Partially decentralized control for ALSTOM gasifier

The gasifier plays a key role in the operation of the whole IGCC power plant. It is a typical multivariable control system with strict constraints on the inputs and outputs which makes it very difficult to control. This paper presents a partially decentralized controller design method based on the stabilizer idea. The method only requires identifying some closed-loop transfer functions and solving an H_∞ optimization problem. The final partially decentralized controller is easy to implement and test in practice. Two partially decentralized controllers are designed for the ALSTOM gasifier benchmark problem, and simulation results show that they both meet the design specifications.     

decentralized observation and control of nonlinear interconnected systems

In this paper, we investigate the problem of H_∞ decentralized tracking control design with a decentralized observer for interconnected nonlinear systems which are characterized by the interconnection of N subsystems. Each subsystem is modeled by a linear constant part perturbed by an additive nonlinearity which is illustrated by the interconnection terms.The proposed feedback control scheme is developed to ensure the asymptotic stability of the augmented system, to reconstruct the non-measurable state variables of each subsystem, to maximize the nonlinearity domain, and to improve the performance of the model reference tracking control by using the H_∞ criterion despite the external disturbances.The proposed control approach is formulated in a minimization problem and derived in terms of linear matrix inequalities (LMIs) whose resolution yields the decentralized control and observation gain matrices.The effectiveness of the proposed control scheme is demonstrated through numerical simulations on a power system with three interconnected machines.     

Determination of L‐ and D‐Enantiomers of Leucine Using Amperometric Biosensors Based on Diamond Paste

Abstract

Four amperometric biosensors, based on diamond paste, are proposed for the determination of the enantiopurity of leucine. The design of the biosensors used physical immobilization in diamond paste of L‐amino acid oxidase for the assay of L‐leucine and D‐amino acid oxidase for the assay of D‐leucine. The response characteristics of the different diamond paste based biosensors were obtained and compared. The linear concentration ranges for the biosensors were in pmol/L to nmol/L magnitude order. The biosensors showed high reliability for the determination of enantiopurity of leucine as a raw material.     

Recursive fuzzy c-means clustering for recursive fuzzy identification of time-varying processes

In this paper we propose a new approach to on-line Takagi-Sugeno fuzzy model identification. It combines a recursive fuzzy c-means algorithm and recursive least squares. First the method is derived and than it is tested and compared on a benchmark problem of the Mackey-Glass time series with other established on-line identification methods. We showed that the developed algorithm gives a comparable degree of accuracy to other algorithms. The proposed algorithm can be used in a number of fields, including adaptive nonlinear control, model predictive control, fault detection, diagnostics and robotics. An example of identification based on a real data of the waste-water treatment process is also presented.     

Diving autopilot design for underwater vehicles using multi-objective control synthesis

This paper presents the mathematical modeling, guidance and robust control synthesis of a highly maneuverable submersible vehicle (or underwater vehicle) when performing a specific mission at shallow submergence conditions. First, the vertical plane motions (heave and pitch) of the vehicle are modeled by a set of maneuvering equations. After model simplification, a state-space model is compactly obtained. Then a state-feedback controller is proposed for the accurate depth-keeping and pitch motion controls of the vehicle. The control actions to the generalized plant can be provided by the mixedH ₂/H _∞ optimal synthesis as well as closed-loop pole constraint with LMIs. The feasibility of the guidance and control approach is verified with direct numerical simulations. The proposed approach ensures reasonable depth-keeping and minimal pitch motions, even under a given uncertainty condition.     

Improved single neuron controller for multivariable stochastic systems with non-Gaussianities and unmodeled dynamics

In this paper, a new adaptive control approach is presented for multivariate nonlinear non-Gaussian systems with unknown models. A more general and systematic statistical measure, called (h,?)$(h,?)$-entropy, is adopted here to characterize the uncertainty of the considered systems. By using the “sliding window” technique, the non-parameter estimate of the (h,?)$(h,?)$-entropy is formulated. Then, the improved neuron based controllers are developed for multivariate nonlinear non-Gaussian systems by minimizing the entropies of the tracking errors in closed loops. The condition to guarantee the strictly decreasing entropy of tracking error is presented. Moreover, the convergence in the mean-square sense has been analyzed for all the weights in the neural controllers. Finally, the comparative simulation results are presented to show that the performance of the proposed algorithm is superior to that of PID control strategy.     

