Accuracy and precision: A new viewon kinematic assessment of solid-state hinges and compliant mechanisms

2021 ◽  
pp. 1045389X2110643
Author(s):  
Lucio Flavio Campanile ◽  
Stephanie Kirmse ◽  
Alexander Hasse
Keyword(s):  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Measurement Theory ◽  
Reference Value ◽  
Strict Sense ◽  
Force System ◽  
Parasitic Motion ◽  
Accuracy And Precision ◽  
Compliant Systems

Compliant mechanisms are alternatives to conventional mechanisms which exploit elastic strain to produce desired deformations instead of using moveable parts. They are designed for a kinematic task (providing desired deformations) but do not possess a kinematics in the strict sense. This leads to difficulties while assessing the quality of a compliant mechanism’s design. The kinematics of a compliant mechanism can be seen as a fuzzy property. There is no unique kinematics, since every deformation need a particular force system to act; however, certain deformations are easier to obtain than others. A parallel can be made with measurement theory: the measured value of a quantity is not unique, but exists as statistic distribution of measures. A representative measure of this distribution can be chosen to evaluate how far the measures divert from a reference value. Based on this analogy, the concept of accuracy and precision of compliant systems are introduced and discussed in this paper. A quantitative determination of these qualities based on the eigenvalue analysis of the hinge’s stiffness is proposed. This new approach is capable of removing most of the ambiguities included in the state-of-the-art assessment criteria (usually based on the concepts of path deviation and parasitic motion).

Analysis of Parasitic Motion in Compliant Mechanisms Using Eigenwrenches and Eigentwists

2018 ◽  
Author(s):  
Werner W. P. J. van de Sande ◽  
Just L. Herder
Keyword(s):  
Compliant Mechanisms ◽  
Screw Theory ◽  
Compliant Mechanism ◽  
Degree Of Freedom ◽  
Compliance Matrix ◽  
Parasitic Motion ◽  
Actual Degree ◽  
Motion Metrics ◽  
Mechanism Kinematic ◽  
Kinematic Information

Parasitic motion is undesired in precision mechanisms, it causes unwanted kinematics. These erroneous motions are especially apparent in compliant mechanisms. Usually an analysis of parasitic motion is only valid for one type of mechanism. Kinematic information is imbedded in the compliance matrix of any mechanism; an eigenscrew decomposition expresses this kinematic information as screws. It uses screw theory to identify the lines along which a force yields a parallel translation and a rotation yields a parallel moment. These lines are called eigenwrenches and eigentwists. Any other load on the compliant mechanism will lead to parasitic motion. This article introduces two parasitic motion metrics using eigenscrew decomposition: the parasitic resultant from an applied screw and the deviation of an actual degree of freedom from a desired degree of freedom. These metrics are applicable to all compliant mechanism and allow comparison between two compliant mechanisms. These metrics are applied to some common compliant mechanisms as an example.

Classification of Compliant Mechanisms and Determination of the Degrees of Freedom Using the Concepts of Compliance Number and Pseudo-Rigid-Body Model

2019 ◽  
Author(s):  
Pratheek Bagivalu Prasanna ◽  
Ashok Midha ◽  
Sushrut G. Bapat
Keyword(s):  
Rigid Body ◽  
Degrees Of Freedom ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Body Model ◽  
Active Compliance ◽  
Kinematic Behavior ◽  
Rigid Body Model

Abstract Understanding the kinematic properties of a compliant mechanism has always proved to be a challenge. A concept of compliance number offered earlier emphasized the development of terminology that aided in its determination. A method to evaluate the elastic degrees of freedom associated with the flexible segments/links of a compliant mechanism using the pseudo-rigid-body model (PRBM) concept is provided. In this process, two distinct classes of compliant mechanisms are developed involving: (i) Active Compliance and (ii) Passive Compliance. Furthermore, these also aid in a better characterization of the kinematic behavior of a compliant mechanism. A more lucid interpretation of the significance of compliance number is provided. Applications of this method to both active and passive compliant mechanisms are exemplified. Finally, an experimental procedure that aids in visualizing the degrees of freedom as calculated is presented.

