Design, Modeling And Application Of Three-axis Rotational Flexure Hinges With High Axial Stiffness

Flexure hinges, which are manufactured by wire cut on the rigid metal body in general, can be used to convert a finite angular displacement around the axis into linear movement of flexible supporting system. Due to their excellenct characters, such as no friction, no abrasion, no lag and lubrication, easy maintenance, compact structure, small volume size, non-moving clearance, and high resolution, the flexure hinges are widely used in many fields, such as precision machines, instruments, micron and nanometer technology, despite their rotational angle is limited.In order to develop the six degree-of-freedom (DOF) vibration isolation platform, flexure hinges with high axial stiffness, low bending and torsional stiffness are used as the connecttions between the legs and the upper and lower platforms to satisfy the requirement of the micro-movement vibration. The flexure hinges can not only be required to rotate around three axes but also possess high stability when working. Up to now, the connecting mechanism between the legs and the upper and lower platforms on the 6-DOF vibration isolation platform mostly adopt one-axis flexure hinges, double-axis flexure hinges, elastomer, or the spherical hinges. The spherical hinges are difficult to realize the high-precision vibration isolation for the ordinary spherical flexures because of the friction, contact clearance and lubrication. In addition, the one-axis flexure hinges, double-axis flexure hinges and elastomer can not replace the three-axis flexure hinges although they can bend and twist. The final performance of the 6-DOF vibration isolation platform is directly influenced by the performance of the connecting mechanism between the legs and the upper and lower platforms on the 6-DOF vibration isolation platform.In this dissertation, a three-axis rotational flexure hinge with high axial stiffness is designed and simulated with finite element method (FEM). The theoretical research of stiffness in each direction and improvement of structure are also explored. Furthermore, the 6-DOF vibration isolation platform structure and system based on the three-axis rotational flexure hinges with high axial stiffness are developed.The main research works and achievements include the following:1. A three-axis rotational flexure hinge with the high axial stiffness and its updated vesion, which are called the hollow cylindrical circular flexure hinge (HCCFH) and hollow cylindrical hybrid flexure hinge (HCHFH) according to their structure features respectively, are designed. Based on the principles and method which are proposed in this dissertation to analyze and model the bending, torsional, and axial stiffness of flexure hinge utilizing FEM, the stiffness of the HCCFH and the HCHFH is analyzed and calculated. The finite element model and second-order fitting equations, which indicate the stiffness varying with the key structural parameters of the HCCFH and the HCHFH, are also established.2. The theory of stiffness of the HCCFH is studied, the main steps of the theoretical research for the stiffness of the flexure hinge are summarized and the integrated theoretical model of the bending and torsional stiffness, which is compared with the finite element analysis model in this dissertation, is deduced. In addition, the key part effecting the axial deformation of the HCCFH is also analyzed and the reference of the axial stiffness formula deduction for the HCCFH is put forward.3. Based on the structure characteristics of the 6-DOF vibration isolation platform using the three-axis rotational flexure hinges with high axial stiffness, the construction of the control system of the 6-DOF vibration isolation platform is initially completed by master-slave configuration.