Identification and quantification of β-caryophyllene in copaiba oil using Raman spectroscopy

Copaiba oleoresin presents several compounds with known biologic activity and physiologic effects, including analgesic and insecticide properties. Among them are the terpenoids (mainly diterpenes and sesquiterpenes) with β-caryophyllene, the main representative of the terpenoids and considered to be a chemical marker. This study employed Raman spectroscopy and principal component analysis (PCA) techniques to identify and quantify the β-caryophyllene marker in copaiba oil samples purchased from popular markets in Brazil. A dispersive Raman spectrometer (830?nm, 250?mW, 2?cm^?1 spectral resolution) was used. Results showed the identification of the main Raman peaks from the β-caryophyllene in copaiba oil samples (main peaks at 507, 771, 1442, 1638, and 1673?cm^?1). The loading vector 2 (PC2) extracted the spectral information from β-caryophyllene in the samples and the eigenvalue 2 (score 2) allowed the estimation of the concentration of this marker in commercial samples, with the concentrations from 15 to 34%. Raman spectroscopy combined with PCA may be considered to be a potential analytical tool for the quality control of Copaifera oil samples by quantifying β-caryophyllene using its unique spectral information.     

Finite-time H∞ control for a class of Markovian jump systems with mode-dependent time-varying delays via new Lyapunov functionals

This paper is concerned with the problem of finite-time _H∞$H_{\infty }$ control for a class of Markovian jump systems with mode-dependent time-varying delays via new Lyapunov functionals. In order to reduce conservatism, a new Lyapunov–Krasovskii functional is constructed. Based on the derived condition, the reliable _H∞$H_{\infty }$ control problem is solved, and the system trajectory stays within a prescribed bound during a specified time interval. Finally, numerical examples are given to demonstrate the proposed approach is more effective than some existing ones.     

Analysis of robust stability and performance for two-degree of freedom control structure with dynamic controller

In the two-degree of freedom control, the performance of good command following and disturbance rejection are considered separately. Qualitatively, good performance is equivalent to minimizing the energy of the error for any inputs. In this work, usingH _∞-formulation in the frequency domain, robust stability and robust performance specifications have been analyzed for the two-degree of freedom control structure with a dynamic controller. When the two-degree of freedom system having a feed-forward loop is controlled by a dynamic controller, two different performance weight functions are imposed and the robust performance specification is proposed in terms of the return ratio and feed-forward loop. The design algorithm in the frequency domain is illustrated for the simplified retail model of Industrial Dynamics to compare three kinds of control laws, which are the output feedback control scheme and two additional dynamic control ones. Numerical simulation results show that the dynamic control laws provide a larger robust stability margin than the output feeback control one and has good performance robustness for disturbance rejection at low frequencies.     

Selecting distribution centre location using an improved fuzzy MCDM approach

A distribution centre (DC) is usually supplied by manufacturing factories and in turn it supplies the consumers. To reduce transportation costs and enhance operation efficiency, selecting a suitable DC location has become a very important issue for both manufacturing and distribution industries. Recently, Chen [1] proposed a fuzzy MCDM (multiple criteria decision-making) approach to selecting the location of a distribution centre. Despite its merits, two limitations were found in his works, i.e. follows: (1) the final fuzzy evaluation value P _i was treated as a triangular fuzzy number. This is not correct because it may not produce a triangular shape and (2) the difference of two final fuzzy evaluation values, i.e. P _i –P _j , was regarded as a triangular fuzzy number. This is also incorrect. Obviously, P _i –P _j may not produce triangular shape because P _i and P _j may not be triangular fuzzy numbers. To resolve the above limitations and enhance the applicability of the fuzzy MCDM to the DC location selection problem, an improved fuzzy MCDM approach is proposed. In this work, the membership functions of P _i and P _i –P _j are developed to construct an improved fuzzy preference relation, which is further employed with the Chen ranking procedure to complete the proposed method. Finally, a numerical example demonstrates the feasibility of the proposed method.     

An Inexpensive Digital Integrator for Gas Chromatography

SUMMARY

An inexpensive gas chromatographic integrator with digital readout is described. The device is precise to ±1 count and shows linear response to within ±2%. It is directly compatible with flame ionization detectors and is easily adapted to thermal conductivity detectors.     

Robust control of nonlinear MAGLEV suspension system with mismatched uncertainties via DOBC approach

Robust control of a class of uncertain systems that have disturbances and uncertainties not satisfying “matching” condition is investigated in this paper via a disturbance observer based control (DOBC) approach. In the context of this paper, “matched” disturbances/uncertainties stand for the disturbances/uncertainties entering the system through the same channels as control inputs. By properly designing a disturbance compensation gain, a novel composite controller is proposed to counteract the “mismatched” lumped disturbances from the output channels. The proposed method significantly extends the applicability of the DOBC methods. Rigorous stability analysis of the closed-loop system with the proposed method is established under mild assumptions. The proposed method is applied to a nonlinear MAGnetic LEViation (MAGLEV) suspension system. Simulation shows that compared to the widely used integral control method, the proposed method provides significantly improved disturbance rejection and robustness against load variation.     

