bluuebunny/crossref_metadata_2025_split huggingface dataset:
Eigenstructure assignment with control gains optimization
Authors: Zhang Qiang , Slater G. L. 
Published: July 2007

AbstractEigenstructure assignment using output feedback is reformulated using an auxiliary principle of minimization of control effort. In the general eigenstructure assignment procedure, the feedback gain matrix is uniquely determined for a set of explicitly specified desired eigenvalues and eigenvectors. However, for the controller design proposed in this paper, only the most necessary constraints are imposed on the desired eigenvalues and eigenvectors, and the unspecified model parameters of the closed‐loop system are determined by minimizing the control effort. Numerical examples are presented for comparison of the proposed method with standard eigenstructure assignment methods, and an experimental example gives an insight into the feasibility of the proposed control algorithm with application to the vibration control of flexible structures undergoing forced vibration.
Discrete computer control of a triple‐inverted pendulum
Authors: Meier Farwig H. Zu , Unbehauen H. 
Published: July 2007

AbstractStabilization of a triple‐inverted pendulum is studied in this paper. The overall control structure is based on a state space approach and employs the computer‐aided design package ‘KEDDC’. The complete set of state variables needed for state feedback are provided by a reduced‐order observer. Theoretical analysis, supported by successful experimental results, shows that our stabilization objective can be achieved by measuring the angles of the three arms of the pendulum as well as the position and velocity of the supporting cart.
Shape optimization analysis: First‐ and second‐order necessary conditions
Authors: Cabuk H. , Modi V. 
Published: July 2007

AbstractIn this paper, first‐ and second‐order necessary conditions for optimality are studied for a domain optimization problem. The optimization problem considered is the minimization of an objective function defined on the domain boundary through the solution of a boundary value problem. In order to derive the first and second variations of the objective function due to boundary variation, the first and second variations of the solution of the boundary value problem are calculated using a perturbation technique. An iterative shape optimization algorithm for potential flow problems in R2 with Dirichlet boundary conditions is presented. In the algorithm a boundary element method (BEM) is employed to solve the Laplace equation numerically. The validity and accuracy of the algorithm have been verified on a problem where the final solution is known. Finally, the problem of designing a 90° bend for two‐dimensional potential flow is solved.
Adaptive root‐locus control for siso processes with time delays
Authors: Wang Feng‐Sheng 
Published: July 2007

AbstractTwo adaptive root‐locus control schemes for processes with time delays have been developed. The control design methodologies are based on classical feedback control and Smith predictor structures with simple pole placement. The overall behaviour of both control systems is adapted along the root loci of the system in each control horizon. Since the Smith predictor structure includes time delay compensation, the tuning gain can be enlarged to improve the performance of the control system. The optimal tuning gain is repeatedly updated by an optimization technique when the estimated model is confirmed. A comparison with simplified model predictive control (SMPC) is also given. SMPC in SISO systems is a special case of the proposed control laws.
Relationship between åström control and the kalman linear regulator—caines revisited
Authors: Warwick Kevin 
Published: July 2007

AbstractThe relationship between minimum variance and minimum expected quadratic loss feedback controllers for linear univariate discrete‐time stochastic systems is reviewed by taking the approach used by Caines. It is shown how the two methods can be regarded as providing identical control actions as long as a noise‐free measurement state‐space model is employed.
A simple way to stabilize discrete systems with jump markov parameters
Authors: Yaz Engin 
Published: July 2007

AbstractA new control method is proposed to stabilize, in the exponential mean‐square sense, linear discrete‐time systems with discrete‐time, discrete‐state jump Markov parameters. This method offers a substantial computational advantage in that it requires only finite‐time solutions of Riccati‐like equations to achieve stabilization.
A comparison of some robust eigenvalue assignment techniques
Authors: Burrows Simon P. , Patton Ron J. 
Published: July 2007

