基于离散元的排种器排种室内玉米种群运动规律

Movement law of maize population in seed room of seed metering device based on discrete element method

高寒干旱地区免耕地表播种作业时,排种器振动与种群运动状态对气吸式排种器的吸种性能有较大影响。为研究气吸式免耕播种机在免耕地表作业时排种器振动参数及振动对排种器内玉米种群运动的影响规律,该文采用BK加速度传感器和Pulse LAN-XI振动测试系统,对2BM-5型气吸式免耕播种机在免耕地表作业时排种器振动特性进行了测试,并应用Matlab软件对振动信号进行了分析。在此基础上基于离散元法模拟了在田间作业振动条件下玉米种群运动规律,并基于室内台架试验进行了验证。播种机田间作业振动信号分析结果表明：播种机前进速度为2、3、4、5、6、7 km/h时,排种器振动的位移功率谱密度较大值的频率为5、6、7 Hz,排种器振动的幅值由2.4到7.9 mm线性增加。由离散元方法仿真得到了种子室内玉米种群最大速度、种群平均速度与播种机作业速度的拟合曲线。台架验证结果表明：气吸式排种器排种性能较好的作业速度为3～5 km/h,较好的振动幅值为6 mm;种群最大速度范围为0.120 3～0.224 3 m/s,种群平均速度范围为0.080 7～0.141 3 m/s,吸种区种群最大速度范围为0.127～0.26 m/s时,气吸式排种器吸种性能较好。该研究可为免耕播种机气吸式排种器吸种性能的提高提供参考。

Development of conservation tillage can improve the ecological environment in alpine arid area of northern China and farming and animal husbandry interlaced zone, conducive to the sustainable development of China agriculture. Due to the regional difference of conservation tillage, developing a precise no-tillage planter suitable for alpine arid area has an important significance for farming and animal husbandry interlaced zone in increasing surface coverage and reducing water loss and soil erosion. As the surface under conservation tillage has a certain amount of straw and stubble, vibration characteristic of planter is different from common cultivation during the operation, and the vibration has great influence on the movement state of seed population. Population movement state affects seed suction performance of air-suction seed metering device, thus influencing the quality of whole operation of no-tillage planter. When the vibration is small, population movement speed is low, liquidity is poor, and suction hole re-suction rate is relatively high; when the vibration is large, population movement speed is high, and it is difficult to suck seeds for suction hole and the leakage rate is relatively high; proper vibration can reduce the leakage rate and the re-suction rate of suction hole. Therefore, for no-tillage surface planting in alpine arid area, metering device vibration and population movement state have great influence on seed suction performance of air-suction seed metering device. The paper aims to study the influence law of vibration parameters of seed metering device on corn population movement in seed metering device during no-tillage surface operation with air-suction no-tillage planter. This paper adopts the BK acceleration sensor and Pulse LAN-XI vibration test system for testing vibration characteristics of seed metering device during no-tillage surface operation with 2BM-5 air-suction no-tillage planter, and the analysis on time domain and frequency domain of vibration signal is conducted with the MATLAB software. Then the time domain and frequency domain results are taken as input parameters of seed metering device model in discrete element software, and the movement law of maize populations under the condition of vibration is simulated in the field work of no-till planter. Seed suction performance bench test verification is performed with the JPS-12 computer vision test bench and LKD-P type suction electromagnetic vibration table, and the analysis on seed metering performance of air-suction seed metering device is conducted under different operation speed and vibration amplitude. Field vibration signal analysis results show that when the field operation speed of planter increases from 2 to 7 km/h, the frequency of the main vibration power of seed metering device is basically kept at 5, 6 and 7 Hz; the vibration amplitude of the seed metering device shows a linear increase from 2.4 to 7.9 mm. Discrete element method simulation results show that the fitting curve between the maximum speed of corn population in seed room and the forward speed of planter has a fitting determination coefficient （R2） of 0.9671. The fitting straight line between the average speed of corn population and the speed of planter has a fitting determination coefficient （R2） of 0.9325. Bench test results show that the operation speed for good seed metering performance of the air-suction seed metering device is 3-5 km/h, and the good vibration amplitude is 6 mm; the maximum speed range of the population is 0.1203-0.2243 m/s, the population average speed range is 0.0807-0.1413 m/s, the maximum speed range of the population in seed suction area is 0.127-0.26 m/s, and the air-suction seed metering device has a good performance. The results can provide theoretical basis for improving the seed suction performance of air-suction seed metering device of no-tillage planter.