Strapdown Optical Seeker Guidance Instructions Extraction and System Stability

2013 ◽  
Vol 397-400 ◽  
pp. 1357-1361
Author(s):  
Yue Zhang
Keyword(s):  
Optical Imaging ◽  
Angular Rate ◽  
Extraction Methods ◽  
Stability Control ◽  
Scale Factor ◽  
System Stability ◽  
Line Of Sight ◽  
Full Field ◽  
Free Running ◽  
Definition Of

In order to realize the guidance and control of the flight system, we focused on the study of different guidance instructions extraction methods and system stability control problems with respect to the characteristics of full-strapdown optical imaging seeker. First, we established the model of strapdown optical imaging seeker and introduced the definition of scale factor and the theoretical compute formula. Then the full field of view accuracy of full-strapdown optical imaging seeker was gained through the experiment and the validity of the scale factor definition has been tested and verified. Finally, we analyzed the system stabilities of different guidance instructions extraction methods. The results showed that if we applied the line of sight angular rate (LOS angular rate) to the system, the scale factor error was 5% when the free-running frequency of the overload autopilot was 20rad/s, and the scale factor error was 8.4% when the free-running frequency was 10rad/s. And if we applied the line of sight angle (LOS angle) to the system, the scale factor error was 33.3%, irrelevant to the free-running frequency. This analysis laid a foundation of guidance application..

scholarly journals Stability and Manoeuvrability Simulation of a Semi-Autonomous Submarine Free-Running Model SUBOFF with an Autopilot System

2021 ◽  
Vol 11 (1) ◽  
pp. 410
Author(s):  
Yu-Hsien Lin ◽  
Yu-Ting Lin ◽  
Yen-Jun Chiu
Keyword(s):  
Optimal Control ◽  
Experimental Tests ◽  
Degree Of Freedom ◽  
Line Of Sight ◽  
Pd Controller ◽  
Free Running ◽  
Simulation Results ◽  
Guidance Algorithm ◽  
Logic Operations ◽  
Six Degree Of Freedom

On the basis of a full-appendage DARPA SUBOFF model (DTRC model 5470), a scale (λ = 0.535) semi-autonomous submarine free-running model (SFRM) was designed for testing its manoeuvrability and stability in the constrained water. Prior to the experimental tests of the SFRM, a six-degree-of-freedom (6-DOF) manoeuvre model with an autopilot system was developed by using logic operations in MATLAB. The SFRM’s attitude and its trim polygon were presented by coping with the changes in mass and trimming moment. By adopting a series of manoeuvring tests in empty tanks, the performances of the SFRM were introduced in cases of three sailing speeds. In addition, the PD controller was established by considering the simulation results of these manoeuvring tests. The optimal control gains with respect to each manoeuvring test can be calculated by using the PID tuner in MATLAB. Two sets of control gains derived from the optimal characteristics parameters were compared in order to decide on the most appropriate PD controller with the line-of-sight (LOS) guidance algorithm for the SFRM in the autopilot simulation. Eventually, the simulated trajectories and course angles of the SFRM would be illustrated in the post-processor based on the Cinema 4D modelling.

Study on Improving Power System Damping by Using DPFC

2014 ◽  
Vol 986-987 ◽  
pp. 1286-1290
Author(s):  
Jin Li ◽  
Ya Min Pi ◽  
Hui Yuan Yang
Keyword(s):  
Power System ◽  
Power Flow ◽  
Transient Stability ◽  
Stability Control ◽  
System Stability ◽  
Single Machine Infinite Bus ◽  
Formula Derivation ◽  
Object Of Study ◽  
Power System Oscillations ◽  
Distributed Power Flow

In this paper, the series converters of Distributed Power Flow Controller are the main object of study. Its mechanism of suppressing power system oscillations is studied by theoretical analysis and formula derivation, which relies on a single-machine infinite-bus power system, installed the series converters. Then based on the mechanism, adopting the classic PI control and the damping controller, designed the transient stability control loop for the series converters. Finally, simulations performed by PSCAD/EMTDC, the results show that DPFC device can effectively suppress oscillation and improve system stability.

