【作者】 李鑫；

【导师】 王金武；

【作者基本信息】 东北农业大学 ， 农业机械化工程， 2019， 硕士

【摘要】 水田杂草在农业水田生态系统中严重抑制着水稻产量与品质,直接影响国家粮食安全产能。据联合国粮农组织统计,近些年中国因草害引起的水稻产量损失率达13%,单年损失粮食上百亿公斤,科学有效地防控草害是实现稻米高产、稳产、优质生产的重要保证。机械除草由于在除草过程中能疏松土壤,提升土壤对养分的吸收能力而备受青睐,目前水田除草机仍以需要拖拉机或人力推拉作业的机型为主,存在作业效率低,劳动强度大,伤苗率高,田间转向困难,无法长时间连续作业等问题,自动化、智能化机具研制仍处于试验阶段且多用于旱田作物。针对水田除草机自动化程度低,装备匮乏等问题,本文研制了一种履带式可远端遥控的水田除草机,其具有对土壤破坏程度轻、整机机动性好、结构紧凑及转弯半径小等特点。安装有间距、高度及转速可调节的除草轮,以期在不同行距、泥脚深度的水田中能够进行有效高速的除草作业,通过试验验证了除草机工作性能及可靠性,研究主要内容如下:(1)针对东北地区水稻种植的农艺要求,考虑除草机作业时间、田间作业效率、作业时伤苗率和除草率、田间行走下陷量及对土壤破坏程度等因素,确定遥控式双行水田行间除草机的总体结构方案。建立除草机转向时的平面运动模型,得到底盘电机所需最大功率,根据无线电的通信原理设计除草机的遥控系统,实现除草机前进、后退、转弯,摄像头舵机摆动、仰俯,除草轮转动的远程遥控。(2)对除草机关键部件进行设计,设计了传动系统,参考相关公式对驱动轮及支重轮等推进装置进行设计,并运用有限元分析软件对其强度进行校核。对除草轮匀速状态下进行静力学研究,确定除草轮的主要结构参数,建立除草装置静力学模型,得到除草装置电机所需最大功率,对除草机电气元件进行选配。(3)运用三维建模软件Pro/ENGINEER Wildfire 5.0对除草机进行实体化建模,对整机性能进行分析,得到重心偏移时除草机最大接地比压为9872 Pa,最小接地比压为7836 Pa,分析除草机横向和纵向稳定性,得到上下坡时纵向极限翻倾角分别为42.8°和28.7°,纵向极限下滑角为31°,横向极限翻倾角为33.9°,横向极限下滑角为31°。(4)运用ANSYS Workbench 14.0软件建立除草装置机架有限元模型,并对其进行自由状态下模态分析,为检验有限元仿真分析的准确性,采用力锤激励模式进行模态试验,验证了仿真计算的准确性。对比分析机架固有频率与外部激振频率之间关系,机架固有频率均避开了外部激振频率,除草装置工作时可有效避免共振的产生,验证了机架结构设计的可靠性。(5)对除草机底盘田间行驶速度、转弯半径及越埂高度分别进行试验,底盘行驶速度范围为0~0.9 m/s,田间最小转弯半径为435 mm,田间最大越埂高度为162 mm,可实现在低田埂水田中的无阻碍行驶作业。(6)将除草率及伤苗率定为单因素及多因素的试验指标,除草机前进速度及除草深度定为单因素及多因素的试验因素,开展了田间除草试验,利用数据处理软件Design-Expert 8.0.6对所得试验结果进行分析和优化,得到了前进速度及除草深度对作业性能影响的主次顺序,探求了除草机作业的最优参数组合。田间试验表明,除草率大小受除草机前进速度及除草深度交互作用影响,影响除草率的因素主次顺序为:除草深度、前进速度。伤苗率大小受除草机前进速度及除草深度交互作用影响,影响伤苗率的因素主次顺序为:前进速度、除草深度。当除草机前进速度为0.45 m/s、除草深度为74 mm时除草性能最优,除草率及伤苗率分别为82.73%与2.63%,满足水田除草的农艺要求。更多还原

