A Dual-Driven High Precision Rotary Platform Based on Stick-Slip Principle

Friction is one of the important factors resulting in the contour error of feed servo systems for high-precision computer numerical control machine tools. The beginning criterion of friction compensation is usually based on the recognition that reverse axis velocity reaches zero at quadrant boundary in circular motion. In fact, reverse velocity cannot reach zero at quadrant boundary. This article investigates the dynamics question behind stick–slip motion, based on re-understanding friction and closed-loop control. Here, the stick–slip motions were distinguished as three kinds: positive, negative and full reversals. Moreover, it is also considered that closed-loop control system must produce inhibition to inner disturbance as to friction. The conclusion that friction compensation should take place before the velocity decreases to zero is obtained. The simulation result well illustrates the theoretical analysis of the nature of stick–slip motion. Compensation experiment shows that friction compensation considering negative friction can easily further decrease friction error in high speed.

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Load and stiffness of a planar ferrofluid pocket bearing

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1177/1350650117739200 ◽

2017 ◽

Vol 232 (1) ◽

pp. 14-25 ◽

Cited By ~ 15

Author(s):

SGE Lampaert ◽

JW Spronck ◽

RAJ van Ostayen

Keyword(s):

Magnetic Field ◽

High Precision ◽

Carrying Capacity ◽

Viscous Friction ◽

Load Carrying Capacity ◽

Stick Slip ◽

Hydrostatic Bearing ◽

Load Carrying ◽

Stiffness Characteristics ◽

The Magnetic Field

A ferrofluid pocket bearings is a type of hydrostatic bearing that uses a ferrofluid seal to encapsulate a pocket of air to carry a load. Their properties, combining a high stiffness with low (viscous) friction and absence of stick-slip, make them interesting for applications that require fast and high precision positioning. Knowledge on the exact performance of these types of bearings is up to now not available. This article presents a method to model the load carrying capacity and normal stiffness characteristics of this type of bearings. Required for this is the geometry of the bearing, the shape of the magnetic field and the magnetization strength of the fluid. This method is experimentally validated and is shown to be correct for describing the load and stiffness characteristics of any fixed shape of ferrofluid pocket bearing.

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Study on the compensation of error by stick-slip for high-precision table

International Journal of Machine Tools and Manufacture ◽

10.1016/j.ijmachtools.2003.10.027 ◽

2004 ◽

Vol 44 (5) ◽

pp. 503-510 ◽

Cited By ~ 46

Author(s):

Xuesong Mei ◽

Masaomi Tsutsumi ◽

Tao Tao ◽

Nuogang Sun

Keyword(s):

High Precision ◽

Stick Slip

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Automatic measurement of SAED patterns from asbestos minerals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100106296 ◽

1988 ◽

Vol 46 ◽

pp. 846-847

Author(s):

J. C. Russ ◽

T. Taguchi ◽

P. M. Peters ◽

E. Chatfield ◽

J. C. Russ ◽

...

Keyword(s):

Diffraction Pattern ◽

High Precision ◽

Diffraction Data ◽

Automatic Measurement ◽

Automatic Method ◽

Important Method ◽

X Ray ◽

Integrated Intensity ◽

Asbestiform Minerals ◽

True Center

Conventional SAD patterns as obtained in the TEM present difficulties for identification of materials such as asbestiform minerals, although diffraction data is considered to be an important method for making this purpose. The preferred orientation of the fibers and the spotty patterns that are obtained do not readily lend themselves to measurement of the integrated intensity values for each d-spacing, and even the d-spacings may be hard to determine precisely because the true center location for the broken rings requires estimation. We have implemented an automatic method for diffraction pattern measurement to overcome these problems. It automatically locates the center of patterns with high precision, measures the radius of each ring of spots in the pattern, and integrates the density of spots in that ring. The resulting spectrum of intensity vs. radius is then used just as a conventional X-ray diffractometer scan would be, to locate peaks and produce a list of d,I values suitable for search/match comparison to known or expected phases.

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On effects of non-systematic reflections on weak-beam images of partial dislocations

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087756 ◽

1991 ◽

Vol 49 ◽

pp. 688-689

Author(s):

K. Z. Botros ◽

S. S. Sheinin

Keyword(s):

High Precision ◽

Stacking Fault ◽

Important Application ◽

Stacking Fault Energy ◽

Sharp Peak ◽

Weak Beam ◽

Partial Dislocations ◽

Deviation Parameter ◽

Beam Diffraction

The main features of weak beam images of dislocations were first described by Cockayne et al. using calculations of intensity profiles based on the kinematical and two beam dynamical theories. The feature of weak beam images which is of particular interest in this investigation is that intensity profiles exhibit a sharp peak located at a position very close to the position of the dislocation in the crystal. This property of weak beam images of dislocations has an important application in the determination of stacking fault energy of crystals. This can easily be done since the separation of the partial dislocations bounding a stacking fault ribbon can be measured with high precision, assuming of course that the weak beam relationship between the positions of the image and the dislocation is valid. In order to carry out measurements such as these in practice the specimen must be tilted to "good" weak beam diffraction conditions, which implies utilizing high values of the deviation parameter Sg.

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Digital differential hysteresis iimage processing displays what the microscope acquires but the eye can't see

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100139585 ◽

1995 ◽

Vol 53 ◽

pp. 642-643

Author(s):

Klaus-Ruediger Peters

Keyword(s):

Image Processing ◽

Visual System ◽

High Precision ◽

Image Data ◽

Processing Technology ◽

Output Data ◽

Contrast Resolution ◽

Pixel Intensity ◽

Data Reading ◽

Hysteresis Properties

Differential hysteresis processing is a new image processing technology that provides a tool for the display of image data information at any level of differential contrast resolution. This includes the maximum contrast resolution of the acquisition system which may be 1,000-times higher than that of the visual system (16 bit versus 6 bit). All microscopes acquire high precision contrasts at a level of <0.01-25% of the acquisition range in 16-bit - 8-bit data, but these contrasts are mostly invisible or only partially visible even in conventionally enhanced images. The processing principle of the differential hysteresis tool is based on hysteresis properties of intensity variations within an image.Differential hysteresis image processing moves a cursor of selected intensity range (hysteresis range) along lines through the image data reading each successive pixel intensity. The midpoint of the cursor provides the output data. If the intensity value of the following pixel falls outside of the actual cursor endpoint values, then the cursor follows the data either with its top or with its bottom, but if the pixels' intensity value falls within the cursor range, then the cursor maintains its intensity value.

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