Roll Vibration Analysis of Planar Aerostatic Bearings through a Distributed Spring Model

2011 ◽  
Vol 346 ◽  
pp. 332-338
Author(s):  
Wei Jiang ◽  
Wen Chuan Jia ◽  
Shan Shan Liu ◽  
Yuan Tai Hu ◽  
Hong Ping Hu
Keyword(s):  
Working Conditions ◽  
Spring Model ◽  
Aerostatic Bearing ◽  
Normal Stiffness ◽  
Ultra Precision ◽  
Aerostatic Bearings ◽  
Precision Motion ◽  
And Control ◽  
Distributed Spring Model ◽  
Stiffness Distribution

The aerostatic bearings used in guide ways in ultra precision motion stages can provide both normal stiffness and roll stiffness, which are critical to the dynamic characteristics and control of systems. The normal stiffness has been widely investigated so far, but the roll one has seldom been studied. A new method for analyzing the roll stiffness is proposed, in which the aerostatic bearing is modeled as a set of distributed springs. The stiffness distribution is obtained by using the derivate of the pressure distribution with respect to the air gap. All the distributed springs are then integrated by using the presented transformation and it leads to an equivalent spatial spring which contains both the normal stiffness and the roll stiffness. A planar aerostatic bearing is taken as an example to illustrate the procedure of the calculation. The proposed method can be used to predict the vibration characteristics of various kinds of aerostatic bearings under working conditions.

Integrated Optimization of Structure and Control in Ultra-Precision Motion Systems

2019 ◽  
Author(s):  
Jing Wang ◽  
Ming Zhang ◽  
Yu Zhu ◽  
Xin Li ◽  
Leijie Wang
Keyword(s):  
Complex Dynamics ◽  
System Level ◽  
Structural Topology ◽  
Worst Case ◽  
Integrated Optimization ◽  
Motion System ◽  
Material Interpolation ◽  
Ultra Precision ◽  
Precision Motion ◽  
And Control

Abstract Ever-increasing demands for precision and efficiency in ultra-precision motion systems will result in a lightweight and flexible motion system with complex dynamics. In this paper, a systematic approach is proposed where control gains, 3D structural topology and actuator configuration are integrated into optimization to derive a system-level optimal design which possesses a high vibration control performance, and still satisfies multiple design constraints. A material interpolation model with high accuracy is proposed for the integrated optimization, a simple integral equation utilizing R-functions and level-set functions is established to represent complex non-overlapping constraints of actuators. Over-actuation degrees are utilized to actively control the dominant flexible modes. Responses of residual flexible modes are restricted by increasing the coincidence of their nodal areas at actuators (sensors) locations. The objective function is the constructed worst-case vibration energy of the flexible modes. A dual-loop solving strategy combining the genetic algorithm and the modified optimal criteria method is adopted to solve the optimization problem. A fine stage in the wafer stage is designed to prove the effectiveness of the proposed method.

Performance Study of Aerostatic Bearings with Arrayed Microhole Restrictors

2011 ◽  
Vol 311-313 ◽  
pp. 386-391
Author(s):  
Peng Li ◽  
Han Chen ◽  
Xue Dong Chen
Keyword(s):  
Carrying Capacity ◽  
Load Carrying Capacity ◽  
Aerostatic Bearing ◽  
Performance Study ◽  
Load Carrying ◽  
Ultra Precision ◽  
New Type ◽  
Computational Fluid Dynamics Cfd ◽  
Aerostatic Bearings ◽  
Micro Vibration

Micro-vibration of aerostatic bearings has been the bottleneck in the improvement of the moving and positioning accuracy of ultra-precision fabrication and metrology equipments. In this study, a new type of aerostatic bearing restrictor has been proposed. The prototype of arrayed microhole restrictor, instead of the conventional single hole restrictor was developed with the aim of reducing the harmful micro-vibration of aerostatic bearings. Computational fluid dynamics (CFD) was employed to numerically calculate the air flow field. It is found that the employment of arrayed microhole restrictors can reduce the amount of micro-vibration while maintain the load carrying capacity and stiffness of the aerostatic bearing. Experimental measurement of the micro-vibration confirms the effectiveness of this new type of restrictor.