End-grafted Sugar Chains as Aqueous Lubricant Additives: Synthesis and Macrotribological Tests of Poly(<Emphasis Type="SmallCaps">l</Emphasis>-lysine)-<Emphasis Type="Italic">graft</Emphasis>-Dextran (PLL-<Emphasis Type="Italic">g</Emphasis>-dex) Copolymers

Comb-like graft copolymers with carbohydrate side chains have been developed as aqueous lubricant additives for oxide-based tribosystems, in an attempt to mimic biological lubrication systems, whose surfaces are known to be covered with sugar-rich layers. As adopted in the previous studies of the graft copolymer poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), which showed both excellent lubricating and antifouling properties, a similar approach was chosen to graft dextran chains onto the same backbone, thus generating PLL-g-dex. PLL-g-dex copolymers readily adsorb from aqueous solution onto negatively charged oxide surfaces. Tribological characterization at the macroscopic scale, either under pure sliding conditions or a mixed sliding/rolling contact regime, shows that PLL-g-dex is very effective for the lubrication of oxide-based tribosystems. The relative lubricating capabilities of PLL-g-dex copolymers compared with PLL-g-PEG copolymers were observed to be highly dependent on the molecular structure of the copolymers (in particular, side-chain density along the backbone) and the measurement conditions (in particular, time between tribocontacts); the PLL-g-dex copolymers with a low degree of grafted side chains (≤20% grafting of available protonated primary amine groups along the backbone) showed better lubricating performance than their PLL-g-PEG counterparts at high tribocontact frequency (≥ca. 0.32 Hz).     

Finite-time boundedness filtering for discrete-time Markovian jump system subject to partly unknown transition probabilities

This paper investigates the problem of finite-time boundedness filtering for discrete-time Markovian jump system subject partly unknown transition probabilities. By using the multiple Lyapunov function approach, a novel sufficient condition for finite-time bounded of _H∞$H_{\infty }$ filtering is derived and the system trajectory stays within a prescribed bound during a specified time interval. Finally, an example is provided to illustrate the usefulness and effectiveness of the proposed method.     

H∞ filtering for a class of discrete-time singular Markovian jump systems with time-varying delays

The problem of _H∞$H_{\infty }$ filtering for a class of discrete-time singular Markovian jump systems with time-varying delays is investigated in this paper. The transition probabilities under consideration are time-varying, i.e., Markovian chain is nonhomogeneous. By using the Lyapunov functional approach and reciprocally convex technique, a less conservative delay-dependent bounded real lemma is developed in terms of linear matrix inequalities. Moreover, a sufficient condition for the existence of the desired filter which guarantees the stochastic admissibility and the _H∞$H_{\infty }$ performance index of the resulting filtering error system is presented. Numerical examples are employed to show the usefulness of the proposed results.     

Robust fault detection for switched positive linear systems with time-varying delays

This paper investigates the problem of robust fault detection for a class of switched positive linear systems with time-varying delays. The fault detection filter is used as the residual generator, in which the filter parameters are dependent on the system mode. Attention is focused on designing the positive filter such that, for model uncertainties, unknown inputs and the control inputs, the error between the residual and fault is minimized. The problem of robust fault detection is converted into a positive L₁ filtering problem. Subsequently, by constructing an appropriate multiple co-positive type Lyapunov–Krasovskii functional, as well as using the average dwell time approach, sufficient conditions for the solvability of this problem are established in terms of linear matrix inequalities (LMIs). Two illustrative examples are provided to show the effectiveness and applicability of the proposed results.     

Three-parameter approach for elastic–plastic fracture of the semi-elliptical surface crack under tension

