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.

Analytical Representation of Nano-Scale Parasitic Motion in Flexure-Based Selectively Compliant Mechanisms

2007 ◽  
Author(s):  
Chinmaya B. Patil ◽  
S. V. Sreenivasan ◽  
Raul G. Longoria
Keyword(s):  
Compliant Mechanisms ◽  
Screw Theory ◽  
Geometric Errors ◽  
Modeling And Analysis ◽  
Parasitic Motion ◽  
Nano Scale ◽  
Flexure Joints ◽  
Improved Design ◽  
Kinetostatic Model ◽  
Spatial Kinematics

Analytical modeling of selectively compliant mechanisms for quantifying the nano-scale parasitic motion is presented. Flexure-based compliant mechanisms are capable of meeting the demanding requirements of the partially constrained ultraprecision motion systems. However, the geometric errors induced by manufacturing tolerances can limit the precision capability. Understanding parasitic motion at the nano-scale necessitates a 3-D model even for mechanisms that are designed to be planar. A spatial kinematics based kinetostatic model is used here. This approach systematically accounts for the geometric errors, and enables estimation of the inherently spatial parasitic motion. Using insights from screw theory, the parasitic motion is classified into intrinsic mechanism errors, and errors that can be minimized by calibration procedures. A metric that quantifies the intrinsic parasitic motion and characterizes the precision capability of the mechanism is identified. Monte Carlo simulation is used to propagate the variance of the geometric errors through the model to determine the statistical moments of the chosen metric. To illustrate the approach, the modeling and analysis is applied to a classical four-bar mechanism with flexure joints. The model is further used to investigate the key system parameters that influence the intrinsic parasitic motion in the mechanism. The simulation results indicate more than 50% improvement in the precision capability of the four-bar mechanism by improved design of flexure joints, without changing the manufacturing tolerance limits.

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.

Robust Design of Flexure Based Nano Precision Compliant Mechanisms With Application to Nano Imprint Lithography

2008 ◽  
Author(s):  
Chinmaya B. Patil ◽  
S. V. Sreenivasan ◽  
Raul G. Longoria
Keyword(s):  
Analytical Model ◽  
Robust Design ◽  
Compliant Mechanisms ◽  
Design Approach ◽  
Iteration Step ◽  
Geometric Errors ◽  
Imprint Lithography ◽  
Flexure Mechanism ◽  
Parasitic Motion ◽  
Nano Imprint

Flexure-based compliant mechanisms are the preferred motion guiding systems for small range, nano-precision positioning applications because of excellent characteristics like friction-free continuous motion. These mechanisms are commonly used in nano fabrication equipment and ultra precision instruments. However, machining imperfections induced geometric errors in the mechanisms are known to cause undesirable parasitic motion and significant loss of precision. A systematic design approach to minimize the sensitivity of the flexure mechanisms to geometric errors induced by machining tolerances is presented here. Central to the design approach is the screw systems based analytical model to study the spatial motion characteristics of flexure mechanisms. Using this model, the parasitic motion is classified into those errors which can be corrected by calibration (extrinsic) and those which are coupled with the mechanism motion and cannot be corrected by apriori calibration (intrinsic). Metric to quantify the intrinsic parasitic motion results naturally from the screw systems analysis, and is used to represent the precision capability of the flexure mechanism. The analytical model enables the selection of geometric parameters of flexure joints of the mechanism via an optimization scheme with the aim of minimizing the parasitic motion metric. The statistical nature of the machining tolerances is accounted for by sampling the random variables at every iteration step of the optimization, leading to a stochastic formulation. The robust design approach is illustrated using a one DOF rotational flexure mechanism that is used in nano-imprint lithography equipment. Numerical results of the optimization indicate up to 40% improvement in the precision capability of the mechanism without any change in the manufacturing tolerance limits. Further, it is shown via eigenscrew analysis of mechanism compliance that the robustness resulting from the optimal flexure joint design can be attributed to the improved compliance distribution.

Membrane-Enhanced Lamina Emergent Torsional Joints for Surrogate Folds

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Guimin Chen ◽  
Spencer P. Magleby ◽  
Larry L. Howell
Keyword(s):  
Change Point ◽  
Degrees Of Freedom ◽  
Compliant Mechanisms ◽  
Parasitic Motion ◽  
Spherical Mechanisms ◽  
Wide Range ◽  
Mechanical Devices ◽  
Planar Fabrication

Lamina emergent compliant mechanisms (including origami-adapted compliant mechanisms) are mechanical devices that can be fabricated from a planar material (a lamina) and have motion that emerges out of the fabrication plane. Lamina emergent compliant mechanisms often exhibit undesirable parasitic motions due to the planar fabrication constraint. This work introduces a type of lamina emergent torsion (LET) joint that reduces parasitic motions of lamina emergent mechanisms, and presents equations for modeling parasitic motion of LET joints. The membrane joint also makes possible one-way joints that can ensure origami-based mechanisms emerge from their flat state (a change point) into the desired configuration. Membrane-enhanced LET (M-LET) joints, including one-way surrogate folds, are described here and show promise for use in a wide range of compliant mechanisms and origami-based compliant mechanisms. They are demonstrated as individual joints and in mechanisms such as a kaleidocycle (a 6R Bricard linkage), degree-4 origami vertices (spherical mechanisms), and waterbomb base mechanisms (an 8R multi-degrees-of-freedom origami-based mechanism).

