Analysis of alignment error in asphere testing using a corrector

2005 ◽  
Author(s):  
Donglin Xue ◽  
Ligong Zheng ◽  
Xuejun Zhang
Keyword(s):  
Alignment Error

scholarly journals Alignment-Free Sensing Module for Absolute and Incremental Lines in Linear Positioning System Based on Tunneling-Magnetoresistance Sensors

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4137
Author(s):  
Chia-Chang Lee ◽  
Yu-Shen Yen ◽  
Chih-Huang Lai
Keyword(s):  
Thin Film Deposition ◽  
Film Deposition ◽  
Alignment Error ◽  
Positioning System ◽  
Large Signal ◽  
Detection Scheme ◽  
Alignment Free ◽  
Reference Layer ◽  
Working Distance ◽  
Incremental Lines

An alignment-free sensing module for the positioning system based on tunneling magnetoresistive (TMR) sensors with an absolute-incremental-integrated scale is demonstrated. The sensors of the proposed system for both lines consist of identical layer stacks; therefore, all sensors can be fabricated in identical processes from thin film deposition to device patterning on a single substrate. Consequently, the relative position of the sensors can be predefined at the lithography stage and the alignment error between sensors caused by the manual installation is completely eliminated. Different from the existing sensing scheme for incremental lines, we proposed to utilize the magnetic tunnel junctions with a perpendicular anisotropy reference layer and an in-plane anisotropy sensing layer. The sensors are placed parallel to the scale plane with magnetization of the sensing layer in the plane, which show the capability of polarity detection for the absolute line and reveal sinusoidal output signal for the incremental line. Furthermore, due to the large signal of TMR, the working distance can be further improved compared with conventional sensors. In addition, the cost of the positioning system is expected to be lowered, since all the sensors are fabricated in the same process without extra installation. Our design may pave a new avenue for the positioning system based on a magnetic detection scheme.

scholarly journals Target alignment in the Shen-Guang II Upgrade laser facility

2018 ◽  
Vol 6 ◽  
Author(s):  
Lei Ren ◽  
Ping Shao ◽  
Dongfeng Zhao ◽  
Yang Zhou ◽  
Zhijian Cai ◽  
...  
Keyword(s):  
Inertial Confinement Fusion ◽  
Short Pulse ◽  
Three Dimensional ◽  
Nanosecond Laser ◽  
Alignment Error ◽  
Inertial Confinement ◽  
Pulse Beam ◽  
Rotation Sensor ◽  
Confinement Fusion ◽  
Laser Facility

The Shen-Guang II Upgrade (SG-II-U) laser facility consists of eight high-power nanosecond laser beams and one short-pulse picosecond petawatt laser. It is designed for the study of inertial confinement fusion (ICF), especially for conducting fast ignition (FI) research in China and other basic science experiments. To perform FI successfully with hohlraum targets containing a golden cone, the long-pulse beam and cylindrical hohlraum as well as the short-pulse beam and cone target alignment must satisfy tight specifications (30 and $20~\unicode[STIX]{x03BC}\text{m}$ rms for each case). To explore new ICF ignition targets with six laser entrance holes (LEHs), a rotation sensor was adapted to meet the requirements of a three-dimensional target and correct beam alignment. In this paper, the strategy for aligning the nanosecond beam based on target alignment sensor (TAS) is introduced and improved to meet requirements of the picosecond lasers and the new six LEHs hohlraum targets in the SG-II-U facility. The expected performance of the alignment system is presented, and the alignment error is also discussed.

scholarly journals The Estimation of Angular Misalignments for Ultra Short Baseline Navigation Systems. Part II: Experimental Results

2013 ◽  
Vol 66 (5) ◽  
pp. 773-787 ◽  
Author(s):  
Hsin-Hung Chen
Keyword(s):  
Trial Data ◽  
Experimental Results ◽  
Experimental Result ◽  
Alignment Error ◽  
Navigation Systems ◽  
Analytical Prediction ◽  
Short Baseline ◽  
Sea Trial ◽  
Alignment Errors ◽  
Cross Track

