| In rice production,farmland weeds are one of the main factors that affect crop yield,and weeding is an important and heavy work in field management,with strong seasonal,short weeding period and large labor consumption.In order to ensure the normal growth of rice and effectively control weeds,mechanical weeding,as an environmentally friendly weeding method,has no many disadvantages such as environmental pollution caused by chemical weeding,high labor cost of manual weeding,etc.In addition,the soil can be turned over in the weeding process,the oxygen content in the soil of the rice root system is increased,and the rice field growth is well promoted.However,due to the complexity of paddy field environment and the agronomic characteristics of close planting of rice,the rapid control of weeds between plants is currently the biggest difficulty in mechanical weeding of rice.Based on the analysis of the research on mechanical weeding technology in paddy fields at home and abroad,and aiming at the technical difficulties of low efficiency of mechanical weeding among rice plants,this paper has carried out theoretical research,structural design and field tests on key weeding components and the whole machine respectively.The main research contents and conclusions of this paper are as follows:Design and simulation of crucial parts of rice mechanical weeding.According to the characteristics of different root sizes of rice seedlings and weeds,the operation mode of weeding among plants was studied,weeding wheels with different structures were designed and the dynamics simulation analysis of interaction with paddy field soil was carried out.By analyzing the stress situation of gear teeth and the degree of soil disturbance under the same working parameters,the optimal gear tooth structure was selected.The simulation results showed that the soil resistance of the 6-tooth weeding wheel was greater than that of the 8-tooth weeding wheel,and the maximum resistance of the weeding wheel with different inclination angles increases first and then decreases with the increase of inclination angle.The average resistance of weeding wheels with different inclination angles to soil increases with the increase of inclination angle.The optimal combination of structural parameters is an 8-tooth weeding wheel with an inclination angle of 35.At this time,the maximum stress is 9.19N,the average stress is 4.69N,and the number of pixels in the disturbed soil image is 48,967,with an area of 61.87cm~2.(1)A kind of synchronous mechanical weeding machine for paddy field was designed.Aiming at the problems of poor adaptability,low weeding speed and high seedling injury rate in the process of mechanical weeding,a two-stage profiling mechanism was designed to improve the adaptability of the device.According to the distribution characteristics of rice mechanical transplanting seedling belt,combined with weeding components between rows and plants and secondary profiling mechanism,weeding monomer was designed,and the interaction between monomer weeding components and paddy soil was simulated by using discrete element analysis software EDEM.The simulation results show that with the increase of the relative position of weeding wheel between two plants,the soil will be disturbed more.When the relative position is 200mm,the soil disturbance degree produced by the weeding unit is the largest,with an area of 112.35cm~2.Based on the research of weeding monomers,the whole machine structure of the weeding machine is designed.The machine is mainly used for mechanical weeding in the early stage of field.The weeding operation speed is 0.7～1.3cm/s.And it is equipped with 7 monomers and 6 rows of weeding operations at a time.The whole machine has a length of 100cm,a width of 200cm and a lifting height of 50cm.Weeds between rows and between plants can be removed simultaneously,so that the operation times of machines and tools in fields can be reduced,and the damage to seedlings can be reduced.(2)Field experiment on mechanical weeding performance.Using the all-factor test method,taking the forward speed of the machine and the type of weeding wheel as experiment factors,and taking the weeding speed and seedling injury rate of the machine as experiment indexes,the weeding effect of the machine under different working parameters in the actual environment of paddy field was tested.The results of field experiments showed that the forward speed had more influence on the rate of weeding and seedling injury than the type of weeding wheel.As the advancing speed of the machine increases,the rate of seedling injury and the rate of careless removal both decrease first and then increase.The comprehensive test results showed that the umbrella-shaped weeding wheel(A)has the highest average weeding rate,at the forward speeds of 1.0m/s,the weeding rate among plants was 78.8%,the weeding rate of the whole device was 91.6%,and the seedling injury rate was 0.2%.At the same time,according to the optimal working speed and width of the machine,the working efficiency of the device when fully configured(7rows)will be 0.4～0.6hm~2/h.The machine has the functions of high efficiency,low seedling injury rate and simultaneous removal of inter-plant weeds and inter-row weeds.Reducing the number of tillage times of machinery in the field can effectively reduce the damage of machinery to seedlings. |
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