基于曲柄弹簧机构的零刚度柔性铰链研究
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摘要
零刚度柔性铰链的转动刚度近似为零,克服了普通柔性铰链需要驱动力矩的缺陷,可应用于柔性夹持器等领域。以纯扭矩作用下的内外环柔性铰链为正刚度子系统,研究负刚度机构并匹配正负刚度,可构造零刚度柔性铰链。提出一种负刚度转动机构——曲柄弹簧机构,建模分析了其负刚度特性;通过匹配正负刚度,分析了曲柄弹簧机构的结构参数对零刚度品质的影响;提出一种可定制刚度和尺寸的线性弹簧——菱形片簧串,建立其刚度模型并进行了有限元仿真验证;最终,完成了一种结构紧凑的零刚度柔性铰链样件的设计、加工和测试。测试结果表明:纯扭矩作用下,±18°转角范围内,零刚度柔性铰链的转动刚度比内外环柔性铰链平均降低了93%。所构造的零刚度柔性铰链结构紧凑,零刚度品质高;所提出的负刚度转动机构和可定制刚度的线性弹簧对柔性机构的研究具有较大的参考价值。
Zero stiffness flexural pivot(ZSFP) has approximately zero rotational stiffness, doesn't require driving moment to function compared to general flexural pivots, and can be applied to fields like compliant grippers. By implementing inner and outer ring flexural pivot(IORFP) under pure torque as positive stiffness sub-system, studying negative stiffness mechanism and matching positive and negative stiffness, ZSFP can be modeled. The study proposes a negative stiffness rotation mechanism—spring-crank mechanism(SCM), and the negative stiffness characteristics of SCM is analyzed with models. Through matching of positive and negative stiffness, how the structural parameters of SCM affect the quality of zero stiffness for ZSFP is further analyzed. The study further proposes a stiffness and size specified spring—string of diamond leaves, which can be used in SCM, and finite element analysis(FEA) is applied to the stiffness models. Thus realizes the design, manufacture and test of a compact structure ZSFP. Test results indicate that under pure torque and ±18° rotational angle, the stiffness of ZSFP decreases 93% on average compared to that of IORFP. The proposed ZSFP has advantages in high structure compactness and quality of zero stiffness; the proposed SCM model and stiffness specified string of diamond leaves possess considerable value to the study of complaint mechanisms.
Zero stiffness flexural pivot(ZSFP) has approximately zero rotational stiffness, doesn't require driving moment to function compared to general flexural pivots, and can be applied to fields like compliant grippers. By implementing inner and outer ring flexural pivot(IORFP) under pure torque as positive stiffness sub-system, studying negative stiffness mechanism and matching positive and negative stiffness, ZSFP can be modeled. The study proposes a negative stiffness rotation mechanism—spring-crank mechanism(SCM), and the negative stiffness characteristics of SCM is analyzed with models. Through matching of positive and negative stiffness, how the structural parameters of SCM affect the quality of zero stiffness for ZSFP is further analyzed. The study further proposes a stiffness and size specified spring—string of diamond leaves, which can be used in SCM, and finite element analysis(FEA) is applied to the stiffness models. Thus realizes the design, manufacture and test of a compact structure ZSFP. Test results indicate that under pure torque and ±18° rotational angle, the stiffness of ZSFP decreases 93% on average compared to that of IORFP. The proposed ZSFP has advantages in high structure compactness and quality of zero stiffness; the proposed SCM model and stiffness specified string of diamond leaves possess considerable value to the study of complaint mechanisms.
引文
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[11]LIU L,BI S,YANG Q.Stiffness characteristics of inner–outer ring flexure pivots applied to the ultra-precision instruments[J].ARCHIVE Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science 1989-1996(vols.203-210),2017:095440621772172.
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[13]AWTAR S,SEN S.A generalized constraint model for two-dimensional beam flexures:Nonlinear strain energy formulation[J].Journal of Mechanical Design,2010,132:81009.
[2]于靖军,裴旭,毕树生,等.柔性铰链机构设计方法的研究进展[J].机械工程学报,2010,46(13):2-13.YU Jingjun,PEI Xu,BI Shusheng,et al.State-of-arts of design method for flexure mechanisms[J].Journal of Mechanical Engineering,2010,46(13):2-13.
[3]MORSCH F M,HERDER J L.Design of a generic zero stiffness compliant joint[C]//ASME International Design Engineering Conferences,2010:427-435.
[4]MERRIAM E G,HOWELL L L.Non-dimensional approach for static balancing of rotational flexures[J].Mechanism&Machine Theory,2015,84(84):90-98.
[5]HOETMER K,WOO G,KIM C,et al.Negative stiffness building blocks for statically balanced compliant mechanisms:Design and testing[J].Journal of Mechanisms&Robotics,2010,2(4):041007.
[6]JENSEN B D,HOWELL L L.The modeling of cross-axis flexural pivots[J].Mechanism and machine theory,2002,37(5):461-476.
[7]WITTRICK W H.The properties of crossed flexure pivots and the influence of the point at which the strips cross[J].The Aeronautical Quarterly,1951,II:272-292.
[8]LIU L,BI S,YANG Q,et al.Design and experiment of generalized triple-cross-spring flexure pivots applied to the ultra-precision instruments[J].Review of Scientific Instruments,2014,85(10):105102.
[9]杨其资,刘浪,毕树生,等.广义三交叉簧片柔性铰链的旋转刚度特性研究[J].机械工程学报,2015,51(13):189-195.YANG Qizi,LIU Lang,BI Shusheng,et al.Rotational stiffness characterization of generalized triple-cross-spring flexure pivots[J].Journal of Mechanical Engineering,2015,51(13):189-195.
[10]LIU L,ZHAO H,BI S,et al.Research of performance comparison of topology structure of cross-spring flexural pivots[C]//ASME 2014 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference,August 17-20,2014,Buffalo,New York,USA.ASME,2014:V05AT08A025.
[11]LIU L,BI S,YANG Q.Stiffness characteristics of inner–outer ring flexure pivots applied to the ultra-precision instruments[J].ARCHIVE Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science 1989-1996(vols.203-210),2017:095440621772172.
[12]SANCHEZ J A G.Criteria for the static balancing of compliant mechanisms[C]//ASME 2010 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference,August 15-18,2010,Montreal,Quebec,Canada.ASME,2010:465-473.
[13]AWTAR S,SEN S.A generalized constraint model for two-dimensional beam flexures:Nonlinear strain energy formulation[J].Journal of Mechanical Design,2010,132:81009.