An algorithm of alignment calibration for Ultra Short Baseline (USBL) navigation systems was presented in the companion work (Part I). In this part (Part II) of the paper, this algorithm is tested on the sea trial data collected from USBL line surveys. In particular, the solutions to two practical problems referred to as heading deviation and cross-track error in the USBL line survey are presented. A field experiment running eight line surveys was conducted to collect USBL positioning data. The numerical results for the sea trial data demonstrated that the proposed algorithm could robustly and effectively estimate the alignment errors. Comparisons of the experimental result with the analytical prediction of roll misalignment estimation in Part I is drawn, showing good agreement. The experimental results also show that an inappropriate estimation of roll alignment error will significantly degrade the quality of estimations of heading and pitch alignment errors.

scholarly journals Fault Reconstruction Approach for Distributed Coordinated Spacecraft Attitude Control System

2015 ◽  
Vol 2015 ◽  
pp. 1-9
Author(s):  
Mingyi Huo ◽  
Yanning Guo ◽  
Xing Huo
Keyword(s):  
Control System ◽  
Attitude Control ◽  
Large Scale ◽  
Sliding Mode ◽  
Reconstruction Error ◽  
Spacecraft Attitude ◽  
Alignment Error ◽  
Spacecraft Attitude Control ◽  
Attitude Control System ◽  
Fault Reconstruction

This work presents a novel fault reconstruction approach for a large-scale system, that is, a distributed coordinated spacecraft attitude control system. The attitude of all the spacecrafts in this distributed system is controlled by using thrusters. All possible faults of thruster including thrust magnitude error and alignment error are investigated. As a stepping stone, the mathematical model of thruster is firstly established based on the thruster configuration. On the basis of this, a sliding mode observer is then proposed to reconstruct faults in each agent of the coordinated control system. A Lyapunov-based analysis shows that the observer asymptotically converges to the actual faults. The key feature of this fault reconstruction approach is that it can achieve a faster reconstruction of the fault in comparison with the conventional fault reconstruction schemes. It can globally reconstruct thruster faults with zero reconstruction error, and this is accomplished within finite time. The effectiveness of the proposed approach is analytically authenticated via simulation study.

Error Analysis by Square 3 x 3 Machining Method for Five-Axis Machining Centers

2020 ◽  
Author(s):  
Shigehiko Sakamoto ◽  
Atsushi Yokoyama ◽  
Kazumasa Nakayasu ◽  
Toshihiro Suzuki ◽  
Shinji Koike
Keyword(s):  
International Standards ◽  
Test Method ◽  
Accuracy Evaluation ◽  
Alignment Error ◽  
Machined Surface ◽  
Machining Center ◽  
Alignment Errors ◽  
Assembly Error ◽  
Five Axis ◽  
Machined Surfaces

Abstract The establishment of international standards for 5-axis control machining centers has been supported by the high interest of each country. Internationally, various accuracy inspection methods have been proposed and widely discussed. Accuracy measuring devices for these purposes have also been proposed. In 2014, inspection methods for 5-axis machines were published in ISO 10791-6 and 10791-7. In this research, we propose a test method to process 9 square faces as a new accuracy evaluation method. We simulate the influence of assembly error by the proposed square 3 × 3 machining method on the machined surface. By processing 9 square faces with different tool angle on the same plane, it was possible to evaluate the influence of assembly errors in the 5-axis machining center on the machined surface. Nine surfaces machined by the square 3 × 3 processing method cause differences in surface height due to alignment errors. In addition, nine machined surfaces become all diagonal not parallelism. The alignment errors of the 5-axis machining center is identified by evaluating the orientation of the machined surfaces. Specifically, we propose a newly method to measure the height difference of nine surfaces. Then, the possibility of identifying the alignment error of the 5-axis machining center using the measurement results is shown.

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