scholarly journals Separation of cortical arteries and veins in optical neurovascular imaging

2014 ◽  
Vol 07 (03) ◽  
pp. 1350069 ◽  
Author(s):  
Linna Zhao ◽  
Yao Li ◽  
Hongyang Lu ◽  
Lu Yuan ◽  
Shanbao Tong
Keyword(s):  
Cerebral Cortex ◽  
Optical Imaging ◽  
Signal To Noise Ratio ◽  
Vascular Diseases ◽  
Region Growing ◽  
Field Method ◽  
Laser Speckle ◽  
Cerebral Vessel ◽  
Full Field ◽  
Arteries And Veins

Separation of arteries and veins in the cerebral cortex is of significant importance in the studies of cortical hemodynamics, such as the changes of cerebral blood flow, perfusion or oxygen concentration in arteries and veins under different pathological and physiological conditions. Yet the cerebral vessel segmentation and vessel-type separation are challenging due to the complexity of cortical vessel characteristics and low spatial signal-to-noise ratio. In this work, we presented an effective full-field method to differentiate arteries and veins in cerebral cortex using dual-modal optical imaging technology including laser speckle imaging (LSI) and optical intrinsic signals (OIS) imaging. The raw contrast images were acquired by LSI and processed with enhanced laser speckle contrast analysis (eLASCA) algorithm. The vascular pattern was extracted and segmented using region growing algorithm from the eLASCA-based LSI. Meanwhile, OIS images were acquired alternatively with 630 and 870 nm to obtain an oxyhemoglobin concentration map over cerebral cortex. Then the separation of arteries and veins was accomplished by Otsu threshold segmentation algorithm based on the OIS information and segmentation of LSI. Finally, the segmentation and separation performances were assessed using area overlap measure (AOM). The segmentation and separation of cerebral vessels in cortical optical imaging have great potential applications in full-field cerebral hemodynamics monitoring and pathological study of cerebral vascular diseases, as well as in clinical intraoperative monitoring.

A Simulation Survey on the Effects of Progressing Faults Within the SCAS of a Flight Control Actuator for Helicopters

2021 ◽  
Author(s):  
Andrea De Martin ◽  
Giovanni Jacazio ◽  
Massimo Sorli ◽  
Giuseppe Vitrani
Keyword(s):  
Flight Control ◽  
Health Management ◽  
Risk Mitigation ◽  
Selection Process ◽  
Stability Control ◽  
Features Selection ◽  
Vertical Walls ◽  
Low Altitude ◽  
Definition Of ◽  
Rotary Wing

Abstract Stability Control Augmentation Systems (SCAS) are widely adopted to enhance the flight stability of rotary-wing aircraft operating in difficult aerodynamic conditions, such as low altitude missions, stationary flight nearby vertical walls or in presence of heavy gusts. Such systems are based upon small electro-hydraulic servosystems controlled in position through a dedicated servovalve. The SCAS operates with limited authority over the main control linkage translating the pilot input in the movement of the main flight control actuator. Being critical for the operability of the helicopter, the definition of a Prognostics and Health Management (PHM) framework for the SCAS systems would provide significant advantages, such as better risk mitigation, improved availability, and a reduction in the occurrences of unpredicted failures which still represent one of the most known downsides of helicopters. This paper provides the results of a preliminary analysis on the effects of the inception and progression of several degradation types within a simulated SCAS system. Signals usually available within such devices are hence combined with measurements provided by additional sensors to check the feasibility of a PHM system with and without dedicated sensors. The resulting features selection process shows that although the dedicated measurements are required to design a complete PHM system, it appears nonetheless possible to obtain valuable information on the health status of the SCAS system without resorting to additional sensors.

