摘要
主流果蔬采收末端执行器根据采收的果蔬品种和果梗木制纤维材质的不同,结构差异较大,均存在占据空间大、结构笨重、易碰撞果实和易造成损伤等问题,不利于果梗切割,因此研究一种结构灵活、占据空间小、切割省力的适用于不同果梗木制纤维的超声切割刀应用于果蔬采收末端执行器非常重要。本研究采用理论-有限元-试验相结合的方式对超声切割刀切割果梗的机理进行分析。首先建立了超声刀具切割果梗的物理场模型,通过对切割过程进行时空分析,建立了其位移、速度、加速度等数学模型,分析了切割过程的时空不连续性,基于断裂力学对果梗切割机理进行研究并绘制Matlab响应面图,可以发现超声切割所需要的力小于常规切割。利用有限元分析软件,对超声刀具进行了模态分析和谐响应分析,得到了刀具在不同频率下的振动模态和利于切割的最佳频率。最后,利用自制试验台采用不同切割速度分别对不同直径的橘子和橙子果梗进行了超声切割试验。试验结果表明:切割速度和激振频率与采收切断力有关,在高频和低频振动下,随着果梗直径增加,切割时间变化在0.4 s内,切割效率稳定;试验中超声切割的最大切断力远小于常规切割,且小于1 N,超声切割可以很有效地降低切断力,减小切割时的冲击作用,相对于常规切割切断能力更强,适合将其应用到采收末端执行器,从而获得更高的采收效率。
Mainstream fruit and vegetable harvesting end-effectors differ greatly in structure according to the varieties of fruits and vegetables harvested and the wood fiber materials of fruit stems,and all of them have the problems of large space occupation,heavy structure,easy collision with fruits and easy damage,which is not conducive to cutting fruit stems.Therefore,it is very important to study an ultrasonic cutting knife with flexible structure,small space occupation and labor saving for cutting different wood fibers of fruit and vegetable harvesting end-effectors.The theory-finite element-experiment method was used to analyze the mechanism of cutting fruit stalks with ultrasonic cutter.Firstly,the physical field model of cutting fruit stalks by ultrasonic tool was established.Through the time-space analysis of the cutting process,the mathematical models of displacement,speed and acceleration were established,and the time-space discontinuity of the cutting process was analyzed.Based on the fracture mechanics,the cutting mechanism of fruit stalks was studied and the Matlab response surface diagram was drawn.It can be found that the force required for ultrasonic cutting was less than that for conventional cutting.Using finite element analysis software,the modal analysis and harmonic response analysis of ultrasonic tool were carried out,and the vibration modes of the tool at different frequencies and the optimal frequency for cutting were obtained.Finally,the ultrasonic cutting experiments of tangrine and orange stalks with different diameters were carried out by using a self-made test bench at different cutting speeds.The experimental results showed that the cutting speed and vibration frequency were related to the cutting force.Under the high-frequency and low-frequency vibration,with the increase of fruit stem diameter,the cutting time was changed within 0.4 s,and the cutting efficiency was stable.In the experiment,the maximum cutting force of ultrasonic cuttingwas much less than that of conventional cutting,which was less than 1 N.Ultrasonic cutting can effectively reduce the cutting force and reduce the impact during cutting.Compared with conventional cutting,ultrasonic cutting had stronger cutting ability,and it was suitable to be applied to the end-effector of harvesting,thus achieving higher recovery efficiency.
作者
辛迪
党柯华
邓家锋
闫云才
牛子杰
XIN Di;DANG Kehua;DENG Jiafeng;YAN Yuncai;NIU Zijie(College of Mechanical and Electronic Engineering,Northwest A&F University,Yangling,Shaanxi 712100,China)
出处
《农业机械学报》
EI
CAS
CSCD
北大核心
2023年第S02期91-100,共10页
Transactions of the Chinese Society for Agricultural Machinery
基金
国家自然科学基金联合基金重点项目(U2243235)
关键词
超声切割
果蔬采收
有限元
断裂力学
机理分析
ultrasonic cutting
fruit and vegetable harvesting
finite element
fracture mechanics
mechanism analysis