AbstractThree techniques for robust eigenvalue assignment are presented. The first is well known and is based on iteratively assigning the closed‐loop eigenvectors so as to be maximally orthogonal to one another. The second has been recently presented by the authors and is an improvement of the first which gives better results for problems where complex‐conjugate eigenvalue pairs are to be assigned. The final method is new and is founded on the iterative replacement of the current closed‐loop eigenvector matrix with a new matrix which is the projection of the columns of the nearest orthogonal matrix into the allowable eigenvector subspaces. Some numerical examples are given which are used to illustrate the improved results obtained using the second technique in place of the first and to compare these with the performance of the last algorithm which is based on an alternative approach.
A turnpike improvement algorithm for piecewise deterministic control
Authors: Boukas K. , Haurie A. , van Delft Ch. 
Published: July 2007

AbstractThis paper proposes a numerical technique, called turnpike improvement, for the approximation of the solution of a class of piecewise deterministic control problems typically associated with manufacturing flow control models. This algorithm exploits the structure of Markov decision processes with continuous state and action spaces that can be associated with piecewise deterministic control systems. The numerical method is applicable whenever a turnpike property holds for some associated infinite horizon deterministic control problem. To illustrate the approach, we use a simple model fully studied from an analytic point of view in the literature. We compare the turnpike improvement technique with a direct approximation of the solution of the continuous‐time Hamilton‐Jacobi dynamic programming equations inspired by Kushner's work. The two approaches agree remarkably on this simple problem. We conclude with a discussion of the relative advantages of the two approaches.
Optimal digital redesign of cascaded analogue controllers
Authors: Shieh L. S. , Decrocq B. B. , Zhang J. L. 
Published: July 2007

AbstractThis paper presents a new, optimal digital redesign technique for finding an optimal cascaded digital controller from the given continuous‐time counterpart by minimizing a quadratic performance index. The control gains can be obtained by solving a set of Lyapunov equations. The developed optimal cascaded digital controller enables the state and/or outputs of the digitally controlled closed‐loop sampled‐data system to optimally match those of the original continuous‐time closed‐loop system at any instant between sampling periods. The developed control law can be implemented using inexpensive and reliable digital electronics with a relatively long sampling period.
A global cartesian space obstacle avoidance scheme for redundant manipulators
Authors: Khadem Siamak E. , Dubey Rajiv V. 
Published: July 2007

AbstractOptimal control of kinematically redundant manipulators involves the use of extra degrees of freedom to improve their performance by energy minimization, singularity avoidance, obstacle avoidance, higher dexterity, etc. In this paper we deal with the obstacle avoidance problem by using modern control theory and choosing an integral‐type performance index which results in a global optimization scheme. Obstacles are expressed as Cartesian space constraints. The state constraint function and control effort are minimized globally as a performance index. The control effort which maximizes the Hamiltonian and minimizes the performance index is used to find the self‐motion of the manipulator. A simulation for a three‐degrees‐of‐freedom redundant planar robot is presented to demonstrate the effectiveness of the scheme.
Optimal control of mechanical systems subjected to periodic loading via chebyshev polynomials
Authors: Joseph Paul , Pandiyan R. , Sinha S. C. 
Published: July 2007

AbstractControllers using full‐state feedback and observer‐based feedback for mechanical systems subjected to periodic follower loads are designed in this paper. The designs are accomplished using an algebraic method incorporating Chebyshev polynomials coupled with principles of optimal control theory. The major advantage of this method is that it transforms differential equations with periodic coefficients to linear algebraic equations. Also, a dual‐system approach to design observers for such periodic systems turns out to be a novel technique and appears to have been employed for the first time. As an example of a mechanical system a triple inverted pendulum subjected to a periodic follower load is chosen and it is shown that both types of controllers can be successfully designed. The computational aspects and the suitability of this method for higher‐order mechanical systems are studied by applying it to one through five‐mass inverted pendulum models. The efficiency of the method is checked against the Runge–Kutta, Adams–Moulton and Gear numerical algorithms available in the IMSL software package by comparing the CPU time taken to evaluate the characteristic exponents of the Floquet transition matrix (FTM) as well as the norm of the control vector at the end of one period. It is shown that the proposed technique becomes much more efficient for higher‐order systems.
Decomposition and suboptimal control in dynamic systems
Authors: Chernousko F. L. 
Published: July 2007

