Impact of detector position accuracy on the MTF measurement of optical lenses

2021 ◽  
Author(s):  
Simone Fohrmann ◽  
Patrik Erichsen ◽  
Markus Schake ◽  
Michael Schulz
Keyword(s):  
Position Accuracy ◽  
Detector Position

scholarly journals RTLIO: Real-Time LiDAR-Inertial Odometry and Mapping for UAVs

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 3955
Author(s):  
Jung-Cheng Yang ◽  
Chun-Jung Lin ◽  
Bing-Yuan You ◽  
Yin-Long Yan ◽  
Teng-Hu Cheng
Keyword(s):  
Feedback Control ◽  
Real Time ◽  
High Frequency ◽  
Indoor Environment ◽  
Indoor Localization ◽  
Sampling Rate ◽  
Outdoor Environment ◽  
Position Accuracy ◽  
Graph Optimization ◽  
Pose Graph Optimization

Most UAVs rely on GPS for localization in an outdoor environment. However, in GPS-denied environment, other sources of localization are required for UAVs to conduct feedback control and navigation. LiDAR has been used for indoor localization, but the sampling rate is usually too low for feedback control of UAVs. To compensate this drawback, IMU sensors are usually fused to generate high-frequency odometry, with only few extra computation resources. To achieve this goal, a real-time LiDAR inertial odometer system (RTLIO) is developed in this work to generate high-precision and high-frequency odometry for the feedback control of UAVs in an indoor environment, and this is achieved by solving cost functions that consist of the LiDAR and IMU residuals. Compared to the traditional LIO approach, the initialization process of the developed RTLIO can be achieved, even when the device is stationary. To further reduce the accumulated pose errors, loop closure and pose-graph optimization are also developed in RTLIO. To demonstrate the efficacy of the developed RTLIO, experiments with long-range trajectory are conducted, and the results indicate that the RTLIO can outperform LIO with a smaller drift. Experiments with odometry benchmark dataset (i.e., KITTI) are also conducted to compare the performance with other methods, and the results show that the RTLIO can outperform ALOAM and LOAM in terms of exhibiting a smaller time delay and greater position accuracy.

NC Machine Position Accuracy Testing and NC System Error Compensation Analysis

2011 ◽  
Vol 130-134 ◽  
pp. 2316-2320
Author(s):  
Ke Zhang ◽  
Zheng Xing Cui ◽  
Li Ya Gai ◽  
Peng Ge ◽  
Dong Gao Cai
Keyword(s):  
Error Compensation ◽  
Laser Interferometer ◽  
Machining Accuracy ◽  
Nc System ◽  
Accuracy Requirement ◽  
Position Accuracy ◽  
Nc Machine ◽  
Nc Machine Tools ◽  
Processing Accuracy ◽  
Modern Manufacturing

NC machine plays an irreplaceable role in the modern manufacturing because of its high machining processing accuracy, quality stable, flexibility. Through using the Renishaw ML10 laser interferometer detect the positioning accuracy and repositioning accuracy of X axis and Z axis of the HTC20 series of NC machine tools. According to the detection result compensate NC system to meet the machining accuracy requirement. The result shows that the error compensation of NC system is a effective method to improve the position accuracy of NC machine.

scholarly journals Evolutionary Algorithm-Based Friction Feedforward Compensation for a Pneumatic Rotary Actuator Servo System

2018 ◽  
Vol 8 (9) ◽  
pp. 1623 ◽  
Author(s):  
Ke Li ◽  
Yeming Zhang ◽  
Shaoliang Wei ◽  
Hongwei Yue
Keyword(s):  
Differential Evolution ◽  
Evolutionary Algorithm ◽  
Differential Evolution Algorithm ◽  
Servo System ◽  
Control Architecture ◽  
Tracking Accuracy ◽  
Pd Control ◽  
Compensation Control ◽  
Position Accuracy ◽  
Rotary Actuator

