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Abstract: Early stage design of precision flexure systems that utilize strain-based displacement sensing is difficult due to the strong coupling between the mechanical and sensing subsystems. Traditional tools for flexure system and compliant mechanism synthesis are not capable of simultaneously optimizing the mechanical and sensing subsystems. The building block synthesis approach developed in this work is the only tool capable of designing compliant mechanisms with integrated strain based sensing. Building block modeling allows for rapid synthesis and vetting of concepts. This approach also allows the designer to determine concept feasibility, identify performance limits and tradeoffs, and obtain 1st order estimates of flexure geometry. In short, this method enables one to find an optimal design and set first order design parameters. The utility of the building block approach is detailed in a case study detailing the synthesis and modeling of three different one degree-of-freedom translational stages that are all derived from the series and parallel addition of fixed-guided cantilever beam building blocks. [Copyright &y& Elsevier]

Abstract: In this paper we introduce the principles necessary to synthesize the complete body of serial flexure system concepts, which satisfy desired design requirements using Freedom and Constraint Topologies (FACT). FACT utilizes a comprehensive library of geometric shapes that represent regions were constraints may be placed for synthesizing flexure systems that possess designer-specified degrees of freedom (DOFs). Prior to the theory of this paper, FACT was limited to the synthesis of parallel flexure systems only. The ability to synthesize serial flexure systems is important because serial flexure systems (i) may possess DOFs not accessible to parallel flexure systems, (ii) exhibit larger ranges of motion, and (iii) enable cancellation of parasitic errors. Geometric shapes that represent motions only accessible to serial flexure systems have been derived and added to the existing body of FACT shapes initially intended for parallel flexure synthesis only. Systematic rules and guidelines have been created that help designers use these shapes to generate every parallel and serial flexure concept that satisfies the desired functional requirements. We demonstrate how to use these shapes to utilize or avoid underconstraint in serial flexure synthesis. A serial flexure system is designed that interfaces the lead screw of a lathe to the carriage that it drives as a case study to demonstrate the theory of this paper. [Copyright &y& Elsevier]

Abstract: In this paper we introduce a visual approach for placing actuators within multi-axis parallel flexure systems such that position and orientation errors are minimized. A stiffness matrix, which links twists and wrenches, is used to generate geometric shapes that guide designers in selecting optimal actuator locations and orientations. The geometric shapes, called actuation spaces, enable designers to (i) visualize the regions wherein actuators should be placed so as to minimize errors, (ii) guide designers in selecting these actuators to maximize the decoupling of actuator inputs, and (iii) determine actuator forces and displacements for actuating specific degrees of freedom. These new principles, the means to practice them, and a comparison of theory verses measured behavior, are demonstrated within a case study. [Copyright &y& Elsevier]

Abstract: In this paper we introduce a new design principle, and complementary geometric entities, that form the basis for a new approach to the synthesis of multi-degree of freedom, purely parallel precision flexure systems. This approach – Freedom and Constraint Topology (FACT) – is unique in that it is based upon sets of geometric entities that contain quantitative information about a flexure system''s characteristics. A first set contains information about a flexure system''s degrees of freedom (its freedom topology) and a second set contains information about the flexure system''s topology (its constraint topology). These sets may be used to visualize the quantitative relationships between all possible flexure designs and all possible motions for a given design problem. We introduce a new principle – complementary topologies – that enables the unique mapping of freedom and constraint spaces. This mapping makes it possible to visualize and determine the general shape(s) that a viable parallel flexure system concept must have in order to permit specified motions. The shapes contain all of the relevant quantitative information that is needed to rapidly sketch early embodiments of complex parallel flexure system concepts. These shapes may then be used to rapidly synthesize a multiplicity of flexure system concepts that have (a) independent rotational and/or linear motions, (b) coupled linear and rotational motions, and (c) redundant constraints that permit the desired motions while improving stiffness, load capacity and thermal stability. This enables early-stage flexure system design via “paper and pencil sketches” without undue complications that arise when one focuses upon detailed mathematical treatments that are better-suited for optimization rather than visualization and synthesis. [Copyright &y& Elsevier]

Abstract: In Part II of this paper we demonstrate how to use freedom and constraint topology (FACT) to synthesize concepts for the multi-degree of freedom, parallel precision flexure systems that fall within the scope of Part I. Several examples are provided to demonstrate how the Principle of Complementary Topologies and geometric entities from Part I are (i) relevant to flexure system characteristics, (ii) used to visualize the possible layout of flexure constraints to achieve a desired motion and (iii) used to select redundant constraints. A synthesis process is presented, and then used to visualize and construct a flexure system concept with the requisite kinematic characteristics and redundant constraints that provide increased stiffness, load capacity, and symmetry. The output of the process is a flexure concept that would then be modeled and refined by existing modeling and analysis methods. [Copyright &y& Elsevier]