Image evaluation and breast density categories as a function of mammary positioning in full-field digital mammography

2019 ◽  
Vol 61 (7) ◽  
pp. 868-874
Author(s):  
Irene Tomoko Nakano ◽  
Gabriel Lucca de Oliveira Salvador ◽  
Hugo Reuters Schelin ◽  
Valeriy Denyak ◽  
Helen Jamil Khoury ◽  
...  
Keyword(s):  
Breast Density ◽  
Area Under The Curve ◽  
Quality Criteria ◽  
Roc Curves ◽  
Full Field ◽  
European Guidelines ◽  
Full Field Digital Mammography ◽  
Definition Of ◽  
The Individual ◽  
The Right

Background Appropriate mammary positioning is an important factor in optimizing image quality in mammography (MMG). Purpose To study the correlation of quality criteria and breast density classification proposed by the American College of Radiology (ACR) and European Guidelines and its influence to achieve a proper positioning, therefore an adequate MMG. Material and methods A total of 128 routine MMG examinations were reviewed for the definition of breast composition parenchyma and assessment of several quality criteria proposed by the ACR and European Guidelines to achieve an adequate MMG. Adequate MMG was defined as a difference between the posterior nipple line (PNL), difference of the mediolateral oblique (MLO) and craniocaudal (CC) incidences > 1 cm. The quality criteria were analyzed as a function of correlation coefficient in order to evaluate the individual impact of each factor and analysis of variance (ANOVA) for all criteria. Receiver operating characteristic (ROC) curves were plotted to evaluate the performance of the criteria on each type of parenchyma. Results Negative correlation of fatty breasts and visibility of the mammary angle, a greater number of skin folds and PNL > 1 cm (r < 0). Dense MMG presented less visibility of the lateral tissue compared with other categories. Area under the curve of ROC analysis revealed values of 53.1% and 54.7% for the right and left breasts, respectively. Conclusion Several factors influenced in the MMG process, but we find that breast parenchyma has a substantial role in affecting these criteria and therefore a correct position for diagnosis, which could compromise MMG diagnostic performance.

scholarly journals Controllers to Chase a High-Speed Evader Using a Pursuer with Variable Speed

2018 ◽  
Vol 8 (10) ◽  
pp. 1976 ◽  
Author(s):  
Jonghoek Kim
Keyword(s):  
Optical Flow ◽  
High Speed ◽  
Angular Rate ◽  
Relative Distance ◽  
Line Of Sight ◽  
Terminal Phase ◽  
Relative Speed ◽  
Variable Speed

This paper proposes a chasing controller to enable a pursuer to chase a high-speed evader such that the relative distance between the evader and the pursuer monotonically decreases as time passes. Our controller is designed to assure that the angular rate of Line-of-Sight joining the pair (the pursuer and the evader) is exactly zero at all time indexes. Assuming that the pursuee can readily observe optical flow, but only poorly detect looming, this pursuer’s movement is hardly detected by the pursuee. Consider the terminal phase when the pursuer is sufficiently close to the evader. As we slow down the relative speed of the pursuer with respect to the evader, we can reduce the probability of missing the high-speed evader. Thus, our strategy is to make the pursuer decrease its speed in the terminal phase, while ensuring that the distance between the evader and the pursuer monotonically decreases as time passes. The performance of our controller is verified utilizing MATLAB simulations.

scholarly journals From Social Ties to Network Processes: Do Tie Definitions Matter?

