Structural optimization for flexure-based parallel mechanisms - Towards achieving optimal dynamic and stiffness properties

Flexure-based parallel mechanisms (FPMs) are a type of compliant mechanisms that consist of a rigid end-effector that is articulated by several parallel, flexible limbs (a.k.a. sub-chains). Existing design methods can enhance the FPMs' dynamic and stiffness properties by conducting a size optimization on their sub-chains. A similar optimization process, however, was not performed for their sub-chains' topology, and this may severely limit the benefits of a size optimization. Thus, this paper proposes to use a structural optimization approach to synthesize and optimize the topology, shape and size of the FPMs' sub-chains. The benefits of this approach are demonstrated via the design and development of a planar X - Y - theta(z), FPM. A prototype of this FPM was evaluated experimentally to have a large workspace of 1.2 mm x 1.2 mm x 6 degrees, a fundamental natural frequency of 102 Hz, and stiffness ratios that are greater than 120. The achieved properties show significant improvement over existing 3-degrees-of-freedom compliant mechanisms that can deflect more than 0.5 mm and 0.5 degrees. These compliant mechanisms typically have stiffness ratios that are less than 60 and a fundamental natural frequency that is less than 45 Hz. (C) 2015 Elsevier Inc. All rights reserved

A hybrid topological and structural optimization method to design a 3-DOF planar motion compliant mechanism

This paper proposes a novel design methodology to synthesize flexure-based parallel manipulators (FPM) for high precision micro/nano-scale manipulation. Unlike traditional synthesis methods, the proposed method uses a structural optimization algorithm that is independent of human intuition, to synthesize compliant joints with optimal stiffness characteristics. This algorithm is able to evolve the topology and shape of the compliant joints. Based on finite element analysis, the synthesized compliant joints are able to achieve better stiffness characteristics than the traditional compliant joints. This allows the synthesized joints to achieve a large deflection range while maintaining their capabilities to resist external wrenches in the non-actuating directions. A planar motion FPM with a workspace of 4 mm2 × 2° is formed by assembling the optimal compliant joints. The actuating compliance of the joints and FPM are validated by experiments and their deviation between the experimental results and the simulation prediction are within 10% and 18% respectively

Integrating mechanism synthesis and topological optimization technique for stiffness-oriented design of a three degrees-of-freedom flexure-based parallel mechanism

This paper introduces a new design approach to synthesize multiple degrees-of-freedom (DOF) flexure-based parallel mechanism (FPM). Termed as an integrated design approach, it is a systematic design methodology, which integrates both classical mechanism synthesis and modern topology optimization technique, to deliver an optimized multi-DOF FPM. This design approach is separated into two levels. At sub-chain level, a novel topology optimization technique, which uses the classical linkage mechanisms as DNA seeds, is used to synthesize the compliant joints or limbs. At configuration level, the optimal compliant joints are used to form the parallel limbs of the multi-DOF FPM and another stage of optimization was conducted to determine the optimal space distribution between these compliant joints so as to generate a multi-DOF FPM with optimized stiffness characteristic. In this paper, the design of a 3-DOF planar motion FPM was used to demonstrate the effectiveness and accuracy of this proposed design approach. (C) 2014 Elsevier Inc. All rights reserved

Effects of rho kinase inhibitors on intraocular pressure and aqueous humor dynamics in nonhuman primates and rabbits

Purpose: This study examines the effects of 2 Rho kinase inhibitors on intraocular pressure (IOP) and aqueous humor dynamics. Methods: IOPs of New Zealand albino rabbits with ocular normotension and cynomolgus macaques (nonhuman primate, NHP) with chronic unilateral laser-induced glaucoma were measured at baseline and periodically after a 9 a.m. dose of H-1152, Y-27632, or vehicle. In a separate group of NHPs, aqueous flow, outflow facility, uveoscleral outflow, and IOP were determined after treatment with Y-27632 or vehicle control. Results: Decreases in IOP were found in rabbits (n = 5) at 6 h after one dose of 2% Y-27632 (29%, P = 0.0002) or 1% H-1152 (35%, P = 0.0001), and in hypertensive eyes of NHPs (n = 7-9) at 3 h after one dose of 2% Y-27632 (35%, P = 0.005) or 1% H-1152 (51%, P = 0.0003). With 2 doses of 1% Y-27632 or vehicle in NHP hypertensive eyes (n = 12), significant drug effects were IOP reduction of 28% (P = 0.05) at 2.5 h after the second dose and increases in aqueous flow (36%; P = 0.013), uveoscleral outflow (59%, P = 0.008), and outflow facility (40%; P = 0.01). In normotensive eyes of the same animals, aqueous flow increased by 21% (P = 0.03). No significant change was found in any of the other parameters. Conclusions: Y-27632 and H-1152 lower IOP in rabbits and hypertensive eyes of NHPs for at least 6 h after single doses. The Y-27632 effect on IOP in hypertensive NHP eyes is caused by increases in outflow facility and uveoscleral outflow. An increase in aqueous humor formation attenuates but does not prevent an IOP decrease

An XY theta(z) Flexure Mechanism with Optimal Stiffness Properties

friction noise; transient analysis; trimmer blade; finite element metho

CCDC 2092056: Experimental Crystal Structure Determination

Related Article: Xiyue Yuan, Yunli Zhao, Tao Zhan, Jiyeon Oh, Jiadong Zhou, Junyu Li, Xiaojing Wang, Zhiqiang Wang, Shuting Pang, Ping Cai, Changduk Yang, Zhicai He, Zengqi Xie, Chunhui Duan, Fei Huang, Yong Cao|2021|Energy Environ.Sci.|14|5530|doi:10.1039/D1EE01957