Measurement of Five DOF Motion Errors in the Ultra Precision Feed Tables

Five degrees-of-freedom (DOF) motion errors of an ultra precision feed table were measured in this study. The laser interferometer was used to measure the yaw and pitch errors and the reversal method was used for the roll error measurement. The linear motion errors in the vertical and horizontal directions were measured using the sequential two point method. The influence of angular motion errors on the linear motion errors while applying the sequential two point method was compensated with the data from the laser interferometer and the reversal method. Capacitive type sensors and an optical straight edge were used while applying the reversal method and the sequential two point method. To demonstrate the effectiveness of our measuring scheme for the ultra precision feed tables, five DOF motion errors of a hydrostatic table driven by a linear motor were measured and presented. From the measured repeatabilities of 5 DOF error motions, it was estimated that the measuring accuracies were ±0.02 μm for the horizontal and vertical linear motion, ±0.04 arcsec for yaw motion, ±0.05 arcsec for pitch motion and ±0.02 arcsec for roll motion.

Download Full-text

INTRODUCTION TO OPERATIONS OF A HIGH-RESOLUTION ACOUSTIC CAMERA ON CRABSTER CR200 AND APPLICATIONS

Jurnal Teknologi ◽

10.11113/jt.v74.4810 ◽

2015 ◽

Vol 74 (9) ◽

Author(s):

JIn-Yeong Park ◽

Hyuk Baek ◽

Hyungwon Shim ◽

Bong-Huan Jun ◽

Pan-Mook Lee

Keyword(s):

High Resolution ◽

Degrees Of Freedom ◽

Current Flow ◽

Good Alternative ◽

Water Current ◽

Roll Motion ◽

Turbid Water ◽

Pitch Motion ◽

Image Objects ◽

Dimensional Reconstruction

This paper describes operations of a high-resolution multi-beam acoustic camera installed on Crabster200 (shortened to CR200) and application researches. The CR200 is a new type of ROVs having six artificial legs driven by BLDC motors. The robot thrusts itself using the legs on seafloor and controls its body posture and attitude. Each leg has four degrees of freedom. And the robot is supposed to inspect and work in fast current flow and turbid water where visibility is very low. The name of “Crabster” came from a combination of crab and lobster because the CR200 imitates behaviors of the two creatures to keep its position against water current flow. In turbid water, performance of typical optical cameras is limited and fails. Therefore, in this case, the acoustic camera can be a good alternative to image objects of interest using acoustic beams. The CR200 is equipped with high-resolution acoustic camera using 3M Hz frequency obtaining maximum 2.9 mm resolution with a rotation which provides two degrees of freedom; roll motion and pitch motion. Yaw motion cannot be provided by the rotator. Then, the CR200 have to rotate its body in place to obtain yaw motion. From these roll motion, pitch motion and yaw motion with image processing, we extract and derive depth perception, 3-dimensional reconstruction and mosaicking, respectively. In this paper, we introduce practical uses of the acoustic camera in offshore and water basin and its application researches. The authors have tried to verify the performance of CR200 as an actively adaptable underwater mobile observant platform.

Download Full-text

Model and Measurement Method of Optical Nonlinearities Caused by the Heterodyne and Homodyne Interference Terms in the Heterodyne Interferometer

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.613.58 ◽

2014 ◽

Vol 613 ◽

pp. 58-63

Author(s):

Hai Jin Fu ◽

Jiu Bin Tan ◽

Peng Cheng Hu ◽

Zhi Gang Fan

Keyword(s):

Measurement Method ◽

Laser Interferometer ◽

Optical Nonlinearity ◽

Laser Source ◽

Optical Nonlinearities ◽

Laser Polarization ◽

Heterodyne Interferometer ◽

Optical Mixing ◽

Ultra Precision ◽

Heterodyne Laser Interferometer

The heterodyne laser interferometer is widely applied in ultra-precision displacement measurement, but its accuracy is seriously restricted by the optical nonlinearity which arises from the optical mixing in the reference and measurement arms. In an ideal heterodyne laser interferometer, the beam from the laser source consists of two orthogonally linear-polarized components with slightly different optical frequencies and the two components can be completely separated by the polarizing optics, one traverses in the reference arm, the other traverses in the measurement arm, both of them are in the form of a pure optical frequency. However, in a real heterodyne laser interferometer, due to the imperfect laser polarization, the optics defect and the misalignment, the two components of the laser beam cant be perfectly separated, therefore both of the reference arm and the measurement arm contain a portion of the two laser components, which leads to an optical mixing in the two arms of the heterodyne interferometer and causes the cyclic nonlinearity of several to tens of nanometers.