Abstract: This paper introduces a moving groove fixture which can be operated in two modes; as (1) a precision fixture or (2) a six-axis nanopositioner. Actuators and flexure bearings are integrated within the structural loop of the fixture, thereby enabling controlled changes in fixtured orientation and position while retaining high fixture stiffness. The combination of positioner and fixture characteristics enables one to adjust the fixtured position/orientation and then repeatably fixture about that position/orientation. Models of the fixture''s six-axis kinematic characteristics and stiffness were generated and used to design a prototype. [Copyright &y& Elsevier]

Abstract: The kinematics, stiffness, and repeatability of a moving groove, dual-purpose positioner-fixture were determined experimentally. A dual-purpose positioner-fixture is an alignment device that may be operated in a fixture mode or a six-axis nanopositioning mode. When operated in fixture mode, experiments show standard deviation in repeatability of 11, 11, and 38nm in x, y, and z; and 0.7, 0.3, and 0.3μrad in θ x , θ y , and θ z . The stiffness characteristics were shown to match predictions within 5%. When operated in nanopositioner mode, the device demonstrated 4nm resolution and a range, of 40μm×40μm×80μm in translation and 800μrad×800μrad×400μrad in rotation. The fixture possesses a load capacity of 450N and a natural frequency of 200Hz when the fixture is preloaded to 225N. [Copyright &y& Elsevier]

Abstract: This paper presents the design of a small-scale nanopositioner, the μHexFlex, which is comprised of a six-axis compliant mechanism and three pairs of two-axis thermo-mechanical micro-actuators. In this paper, we cover the modeling, design and fabrication of the μHexFlex. Specific attention is given to: (1) the use of constraint-based design in generating the compliant mechanism design, (2) the modeling of the actuators, and (3) the system model which links the actuator input and mechanism response. The measured, quasi-static performance of a 3mm diameter prototype shows a maximum range of 8.4μm×12.8μm×8.8μm and 19.2mrad×17.5mrad×33.2mrad (1.1°×1.0°×1.9°). Experimental results indicate that a constant mechanical/electrical material property system model may be used to predict the position and orientation over a range of 3.0μm×4.4μm×3.0μm and 6.3mrad×6.3mrad×8.7mrad (0.36°×0.36°×0.5°). The dynamic characteristics of the device were investigated experimentally. Experimental results show a lowest natural frequency of 4kHz. The resolution characteristics of the device have been measured at 1Å/mV. The device was created using deep reactive ion etching (DRIE). Bulk fabrication costs are estimated at less than $ 2 per device. [Copyright &y& Elsevier]

This paper presents the design of a novel, low-cost nano-manipulator which uses a six-axis compliant mechanism which is driven by electromagnetic actuators. The mechanism''s monolithic, planar geometry is easily fabricated via planar manufacturing processes, enables compact packaging and incorporates a flexure mechanism for achieving small transmission ratios. The manipulator tolerates ±1mm actuator misalignment with less than 0.1% full-scale position error. Measurements over a 100nm × 100nm × 100nm work volume show resolution better than our measurement capability of 5nm and open-loop parasitic errors less than 5nm. Measurements over a 100μm × 100μm × 100μm work volume show open loop errors less than 0.2% full-scale. The mechanism''s equilateral symmetry and planar geometry make it possible to limit thermal drift in position and orientation to less than 23nm and 4μrad over a 30min start up period. The nano-manipulator, built at US$ 2000 cost (excludes electronics), is used as an ultra-precision fiber optic aligner. [Copyright &y& Elsevier]

This work focuses on the design, development, and testing of an inexpensive, low-profile, cartwheel flexure mechanism for torque measurement. It has been designed primarily for use in a rehabilitation and diagnostics instrument for the treatment of ankle injuries. The sensor is manufactured rapidly and at low-cost using an Omax™ abrasive waterjet machine. Strain gauges are bonded to the flexure beams to measure applied strain using a full wheatstone bridge circuit. Displacement, force, and torque are then calculated from the measured circuit voltage; power and velocity can also be determined if required by the application. Experimental results show that there exists a linear relationship between applied torque and output voltage of the wheatstone bridge for the nested cartwheel flexure design. Furthermore, results of preliminary tests of an ankle rehabilitation device show that it fulfills a need not currently satisfied by current rehabilitation and diagnostic technology in physical medicine and rehabilitation. [ABSTRACT FROM AUTHOR]