Systematic three-dimensional elastic–plastic finite element analyses are carried out for a semi-elliptical surface crack in plates under tension. Various aspect ratios (a/c) of three-dimensional fields are analyzed near the semi-elliptical surface crack front. It is shown that the developed J–Q annulus can effectively describe the influence of the in-plane stress parameters as the radial distances (r/(J/σ₀)) are relatively small, while the approach can hardly characterize it very well with the increase of r/(J/σ₀) and strain hardening exponent n. In order to characterize the important stress parameters well, such as the equivalent stress σ_e, the hydrostatic stress σ_m and the stress triaxiality R_σ, the three-parameter J–Q_T–T_z approach is proposed based on the numerical analysis as well as a critical discussion on the previous studies. By introducing the out-of-plane stress constraint factor T_z and the Q_T term, which is determined by matching the finite element analysis results, the J–Q_T–T_z solution can predict the corresponding three-dimensional stress state parameters and the equivalent strain effectively in the whole plastic zone. Furthermore, it is exciting to find that the values of J-integral are independent of n under small-scale yielding condition when the stress-free boundary conditions at the side and back surfaces of the plate have negligible effect on the stress state along the crack front, and the normalized J tends to a same value when φ equals about 31.5° for different a/c and n. Finally, the empirical formula of T_z and the stress components are provided to predict the stress state parameters effectively.     

Alternative optimisation strategies and CAM software for multipass rough turning operations

The development of constrained optimisation analyses and strategies for selecting optimum cutting conditions in multipass rough turning operations based on minimum time per component criterion is outlined and discussed. It is shown that a combination of theoretical economic trends of single and multipass turning as well as numerical search methods are needed to arrive at the optimum solution. Numerical case studies supported the developed solution strategies and demonstrated the economic superiority of multipass strategies over single pass. Alternative approximate multipass optimisation strategies involving equal depth of cut per pass, single pass optimisation strategies and limited search techniques have also been developed and compared with the rigorous optimisation strategies. The approximate strategies have been shown to be useful, preferably for on-line applications such as canned cycles on CNC machine controllers, but recourse to the rigorous multipass strategies should be regarded as the reference for use in assessing alternative approximate strategies or for CAM support usage.Nomenclature d _i depth of cut for theith pass - d _opt optimum depth of cut - d _T total depth of cut to be removed - D _i workpiece diameter before theith pass - D _o,D _m initial and final workpiece diameter (afterm passes) - f _i feed for theith pass - f _max,f _min machine tool maximum and minimum feed - f _opt optimum cutting feed - f _sj, V_sj available feed and speed steps in a conventional machine tool - f _sgl, f_rec optimum and handbook recommended single pass cutting feeds - F _pmax maximum permissible cutting force - L workpiece length of cut - m continuous number of passes - m _H next higher integer number of passes from a givenm - m _HW upper limit to the optimum integer number of passesm _opt - m _L next lower integer number of passes from a givenm - m _LW lower limit to the optimum integer number of passesm _opt - m _o optimum (continuous) number of passes - m _opt optimum integer number of passes - N _a machine tool critical rotational speed whenP _a=P _max - N _max,N _min machine tool maximum and minimum rotational speed - n,n ₁,n ₂,K speed, feed and depth of cut exponents and constant in the extended Taylor's tool-life equation - P _a,P _max machine tool low speed and maximum power constraints - T _i tool-life using the cutting conditions for theith pass - T _L loading and unloading time per component - T _R tool replacement time - T _s tool resetting time per pass - T _T production time per component - T _TDi multi-passT _T equation with workpiece diameter effect - T _TDm, T_TDo multi-passT _T equations with constant diameterD _m andD _o, respectively - T _Topt overall optimum time per component - T _Tsgl optimum time per component for single pass turning - T _{T2re c} handbook recommended time per component - V _i cutting speed for theith pass - V _max,V _min machine tool maximum and minimum cutting speed - V _sgl,V _rec optimum and handbook recommended single pass cutting speeds - V _opt optimum cutting speed - a, E, W empirical constants in theP _a/F _pmax/P _max equations - , , feed, depth and speed exponents inF _pmax andP _max equations     

Growth and properties analysis of metal-organic chemical vapor deposited MgxZn1-xO films on C-Al2O3 substrates

Mg_xZn_1−xO (0 〈 x ⩽ 0.12) thin films with the wurtzite structure have been successfully grown on c-Al₂O₃ substrates by metal-organic chemical vapor deposition (MOCVD). X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), photoluminescence (PL) spectrometry, and transmission measurements are performed to study the characteristics of Mg _x Zn_1−x O thin films. Results show that with increasing Mg content, the diffraction peak of Mg _x Zn_1−x O thin films shifts towards a higher diffraction angle (the biggest shift is 0.22°), and the full width at half maximum (FWHM) of the diffraction peak is broadened. Meanwhile, a blue-shift occurs at the near-band-edge (NBE) emission peak and the largest blue-shift of the band gap of the Mg _x Zn_1−x O films is 113 meV with Mg content x50.12. Therefore, the energy band gap of the Mg _x Zn_1−x O films is determined by Mg content in the thin films and the energy band gap increases with an increase of Mg content.