Design and Control of a Linear Electrostrictive Motor

1999 ◽  
Author(s):  
Min Hu ◽  
Hejun Du ◽  
Shihfu Ling ◽  
Yong Li ◽  
Zhaoying Zhou
Keyword(s):  
Thrust Force ◽  
Electrical Discharge Machining ◽  
Precision Motion Control ◽  
Micro Electrical Discharge Machining ◽  
Ultra Precision ◽  
Precision Motion ◽  
P Type ◽  
And Control ◽  
High Thrust ◽  
Maximum Thrust

Abstract This paper presents a novel linear electrostrictive motor with high resolution and large stroke for ultra-precision motion control. High thrust force is obtained by taking use an electromagnetic clamping mechanism with force magnifying structure in the motor design. An operator alterable P-type iterative learning control algorithm is proposed for the digital control of the motor. A prototype of the motor, which is 60mm in diameter and 120mm in length, is designed, built and tested. Experimental results show that the prototype has a mechanical resolution of 0.02μm, less than 2μm yawing error and maximum thrust force of 30N. Applications of the motor include producing the servo feed motions required in micro electrical discharge machining (micro-EDM) system or as a precision motion device for other micro machining systems.

Investigating the influences of pressure-equalizing grooves on characteristics of aerostatic bearings based on CFD

2019 ◽  
Vol 71 (7) ◽  
pp. 853-860
Author(s):  
Ruzhong Yan ◽  
Liaoyuan Wang ◽  
Shengze Wang
Keyword(s):  
Optimization Design ◽  
Load Capacity ◽  
Static Characteristic ◽  
Aerostatic Bearing ◽  
Content Type ◽  
Distribution Form ◽  
Pressure Distributions ◽  
Static Performance ◽  
Ultra Precision ◽  
Aerostatic Bearings

Purpose The purpose of this study is to reveal the influence law of pressure-equalizing grooves on aerostatic bearings and improve the static performance of bearings by optimizing the distribution form of grooves. Design/methodology/approach In view of two kinds of common restrictor distribution forms on the thrust surface, the linear and the rectangular, six kinds of pressure-equalizing groove schemes were proposed – the line-shape, the extended-shape, the S-shape, the oblong-shape, the X-shape and the reticular-shape. Based on the analysis of lubrication theory of the orifice-type aerostatic bearing, the numerical simulations of different bearings were carried out. The pressure distributions and static characteristic curves of different bearings were obtained. Findings The study reveals that the adoption of the pressure-equalizing grooves can substantially improve the load capacity and static stiffness of the bearing and make the bearing maintain a uniform stress, which enhances operating accuracy and life of the bearing. The superior function of the reticular-shape groove is highlighted. Originality/value The research results can effectively guide the optimization design of aerostatic bearings and provide a crucial technical reference for application of ultra-precision aerostatic supporting system.

scholarly journals Dynamic Quality of an Aerostatic Thrust Bearing with a Microgroove and Support Center on Elastic Suspension

Mathematics ◽  
2021 ◽  
Vol 9 (13) ◽  
pp. 1492
Author(s):  
Vladimir Kodnyanko ◽  
Stanislav Shatokhin ◽  
Andrey Kurzakov ◽  
Lilia Strok ◽  
Yuri Pikalov ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Negative Impact ◽  
Aerostatic Bearing ◽  
Elastic Suspension ◽  
Variable Parameters ◽  
Aerostatic Bearings ◽  
Improved Design ◽  
Dynamic Quality ◽  
Bearing Layer

The disadvantage of aerostatic bearings is their low dynamic quality. The negative impact on the dynamic characteristics of the bearing is exerted by the volume of air contained in the bearing gap, pockets, and microgrooves located at the outlet of the feeding diaphragms. Reducing the volume of air in the flow path is a resource for increasing the dynamic quality of the aerostatic bearing. This article presents an improved design of an axial aerostatic bearing with simple diaphragms, an annular microgroove, and an elastic suspension of the movable center of the supporting disk. A mathematical model is presented and a methodology for calculating the static characteristics of a bearing and dynamic quality indicators is described. The calculations were carried out using dimensionless quantities, which made it possible to reduce the number of variable parameters. A new method for solving linearized and Laplace-transformed boundary value problems for transformants of air pressure dynamic functions in the bearing layer was applied, which made it possible to obtain a numerical solution of problems sufficient for practice accuracy. The optimization of the criteria for the dynamic quality of the bearing was carried out. It is shown that the use of an elastic suspension of the support center improves its dynamic characteristics by reducing the volume of compressed air in the bearing layer and choosing the optimal volume of the microgroove.

