【作者】 刘志刚；

【导师】 王德成；

【作者基本信息】 中国农业大学 ， 农业机械化工程， 2013， 博士

【摘要】 沙生灌木是我国西部地区防沙治沙、改良沙化土地的重要植物,在我国沙化危害治理中发挥着重要作用。沙生灌木具有适时平茬复壮的生物学特性,但由于大部分沙生灌木未及时平茬,出现了不同程度的生长退化,致使涉及的区域面临二次沙化的危险。沙生灌木不仅具有重要的生态效益,同时还可以带来较好的经济效益。论文研究内容作为国家科技支撑计划项目的关键任务,目标就是突破机械化平茬沙生灌木的瓶颈技术,研制出符合我国国情的沙生灌木收割装备。论文评述了国内沙生灌木生长环境和生物学特性及国内外相关研究动态,在总结分析典型沙生灌木沙柳、柠条基本特性和切割特性的基础上,进行了往复铲式、往复单动刀式、旋转甩刀式、圆锯片式4种切割器的设计与试验。试验表明,往复式切割器适用于收割平坦地形生长的低龄小径级灌木；圆锯片式切割器适用于三年及以上生木质化程度较高灌木的平茬复壮作业；而往复铲式和旋转甩刀式切割器不适合用于灌木平茬作业。论文基于切割器切割灌木时的切割效率、能耗和切割效果,对切割机构、运动参数进行了综合比较与优化,并设计研发了2种灌木平茬机。针对低龄小径级灌木的平茬问题,设计了具有对称双曲柄连杆机构的往复双动刀式灌木平茬机,分析了其割刀位移、速度、加速度与曲柄转角的关系,并进行了仿真验证。针对地势条件复杂,木质化程度高的多年生灌木平茬问题,设计了具有横、纵向仿形功能的圆锯片式自走灌木平茬机,分析了锯片直径、齿数、单齿进给量、锯片转速与机具前进速度的关系,并提出人工操纵仿形与机具自适应仿形相结合的灌木平茬仿形方式。利用往复双动刀式灌木平茬机对二年生柠条进行平茬试验,其最佳工作参数为：曲柄转速n=632r/min,切割速比λq=1.6。此工作参数下各项指标为：茬高不合格率小于等于2.5%,破茬率小于等于3.1%,漏割率小于等于2.5%,生产率0.38hm2/h。利用圆锯片式自走灌木平茬机对五年生沙柳进行平茬试验,其最佳工作参数为：圆锯片线速度为50m/s；灌丛株数小于80株/丛时机具的行走速度为0.44m/s,灌丛株数在80～110株/丛之间时机具的行走速度为0.34m/s,灌丛株数大于110株/丛时机具的行走速度为0.24m/s;沙柳丛植株数量、植株直径、丛下沙丘高度对机具作业速度影响较大,平茬时应根据灌丛的生长情况适时调整机具前进速度。研究和试验表明,论文设计研制的圆锯片式自走灌木平茬机实现了人工手动仿形与机具自适应仿形相结合的仿形方式,具有切割灌木时超低速行走与灌木丛间高速行走移动相结合的机具行走功能；铰接式车体结构确保了机具在停止或前进时切割部件均能以铰接点为中心形成扇面切割轨迹,提高了机具灵活性,增大了收割幅宽和收割效率；设计开发的双四连杆结构与拉伸弹簧结合仿形机构、主机与切割部件机架采用旋转轴铰接机构,实现了圆锯片式灌木平茬机自适应纵向、左右两侧横向仿形：设计开发的相向向外旋转的圆锯片,配合倒V型诱导杆,实现了切割后枝条的集条,为后期高效移出田间创造条件。论文研发的沙生灌木平茬机在田间试验中体现了较好的作业效果,能够满足我国目前不同类型灌木林平茬复壮的需要,具有较好的推广应用前景。更多还原

