基于能量平衡的设施蔬菜收获机拉拔切割过程力学特性分析  

Mechanical characteristic analysis of drawing and cutting process for greenhouse vegetable harvester based on energy balance theory

作　　者：高国华[1] 王凯[1] 苑严伟[2] 刘婧芳[1] 王天宝[1] 孙晓娜 Gao Guohua;Wang Kai;Yuan Yanwei;Liu Jingfang;Wang Tianbao;Sun Xiaona(College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology, Beijing 100124, China;Chinese Academy of Agricultural Mechanization Sciences, Beijing 100101, China)

机构地区：[1]北京工业大学机械工程及应用电子技术学院,北京100124 [2]中国农业机械化科学研究院,北京100101

出　　处：《农业工程学报》2017年第24期58-64,共7页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家重点研发计划(2I001014201701)

摘　　要：为深入研究设施蔬菜收获机拉拔切割过程力学特性及其切割机理,该文以生菜根茎部为蔬菜收获机切割特例,自行设计和改造了一台可对切割力和刀具位移进行实时测量的蔬菜根茎部切割装置,并对处于拉拔状态下的生菜根茎部进行了切割试验。根据试验结果分析,将整个切割过程分为变形阶段、破裂阶段和切割阶段,并利用能量平衡理论分析了各个阶段能量之间的转化关系。利用指数函数对变形阶段切割力进行了数学拟合建模,误差在-5.3%~7.8%;利用能量法分析推导出了切割阶段的切割力数学模型,误差在-9.6%~8.2%;破裂阶段的切割力模型简化为直线减小。试验和模型所得切割力曲线得到了很好的吻合,证明了对生菜根茎部切割过程建模的正确性。研究结果表明:拉拔力有利于减小切割阶段的切割力,但过大的拉拔力容易导致切割断口不平齐、收获效果不佳。该研究结果有助于理解蔬菜根茎部切割特性及其切割机理,可为今后改进蔬菜切割装置提供参考。A novel vegetable cutting mechanism is designed and fabricated,which is capable of measuring cutting force and blade displacement in real time.Rhizome tissue of lettuce is selected as cutting object of vegetable cutting mechanism.And a series of experiments were carried out with the vegetable cutting mechanism under drawing force.The drawing force has contribution to separating rhizome tissue of lettuce from soil slightly,which will facilitate the process of cutting rhizome tissue of lettuce by vegetable cutting mechanism.Cutting speed,cutting method,blade parameters,and so on can't affect the process phase of cutting.However,larger cutting speed can reduce sampling size of cutting force,resulting in the distortion of the relation curve of cutting force and cutting depth.So,experimental conditions are the cutting speed of50mm/min,the drawing force of30N,the cutting position of10mm above stem of lettuce,and the cutting method of cutting vertically.Blade parameters are blade width of0.5mm,wedge angle of blade of20°,and material of cast iron.According to the experimental results,the cutting process can be divided into3phases:Deformation phase,rupture phase and cutting phase.The process that blade cuts into rhizome tissue of lettuce is defined as deformation phase.In the deformation phase,the work done by blade is converting the elastic energy stored in the rhizome tissue of lettuce.The epidermal fiber structure of rhizome tissue is changed under pressure of blade.Therefore,it's difficult to establish a physical model and an analytical model for deformation phase.However,the cutting force of deformation phase is represented as a typical nonlinear J shape curve,so an exponential function is used to fit it in this paper.Once the blade breaks into the surface of the rhizome tissue,the cutting force suddenly decreases while crack is created,which is defined as rupture phase.The time of rupture phase is very short,so there is almost no energy conversion between the blade and the vegetable.Only elastic energy stored in th

关 键 词：机械化 切割 模型 生菜根茎 能量平衡理论 拉拔 

分 类 号：S225.92[农业科学—农业机械化工程]