Download Full-text

Ultra-precision Machining of Micro-step Pillar Array Using a Straight-Edge Milling Tool

Nanomanufacturing and Metrology ◽

10.1007/s41871-020-00076-1 ◽

2020 ◽

Vol 3 (4) ◽

pp. 260-268

Author(s):

Kui Liu ◽

Hu Wu ◽

Rui Huang ◽

Nicholas Yew Jin Tan

Keyword(s):

Straight Edge ◽

Precision Machining ◽

Pillar Array ◽

Milling Tool ◽

Ultra Precision

Download Full-text

A 3D passive dynamic biped with yaw and roll compensation

Robotica ◽

10.1017/s0263574700003040 ◽

2001 ◽

Vol 19 (3) ◽

pp. 275-284 ◽

Cited By ~ 51

Author(s):

M. Wisse ◽

A. L. Schwab ◽

R. Q. vd. Linde

Keyword(s):

Degrees Of Freedom ◽

High Energy ◽

Roll Motion ◽

Multibody Model ◽

The Third ◽

High Energy Efficiency ◽

Dynamic Compensator ◽

Third Dimension ◽

The Stability ◽

Natural Dynamics

Autonomous walking bipedal machines, possibly useful for rehabilitation and entertainment purposes, need a high energy efficiency, offered by the concept of ‘Passive Dynamic Walking' (exploitation of the natural dynamics of the robot). 2D passive dynamic bipeds have been shown to be inherently stable, but in the third dimension two problematic degrees of freedom are introduced: yaw and roll.We propose a design for a 3D biped with a pelvic body as a passive dynamic compensator, which will compensate for the undesired yaw and roll motion, and allow the rest of the robot to move as if it were a 2D machine. To test our design, we perform numerical simulations on a multibody model of the robot. With limit cycle analysis we calculate the stability of the robot when walking at its natural speed.The simulation shows that the compensator, indeed, effectively compensates for both the yaw and the roll motion, and that the walker is stable.

Download Full-text

Research on geometric error measurement system of machining center BV75 based on laser interferometer

MATEC Web of Conferences ◽

10.1051/matecconf/20164004002 ◽

2016 ◽

Vol 40 ◽

pp. 04002 ◽

Cited By ~ 1

Author(s):

Lijuan Shi ◽

Jinying Chen ◽

Zhaokun Li ◽

Huamei Bian

Keyword(s):

Measurement System ◽

Laser Interferometer ◽

Geometric Error ◽

Error Measurement ◽

Machining Center ◽

Geometric Error Measurement

Download Full-text

Structural Analysis of a Grinding Machine with Linear Motion Guide Applied

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.336-338.1014 ◽

2013 ◽

Vol 336-338 ◽

pp. 1014-1019

Author(s):

Seon Yeol Oh ◽

Han Seok Bang ◽

B. Y. Choi ◽

Woo Chun Choi ◽

S. J. Cho

Keyword(s):

Finite Element ◽

Structural Analysis ◽

Structural Design ◽

Element Model ◽

Linear Motion ◽

Precision Grinding ◽

Base Side ◽

Ultra Precision ◽

Linear Motion Guide ◽

Grinding Machine

A finite element model of an ultra-precision grinding machine that can have high precision and high stiffness is constructed and structural analysis is done with equivalent stiffnesses of linear motion guides by after structural design and the deformation of the grinding machine is obtained. In order to reduce the deformation of the grinding machine that causes bad influence, structural complement is conducted by adding ribs at the lower part of the column. Also, the straightness of the grinding machine is improved by lifting that the base side of the column.

Download Full-text

Dynamic response of a wedge through asymmetric free fall in 2 degrees of freedom

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

10.1177/1475090217733150 ◽

2017 ◽

Vol 233 (1) ◽

pp. 229-250 ◽

Cited By ~ 4

Author(s):

Parviz Ghadimi ◽

Sasan Tavakoli ◽

Abbas Dashtimanesh ◽

Pouria Taghikhani

Keyword(s):

Experimental Data ◽

Dynamic Response ◽

Degrees Of Freedom ◽

Time Derivative ◽

Free Fall ◽

Added Mass ◽

Roll Motion ◽

Physical Parameters ◽

Two Dimensional ◽

Roll Speed

In this article, a mathematical model is presented for simulation of the coupled roll and heave motions of the asymmetric impact of a two-dimensional wedge body. This model is developed based on the added mass theory and momentum variation. To this end, new formulations are introduced which are related to the added mass caused by heave and roll motions of the wedge. These relations are developed by including the asymmetrical effects and roll speed. In addition, by considering the roll speed, a particular method is presented for the time derivative of half-wetted beam of an asymmetric wedge. Furthermore, two equations are derived for the roll and heave motions in which damping terms appear. Validity of the proposed method is verified by comparing the predicted results against available experimental data in two conditions of roll motion and no roll motion. Favorable agreement is observed between the predicted results and experimental data. The pressure and hydrodynamic load are computed, and the differences between the results associated with the considered conditions are explored. Subsequently, the effects of different physical parameters including deadrise angle, initial roll angle, and initial velocity on the dynamic response of a two-dimensional wedge section are investigated. Ultimately, time histories of hydrodynamic coefficients are determined in order to provide a better understanding of the derived equations.

Download Full-text