Extensible-Link Kinematic Model for Characterizing and Optimizing Compliant Mechanism Motion

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Justin Beroz ◽  
Shorya Awtar ◽  
A. John Hart
Keyword(s):  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Kinematic Model ◽  
Model Development ◽  
Taylor Series Expansion ◽  
Analytical Determination ◽  
Motion Trajectory ◽  
Model Framework ◽  
Error Components

We present an analytical model for characterizing the motion trajectory of an arbitrary planar compliant mechanism. Model development consists of identifying particular material points and their connecting vectorial lengths in a manner that represents the mechanism topology; whereby these lengths may extend over the course of actuation to account for the elastic deformation of the compliant mechanism. The motion trajectory is represented within the model as an analytical function in terms of these vectorial lengths, whereby its Taylor series expansion constitutes a parametric formulation composed of load-independent and load-dependent terms. This adds insight to the process for designing compliant mechanisms for high-accuracy motion applications because: (1) inspection of the load-independent terms enables determination of specific topology modifications that reduce or eliminate certain error components of the motion trajectory; and (2) the load-dependent terms reveal the polynomial orders of principally uncorrectable error components in the trajectory. The error components in the trajectory simply represent the deviation of the actual motion trajectory provided by the compliant mechanism compared to the ideally desired one. A generalized model framework is developed, and its utility demonstrated via the design of a compliant microgripper with straight-line parallel jaw motion. The model enables analytical determination of all geometric modifications for minimizing the error trajectory of the jaw, and prediction of the polynomial order of the uncorrectable trajectory components. The jaw trajectory is then optimized using iterative finite elements simulations until the polynomial order of the uncorrectable trajectory component becomes apparent; this reduces the error in the jaw trajectory by 2 orders of magnitude over the prescribed jaw stroke. This model serves to streamline the design process by identifying the load-dependent sources of trajectory error in a compliant mechanism, and thereby the limits with which this error may be redressed by topology modification.

Load-Flow Based Design of Compliant Mechanisms With Embedded Soft Actuators

2019 ◽  
Author(s):  
Sree Kalyan Patiballa ◽  
Sreeshankar Satheeshbabu ◽  
Girish Krishnan
Keyword(s):  
Embedded System ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Flow Behavior ◽  
Load Flow ◽  
Mechatronic Systems ◽  
Soft Systems ◽  
Single Input Single Output ◽  
Single Output ◽  
Compliant Systems

Abstract Transmission members such as gears and linkages are ubiquitously used in mechatronic systems to tailor the performance of actuators. However, in most bio-inspired soft systems the actuation and transmission members are closely integrated, and sometimes indistinguishable. Embedded actuation is greatly advantageous for attaining high stroke and transferring large output forces. This paper attempts at a systematic synthesis of compliant systems with embedded contractile actuators and passive members to achieve a particular kinematic objective. The paper builds on recent understanding of a compliant mechanism topology where the constituent members can be functionally classified as load transferring transmitters and strain energy storing constraints. The functional equivalence between the transmitter members and actuators are used to replace transmitters in tension with contractile actuators, thus realizing a compliant embedded system. Once a single-input single-output compliant mechanism is designed, and its load flow behavior mapped, systematic guidelines and best practices are established for embedding actuators within the topology to increase performance without altering the kinematic behavior. Several examples, including a prototype that used soft pneumatic artificial muscles is presented to validate the synthesis framework. The initial results will form the basis for designing fully autonomous compliant systems with embedded actuators and sensors without the use of computationally expensive techniques.

An Instant Center Approach Toward the Conceptual Design of Compliant Mechanisms

2005 ◽  
Vol 128 (3) ◽  
pp. 542-550 ◽  
Author(s):  
Charles J. Kim ◽  
Sridhar Kota ◽  
Yong-Mo Moon
Keyword(s):  
Conceptual Design ◽  
Building Block ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Geometry Optimization ◽  
Building Blocks ◽  
Cross Sectional ◽  
Rigid Body Model ◽  
Cross Sectional Size