THE EVALUATION OF SURFACE MORPHOLOGY USING FLEXURE GUIDED NANO-POSITIONING SYSTEM AND ULTRA-PRECISION LATHE

2012 ◽  
Vol 06 ◽  
pp. 172-177
Author(s):  
Nam-Su Kwak ◽  
Jae-Yeol Kim
Keyword(s):  
Surface Morphology ◽  
Piezoelectric Actuator ◽  
Control Method ◽  
Positioning System ◽  
Motion Error ◽  
Precision Stage ◽  
Cnc Lathe ◽  
Single Crystal Diamond ◽  
Ultra Precision ◽  
And Control

In this study, piezoelectric actuator, Flexure guide, Power transmission element and control method and considered for Nano-positioning system apparatus. The main objectives of this thesis were to develop the 3-axis Ultra-precision stages which enable the 3-axis control by the manipulation of the piezoelectric actuator and to enhance the precision of the Ultra-Precision CNC lathe which is responsible for the ductile mode machining of the hardened-brittle material where the machining is based on the single crystal diamond. Ultra-precision CNC lathe is used for machining and motion error of the machine are compensated by using 3-axis Ultra-precision stage. Through the simulation and experiments on ultra-precision positioning, stability and priority on Nano-positioning system with 3-axis ultra-precision stage and control algorithm are secured by using NI Labview. And after applying the system, is to analyze the surface morphology of the mold steel (SKD61)

Development and Experimental Performance Verification of a Magneto-Aerostatic Bearing for Cartridge of Dental Handpieces

2012 ◽  
Author(s):  
Guan-Chung Ting ◽  
Kuang-Yuh Huang ◽  
Keng-Ning Chang
Keyword(s):  
High Speed ◽  
Ball Bearings ◽  
Aerostatic Bearing ◽  
Operation Conditions ◽  
Air Inlet ◽  
Efficient Performance ◽  
Aerostatic Bearings ◽  
Repulsive Forces ◽  
Radial Loading ◽  
Air Film

Bearings for high-speed rotors are the key component of dental handpieces. The friction induced by conventional ball bearings restricts its speed and reduces its efficiency. In order to significantly improve the efficiency of dental handpieces, a mini-type cartridge that integrates a turbine and a spindle with radial aerostatic bearings and axial passive magnetic bearings has been ingeniously designed and realized. Around the rotating spindle, there is a high-pressured air film built up by a pair of radial aerostatic bearings, and magnet rings are applied to create repulsive forces to axially support the rotating spindle. The high-pressured air film comes from the specifically designed separable orifice restrictors, which can be easily and precisely manufactured. Frictionless bearing effect can be achieved by aerostatic principle, and the magnetic principle is applied to create large repulsive force against the axial working force. A tri-directional air inlet is designed to reduce radial loading force of a spindle during working. The modularized form of the magneto-aerostatic bearing allows it to be easily assembled and replaced in the very compact space of a mini-type cartridge. Through analytical simulations with fluid-dynamics software (CFD) and experiments, the magneto-aerostatic bearing is optimized to bring out efficient performance in its limited space. The experiments have verified that its noise level is 15dB lower than the conventional cartridge with ball bearings, and its startup air pressure is reduced from 0.4 bar to 0.1 bar. Under the same operation conditions, the newly developed cartridge with magneto-aerostatic bearings creates twice higher speed than that of the conventional one.