AbstractA non‐linear dynamic system subject to bounded control forces is considered. It is shown that under certain conditions the feedback control can be chosen in such a way that the system reaches the prescribed terminal state in finite time. This control is obtained through decomposition of the system into subsystems with one degree of freedom each and applying the approach of differential games. Explicit formulae for the bounded control forces and the time of motion are presented. The obtained control is robust and can cope with small disturbances and parameter variations. Applications to robot control are discussed. The obtained feedback control is compared with another one which does not take small non‐linearities and disturbances into account.
A multi‐input/multi‐output optimal PI controller for redundant robots in the presence of flexible disturbances
Authors: Barbieri Enrique 
Published: July 2007

AbstractThe two‐stage synthesis of a multi‐input/multi‐output optimal proportional‐integral (PI) controller is described for linear, time‐invariant systems. In the first stage the PI controller is designed by solving a steady state algebraic Riccati equation. As a result, the optimal cost is expressed in terms of the system's constant output set‐points. In the second stage the cost is further reduced by optimally selecting the output set‐points to minimize a static quadratic performance index subject to linear algebraic constraints. The design framework is applied to a planar redundant robotic manipulator equipped with four joints and mounted at the tip of a long flexible arm. We then address the problem of self‐motion control in the presence of vibratory disturbances.
A gradient flow approach to computing lq optimal output feedback gains
Authors: Yan Wei‐Yong , Teo Kok L. , Moore John B. 
Published: July 2007

AbstractThis short communication considers the linear quadratic problem with static output feedback. It is shown that an optimal solution can be successfully computed by finding the limiting solution of an ordinary differential equation which is given in terms of the gradient flow associated with the cost function. Several properties are obtained concerning the gradient flow. For example, it is shown that the flow contains a subsequence convergent to a locally optimal output feedback gain. In the special case of state feedback the flow is guaranteed to converge to the optimal gain. The effectiveness of the method is demonstrated by an example.
Mixed H2/H∞ control with pole placement in a class of regions
Authors: Bambang Riyanto T. , Shimemura Etsujiro , Uchida Kenko 
Published: July 2007

AbstractThe problem of mixed H2/H∞ control with pole placement is considered for linear time‐invariant systems. This is the problem of determining a controller for linear time‐invariant systems which minimizes the H2‐norm of a certain closed‐loop transfor function subject to an H∞‐norm constraint on another closed‐loop transfer function and an additional constraint on the location of the closed‐loop poles in the complex plane. An optimization problem is posed for the pole‐constrained H2/H∞, problem in such a way that the objective function is expressed as a weighted sum of the actual H2 cost and its upper bound. A necessary condition for the optimization problem is derived via the Lagrange multiplier technique. The condition involves a set of highly coupled equations. By sacrificing the H2 performance, an alternative optimization problem is posed in order to simplify the necessary condition. An iterative algorithm for solving the coupled equations arising in the necessary conditions is proposed and numerical examples are presented.
Nonlinear optimal control of washing machine based on approximate solution of HJB equation
Authors: Milasi Rasoul M. , Yazdanpanah Mohammad‐Javad , Lucas Caro 
Published: July 2007

AbstractPerformance of a washing machine depends on different parameters, namely water temperature, degree of soiling, water volume, and motor speed. In this paper, firstly, a nonlinear model is derived based on the empirical data. In addition, validity of the proposed model is also verified. Secondly, to optimize the performance, a quadratic energy function is considered, which is minimized subject to the nonlinear model of the Washing Machine. Finding the corresponding control law requires solving a partial differential equation called Hamiltonian–Jacobi–Bellman (HJB) equation. An approximate solution for HJB equation using the second‐, third‐, and fourth‐order terms of Taylor's series expansion is utilized. Simulation results reveal that the higher‐order controller leads not only to a lower cost function but also to a better performance. Copyright © 2007 John Wiley & Sons, Ltd.
Prenatal diagnosis of a fetus with androgen insensitivity syndrome (AIS)
Authors: Yalinkaya Ahmet , Yayla Murat , Erdemoglu Mahmut 
Published: July 2007

