scholarly journals Structured H∞ Control for Spacecraft with Flexible Appendages

Entropy ◽  
2021 ◽  
Vol 23 (8) ◽  
pp. 930
Author(s):  
Yuntian Zhang ◽  
Aiping Pang ◽  
Hui Zhu ◽  
Huan Feng
Keyword(s):  
Low Frequency ◽  
Low Complexity ◽  
Performance Criteria ◽  
Solar Array ◽  
Engineering Practice ◽  
Multiple Control ◽  
H Infinity ◽  
Performance Requirements ◽  
Comprehensive Performance ◽  
Flexible Appendages

Spacecraft with large flexible appendages are characterized by multiple system modes. They suffer from inherent low-frequency disturbances in the operating environment that consequently result in considerable interference in the operational performance of the system. It is required that the control design ensures the system’s high pointing precision, and it is also necessary to suppress low-frequency resonant interference as well as take into account multiple performance criteria such as attitude stability and bandwidth constraints. Aiming at the comprehensive control problem of this kind of flexible spacecraft, we propose a control strategy using a structured H-infinity controller with low complexity that was designed to meet the multiple performance requirements, so as to reduce the project cost and implementation difficulty. According to the specific resonant mode of the system, the design strategy of adding an internal mode controller, a trap filter, and a series PID controller to the structured controller is proposed, so as to achieve the comprehensive control goals through cooperative control of multiple control modules. A spacecraft with flexible appendages (solar array) is presented as an illustrative example in which a weighted function was designed for each performance requirement of the system (namely robustness, stability, bandwidth limit, etc.), and a structured comprehensive performance matrix with multiple performance weights and decoupled outputs was constructed. A structured H-infinity controller meeting the comprehensive performance requirements is given, which provides a structured integrated control method with low complexity for large flexible systems that is convenient for engineering practice, and provides a theoretical basis and reference examples for structured H-infinity control. The simulation results show that the proposed controller gives better control performance compared with the traditional H-infinity one, and can successfully suppress the vibration of large flexible appendages at 0.12 Hz and 0.66 Hz.

scholarly journals Robust H∞ Control for the Spacecraft with Flexible Appendages

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Aiping Pang ◽  
Hui Zhu ◽  
Junjie Zhou ◽  
Zhen He ◽  
Jing Yang
Keyword(s):  
Controller Design ◽  
Flexible Structures ◽  
Solar Array ◽  
Attitude Stability ◽  
Performance Requirements ◽  
Performance Matrix ◽  
Oscillation Suppression ◽  
Comprehensive Performance ◽  
Pointing Accuracy ◽  
Flexible Appendages

Aiming at the oscillation suppression of spacecraft with large flexible appendages, we propose a control strategy using H∞ control. The weighting functions are designed for the specific flexible modes of the spacecraft and the frequency of harmonic interference in its operating environment. Taking into account the structural uncertainty of systematic modeling and the comprehensive performance requirements of system bandwidth constraint and attitude stability, the H∞ comprehensive performance matrix is constructed. A space telescope with a large flexible solar array is presented as an illustrative example, and a control design that meets the requirement for pointing accuracy is proposed. The simulation results show that the designed controller satisfies the requirements of attitude stability and high pointing accuracy and has effectively suppressed the disturbance of endemic frequency. The design scheme and selection method of the weight function shown in this paper can be a reference for the controller design for oscillation suppression of this type of spacecraft with flexible structures.

scholarly journals Design framework for a seamless smart glove using a digital knitting system

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Yewon Song ◽  
Seulah Lee ◽  
Yuna Choi ◽  
Sora Han ◽  
Hyuna Won ◽  
...  
Keyword(s):  
Systematic Approach ◽  
Performance Criteria ◽  
Wearable Electronics ◽  
Design Development ◽  
Performance Requirements ◽  
Development Framework ◽  
Promising Strategy ◽  
Cad Cam ◽  
Wearable Electronic ◽  
Electronic Textile

AbstractThe wearable electronics integrated with textile-based devices is a promising strategy to meet the requirements of human comfort as well as electrical performances. This research presents a design and development framework for a seamless glove sensor system using digital knitting fabrication. Based on the performance requirements of glove sensors for controlling a prosthetic hand, desirable design components include electrical conductivity, comfort, formfit, electrical sensitivity, and customizable design. These attributes are determined and achieved by applying appropriate materials and fabrication technologies. In this study, a digital knitting CAD/CAM system is utilized to meet the desired performance criteria, and two prototypes of the seamless glove sensor systems are successfully developed for the detection of both human and robotic finger motions. This digital knitting system will provide considerable potential for customized design development as well as a sustainable production process. This structured, systematic approach could be adapted in the future development of wearable electronic textile systems.