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).

Case Studies and a Note on the Degrees-of-Freedom in Compliant Mechanisms

1996 ◽  
Author(s):  
G. K. Ananthasuresh ◽  
Larry L. Howell
Keyword(s):  
Case Studies ◽  
Degrees Of Freedom ◽  
Compliant Mechanisms

Abstract The presence of compliant members in a mechanism makes the determination of its degrees-of-freedom out of reach of the traditional Grübler’s formula, as this formula does not account for the additional mobility allowed by compliance. Recent research efforts have led to a generalization of Grübler’s formula that encompasses compliant mechanisms as well. The objective of this work is to apply the formula to a set of practical compliant devices, and further clarify and simplify the approach. This is accomplished as follows: i) The concept of “virtual rigid segments” is introduced to facilitate the identification of the segment compliance of distributed segments with forces applied to them. ii) The motion of compliant devices is interpreted by identifying the inputs equal in number to the calculated possible degrees of freedom. iii) A wide variety of case studies are presented to illustrate the method of application and the value of the approach.

Two-Stage Procedure for the Quantitative Determination of Autoprothrombin III Concentration and Some Applications

1967 ◽  
Vol 18 (01/02) ◽  
pp. 198-210 ◽  
Author(s):  
Ronald S Reno ◽  
Walter H Seegers
Keyword(s):  
Prothrombin Time ◽  
Factor Vii ◽  
Two Stage ◽  
Pronounced Increase ◽  
One Stage ◽  
Assay Procedure ◽  
Bovine Plasma ◽  
The One ◽  
Autoprothrombin C

SummaryA two-stage assay procedure was developed for the determination of the autoprothrombin C titre which can be developed from prothrombin or autoprothrombin III containing solutions. The proenzyme is activated by Russell’s viper venom and the autoprothrombin C activity that appears is measured by its ability to shorten the partial thromboplastin time of bovine plasma.Using the assay, the autoprothrombin C titre was determined in the plasma of several species, as well as the percentage of it remaining in the serum from blood clotted in glass test tubes. Much autoprothrombin III remains in human serum. With sufficient thromboplastin it was completely utilized. Plasma from selected patients with coagulation disorders was assayed and only Stuart plasma was abnormal. In so-called factor VII, IX, and P.T.A. deficiency the autoprothrombin C titre and thrombin titre that could be developed was normal. In one case (prethrombin irregularity) practically no thrombin titre developed but the amount of autoprothrombin C which generated was in the normal range.Dogs were treated with Dicumarol and the autoprothrombin C titre that could be developed from their plasmas decreased until only traces could be detected. This coincided with a lowering of the thrombin titre that could be developed and a prolongation of the one-stage prothrombin time. While the Dicumarol was acting, the dogs were given an infusion of purified bovine prothrombin and the levels of autoprothrombin C, thrombin and one-stage prothrombin time were followed for several hours. The tests became normal immediately after the infusion and then went back to preinfusion levels over a period of 24 hrs.In other dogs the effect of Dicumarol was reversed by giving vitamin K1 intravenously. The effect of the vitamin was noticed as early as 20 min after administration.In response to vitamin K the most pronounced increase was with that portion of the prothrombin molecule which yields thrombin. The proportion of that protein with respect to the precursor of autoprothrombin C increased during the first hour and then started to go down and after 3 hrs was equal to the proportion normally found in plasma.

SIMPLIFIED DEXAMETHASONE SUPPRESSION TEST

1969 ◽  
Vol 61 (2) ◽  
pp. 219-231 ◽  
Author(s):  
V. H. Asfeldt
Keyword(s):  
Cushing’S Syndrome ◽  
Normal Subjects ◽  
Cushing's Syndrome ◽  
Dexamethasone Suppression Test ◽  
Clinical Value ◽  
Suppression Test ◽  
The One ◽  
Steroid Excretion ◽  
Dexamethasone Suppression

ABSTRACT This is an investigation of the practical clinical value of the one mg dexamethasone suppression test of Nugent et al. (1963). The results, evaluated from the decrease in fluorimetrically determined plasma corticosteroids in normal subjects, as well as in cases of exogenous obesity, hirsutism and in Cushing's syndrome, confirm the findings reported in previous studies. Plasma corticosteroid reduction after one mg of dexamethasone in cases of stable diabetes was not significantly different from that observed in control subjects, but in one third of the insulin-treated diabetics only a partial response was observed, indicating a slight hypercorticism in these patients. An insufficient decrease in plasma corticosteroids was observed in certain other conditions (anorexia nervosa, pituitary adenoma, patients receiving contraceptive or anticonvulsive treatment) with no hypercorticism. The physiological significance of these findings is discussed. It is concluded that the test, together with a determination of the basal urinary 17-ketogenic steroid excretion, is suitable as the first diagnostic test in patients in whom Cushing's syndrome is suspected. In cases of insufficient suppression of plasma corticosteroids, further studies, including the suppression test of Liddle (1960), must be carried out.