As with conventional mechanisms, the conceptual design of compliant mechanisms is a blend of art and science. It is generally performed using one of two methods: topology optimization or the pseudo-rigid-body model. In this paper, we present a new conceptual design methodology which utilizes a building block approach for compliant mechanisms performing displacement amplification/attenuation. This approach provides an interactive, intuitive, and systematic methodology for generating initial compliant mechanism designs. The instant center is used as a tool to construct the building blocks. The compliant four-bar building block and the compliant dyad building block are presented as base mechanisms for the conceptual design. It is found that it is always possible to obtain a solution for the geometric advantage problem with an appropriate combination of these building blocks. In a building block synthesis, a problem is first evaluated to determine if any known building blocks can satisfy the design specifications. If there are none, the problem is decomposed to a number of sub-problems which may be solved with the building blocks. In this paper, the problem is decomposed by selecting a point in the design space where the output of the first building block coincides with the second building block. Two quantities are presented as tools to aid in the determination of the mechanism's geometry – (i) an index relating the geometric advantage of individual building blocks to the target geometric advantage and (ii) the error in the geometric advantage predicted by instant centers compared to the calculated value from FEA. These quantities guide the user in the selection of the location of nodes of the mechanism. Determination of specific cross-sectional size is reserved for subsequent optimization. An example problem is provided to demonstrate the methodology's capacity to obtain good initial designs in a straightforward manner. A size and geometry optimization is performed to demonstrate the viability of the design.

Analytical and Experimental Characterization of Parasitic Motion in Flexure-Based Selectively Compliant Precision Mechanisms

2008 ◽  
Author(s):  
Chinmaya B. Patil ◽  
S. V. Sreenivasan ◽  
Raul G. Longoria
Keyword(s):  
Degrees Of Freedom ◽  
Compliant Mechanisms ◽  
Ideal Behavior ◽  
Modeling And Analysis ◽  
Flexure Mechanism ◽  
Parasitic Motion ◽  
Pure Rotation ◽  
The One ◽  
Spatial Kinematics

Flexure-based selectively compliant mechanisms with less than six degrees of freedom are capable of meeting the demanding requirements of ultra precision positioning and scanning systems. However, machining imperfections induce undesirable motion and limit the mechanisms precision capability. A spatial kinematics based kinetostatic model is presented here that not only enables determination of inherently spatial parasitic motion due to machining imperfections, but also offers critical geometric insight into the motion characteristics of flexure mechanisms. The analytical development reveals that the geometric errors induced by machining imperfections perturb the special screw systems of motion of ideal flexure mechanisms to their corresponding general screw systems. This insight leads to clearly defined metrics that can capture the non-ideal behavior using screw system theory and is applicable to all selectively compliant mechanisms. This result is illustrated using one and two DOF mechanisms as examples. In the case of rotational DOF flexure mechanisms, the pitch of twist of motion captures the difference between the special and general screw systems and represents the intrinsic parasitic motion. The machining imperfections are regarded as Gaussian random variables with known variance, and the model is used to determine the variance of the pitch of twist via Monte Carlo simulation, leading to determination of the precision capability of the flexure mechanisms. The modeling and analysis is illustrated using one and two DOF rotation flexure mechanisms. Finally, the details of a test setup built to determine the parasitic motion of the one DOF rotational mechanism are presented. Experimental results indicate that the one DOF flexure mechanism is indeed executing screw motion rather than pure rotation.

A Flexible-Link Model for Compliant Member Synthesis

2006 ◽  
Author(s):  
Ahmad Smaili ◽  
Mazen Hassanieh
Keyword(s):  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Elliptic Integral ◽  
New Approach ◽  
Proposed Model ◽  
Gradient Optimization ◽  
Rigid Body Model ◽  
Optimum Solution ◽  
Nonlinear Deformations

A new approach for the synthesis of a compliant link experiencing nonlinear deformations is herein introduced. The model is being proposed as an alternative to the pseudo-rigid-body model widely used in compliant mechanisms synthesis. The proposed approach is based on the exact elliptic integral equations that govern beam deformations. The model entails the determination of a few parameters in an optimum sense that would move the endpoint of the beam through several desired positions with minimal error. A tabu-gradient optimization algorithm is employed to search the design space for an optimum solution that minimizes the square of the error between the desired and the generated endpoint positions while satisfying a set of relevant constraints. Attributes of the model are highlighted by way of several examples. A brief outline on how the proposed model is used as the basis for compliant mechanism synthesis is presented and demonstrated by way of two examples.