Automated simulation techniques for uncovering high-performance bioinspired cellular structures under blast loads

2021 ◽  
pp. 109963622110204
Author(s):  
Abdallah Ghazlan ◽  
Tuan Ngo ◽  
Tay Son Le ◽  
Tu Van Le
Keyword(s):  
Energy Dissipation ◽  
Trabecular Bone ◽  
Reaction Force ◽  
Blast Loading ◽  
Performance Criteria ◽  
Superior Performance ◽  
Cellular Structures ◽  
Design Parameters ◽  
Engineering Practice ◽  
Automated Simulation

Trabecular bone possesses a complex hierarchical structure of plate- and strut-like elements, which is analogous to structural systems encountered in engineering practice. In this work, key structural features of trabecular bone are mimicked to uncover effective energy dissipation mechanisms under blast loading. To this end, several key design parameters were identified to develop a bone-like unit cell. A computer script was then developed to automatically generate bone-like finite element models with many combinations of these design parameters, which were simulated under blast loading. The optimal structure was identified and its performance was benchmarked against traditional engineered cellular structures, including those with hexagonal, re-entrant and square cellular geometries. The bone-like structure showed superior performance over its engineered counterparts using the peak transmitted reaction force and energy dissipation as the key performance criteria.

scholarly journals Low-Complexity Decentralized Active Damping of One-Dimensional Structures

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Petr Hušek ◽  
Filip Svoboda ◽  
Martin Hromčík ◽  
Zbyněk Šika
Keyword(s):  
Damping Ratio ◽  
Stability Margin ◽  
Low Complexity ◽  
Active Damping ◽  
Fine Tuning ◽  
Control Performance ◽  
Control Laws ◽  
H Infinity ◽  
One Dimensional ◽  
Mu Synthesis

In the paper, we propose distributed feedback control laws for active damping of one-dimensional mechanical structures equipped with dense arrays of force actuators and position and velocity sensors. We consider proportional position and velocity feedback from the neighboring nodes with symmetric gains. Achievable control performance with respect to stability margin and damping ratio is discussed. Compared to full-featured complex controllers obtained by modern design methods like LQG, H-infinity, or mu-synthesis, these simplistic controllers are more suitable for experimental fine tuning and are less case-dependent, and they shall be easier to implement on the target future smart-material platforms.

Coarse graining spectral analysis of HR and BP variability in patients with autonomic failure

1996 ◽  
Vol 271 (4) ◽  
pp. H1555-H1564 ◽  
Author(s):  
A. P. Blaber ◽  
R. L. Bondar ◽  
R. Freeman
Keyword(s):  
Heart Rate ◽  
Autonomic Failure ◽  
Spectral Power ◽  
Low Frequency ◽  
Coarse Graining ◽  
Low Complexity ◽  
System Response ◽  
High Signal ◽  
Neural Input ◽  
Signal Complexity

We examined heart rate and blood pressure variability (HRV and BPV) during graded tilt (5 min in each position: supine, -10 degrees, 10 degrees, 30 degrees, 60 degrees, -10 degrees, supine) in autonomic failure patients and age-matched controls. Heart rate was not different between patients and controls and increased with tilt (P < 0.001). Total HRV was reduced in patients (P < 0.03). Patients had reduced low-frequency (0-0.15 Hz) HRV and BPV (P < 0.005). With tilt, low-frequency BPV increased in controls, whereas high-frequency (> 0.15 Hz) BPV increased in patients. The slope of the fractal component (beta) for HRV and BPV was not different between patients and controls. HRV-beta increased (1.5-1.9, P < 0.01) with tilt, but BPV-beta (approximately 1.8) was unaffected. Values of beta close to 1 indicate high signal regulatory complexity, and values of beta close to 2 indicate low complexity. HRV and BPV provide clear evidence of impaired sympathetic and parasympathetic autonomic nervous system response to tilt with autonomic failure. The similarity in signal complexity with reduced fractal and harmonic spectral power, in patients compared with controls, suggests unchanged cardiovascular neural input and integration with reduced output in autonomic failure.