A Validated 2D-LC-UV Method for Simultaneous Determination of Imatinib and N-demethylimatinib in Plasma and Its Clinical Application for Therapeutic Drug Monitoring with GIST Patients

2020 ◽  
Vol 17 ◽  
Author(s):  
Houli Li ◽  
Di Zhang ◽  
Xiaoliang Cheng ◽  
Qiaowei Zheng ◽  
Kai Cheng ◽  
...  
Keyword(s):  
Therapeutic Drug Monitoring ◽  
One Dimension ◽  
Therapeutic Drug ◽  
Plasma Samples ◽  
Column Temperature ◽  
Injection Volume ◽  
Target Analytes ◽  
The One ◽  
Middle Column

Background: The trough concentration (Cmin) of Imatinib (IM) is closely related to the treatment outcomes and adverse reactions of patients with gastrointestinal stromal tumors (GIST). However, the drug plasma level has great interand intra-individual variability, and therapeutic drug monitoring (TDM) is highly recommended. Objective: To develop a novel, simple, and economical two-dimensional liquid chromatography method with ultraviolet detector (2D-LC-UV) for simultaneous determination of IM and its major active metabolite, N-demethyl imatinib (NDIM) in human plasma, and then apply the method for TDM of the drug. Method: Sample was processed by simple protein precipitation. Two target analytes were separated on the one-dimension column, captured on the middle column, and then transferred to the two-dimension column for further analysis. The detection was performed at 264 nm. The column temperature was maintained at 40˚C and the injection volume was 500 μL. Totally 32 plasma samples were obtained from patients with GIST who were receiving IM. Method: Sample was processed by simple protein precipitation. Two target analytes were separated on the one-dimension column, captured on the middle column, and then transferred to the two-dimension column for further analysis. The detection was performed at 264 nm. The column temperature was maintained at 40˚C and the injection volume was 500 μL. Totally 32 plasma samples were obtained from patients with GIST who were receiving IM. Conclusion: The novel 2D-LC-UV method is simple, stable, highly automated and independent of specialized technicians, which greatly increases the real-time capability of routine TDM for IM in hospital.

scholarly journals The Concept of Accuracy Analysis of the Vertical Displacements Gained from the Hydrostatic Levelling Systems’ Measurements

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4842
Author(s):  
Waldemar Kamiński
Keyword(s):  
Accuracy Assessment ◽  
Theoretical Models ◽  
Vertical Displacement ◽  
Serial Connection ◽  
Vertical Displacements ◽  
Comprehensive Determination ◽  
The One ◽  
The Individual ◽  
Reference Sensor

Nowadays, hydrostatic levelling is a widely used method for the vertical displacements’ determinations of objects such as bridges, viaducts, wharfs, tunnels, high buildings, historical buildings, special engineering objects (e.g., synchrotron), sports and entertainment halls. The measurements’ sensors implemented in the hydrostatic levelling systems (HLSs) consist of the reference sensor (RS) and sensors located on the controlled points (CPs). The reference sensor is the one that is placed at the point that (in theoretical assumptions) is not a subject to vertical displacements and the displacements of controlled points are determined according to its height. The hydrostatic levelling rule comes from the Bernoulli’s law. While using the Bernoulli’s principle in hydrostatic levelling, the following components have to be taken into account: atmospheric pressure, force of gravity, density of liquid used in sensors places at CPs. The parameters mentioned above are determined with some mean errors that influence on the accuracy assessment of vertical displacements. In the subject’s literature, there are some works describing the individual accuracy analyses of the components mentioned above. In this paper, the author proposes the concept of comprehensive determination of mean error of vertical displacement (of each CPs), calculated from the mean errors’ values of components dedicated for specific HLS. The formulas of covariances’ matrix were derived and they enable to make the accuracy assessment of the calculations’ results. The author also presented the subject of modelling of vertical displacements’ gained values. The dependences, enabling to conduct the statistic tests of received model’s parameters, were implemented. The conducted tests make it possible to verify the correctness of used theoretical models of the examined object treated as the rigid body. The practical analyses were conducted for two simulated variants of sensors’ connections in HLS. Variant no. I is the sensors’ serial connection. Variant no. II relies on the connection of each CPs with the reference sensor. The calculations’ results show that more detailed value estimations of the vertical displacements can be obtained using variant no. II.

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