that the torque-speed property was. The system would always achieve best efficiency at 2/3 of its maximum load. The efficiency was in proportion with the throttle openness and would not exceed 67%. In order to coup with the problem in efficiency, the system was redesigned to be a volume speed control circuit. Components were changed and system refitted.With said work done, suitable soil condition and way to prevent mat seedling shattering was fond out. The prototype was improved. Experiment showed that the performance of the refitted prototype in choosen condition was better than prior.