闭环控制经编送经系统

经编机送经控制系统是一个时刻发生变化的非线性系统,针对经编生产,特别是高速经编机生产要求,送经系统应具有快速响应性、高控制精度和稳定性的特性,为此设计了采用闭环控制的经编送经系统。主要介绍该系统的原理、方法和组件构成,以及对系统的测试分析方法。系统采用DSP数字控制器作为送经控制单元的核心部件,通过测速压辊得到经轴盘头的即时外周长和实际送经量,获取下一周期经轴电动机速度,根据送经量的偏差,再通过控制器的智能PID计算、修正,形成全闭环控制来实现送经系统的实时在线调整。对比实验结果表明,设计的经编送经闭环系统合理、可行,并具有高精度、响应性和稳定性。     

经编多速电子送经系统控制过程与控制算法

为了开发和优化经编多速电子送经系统,最大程度提高经编设备的产品适应性和经编产品质量,对经编机多速电子送经系统的控制过程进行了详细分析,阐述了经轴电机根据主轴速度、外周长的变化在不同速度之间切换的过程;在分析控制过程的基础上,对多速电子送经系统的控制算法进行深入研究,根据主轴转速、工艺要求的送经量算出了电机转速的操作值。经过实际织造证明,该系统的送经误差可控制在±1%以内,保证准确地实现送经。     

经编机启停过程中的闭环送经控制特性

在阐述基于闭环控制的经编电子送经系统结构的基础上,文章主要研究了闭环送经控制系统在经编机启停过程中主轴转速的变化对经轴送经的影响,并对送经系统在启停过程中的经轴滞后于主轴运动和经纱张力变化进行了测试与分析。根据测得的经编机启停过程中经轴电机响应性能和送经张力变化规律,设计了一种经编机启停过程中的送经补偿方法,可显著提高经编机启停过程中送经张力的平稳性,进而改善经编产品品质。     

全闭环经编送经系统PID控制算法设计

针对先进经编机用电子送经系统精度高、响应速度快的要求,设计了一种全闭环控制的电子送经系统,它主要由控制单元、送经驱动装置、测速反馈装置和主轴信号装置4个部分组成。阐述了该全闭环送经系统的控制过程,并对其控制算法进行了研究。为了提高系统的快速响应性能,设计了修正PID(比例-积分-微分)控制算法,即当经编机正常运转时,则采用PID控制以提高系统的控制精度;而当开停车时,采用PD(比例-微分)控制以减少超调量,增强系统的快速响应能力。     

经编电子送经系统的滞后响应

为减少由开、停机过程中经纱张力波动引起的经编停车横条织疵,通过实验测试经编机电子送经系统在开、停机过程中主轴与经轴电动机的运动曲线。分析认为：开、停机过程中送经系统经轴电机滞后于主轴运动,开机时滞后时间随着主轴转速的升高而减小,滞后角度逐步增大;停机时滞后时间随着主轴转速的降低而变化不大,滞后角减小,引起经纱张力呈现“正常→偏松状态下的松、紧变化→较紧状态下的松、紧变化→正常”的波动。同时,还对主控制器性能、系统控制程序、伺服控制模式、送经伺服性能、伺服参数设置和主轴编码器等影响经编送经系统滞后的主要因素进行了讨论。     

电子送经高速经编机控制系统

电子送经高速经编机是国外80年代发展起来的一种新型经编设备,与普通高速经编机相比,具有很大优越性.采用计算机控制数字伺服系统,送经精度高,织物成圈均匀,可随意调节送经量,工艺设计方便,产品开发迅速,目前国外已基本上用电子送经装置代替了机械送经装置。本文主要介绍电子送经高速经编机的控制原理、控制算法及其系统的实现。     

EBC经编电子送经系统

EBC经编电子送经系统是数字化控制技术在经编机中的应用。在介绍该系统组成和系统要求的基础上,深入探讨EBC经编电子送经系统的工作原理和经编送经过程的实现,分析恒速送经和多速送经的控制单元算法。结果表明,该EBC电子送经系统送经精度高,送经稳定性好,送经量可调范围大,且织物成圈均匀,工艺设计方便,操作简单。因此使用EBC经编电子送经系统将有效提高经编织物产品的布面质量。     

基于单神经元自适应算法的经纱张力控制器设计

经纱张力稳定性是影响织物质量的重要因素之一。为得到经轴转速与经纱张力之间的数学关系,实现控制器对经纱张力的准确控制,建立了织机运行过程中的经纱动力学模型。设计了以单神经元自适应算法为控制算法、以单片机MCF5213为处理器的电子送经/卷取控制器。将单神经元自适应控制算法与常规PID算法的控制效果做仿真比较,结果表明,单神经元自适应控制对外界扰动具有更好的抑制性能。以RFJA10喷气织机作为现场调试平台进行台架试验。实验数据表明,该控制器控制效果良好,提高了张力控制系统的动态性能和稳定性。     

基于模型预测的经编送经动态张力补偿系统设计

经编机编织过程中首先要实现控制经纱在1个横列内不同角度区域张力值的变化,才能达成纱线的动态张力补偿控制。为解决当前系统控制经轴送经量出现的纱线张力波动大,且无法精确到控制1个横列内不同角度纱线张力等缺陷,设计了一种基于模型预测的经编送经动态张力补偿系统。通过结合经编机成圈机构运动规律进行分析,设计出系统的硬件和软件平台,优化张力传感器选型,设计了电子凸轮规划曲线算法和模型预测控制算法,实现了纱线动态张力补偿控制。通过理论分析和实验测试,从反馈的纱线动态张力值曲线分析验证了该模型预测控制算法能够使纱线张力峰值降低至少56%以上。     

基于前馈控制的经编机横移系统高速定位

经编机电子梳栉横移系统通常采用普通PID控制,难以满足梳栉横移高速、高响应和精准定位的要求.针对这一问题,在分析伺服电动机物理模型的基础上设计了由普通位置环、速度环和电流环组成的三闭环PID交流伺服控制系统,并在系统中引入电流环和速度环的前馈控制来提高梳栉的高速定位控制性能.通过MatLab软件的仿真测试和RSE4-1...     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.