Design And Research Of Vertical Micro-tiller For Urban Micro Agriculture

As my country’s urbanization accelerates,the urban micro-agriculture(UMA),which can not only produce green,healthy and pollution-free foods but also satisfy the pastoral pleasure of green planting of fruits and vegetables,has developed rapidly.In order to reduce the labor intensity and improve work efficiency of UMA operators,it is necessary to develop tillage machinery suitable for UMA.A vertical mini-tiller suitable for UMA to loosen soil was developed and theoretical and experimental research was conducted related to it.(1)According to the operating characteristics of UMA,a new type vertical micro-tiller of self-adaptive variable tillage was proposed,and it is powered by electricityand takes a three-axis motion frame as the operating mechanism.The overall design of the micro-tiller was carried out,the design and selection of the operating mechanism,the head of adaptive variable tillage,the drive motor and reducer,the motor controller and other components were completed.(2)Based on the particle dynamics theory and empirical formulas,the linetype of the vertical spiral knife was designed,and its equation was deduced.From the point of view of micro-particle science,the soil particles of transient and steady state were analyzed,and its motion trajectory equation and cutting power consumption formula were obtained.The main factors affecting the power consumption were determined and there are the forward speed,the rotation speed,and the structural parameters of the knife.(3)Combined with the characteristics of urban micro-agricultural soil,the SPH algorithm was used to establish soil constitutive model,and a simulation model of the vertical spiral knife cutting soil was built.The model was used to analyze the soil resistance and work of the tiller during the cutting process.The simulation results are verified by using empirical formula calculations and soil bin tests.The results show that:(1)The cutting resistance of the knife shows a cyclical change law similar to a sine curve,and its maximum and minimum value is 550 N and 200 N respectively when the forward speed of the cutter head is 0.1m/s and the rotation speed is 150r/min;(2)In the soil model,particles at three depths are taken for motion analysis,and the velocity,acceleration,and displacement curves of the soil particles indicate that the tiller has a good soil loosening effect during the operation.(3)The average cutting power of the plow knife on the single-side knife rest is 487.78 W after the tillage amplitude is stabilized and its relative error is 0.86% and 6.0% compared with the calculation value by empirical formula and the soil tank verification test result respectively,,which verifying the feasibility of the simulation analysis.(4)with vertical spiral plow knife speed,rotating speed of cutter head and plow knife structure parameters as the factor,the power consumption per tillage as test index,the three factors and three levels orthogonal virtual experiment was conducted.Based on the test results,the regression equation between the factors and indexes is established.Then the optimization model of a plow knife cutting process with the minimum power consumption as the goal was set up,and the calculation results show that: the minimum power consumption per tillage is 1.8828W/mm,when the cutter head forward speed is 0.10m/s,the rotating speed is 16.2571rad/s,and the number of blade helical turns is 2.75.(5)The soil tank test bed of the whole micro-tiller was built.The experimental results show that:(1)when the cutter head rotation speed is 190r/min,the maximum impact stress of the knife rest on the wall of the vegetables basin is 154.7MPa,which is smaller than the maximum tensile strength of the plastic and the impact force can be reduced by 107.1MPa by sticking a buffer piece on the knife rest.(2)the soil fragmentation rate of the two types of soil by micro tillage machine is more than 60%,which meets the national standard requirements,and the soil fragmentation rate of vegetative soil is higher.(3)simulation optimization verification test verified the consistency between the experimental results and simulation optimization results;(4)the micro tillage machine could automatically adjust the tillage amplitude to adapt to the demands of different sizes of vegetable POTS.