Fractal Pattern Recognition of Image Profiles for Manufacturing Process Monitoring and Control

2018 ◽  
Author(s):  
Farhad Imani ◽  
Bing Yao ◽  
Ruimin Chen ◽  
Prahalada Rao ◽  
Hui Yang
Keyword(s):  
Additive Manufacturing ◽  
Process Monitoring ◽  
Manufacturing Process ◽  
Manufacturing Systems ◽  
Experimental Studies ◽  
Precision Machining ◽  
Monitoring And Control ◽  
Process Monitoring And Control ◽  
Ultra Precision ◽  
And Control

Nowadays manufacturing industry faces increasing demands to customize products according to personal needs. This trend leads to a proliferation of complex product designs. To cope with this complexity, manufacturing systems are equipped with advanced sensing capabilities. However, traditional statistical process control methods are not concerned with the stream of in-process imaging data. Also, very little has been done to investigate nonlinearity, irregularity, and inhomogeneity in image stream collected from manufacturing processes. This paper presents the multifractal spectrum and lacunarity measures to characterize irregular and inhomogeneous patterns of image profiles, as well as detect the hidden dynamics of the underlying manufacturing process. Experimental studies show that the proposed method not only effectively characterizes the surface finishes for quality control of ultra-precision machining but also provides an effective model to link process parameters with fractal characteristics of in-process images acquired from additive manufacturing. This, in turn, will allow a swift response to processes changes and consequently reduce the number of defective products. The proposed fractal method has strong potentials to be applied for process monitoring and control in a variety of domains such as ultra-precision machining, additive manufacturing, and biomanufacturing.

scholarly journals Precarious or Protected? Evaluating Work Quality in the Legal Sex Industry

2016 ◽  
Vol 21 (4) ◽  
pp. 173-187 ◽  
Author(s):  
Alice Orchiston
Keyword(s):  
Sex Work ◽  
Working Conditions ◽  
Sex Workers ◽  
Sex Industry ◽  
Labour Law ◽  
Industry Regulation ◽  
Regulatory Model ◽  
And Control ◽  
The Relationship ◽  
Legal Sex

Decriminalising (or legalising) sex work is argued to improve sex workers’ safety and provide access to labour rights. However, there is a paucity of empirical research comparing how different regulatory approaches affect working conditions in the sex industry, especially in relation to venues that are managed by third parties. This article uses a mixed methods study of the Australian legal brothel sector to critically explore the relationship between external regulation and working conditions. Two dominant models of sex industry regulation are compared: decriminalisation and licensing. First, the article documents workplace practices in the Australian legal brothel sector, examining sex workers’ agency, autonomy and control over the labour process. Second, it analyses the capacity of each regulatory model to protect sex workers from unsafe and unfair working conditions. On the basis of these findings, the article concludes that brothel-based sex work is precarious and substantively excluded from the protective mantle of labour law, notwithstanding its legality. It is argued that the key determinant of conditions in the legal brothel sector is the extent to which the state enforces formal labour protections, as distinct from the underlying regulatory model adopted.

scholarly journals Vibration Analysis and Control of a Vibration Screed System for Asphalt Pavers

2020 ◽  
Vol 25 (3) ◽  
pp. 363-372
Author(s):  
Vanliem Nguyen ◽  
Zhenpeng Wu ◽  
Beiping Zhang ◽  
Zhang Jian Run
Keyword(s):  
Working Conditions ◽  
Vibration Analysis ◽  
Excitation Frequency ◽  
Mean Square ◽  
Dynamic Parameters ◽  
Objective Functions ◽  
Nonlinear Dynamic Model ◽  
Compression Efficiency ◽  
Centre Of Gravity ◽  
And Control

To reduce shaking of a vibration screed system (VSS) and improve the paving performance of an asphalt paver (AP), the root-mean-square (RMS) acceleration responses at points on the front and rear screed floors are analyzed via an experimental method. A 3D nonlinear dynamic model of the VSS is also built to evaluate the influence of the dynamic parameters of the VSS on the compression efficiency, paving quality, and working stability of the AP based on the objective functions of the vertical, pitching, and rolling RMS values at the centre of gravity of the screed. The angular deviations, $alpha$ and $gamma$, of the tamper are then controlled to improve the paving performance. The research results show that the excitation frequency, $f_{t}$, and both angular deviations, $alpha$ and $gamma$, of the tamper strongly affect the paving performance. The compression efficiency is quickly enhanced, while both paving quality and working stability are significantly reduced with increasing the excitation frequency $f_{t}$ and reducing the angular deviations. $alpha$ and $gamma$. and vice versa. Additionally, the screed shaking and paving performance of the AP are remarkably improved by control of the angular deviations, $alpha$ and $gamma$, under different working conditions.

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