【Abstract】 Sandy shrub is the important plant for preventing and controlling desertification, and improving desertification land in Chinese western region. And it plays an important role in managing desertification hazards in our country. Owing to its biological characteristics that it needs to be stumped timely, mostly sandy shrub shows various degrees of degeneration because it hasn’t been stumped in time, and now it runs the risk of secondary desertification. Sandy shrub not only has great ecological benefits, but also has great economic benefits. The paper is one of the key tasks of national science and technology support project. The research purpose is to break through the key sandy shrub mechanize harvesting technology, and to develop sandy shrubs harvesting equipment that adapted to Chinese situations.Sandy shrubs growing environment and biological characteristics in our country and relevant research dynamic at home and abroad were discussed. On the basis of summarizing and analyzing the fundamental characteristics and cutting performance of typical sandy shrubs salix and caragana korshinskii, design and experiments on reciprocating shovel type cutter, reciprocating single acting type cutter, rotary sling blade type cutter and saw blade were carried out. The results indicate that the reciprocating cutter is suitable for harvesting young and low diameter shrub in flat terrain, and the circular saw blade cutter is suitable for harvesting more than3years old shrub with higher degree lignifications. However, reciprocating shovel type cutter and rotary sling blade type cutter are not suitable for harvesting shrub.Based on the cutting efficiency, energy consumption and cutting effect of the cutter, comprehensive comparison and optimization of cutting mechanism and motion parameter were carried out and two kinds of shrubs stubble machine were designed. In order to harvest young and low diameter shrub, a kind of reciprocating double knife shrub harvester with symmetrical double crank and rocker mechanism was designed. The relationship between the displacement, velocity, acceleration and the crank rotation angle of cutter was analyzed and was verified by simulation. According to the shrub tending problem on complex growth terrain conditions and higher degree lignifications, a self-propelled saw-blade shrub stumping machine with transverse and longitudinal profiling function was designed. The relationship between disc diameter, number of teeth, and feed rate of each tooth, rotation speed of saw-blade and machine speed was analyzed. New shrub stumping profiling method, a combination of artificial manipulation profiling and machine self-adaption profiling, was proposed.According to the harvesting experiment on2-year-old caragana microphylla by using reciprocating double knife shrub harvester, following results were obtained. The best work parameters are crank rotation speeds n is632r/min and cutting speed ratio λq is1.6and the indicators are the fraction defective of stubble height is less than or equal to2.5%, the broken stubble rate is less than or equal to3.1%, loss cutting rate is less than or equal to2.5%, and productivity is0.38hm2/h.The experiment of self-propelled saw-blade shrub stumping machine on5-year-old salix mongolica was carried out, and the best stubble parameters were concluded as follows. The proper linear cutting velocity is50m/s, and the travel speed is0.44m/s when the number of shrubs plant is less than80per clump, and is0.34m/min when the number of shrubs plant is from80to110per clump, and is0.24m/min when the number of shrubs plant is more than110per clump. The number and diameter of the plant of salix psammophila clump, and the dune height have larger effect on machine operation speed. The machine walking speed should be adjusted timely according to brush growing situation. Research and experiment results show that self-propelled saw-blade shrub stumping machine designed in the paper can realize profiling combined manual copying and machine adaptive imitation, and can meet the machine walking requirement combined lowest harvesting walking speed on the brush and highest moving walking speed among the brush. The designed articulated body structure can make sure that the joint-point-centered arc cutting trajectory of the cutting parts can be formed during stopping or walking. And it improves the machine flexibility, enhances the harvesting width, and increases the harvesting efficiency. The innovative structures, the profiling structure combined double four-linkage structure and extension spring and the rotating-shaft articulated structure between mainframe and cutting parts, can implement self-adapting transverse and longitudinal profiling. The counter-outward-rotating circular saw-blade cooperated with inverted V-induction-rod can collapse the after cut branches and create conditions for branches removed from the field efficiently in future.The sandy shrub stubble machine designed in the paper shows good working performance in the field experiment. It can meet the requirement of stumping and rejuvenation for different types of shrub, and has a good application prospect in our country.更多还原