基于恒力机构的香蕉落梳装置设计与自适应性分析
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摘要
针对香蕉机械化落梳过程中出现的自适应性差的问题,设计了基于恒力机构的可自适应环抱蕉茎插切式香蕉落梳装置,并对落梳装置的径向自适应性和转动自适应性进行了分析。采用两斜置压缩弹簧的结构,引入负刚度,再与正刚度的水平压缩弹簧并联组成恒力机构,提高了落梳刀具组对果轴粗细的径向自适应性,对恒力机构的力-位移特性曲线和刚度-位移特性曲线进行分析,并优选关键参数,得出斜置压缩弹簧的刚度系数k1=12 N/mm,水平压缩弹簧的刚度系数k2=3 N/mm,初始状态斜置压簧的倾斜角θ0=36. 87°,恒力行程对应的落梳刀组包络圆直径范围为80～100 mm,对应的恒力f=180 N。在加载有扭簧的虎克铰链基础上设计了可释放两个转动自由度的落梳刀盘,根据测定的香蕉果轴弯曲度设置刀盘旋转角范围为±10°,根据建立的三维模型中的几何参数得出,落梳刀具末端的工作空间是一个半径为300 mm的球面。对落梳刀具末端的柔度矩阵进行分析,结果显示,落梳刀盘旋转角为0°,即刀盘与机架上底面平行时线柔度最大,最大值为0. 818 2 mm/N,落梳刀盘旋转角为10°时线柔度最小,最小值为0. 77 mm/N,说明落梳刀具末端的线柔度随刀盘旋转角的增大而减小。试验结果表明,梳柄切口符合试验指标的蕉梳占所有样本的81. 25%,切口质量良好,该装置设计合理,且满足实际落梳作业的要求。
Aiming to solve the problem of poor adaptability in the process of mechanized banana crowncutting,an adaptable banana crown-cutting device by stalk-surrounding and insert-cutting was designed,which was based on constant-force mechanism,and the radial adaptability and rotational adaptability of banana crown-cutting device were analyzed. A constant-force mechanism was introduced in the device,including two oblique compression springs provided negative stiffness and one horizontal compression spring provided positive stiffness,which enhanced the radial adaptability of the device. The forcedisplacement characteristic curves and stiffness-displacement characteristic curves of the constant-force mechanism were analyzed and the key parameters were also optimized. The stiffness coefficient of oblique spring in the constant-force mechanism was 12 N/mm and the stiffness coefficient of horizontal spring was3 N/mm. In the initial state,the inclination angle of the oblique spring was 36. 87°. The diameter of the enveloping circle was 80 ～ 100 mm when the device was in constant force state,meanwhile,the constant force was 180 N. Based on the Hooke hinge,reversible cutting platforms that can release two free rotational degrees were designed. The cutting platforms' rotational angle was set as ± 10°,according to the curvature of banana stalks. According to the geometric parameters of the established 3 D model,the working space at the end of the cutter was a spherical surface with a radius of 300 mm. The flexibility matrix of the cutter-end was analyzed. The result showed that when the rotational angle of the cutting platform was 0°,the flexibility of the cutter-end was the largest and the maximum value was 0. 818 2 mm/N,and when the rotational angle of the cutting platform was 10°,the flexibility of the cutter-end was the smallest and the minimum value was 0. 77 mm/N. The results showed that the flexibility of the cutter-end was decreased gradually when the cutting platforms' reversal angle became bigger. The tests showed that81. 25% of samples fulfilled requirements,the quality of the incisions were good. The machine,which was reasonably designed,fulfilled the requirements of banana crown-cutting.
