PID control system analysis and design

With its three-term functionality offering treatment of both transient and steady-state responses, proportional-integral-derivative (PID) control provides a generic and efficient solution to realworld control problems. The wide application of PID control has stimulated and sustained research and development to "get the best out of PID", and "the search is on to find the next key technology or methodology for PID tuning". This article presents remedies for problems involving the integral and derivative terms. PID design objectives, methods, and future directions are discussed. Subsequently, a computerized, simulation-based approach is presented, together with illustrative design results for first-order, higher order, and nonlinear plants. Finally, we discuss differences between academic research and industrial practice, so as to motivate new research directions in PID control

PID control system analysis, design, and technology

Designing and tuning a proportional-integral-derivative (PID) controller appears to be conceptually intuitive, but can be hard in practice, if multiple (and often conflicting) objectives such as short transient and high stability are to be achieved. Usually, initial designs obtained by all means need to be adjusted repeatedly through computer simulations until the closed-loop system performs or compromises as desired. This stimulates the development of "intelligent" tools that can assist engineers to achieve the best overall PID control for the entire operating envelope. This development has further led to the incorporation of some advanced tuning algorithms into PID hardware modules. Corresponding to these developments, this paper presents a modern overview of functionalities and tuning methods in patents, software packages and commercial hardware modules. It is seen that many PID variants have been developed in order to improve transient performance, but standardising and modularising PID control are desired, although challenging. The inclusion of system identification and "intelligent" techniques in software based PID systems helps automate the entire design and tuning process to a useful degree. This should also assist future development of "plug-and-play" PID controllers that are widely applicable and can be set up easily and operate optimally for enhanced productivity, improved quality and reduced maintenance requirements

81-Element single-layer reflectarray with double-ring phasing elements for wideband applications

A microstrip reflectarray antenna utilizes a planar array of printed patch elements and a conventional prime or offset feed to form an alternative to the parabolic reflector [1]. It transforms the spherical wave of the feed into the planar wave by employing microstrip patch elements as radiators and phase shifters. Due to the use of planar technology, it offers a good balance between conventional reflector antennas and phased arrays. Because it uses many radiating elements it provides flexibility with respect to radiation pattern formation [2-4]. Its disadvantage is a limited operational bandwidth, which for the case of moderate gain is mainly due to a limited phase range and a high phase slope of the elements. In the wave transformation process, a full phasing range of 360° is desirable for unit cells containing patch elements. However, a variable size patch antenna developed on a single layer substrate offers a phasing range of about 300°. To overcome this problem, multilayer substrates including stacked variable-size patches for phasing the unit cells of a reflectarray have been devised to extend the phase range to multiples of 360°. The multi-layer approach with stacked patches not only extends the phase range but also reduces the slope of the phase curve as a function of patch dimensions [5-6]. However, the use of multi-layer substrates means that in practice layers of the reflectarray have to be manufactured separately and the assembly should leave no air gaps. This results in an elaborate and expensive manufacturing process. To overcome this problem, printed double-ring elements to form a single-layer reflectarray have been proposed. The double rings improve the phasing range of unit cells by utilizing multi-resonance behaviour. The extended range for unit cells containing double-ring elements has been demonstrated for the case of normal (TEM) wave incidence [7]. The assumption of normal incidence is less accurate for peripheral elements. Therefore in [8], TE and TM waves were considered to obtain an oblique incidence to obtain more accurate phasing characteristics of unit cells. © 2010 IEEE

Hamiltonian Formalism of the de-Sitter Invariant Special Relativity

Lagrangian of the Einstein's special relativity with universal parameter $c$ ($\mathcal{SR}_c$) is invariant under Poincar\'e transformation which preserves Lorentz metric $\eta_{\mu\nu}$. The $\mathcal{SR}_c$ has been extended to be one which is invariant under de Sitter transformation that preserves so called Beltrami metric $B_{\mu\nu}$. There are two universal parameters $c$ and $R$ in this Special Relativity (denote it as $\mathcal{SR}_{cR}$). The Lagrangian-Hamiltonian formulism of $\mathcal{SR}_{cR}$ is formulated in this paper. The canonic energy, canonic momenta, and 10 Noether charges corresponding to the space-time's de Sitter symmetry are derived. The canonical quantization of the mechanics for $\mathcal{SR}_{cR}$-free particle is performed. The physics related to it is discussed.Comment: 24 pages, no figur

Pion photoproduction on the nucleon in the quark model

We present a detailed quark-model study of pion photoproduction within the effective Lagrangian approach. Cross sections and single-polarization observables are investigated for the four charge channels, $\gamma p\to \pi^+ n$, $\gamma n\to \pi^- p$, $\gamma p\to \pi^0 p$, and $\gamma n\to \pi^0 n$. Leaving the $\pi N\Delta$ coupling strength to be a free parameter, we obtain a reasonably consistent description of these four channels from threshold to the first resonance region. Within this effective Lagrangian approach, strongly constrainted by the quark model, we consider the issue of double-counting which may occur if additional {\it t}-channel contributions are included.Comment: Revtex, 35 pages, 16 eps figures; version to appear on PR

An Exploratory Study of the Effects of CRM Practices on CRM Effectiveness and Business Performance

Continual advances in information technology (IT) have opened new business opportunities in global marketplaces. As a result, many businesses have turned to CRM to gain greater insights into their customers and apply this knowledge toward forging long-term relationships with them. This study examines the relationships of CRM practices (marketing and operational programs) with three antecedent elements (IT investments, absorptive capacity, strategic alignment), CRM effectiveness and firm (business) performance. The results of a survey suggest the following: absorptive capacity and strategic alignment have positive effects on CRM practices, CRM practices affect CRM effectiveness, CRM effectiveness affects firm performance, and CRM effectiveness mediates the effect of CRM practices (marketing programs) on firm performance. Hence, the CRM practices a business adopts will have an impact on its performance

