Research on zero-stiffness flexure hinge (ZSFH) based on spring four-bar linkage(4BSL).

• The zero-stiffness flexure hinge based on spring four-bar linkage is designed. • The rectangular leaf spring string is constructed for the spring four-bar linkage. • The range of negative stiffness of the spring four-bar linkage is determined. • The zero-stiffness quality of the zero-stiffness flexure hinge is analyzed in detail. • Samples of the zero-stiffness flexure hinge are made and tested. In order to overcome the spring back behavior of the conventional flexure hinge, the positive and negative stiffness matching method is used. The spring four-bar linkage(4BSL) is designed as a negative stiffness rotation mechanism, while the inner and outer ring of the flexure hinge (IORFH) is used as a positive stiffness mechanism. By coupling the 4BSL and the IORFH, a novel Zero-stiffness Flexure Hinge(ZSFH) is constructed. The negative stiffness characteristics of the 4BSL are analyzed and the spring of 4BSL is designed as linear rectangular leaf spring string. The zero-stiffness quality of the ZSFH based on 4BSL (ZSFH_4BSL) is analyzed, and the influence of structural parameters of the ZSFH_4BSL on zero-stiffness quality is explored. Samples are made and verified by experiments. The test results show that in the range of ±20°, the torque is reduced by 95% compared with the IORFH, and the relative error between the test result and the theoretical result is less than 7%, which verifies the validity of the theoretical analysis and the excellence of the design scheme. [ABSTRACT FROM AUTHOR]