AbstractObjective The aim of this study is to describe a fetus with androgen insensitivity syndrome diagnosed at mid‐second trimester.Case and Methods Nuchal translucency was measured thick and double test was found higher. The patient referred to our center at 16th weeks of gestation. Fetal ultrasound examination and amniocentesis was performed.Results The nuchal translucency (NT) of fetus in present pregnancy was measured approximately 10 mm at 13 weeks and Down syndrome risk was calculated 1 in 10 by double test. On ultrasound examination; thick nuchal fold (NF) and short fetal limbs were found, and the fetus was seen a female and amniocentesis was performed. Three weeks later the fetal karyotype was reported normal as 46,XY. Thereupon the fetus reexamined for 2D and 4D ultrasound, and confirmed previous findings. The fetus was terminated at 19th weeks and seen a female phenotype. The fetal gonads removed in abdomen and testicles confirmed histopatologically.Conclusion In generally, diagnosis of AIS is most made postnatally. This is the second case in English literature, which diagnosed mid‐second trimester. In this situation, the fetus with thick NT/NF and short limbs may be AIS, therefore appearance of fetal sex on ultrasound should be compared with genetic sex Copyright © 2007 John Wiley & Sons, Ltd.
Distal partial trisomy 1q: report of two cases and a review of the literature
Authors: Utine G. E. , Aktas D. , Alanay Y. , Gücer S. , Tuncbilek E. , Mrasek K. , Liehr T. 
Published: July 2007

AbstractWe report on two cases with partial trisomy 1q syndrome. One case was a mid‐trimester fetus with multiple malformations that was prenatally diagnosed with a de novo distal partial trisomy 1q. Prenatal ultrasound at 24th gestational week demonstrated the presence of cleft lip and palate, increased biparietal diameter and decreased abdominal circumference. Cytogenetic analysis (GTG banding) and subsequent fluorescence in situ hybridization (FISH) using whole chromosome paint 1 and multicolor banding (MCB) demonstrated an aberrant karyotype 46,XY,dup(1)(q31q43∼44). The second case was a newborn male infant with multiple congenital malformations. He had a derivative chromosome 18 as a result of a maternal insertion involving chromosomes 1 and 18. Further analyses including MCB showed his karyotype as 46,XY,ins(18;1)(q22;q23q31.1∼32). The present cases and a review of the literature suggest that partial trisomy of the long arm of chromosome 1 is a distinct clinical entity. Copyright © 2007 John Wiley & Sons, Ltd.
Isolated fetal hydrothorax with hydrops: a systematic review of prenatal treatment options
Authors: Deurloo K. L. , Devlieger R. , Lopriore E. , Klumper F. J. , Oepkes D. 
Published: July 2007

AbstractObjective To evaluate the effect of prenatal therapeutic interventions on perinatal outcome in pregnancies complicated by isolated fetal hydrothorax with hydrops.Methods A systematic review of the literature from January 1982 to January 2006 of perinatal outcome in pregnancies with isolated fetal hydrothorax with hydrops with any form of prenatal treatment was conducted.Results Forty‐four articles met our selection criteria, reporting a total of 172 fetuses treated prenatally. Reported treatment options were single (n = 13) or serial thoracocentesis (n = 18), thoraco‐amniotic shunt placement (n = 100) or a combination of thoracocentesis and shunting (n = 36). Four case‐reports described pleurodesis with OK‐432, (n = 3) and intrapleural injection of autologous blood (n = 2). Overall survival rate was 63%, ranging from 54% for single thoracocentesis to 80% in the 5 cases treated with pleurodesis, without statistically significant differences between the treatment modalities. Shunt‐placement with or without prior thoracocentesis was most often described, with survival rates of 67 and 61% respectively.Discussion The available literature consists exclusively of case reports and case series. This systematic review suggests that with prenatal intervention, perinatal survival rates around 63% are possible. There is a need for prospective, adequately controlled studies with long‐term follow‐up to determine the best treatment and more reliable outcome data in pregnancies complicated by fetal hydrothorax with hydrops. Copyright © 2007 John Wiley & Sons, Ltd.
Medical therapy for diabetes is associated with increased use of lower endoscopy
Authors: Lewis James D. , Capra Angela M. , Achacoso Ninah S. , Ferrara Assiamira , Levin Theodore R. , Quesenberry Charles P. , Habel Laurel A. 
Published: July 2007