Dynamic Modeling and Experimental Validating of Large Semi-Rigid Structures

2014 ◽  
Vol 30 (2) ◽  
pp. 193-198
Author(s):  
D.-X. Li ◽  
W. Liu ◽  
X.-Y. Sun
Keyword(s):  
Dynamic Model ◽  
Dynamic Modeling ◽  
Large Scale ◽  
Complex Structure ◽  
Low Frequency ◽  
Space Structure ◽  
Solar Array ◽  
Large Power ◽  
Stiffness Properties ◽  
Structural Weakness

ABSTRACTA new type of large semi-rigid solar array structure with a new structural concept of rigid-flexible combination has developed for space application. Due to the good features of large scale and lightweight, such structure can well satisfy to the large power requirements of spacecraft and thus has drawn increasing attention recently. However, its structural weakness of inherently flexibility makes low frequency vibrations happen much easier. It is highly required to obtain an accurate dynamic model for predicting the dynamic characteristics of this kind of semi-rigid space structure. Because this structure is composed of different components that have quite different stiffness properties respectively, it is very difficult to build up an accurate dynamic model of this complex structure. In this paper, a novel analytical dynamic model is developed for solving this problem. To validate the correctness of the proposed model, experiment studies are conducted. By comparing the simulation results with experimental results, it can be concluded that this dynamic modeling method presented in the paper is credible. The present study is significant for the structural construction and application of this special structure.

scholarly journals Degraded Image Enhancement Using Dual-Domain-Adaptive Wavelet and Improved Fuzzy Transform

2020 ◽  
Author(s):  
Yuehua Huo ◽  
Weiqiang Fan ◽  
Xiaoyu Li
Keyword(s):  
Performance Evaluation ◽  
Image Enhancement ◽  
High Frequency ◽  
Low Frequency ◽  
Original Image ◽  
Fuzzy Transform ◽  
Adaptive Wavelet ◽  
Comprehensive Performance ◽  
Degraded Image ◽  
Dual Domain

Abstract A novel enhancement algorithm of degraded image based on dual-domain-adaptive wavelet and improved fuzzy transform is proposed, aiming at the problem of surveillance videos degradation caused by complex lighting conditions underground. The dual-domain filtering (DDF) is used to decompose the image into low-frequency sub-image and high-frequency sub-images. The contrast limited adaptive histogram enhancement (CLAHE) is used to adjust the overall brightness and contrast of the low-frequency sub-image. Discrete wavelet transform (DWT) is used to obtain low frequency sub-band (LFS) and high frequency sub-band (HFS). The wavelet shrinkage threshold method based on Bayesian estimation is used to calculate the wavelet threshold corresponding to the HFS at different scales. A Garrate threshold function that introduces adaptive adjustment factor and enhancement coefficient is designed to adaptively de-noise and enhance the HFS coefficients corresponding to wavelet thresholds at different scales. Meanwhile, the gamma function is used to realize the correction of the LFS coefficients. The constructed PAL fuzzy enhancement operator is used to perform contrast enhancement and highlight area suppression on the reconstructed image to obtain an enhanced image. The proposed algorithm is evaluated by subjective vision and objective indicators. The experimental results show that the proposed algorithm can significantly improve the overall brightness and contrast of the original image, suppress noise of dust & spray, enhance the image details and improve the visual effect of the original image. Compared with the images enhanced by the STFE, GTFE, CLAHE, SSR, MSR, DGR, and MSWT algorithms, the comprehensive performance evaluation indicators of the images enhanced by the proposed algorithm are increased by 312.50%, 34.69%, 53.49%, 22.22%, 32.00%, 10.00%, 60.98%, 3.13%, respectively. At the same time, comprehensive performance evaluation indicator of the enhance image and the robustness is the best, which is more suitable for image enhancement in different mine environments.

scholarly journals Integrating detection of copy neutral chromosomal losses in a clinical setting in leukemia and lymphoma by means of allelic imbalance and read depth ratio comparison

2019 ◽  
Author(s):  
Marcus C. Hansen ◽  
Oriane Cédile ◽  
Maja Ludvigsen ◽  
Eigil Kjeldsen ◽  
Peter L. Møller ◽  
...  
Keyword(s):  
Chromosomal Aberrations ◽  
Neutral Loss ◽  
Low Frequency ◽  
Read Depth ◽  
Low Complexity ◽  
Supplementary Information ◽  
Simple Method ◽  
Exact Test ◽  
Paired Samples ◽  
Depth Ratio

