基于Smith预估器的PID自适应控制及其应用

针对大时滞时变对象 ,把Smith补偿控制原理和PID参数的自适应调整方法结合起来 ,提出了基于BP神经网络整定Smith PID控制算法 ,即在Smith预估补偿控制系统中 ,利用BP神经网络在线自学习整定PID参数 ,使PID参数实现最佳的非线性组合 ,以适应对象特性的变化 ,从而克服了常规PID算法不适应大时滞系统控制和常规Smith算法过于依赖模型精度的缺陷。仿真研究和实际应用表明 ,本文算法具有很强的鲁棒性和良好的控制品质 ,工程应用控制效果令人满意。     

PID过程控制及其参数整定策略浅析

PID控制方法在自动化过程控制中有着广泛的应用。本文在论述PID控制器原理、控制算法的基础上,重点分析了控制器参数的整定问题,给出了参数整定的有效方法,并介绍了参数自整定的基本实施方法及其研究应用情况。     

单神经元PID控制算法在智能车控制系统的应用

针对传统PID控制算法对智能车的舵机和电机进行控制时,其控制参数很难随环境变化进行自整定,进而影响智能车的运行状态的问题,提出单神经元PID控制算法,该算法具有参数自整定能力强、现场调整参数少、调整周期短及稳定性好等优点。通过对智能车的系统结构和运动学模型进行分析,根据单神经元PID算法的控制策略,进行多种算法的仿真测试并将其应用在实际的智能车控制试验中。结果表明:单神经元PID控制算法能够使控制系统以较好的状态运行,实现智能车快速稳定的自主循迹行驶。     

基于模糊PID的空压机恒压供气控制系统研究

针对空压机供气滞后大、供气不稳定等问题,对精确控制空压机恒压供气的方法进行了研究。通过常规PID控制算法以及模糊PID参数自整定控制算法对恒压供气控制系统进行了数学建模以及仿真,寻找一种更佳的恒压供气控制方法,使得系统供气更稳定,控制精度更高。     

模糊自适应PI控制在空调系统中的研究

以空气焓差法试验台空调系统的温度控制系统为具体仿真对象建立了数学模型,该空调系统可以看作是一阶惯性加纯滞后的环节,而且对象的过程参数和时延时间是时变的,传统的PID控制无法获得理想的控制效果。提出了一种无需辨识环节的具有智能的模糊自适应PI的控制算法并将其应用在该空调系统中,该算法对模糊控制和PI控制进行有机结合,根据实际控制经验,通过模糊控制规则对控制回路中PI控制器的参数进行实时整定,并将该控制算法和经过良好整定的PI控制器在空调系统中的控制性能进行比较。仿真结果表明,模糊自适应PI控制提高了系统的鲁棒性、减小了超调量、提高了抗干扰能力、缩短了调整时间。     

具有最优指标的PID参数自整定系统

在分析研究各种过程参数辨识和PID整定方法的基础上,提出了以误差积分准则为最优性能指标的一种PID参数自整定方法。这种方法的要点是仅采用几个特征量,就能比较准确地在线测算过程特性参数,引入采样时间Ts作为附加参数,修改Lopez公式系数;以修改系数后的Lopez公式作为PID参数预整定的关系式;在预整定基础上进行适当修改,使控制系统达到最佳状态。数字仿真和实时控制表明,这是一种较好的实用的自整定方法,适用于相当广泛的一类过程对象。     

PID参数工程整定方法研究

本文分析了PID控制模型中比例积分微分的作用,介绍了传统PID参数整定的方法,并总结了PID参数经验整定方法,应用该方法对碱液降膜蒸发流量液位串级控制系统主调和副调PID参数进行调整,并取得了较稳定的控制效果。     

基于LabVIEW的锅炉温度过程控制系统仿真

以经典PID控制算法为理论基础,Lab VIEW为开发平台,实现了锅炉温度控制系统的动态仿真,重点说明了增量式PID控制算法的具体实现方法。该系统能取代传统仪器用于验证PID控制规律的控制特点,完成锅炉温度控制系统的参数整定与调试,节省了硬件投资,具有推广应用价值。     

改进型单级三冲量汽包水位控制系统应用研究

结合工程实例,分析了串级三冲量与单级三冲量控制系统原理和DCS组态实现,指出了串级三冲量控制系统在工况条件下PID参数整定存在的问题,提出了一种改进型单级三冲量控制系统。生产实践表明:该系统稳定可靠,PID参数整定更加简单快捷,操作方便且控制效果好。     

STD工业控制机在煤气辊道窑温度控制系统中的应用

介绍了ＳＴＤＶ４０工业控制机在煤气辊道窑温度控制系统中的应用。实现了对整个辊道窑３０个温度点的集中监视和对其中２２个温度的自动控制，满足了生产工艺的要求。在实现中，选用参数整定方便的控制算法，实现了对辊道窑的高精度控制，大大提高了产品质量，降低了废品率，为企业创造了良好的经济效益。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。