The friction interference in the pneumatic rotary actuator is the primary factor affecting the position accuracy of a pneumatic rotary actuator servo system. The paper proposes an evolutionary algorithm-based friction-forward compensation control architecture for improving position accuracy. Firstly, the basic equations of the valve-controlled actuator are derived and linearized in the middle position, and the transfer function of the system is further obtained. Then, the evolutionary algorithm-based friction feedforward compensation control architecture is structured, including that the evolutionary algorithm is used to optimize the controller coefficients and identify the friction parameters. Finally, the contrast experiments of four control strategies (the traditional PD control, the PD control with friction feedforward compensation without evolutionary algorithm tuning, the PD control with friction feedforward compensation based on the differential evolution algorithm, and the PD control with friction feedforward compensation based on the genetic algorithm) are carried out on the experimental platform. The experimental results reveal that the evolutionary algorithm-based friction feedforward compensation greatly improves the position tracking accuracy and positioning accuracy, and that the differential evolution-based case achieves better accuracy. Also, the system with the friction feedforward compensation still maintains high accuracy and strong stability in the case of load.

VMAT monthly QA using two techniques: 2D ion chamber array with an isocentric gantry mount and an in vivo dosimetric device attached to gantry

2013 ◽  
Vol 13 (2) ◽  
pp. 240-246 ◽  
Author(s):  
P. Myers ◽  
S. Stathakis ◽  
C. Buckey ◽  
N. Papanikolaou
Keyword(s):  
Dose Rate ◽  
Volumetric Modulated Arc Therapy ◽  
Field Measurements ◽  
Rate Variation ◽  
Speed Variation ◽  
Ion Chamber ◽  
Position Accuracy ◽  
Picket Fence ◽  
Isocentric Gantry

AbstractPurposeVarian RapidArc is a volumetric modulated arc therapy (VMAT) that obtains a conformal dose around the desired structure by employing variable gantry speed, dose rate and dynamic multileaf collimator (DMLC) speed as the gantry rotates about machine isocenter. This study is meant to build upon previous research by Ling et al. by completing the tests with an in vivo dosimetric device attached to the linac gantry and a 2D ionisation chamber array with an isocentric gantry mount.Materials and methodsTwo PTW detectors, seven29 array with gantry mount and DAVID, were attached to the linear accelerator gantry, allowing each device to remain perpendicular to the beam at all gantry angles. Three tests for RapidArc evaluation were performed on these devices including: dose rate and gantry speed variation, DMLC speed and dose rate variation and DMLC position accuracy. The reproducibility of the arc data was also reported.ResultsA picket fence plan varying dose rates (111 to 600 MU/minute) and gantry speeds (5·5 to 4·3°/second) was delivered consisting of seven sections of different combinations. These measurements were compared with static gantry, open field measurements and found to be within 2·39% for the DAVID device and 0·84% for the seven29. A four-section picket fence of varying DMLC speeds (0·46, 0·92, 1·84 and 2·76 cm/second) was similarly evaluated and found to be within 1·99% and 3·66% for the DAVID and seven29, respectively. For DMLC position accuracy, a picket fence arc plan was compared with a static picket fence and found to agree within 0.38% and 2.91%. Reproducibility for these three RapidArc plans was found to be within 0·30% and 2·70% for the DAVID and seven29.ConclusionThe DAVID and seven29 detectors were able to perform the RapidArc quality assurance tests efficiently and accurately and the results were reproducible. Periodic verification of DMLC movement, dose rate variation and gantry speed variation relating to RapidArc delivery can be completed in a timelier manner using this equipment.

scholarly journals Position accuracy and electromyographic responses during head reposition in young adults with chronic neck pain

2010 ◽  
Vol 20 (5) ◽  
pp. 1014-1020 ◽  
Author(s):  
Chih-Hsiu Cheng ◽  
Jaw-Lin Wang ◽  
Jiu-Jenq Lin ◽  
Shwu-Fen Wang ◽  
Kwan-Hwa Lin
Keyword(s):  
Young Adults ◽  
Neck Pain ◽  
Chronic Neck Pain ◽  
Position Accuracy
Sign in / Sign up

Export Citation Format

Share Document