Aiming to solve the problem of poor adaptability in the process of mechanized banana crowncutting,an adaptable banana crown-cutting device by stalk-surrounding and insert-cutting was designed,which was based on constant-force mechanism,and the radial adaptability and rotational adaptability of banana crown-cutting device were analyzed. A constant-force mechanism was introduced in the device,including two oblique compression springs provided negative stiffness and one horizontal compression spring provided positive stiffness,which enhanced the radial adaptability of the device. The forcedisplacement characteristic curves and stiffness-displacement characteristic curves of the constant-force mechanism were analyzed and the key parameters were also optimized. The stiffness coefficient of oblique spring in the constant-force mechanism was 12 N/mm and the stiffness coefficient of horizontal spring was3 N/mm. In the initial state,the inclination angle of the oblique spring was 36. 87°. The diameter of the enveloping circle was 80 ～ 100 mm when the device was in constant force state,meanwhile,the constant force was 180 N. Based on the Hooke hinge,reversible cutting platforms that can release two free rotational degrees were designed. The cutting platforms' rotational angle was set as ± 10°,according to the curvature of banana stalks. According to the geometric parameters of the established 3 D model,the working space at the end of the cutter was a spherical surface with a radius of 300 mm. The flexibility matrix of the cutter-end was analyzed. The result showed that when the rotational angle of the cutting platform was 0°,the flexibility of the cutter-end was the largest and the maximum value was 0. 818 2 mm/N,and when the rotational angle of the cutting platform was 10°,the flexibility of the cutter-end was the smallest and the minimum value was 0. 77 mm/N. The results showed that the flexibility of the cutter-end was decreased gradually when the cutting platforms' reversal angle became bigger. The tests showed that81. 25% of samples fulfilled requirements,the quality of the incisions were good. The machine,which was reasonably designed,fulfilled the requirements of banana crown-cutting.
引文
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[24]王颜,房立金,周生啟.仿生变刚度关节设计与试验[J/OL].农业机械学报,2018,49(1):390-396.WANG Yan,FANG Lijin,ZHOU Shengqi. Design of bionic variable stiffness joint[O/L]. Transactions of the Chinese Society for Agricultural Machinery,2018,49(1):390-396. http:∥www. j-csam. org/jcsam/ch/reader/view_abstract. aspx? flag=1&file_no=20180149&journal_id=jcsam. DOI:10. 6041/j. issn. 1000-1298. 2018. 01. 049.(in Chinese)
[25]鹿玲,张东胜,许允斗,等.五自由度混联机器人尺度与结构优化设计[J/OL].农业机械学报,2018,49(4):412-419.LU Ling,ZHANG Dongsheng,XU Yundou,et al. Dimension and structure optimization design of 5-DOF hybrid manipulator[J/OL]. Transactions of the Chinese Society for Agricultural Machinery,2018,49(4):412-419. http:∥www. j-csam. org/jcsam/ch/reader/view_abstract. aspx? flag=1&file_no=20180449&journal_id=jcsam. DOI:10. 6041/j. issn. 1000-1298.2018. 04. 049.(in Chinese)
[2]张锡炎.香蕉产业发展面临的重大问题和对策措施[J].中国果业信息,2017(1):7-10.
[3]顾天竹,周启凡.中国香蕉生产布局的时空演变分析[J].江苏农业科学,2017,45(5):315-319.
[4]李佳琪.世界香蕉贸易格局变化对中国香蕉市场的影响研究[D].海口:海南大学,2015.LI Jiaqi. The study on world banana trade pattern and its influence on Chinese banana market[D]. Haikou:Hainan University,2015.(in Chinese)
[5]杨培生,郑服丛,钟思现,等.澳大利亚香蕉产业考察报告[J].中国热带农业,2007(2):26-28.
[6]刘嘉龙,李君,杨洲.香蕉采后处理装备的发展现状[J].农机化研究,2014,36(11):249-252.LIU Jialong,LI Jun,YANG Zhou. Review current status of postharvest handling equipment for banana[J]. Journal of Agricultural Mechanization Research,2014,36(11):249-252.(in Chinese)
[7]朱正波,杨洲,孙健峰,等.香蕉落梳机气动夹持部件参数优化与试验[J].农业工程学报,2016,32(4):33-39.ZHU Zhengbo,YANG Zhou,SUN Jianfeng,et al. Parameter optimization and experiment of pneumatic holding part for banana crown cutting[J]. Transactions of the CSAE,2016,32(4):33-39.(in Chinese)
[8]陈兆春,杨洲,朱正波,等.香蕉梳柄的结构特征及其力学特性试验[J].江苏农业科学,2017,45(5):223-227.
[9]王艾伦,刘云.大尺度重型构件夹持机构近恒力优化设计[J].机械设计,2008,25(5):39-42.WANG Ailun,LIU Yun. Approximate constant force optimization design on clamping mechanism of macro scaled heavy component parts[J]. Journal of Mechine Design,2008,25(5):39-42.(in Chinese)
[10] CHEN Y,LAN C. An adjustable constant-force mechanism for adaptive end-effector operations[J]. Journal of Mechanical Design,2012,134:0310053.