2018 ◽  
Vol 5 (2) ◽  
Author(s):  
Ed Fincham ◽  
Dragan Gašević ◽  
Abelardo Pardo
Keyword(s):  
Learning Environments ◽  
Social Ties ◽  
Large Body ◽  
Extraction Methods ◽  
Future Research ◽  
Learning Technology ◽  
Discussion Forums ◽  
Methodological Choices ◽  
E Learning ◽  
Definition Of

The widespread adoption of digital e-learning environments and other learning technology has provided researchers with ready access to large quantities of data. Much of this data comes from discussion forums and has been studied with analytical methods drawn from social network analysis. However, within this large body of research there exists considerable variation in the definition of what constitutes a social tie, and the consequences of this choice are rarely described or examined. This paper presents findings from two distinct learning environments regarding different social tie extraction methods and their influence on the structural and statistical properties of the induced networks, and the association between measures of centrality and academic performance. Our findings indicate that social tie definitions play an important role in shaping the results of our analyses. The primary purpose of this paper is to raise awareness of the consequences that such methodological choices may have, and to promote transparency in future research.

scholarly journals Calibration of a Multichannel Water Vapor Raman Lidar through Noncollocated Operational Soundings: Optimization and Characterization of Accuracy and Variability

2010 ◽  
Vol 27 (1) ◽  
pp. 108-121 ◽  
Author(s):  
Davide Dionisi ◽  
Fernando Congeduti ◽  
Gian Luigi Liberti ◽  
Francesco Cardillo
Keyword(s):  
Water Vapor ◽  
National Research Council ◽  
Calibration Procedure ◽  
System Stability ◽  
Calibration Coefficient ◽  
Spatial And Temporal Variability ◽  
Raman Lidar ◽  
Measurement Session ◽  
Definition Of ◽  
Water Vapor Mixing Ratio

Abstract This paper presents a parametric automatic procedure to calibrate the multichannel Rayleigh–Mie–Raman lidar at the Institute for Atmospheric Science and Climate of the Italian National Research Council (ISAC-CNR) in Tor Vergata, Rome, Italy, using as a reference the operational 0000 UTC soundings at the WMO station 16245 (Pratica di Mare) located about 25 km southwest of the lidar site. The procedure, which is applied to both channels of the system, first identifies portions of the lidar and radiosonde profiles that are assumed to sample the same features of the water vapor profile, taking into account the different time and space sampling. Then, it computes the calibration coefficient with a best-fit procedure, weighted by the instrumental errors of both radiosounding and lidar. The parameters to be set in the procedure are described, and values adopted are discussed. The procedure was applied to a set of 57 sessions of nighttime 1-min-sampling lidar profiles (roughly about 300 h of measurements) covering the whole annual cycle (February 2007–September 2008). A calibration coefficient is computed for each measurement session. The variability of the calibration coefficients (∼10%) over periods with the same instrumental setting is reduced compared to the values obtained with the previously adopted, operator-assisted, and time-consuming calibration procedure. Reduction of variability, as well as the absence of evident trends, gives confidence both on system stability as well as on the developed procedure. Because of the definition of the calibration coefficient and of the different sampling between lidar and radiosonde, a contribution to the variability resulting from aerosol extinction and to the spatial and temporal variability of the water vapor mixing ratio is expected. A preliminary analysis aimed at identifying the contribution to the variability from these factors is presented. The parametric nature of the procedure makes it suitable for application to similar Raman lidar systems.

Reservoir to market: generating project value by coupling surface facilities with reservoir data in integrated asset modelling

2017 ◽  
Vol 57 (2) ◽  
pp. 652
Author(s):  
Stephen Stokes
Keyword(s):  
Supply Chain ◽  
Development Planning ◽  
Cutting Edge ◽  
Concept Design ◽  
Full Spectrum ◽  
Full Field ◽  
Field Development ◽  
Cost Reductions ◽  
Definition Of ◽  
Assessing Sensitivity

Reservoir to market is a cutting-edge integrated asset modelling (IAM) initiative that is deployed to deliver robust field development and concept design solutions with enhanced project economics. The approach offers the potential to identify supply-chain cost reductions across the full spectrum of upstream developments, from full field development planning to individual equipment item modification. The process offers particular value in Greenfield and Brownfield development planning, in identifying and assessing sensitivity options and in definition of the optimum concept.

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