On the Mobility of Compliant Mechanisms

1994 ◽  
Author(s):  
Morgan D. Murphy ◽  
Ashok Midha ◽  
Larry L. Howell
Keyword(s):  
Mathematical Model ◽  
Rigid Body ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Final Design ◽  
Design Options ◽  
Potential Mobility ◽  
Topological Synthesis

Abstract The topological synthesis for a compliant mechanism leads to a very large number of design options from which to select a final design. Therefore, an evaluation of a mechanism’s ability to meet selected criteria provides a means of reducing a large number of possible designs to a smaller set of acceptable designs. One criterion deals with a mechanism’s potential mobility. For mechanisms containing flexible members, the response to inputs, in general, is comprised of both rigid-body and elastic deflections of their members. This paper deals primarily with the development of a technique for the determination of mobility characteristics of compliant mechanisms, employing a mathematical model previously developed for compliant mechanisms.

scholarly journals Displacement Analysis of Compliant Mechanism

2019 ◽  
Vol 9 (1) ◽  
pp. 4028-4032
Keyword(s):  
High Resolution ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Primary Objective ◽  
Micro Manufacturing ◽  
Object Position ◽  
Compliant Systems ◽  
Analysis Models ◽  
Molecular Deformation ◽  
Rotational Direction

Everyone expects accurate outcomes in the fast-moving and extremely competitive globe today. The urgent need for precision led to developing new processes in a rapidly increasing mechanical and mechatronic globe, which serve the primary objective of accuracy. This special class of mechanism is called compliant mechanisms, which are used to improve the precision without compromising the accuracy of a member because of the steadiness and flexion. Motion is produced by the molecular deformation in compliant systems, leading to two main features of bending–soft movement and a tiny scope of movement. Scan The demand for contemporary techniques, for example the production of micronanos, characterization systems, such as microscopes is present in the scan processes. For the accurate control / manipulation of object position, different compliant based mechanisms are created. Flexures are compliant, elastic structures which produce smooth motions, tiny range and high resolution for their functionality. These processes can be used in precise apps such as micro soldering, lithographic micro-manufacturing wafer alignment. The primary aim is therefore to design an accurate system in a linear as well as in a rotational direction that gives accurate movement.The software of ANSYS is used to generate compliant mechanism parametric and static analysis models.

Position-Space-Based Compliant Mechanism Reconfiguration Approach and Its Application in the Reduction of Parasitic Motion

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Haiyang Li ◽  
Guangbo Hao ◽  
Richard C. Kavanagh
Keyword(s):  
Parallel Mechanism ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Geometrical Shape ◽  
Position Space ◽  
Element Analysis ◽  
Parasitic Motion ◽  
Compliant Parallel Mechanism ◽  
Motion Characteristics ◽  
Cross Axis

This paper introduces a position-space-based reconfiguration (PSR) approach to the reconfiguration of compliant mechanisms. The PSR approach can be employed to reconstruct a compliant mechanism into many new compliant mechanisms, without affecting the mobility of the compliant mechanism. Such a compliant mechanism can be decomposed into rigid stages and compliant modules. Each of the compliant modules can be placed at any one permitted position within its position space, which does not change the constraint imposed by the compliant module on the compliant mechanism. Therefore, a compliant mechanism can be reconfigured through selecting different permitted positions of the associated compliant modules from their position spaces. The proposed PSR approach can be used to change the geometrical shape of a compliant mechanism for easy fabrication, or to improve its motion characteristics such as cross-axis coupling, lost motion, and motion range. While this paper focuses on reducing the parasitic motions of a compliant mechanism using this PSR approach, the associated procedure is summarized and demonstrated using a decoupled XYZ compliant parallel mechanism as an example. The parasitic motion of the XYZ compliant parallel mechanism is modeled analytically, with three variables which represent any permitted positions of the associated compliant modules in their position spaces. The optimal positions of the compliant modules in the XYZ compliant parallel mechanism are finally obtained based on the analytical results, where the parasitic motion is reduced by approximately 50%. The reduction of the parasitic motion is verified by finite-element analysis (FEA) results, which differ from the analytically obtained values by less than 7%.

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