[11] CARRELLA A,BRENNAN M J,WATERS T P,et al. Force and displacement transmissibility of a nonlinear isolator with high-static-low-dynamic-stiffness[J]. International Journal of Mechanical Sciences,2012,55(1):22-29.
[12] CARRELLA A,BRENNAN M J,KOVACIC I,et al. On the force transmissibility of a vibration isolator with quasi-zerostiffness[J]. Journal of Sound and Vibration,2009,322(4-5):707-717.
[13] CARRELLA A,BRENNAN M J,WATERS T P. Static analysis of a passive vibration isolator with quasi-zero-stiffness characteristic[J]. Journal of Sound and Vibration,2007,301(3-5):678-689.
[14] LAN C,YANG S,WU Y. Design and experiment of a compact quasi-zero-stiffness isolator capable of a wide range of loads[J]. Journal of Sound and Vibration,2014,333(20):4843-4858.
[15]常洪烨.考虑柔铰非线性的柔性Sarrus恒力机构设计[D].西安:西安电子科技大学,2014.CHANG Hongye. A design of a compliant constant-force mechanism based on Sarrus considering the hinge's nonlinearity[D].Xi'an:Xidian University,2014.(in Chinese)
[16] LAN C,WANG J,CHEN Y. A compliant constant-force mechanism for adaptive robot end-effector operations[C]∥Robotics and Automation(ICRA),2010 IEEE International Conference on,2010.
[17] WANG P,XU Q. Design and modeling of constant-force mechanisms:a survey[J]. Mechanism and Machine Theory,2018,119:1-21.
[18] TOLMAN K A,MERRIAM E G,HOWELL L L. Compliant constant-force linear-motion mechanism[J]. Mechanism and Machine Theory,2016,106:68-79.
[19] HAO G,MULLINS J,CRONIN K. Simplified modelling and development of a bi-directionally adjustable constant-force compliant gripper[J]. Proceedings of the Institution of Mechanical Engineers,Part C:Journal of Mechanical Engineering Science,2015,231(11):2110-2123.
[20]汪满新.一种五自由度混联机器人静柔度建模与设计方法研究[D].天津:天津大学,2015.WANG Manxin. Investigation into compliance modeling and design methodology of a five degree of freedom hybrid robot[D].Tianjin:Tianjin University,2015.(in Chinese)
[21] JIN M,ZHANG X,ZHU B,et al. Spring-joint method for topology optimization of planar passive compliant mechanisms[J].Chinese Journal of Mechanical Engineering,2013,26(6):1063-1072.
[22] HUANG S,SCHIMMELS J M. The bounds and realization of spatial compliances achieved with simple serial elastic mechanisms[J]. IEEE Transactions on Robotics and Automation,2000,16(1):99-103.
[23] CHEN G,ZHANG Z,WANG H. A general approach to the large deflection problems of spatial flexible rods using principal axes decomposition of compliance matrices[J]. Journal of Mechanisms and Robotics-transactions of the ASME,2018,10:0310123.
[24]王颜,房立金,周生啟.仿生变刚度关节设计与试验[J/OL].农业机械学报,2018,49(1):390-396.WANG Yan,FANG Lijin,ZHOU Shengqi. Design of bionic variable stiffness joint[O/L]. Transactions of the Chinese Society for Agricultural Machinery,2018,49(1):390-396. http:∥www. j-csam. org/jcsam/ch/reader/view_abstract. aspx? flag=1&file_no=20180149&journal_id=jcsam. DOI:10. 6041/j. issn. 1000-1298. 2018. 01. 049.(in Chinese)
[25]鹿玲,张东胜,许允斗,等.五自由度混联机器人尺度与结构优化设计[J/OL].农业机械学报,2018,49(4):412-419.LU Ling,ZHANG Dongsheng,XU Yundou,et al. Dimension and structure optimization design of 5-DOF hybrid manipulator[J/OL]. Transactions of the Chinese Society for Agricultural Machinery,2018,49(4):412-419. http:∥www. j-csam. org/jcsam/ch/reader/view_abstract. aspx? flag=1&file_no=20180449&journal_id=jcsam. DOI:10. 6041/j. issn. 1000-1298.2018. 04. 049.(in Chinese)