AbstractChromosomal aberrations are common features of hematological malignancies, with several recurrent aberrations recognized as important diagnostic or prognostic molecular markers. While genome-wide genotyping and genomic hybridization microarray analyses have been implemented in clinical laboratories for several years the usage of next generation sequencing for detection of acquired copy number alterations has not yet reached full clinical integration. One evident problem is the identification of copy neutral loss of heterozygosity (CN-LoH), which is not detectable by sequencing read depth correlation or the analogous microarray CGH. We selected 23 paired samples of hematological disorders from 14 individuals, focusing on leukemia and lymphomas, and tested whether a low complexity approach, relying on Fisher’s exact test or χ2, is efficient for the analysis of variant allele frequencies with read-depth ratio correlations in order to resolve both copy-altering and neutral chromosomal aberrations. This combination helped to identify 69 altered chromosomes and offered mutual confirmation. Moreover, six CN-LoHs (>1% AF shifts, p<0.01) were found with one additional suspected low frequency deletion (~10-15% burden) in a case of CLL. We conclude that this simple method is directly clinically applicable for the detection of copy neutral chromosomal loss of single genes from WES with intermediate coverage.AvailabilityMentioned plot software is available at Harvard Dataverse http://doi.org/10.7910/DVN/[email protected] or [email protected] informationSupplementary plots are available

scholarly journals Performance assessment of a 619kW photovoltaic power plant in the northeast of peninsular Malaysia

2020 ◽  
Vol 20 (1) ◽  
pp. 9
Author(s):  
M. Nirrmahl Raj ◽  
Jagadeesh Pasupuleti
Keyword(s):  
Power Plants ◽  
Peninsular Malaysia ◽  
Performance Criteria ◽  
Plant Performance ◽  
Performance Ratio ◽  
Generation Model ◽  
Future Studies ◽  
Performance Requirements ◽  
One Year ◽  
East Asia Region

<span lang="EN-GB">Photovoltaic (PV) power plants are becoming widely implemented and in larger scale around the world. Understanding performance criteria is crucial in the benchmark of PV plants and ascertaining performance requirements during both design and operational stage of a PV plant. Performance Ratio (PR) and Capacity Factor (CF) are two generally accepted benchmarks for the assessment of a grid connected PV plant. However, within the South East Asia region, and especially within Malaysia, there is a lack of compilation and benchmark for the PR and CF values of existing and operational PV plants. This lack of data is disadvantageous for the designing and assessment of performance of any PV plants in the area. Thus, the focus of this study is to assess the PR and CF performance a 619kW PV plant in the Northeast of Peninsular Malaysia, with the ultimate goal of proposing a standard. From the continuous operation of the said PV plant for the duration of one year, the plant energy production has been obtained and is compared with the simulated energy generation model. Based on the comparison, the plant is determined to be operating with PR value of 0.77 and CF value of 12%. The plant is evaluated to be operating within benchmark values</span><span lang="EN-GB">. These values not only verify the performance of the studied PV plant, they also present a form of comparison </span><span lang="EN-GB">for future studies.</span>

scholarly journals A Concurrent Modelling to Generate Alternatives Approach Using the Firefly Algorithm

2013 ◽  
Vol 5 (2) ◽  
pp. 33-45 ◽  
Author(s):  
Raha Imanirad ◽  
Xin-She Yang ◽  
Julian Scott Yeomans
Keyword(s):  
System Performance ◽  
Firefly Algorithm ◽  
Multiple Solution ◽  
Performance Criteria ◽  
Objective Measures ◽  
Computationally Efficient ◽  
New Approach ◽  
Performance Requirements ◽  
Decision Variables ◽  
Performance Specifications

Real world” decision-making applications generally contain multifaceted performance requirements riddled with incongruent performance specifications. There are invariably unmodelled elements, not apparent during model construction, which can greatly impact the acceptability of the model’s solutions. Consequently, it is preferable to generate numerous alternatives that provide dissimilar approaches to the problem. These alternatives should possess near-optimal objective measures with respect to all known objective(s), but be maximally different from each other in terms of their decision variables. This maximally different solution creation approach is referred to as modelling-to-generate-alternatives (MGA). This study demonstrates how the Firefly Algorithm can concurrently create multiple solution alternatives that both satisfy required system performance criteria and yet are maximally different in their decision spaces. This new approach is computationally efficient, since it permits the concurrent generation of multiple, good solution alternatives in a single computational run rather than the multiple implementations required in previous MGA procedures.

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