【Abstract】 Rice field weeds are an important part of the agricultural paddy ecosystem.T hey compete with rice for growth space,fertilizer nutrients,light,water and heat,resulting in a decline in rice yield and quality,directly affecting national food security capacity.According to the data of FAO,the loss rate of rice yield caused by weed damage in China has reached about 13%,and ten billion kilograms of grain have been lost per year.Scientific and effective prevention and control of weed damage is an important guarantee for achieving high,stable and high-quality rice production.Mechanical weeding is favored because it can loosen the soil during the weeding process and enhance the soil’s ability to absorb nutrients.At present,the paddy field weed er is still mainly used for tractors or manual push-pull operations,there are some problems,such as low efficiency,high labor intensity,high rate of seedling injury,difficulty in field turning,and unable to work continuously for a long time.The development of intelligent automation machine is still in progress and it mostly acts on dry-land crops.In view of the low degree of automation and lack of equipment in the paddy field weeder,this paper developed a crawler-type controlled paddy field weeder with light soil damage,good vehicle maneuverability,compact structure,small turning radius,etc.The weeding wheel with adjustable pitch,height and speed in order to carry out effective high-speed weeding work in paddy fields with different line spacing and mud depth.The performance of the machine is verified by tests.The main contents of the research are as follows:(1)According to the agronomic requirement of rice planting in Northeast China,considering the factors such as operation time,field operation efficiency,seedling injury rate and weeding rate during operation,field walking subsidence and soil damage degree,the overall structure scheme of remotely-controlled double row paddy field inter-row weeder was determined.The plane motion model of the turning machine was established,and the maximum power of the chassis motor was deduced.The remote control system of the machine was designed according to the principle of radio receiving and sending,which realized the remote control of the forward,backward,turning of the machine,the swing and pitch of the camera steering gear,t he rotation of the weeding wheel.(2)Designed the key components of the whole machine,designed the transmission system of the machine,designed the propulsion device such as the driving wheel and the supporting wheel reference to the relevant formula,supporting wheel was checked by the finite element analysis software.The statics research was carried out on the weed wheel at a constant speed to determine the main parameters of the weeding wheel,established the static model of the weeding device,derive the maximum power required of the weeding device motor,and selected the electrical components of the machine.(3)The paper established 3D modeling by Pro/ENGINEER Wildfire 5.0,and the performance of the machine was analyzed.The maximum grounding pressure was 9872 Pa,and the minimum ground pressure was 7836 Pa when the center of gravity was shifted.By analyzing the lateral and vertical stability of the machine,the vertical ultimate tilt angle was 42.8° and 28.7° when the machine gone uphill and gone downhill,the vertical limit slip angle was 31°,the lateral limit tilt angle was 33.9°,and the lateral limit slip angle was 31°.(4)Workbench 14.0 software was used to solve the modal frequency and mode shape of the non 0 first 4th order of the weeding device frame,and the accuracy of theoretical calculation and modal test was tested.Comparing and analyzing the relationship between the natural frequency of the frame and the external excitation frequency,the natural frequency of the frame avoided the external excitation frequency.When the weeding device worked,the resonance can be effectively avoided,and the reliability of the frame structure design was verified.(5)The field running speed,turning radius and height of the machine chassis were teste d respectively.The chassis running speed ranged from 0 to 0.9 m/s,the minimum turning radius was 435 mm,and the maximum height of the field crossing was 162 mm,it can realize the operation of unimpeded driving in the low ridge paddy field.(6)The field weeding test was carried out,the forward speed and depth of the machine were selected as the tested factors,and the weeding rate and seedling injury rate were selected as the tested indicators.The field single factor and multi-factor tests were carried out respectively.The paper analyzed the test data by data processing software,determined the order of the factors affecting the performance of the operation.Field tests showed that the interaction between the forward speed and the weeding depth had a significant effect on the weeding rate.The primary and secondary factors affecting the weeding rate were: weeding depth and forward speed.The interaction between the forward speed and the weeding depth had a significant effect on the injury rate.The pri mary and secondary factors affecting the injury rate were: forward speed and weeding depth.When the forward speed of the implement was 0.45 m/s and the weeding depth was 74 mm,the weeding performance was the best,the weeding rate and the injury rate were 82.73% and 2.63%,respectively,which satisfied the agronomic requirements of weeding in paddy fields.更多还原