PU.1 regulates Ig light chain transcription and rearrangement in pre-B cells during B cell development

B cell development and Ig rearrangement are governed by cell type- and developmental stage-specific transcription factors. PU.1 and Spi-B are E26-transformation-specific transcription factors that are critical for B cell differentiation. To determine whether PU.1 and Spi-B are required for B cell development in the bone marrow, Spi1 (encoding PU.1) was conditionally deleted in B cells by Cre recombinase under control of the Mb1 gene in Spib (encoding Spi-B)-deficient mice. Combined deletion of Spi1 and Spib resulted in a lack of mature B cells in the spleen and a block in B cell development in the bone marrow at the small pre-B cell stage. To determine target genes of PU.1 that could explain this block, we applied a gain-of-function approach using a PU.1/Spi-B- deficient pro-B cell line in which PU.1 can be induced by doxycycline. PU.1-induced genes were identified by integration of chromatin immunoprecipitation-sequencing and RNA-sequencing data. We found that PU.1 interacted with multiple sites in the Igk locus, including Vk promoters and regions located downstream of Vk second exons. Induction of PU.1 induced Igk transcription and rearrangement. Upregulation of Igk transcription was impaired in small pre-B cells from PU.1/Spi-B-deficient bone marrow. These studies reveal an important role for PU.1 in the regulation of Igk transcription and rearrangement and a requirement for PU.1 and Spi-B in B cell development

Mechanism of action and resistant profile of anti-HIV-1 coumarin derivatives

Dicamphanoyl khellactone (DCK) is a coumarin derivative that can potently inhibit HIV-1 replication. DCK does not inhibit RNA-dependent DNA synthesis. However, an HIV reverse transcriptase (RT) inhibitor-resistant strain, HIV-1/RTMDR1, is resistant to DCK. Thus, it is possible that HIV-1 RT is the target of DCK. To test this possibility, DCK-resistant viruses were selected in the presence of DCK. Our results indicate that a single amino acid mutation, E138K in HIV-1 RT, is sufficient to confer DCK resistance. Interestingly, a DCK derivative, 3'R,4'R-Di-O-(-)-camphanoyl-2-ethyl-2',2'-dimethyldihydropyrano[2,3-f]chromo ne (DCP8), is effective against HIV-1/RTMDR1. However, the DCK-escape virus carrying the E138K mutation remains resistant to DCP8. Since DCK did not inhibit the RNA-dependent DNA polymerase activity of HIV-1 RT when using poly-rA or poly-rC as template, we evaluated the effect of DCK on the DNA-dependent DNA polymerase activity of HIV-1 RT. Our results indicate that DCK can inhibit the DNA-dependent DNA polymerase activity of HIV-1 RT. In conclusion, DCK is a unique HIV-1 RT inhibitor that inhibits the DNA-dependent DNA polymerase activity. In contrast, DCK did not significantly affect the RNA-dependent DNA polymerase activity when poly-rA or poly-rC was used as templates. An E138K mutation in the non-nucleoside RT inhibitors (NNRTIs) binding pocket of HIV-1 RT confers resistance to DCK and its chromone derivative, DCP8

A Price Worth Paying: The Case for Controlling Marine Emissions in the Pearl River Delta

The Pearl River Delta (PRD) is a region with a single airshed, but different administrative and legal practices for controlling air quality. Under the Regional Cooperation Plan on Building a Quality Living Area (QLA Plan) released in June 2012 the Governments of Hong Kong, Guangdong and Macau have outlined a strategy to collaborate in reducing emissions from vessels throughout the PRD. This report provides evidence designed to assist policymakers in the region with this objective. It focuses on regulating toxic exhaust emissions from ocean-going vessels (OGVs) -- the most significant contributors of marine emissions. The findings show that marine sources of sulphur dioxide (SO2) emissions currently account for 519 premature deaths per annum in the PRD. These deaths could be reduced by 91% should an Emission Control Area (ECA) mandating the use of fuels with lower sulphur content be introduced. The report also demonstrates that three less comprehensive control measures would also reduce OGV emissions and associated public health impacts by 41-62%. Policymakers are encouraged to introduce these measures as stepping-stones on the way to establishment of an ECA for the PRD

Identification of a negative regulatory role for Spi-C in the murine B cell lineage

Spi-C is an E26 transformation-specific family transcription factor that is highly related to PU.1 and Spi-B. Spi-C is expressed in developing B cells, but its function in B cell development and function is not well characterized. To determine whether Spi-C functions as a negative regulator of Spi-B (encoded by Spib), mice were generated that were germline knockout for Spib and heterozygous for Spic (Spib-/-Spic+/-). Interestingly, loss of one Spic allele substantially rescued B cell frequencies and absolute numbers in Spib-/- mouse spleens. Spib-/-Spic+/- B cells had restored proliferation compared with Spib-/- B cells in response to anti-IgM or LPS stimulation. Investigation of a potential mechanism for the Spib-/-Spic+/- phenotype revealed that steady-state levels of Nfkb1, encoding p50, were elevated in Spib-/-Spic+/- B cells compared with Spib-/- B cells. Spi-B was shown to directly activate the Nfkb1 gene, whereas Spi-C was shown to repress this gene. These results indicate a novel role for Spi-C as a negative regulator of B cell development and function