Design and Performance Optimization of Large Stroke Spatial Flexures

Abstract

Flexure hinges inherently lose stiffness in supporting directions when deflected. In this paper a method is presented for optimizing the geometry of flexure hinges, which aims at maximizing supporting stiffnesses. In addition, the new ∞-flexure hinge design is presented. The considered hinges are subjected to a load and deflected an angle of up to ±20 deg. The measure of performance is defined by the first unwanted natural frequency, which is closely related to the supporting stiffnesses. During the optimization, constraints are applied to the actuation moment and the maximum occurring stress. Evaluations of a curved hinge flexure, cross revolute hinge, butterfly flexure hinge, two cross flexure hinge types, and the new ∞-flexure hinge are presented. Each of these hinge types is described by a parameterized geometric model. A flexible multibody modeling approach is used for efficient modeling while it accounts for the nonlinear geometric behavior of the stiffnesses. The numerical efficiency of this model is very beneficial for the design optimization. The obtained optimal hinge designs are validated with a finite element model and show good agreement. The optimizations show that a significant increase in supporting stiffness, with respect to the conventional cross flexure hinge, can be achieved with the ∞-flexure hinge.

Design and analysis of porous flexure hinge based on dual-objective topology optimization of three-dimensional continuum

“…Gómez et al [32] used a combination of linear strain energy formula, parameter thickness distribution definition and a series of optimization algorithms to optimize the shape of the leaf spring to reduce the range of stress. Wiersma et al [33] proposed a method for optimizing the geometry of flexure hinges, which aims at maximizing supporting stiffness. And the optimizations show that the designed hinge can achieve a significant increase in supporting stiffness with respect to the conventional cross-flexure hinge.…”

Multibody-Based Topology Synthesis Method for Large Stroke Flexure Hinges

“…This element typically has only limited support when considering the stiffness properties in deformed state, except for translational stiffness in z-direction. Furthermore it provides high compliance in the desired degree of freedom (z-rotation).Torsionally reinforced leafspring:In order to improve torsional stiffness around the y-axis and in-plane bending stiffness around the x-axis, the so-called torsionally reinforced leafspring (TRLS,figure 3b)is presented, which is inspired on the infinity hinge[3]. This building block consists of a single central leafspring reinforced with one or more folded leafsprings to improve torsional and in-plane bending stiffness.…”

Design and optimization of large stroke flexure mechanisms

“…However, these models are limited to 2D analysis or are only applicable to relatively simple exure mechanisms, such as the parallelogram exure mechanism or the cross-spring pivot, which are o en unsuited for large range of motion applications due to their strong decrease in support sti ness when de ected. More complex geometries allow performance improvements for large range of motion applications [27,108], which require numerical models to evaluate performance. However, due to the complex relation between the geometry of the exures, the large de ections involved, and the resulting performance of the system, designing a "good" exure mechanism suited for large stroke applications is far from trivial.…”

“…In this paper, the goal is the development of a topology optimization suited for large de ection angles, with which the guiding sti ness can be greatly increased for exure hinges vastly exceeding 10 degrees range of motion. e advantages of optimizing the dimensions of large-stroke exure hinges is already shown in previous studies [27,108]. For these shape optimizations, Wiersma described an optimization method which utilizes a parameterized exible multibody model with nonlinear nite beam elements combined with a Nelder Mead algorithm to nd the optimal shape.…”