AbstractBackgroundDiabetes mellitus is associated with an increased risk of colorectal neoplasia and diabetes medications may further influence the risk. Observational studies of the effect of diabetes medications on colonic neoplasia may be biased if use of diabetes medications is associated with undergoing lower endoscopy. This study examined the association between diabetes therapies and use of lower endoscopy.MethodsThis retrospective cohort study included patients with diabetes in an integrated, prepaid health plan. The primary exposure variables were use of sulfonylureas, metformin, thiazolidinediones (TZDs), and insulin. The outcome measure was completion of a flexible sigmoidoscopy or colonoscopy. Cox proportional hazards modeling, accounting for the time‐varying nature of the medication exposures, was used to generate estimates of the relative hazard (HR) of lower endoscopy with different medications.ResultsThe study included 44 169 patients followed for a mean duration of 4.2 years (SD = 2.5 years); 34% underwent at least one lower endoscopy. Patients who filled a diabetes medication prescription were more likely to undergo lower endoscopy (HR = 1.13, 95%CI 1.06–1.21). Compared to those taking only sulfonylureas, patients receiving sulfonylureas and metformin (HR = 1.12, 95%CI 1.06–1.18) or metformin alone (HR = 1.17, 95%CI 1.07–1.26) were more likely to undergo lower endoscopy. For all medications, new use was associated with undergoing lower endoscopy (p < 0.05 for all comparisons).ConclusionsDiabetic patients receiving medications are more likely to undergo lower endoscopy than those on diet control alone, particularly in the first year after initiating a new medication class and if taking metformin. Copyright © 2007 John Wiley & Sons, Ltd.
Insight into chain dimensions in PEO/water solutions
Authors: Hammouda Boualem , Ho Derek L. 
Published: July 2007

AbstractSmall‐Angle Neutron Scattering has been performed from poly(ethylene oxide) in deuterated water at temperature ranging from 10 to 80 °C. A simple fitting model was used to obtain a correlation length and a Porod exponent. The correlation length L characterizes the average distance between entanglements in the semidilute region and is proportional to the individual coil sizes in the dilute region. L was found to increase with temperature in the semidilute region but it decreases with temperature in the dilute region. This decrease is the precursor to the single‐chain collapse which applies to very dilute polymer solutions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2196–2200, 2007
Protein–thiol substitution or protein dethiolation by thiol/disulfide exchange reactions: The albumin model
Authors: Summa Domenico , Spiga Ottavia , Bernini Andrea , Venditti Vincenzo , Priora Raffaella , Frosali Simona , Margaritis Antonios , Giuseppe Danila Di , Niccolai Neri , Simplicio Paolo Di 
Published: July 2007

AbstractDethiolation experiments of thiolated albumin with thionitrobenzoic acid and thiols (glutathione, cysteine, homocysteine) were carried out to understand the role of albumin in plasma distribution of thiols and disulfide species by thiol/disulfide (SH/SS) exchange reactions. During these experiments we observed that thiolated albumin underwent thiol substitution (Alb‐SS‐X+RSH↔Alb‐SS‐R+XSH) or dethiolation (Alb‐SS‐X+XSH↔Alb‐SH+XSSX), depending on the different pKa values of thiols involved in protein–thiol mixed disulfides (Alb‐SS‐X). It appeared in these reactions that the compound with lower pKa in mixed disulfide was a good leaving group and that the pKa differences dictated the kind of reaction (substitution or dethiolation). Thionitrobenzoic acid, bound to albumin by mixed disulfide (Alb‐TNB), underwent rapid substitution after thiol addition, forming the corresponding Alb‐SS‐X (peaks at 0.25–1 min). In turn, Alb‐SS‐X were dethiolated by the excess nonprotein SH groups because of the lower pKa value in mixed disulfide with respect to that of other thiols. Dethiolation of Alb‐SS‐X was accompanied by formation of XSSX and Alb‐SH up to equilibrium levels at 35 min, which were different for each thiol. Structures by molecular simulation of thiolated albumin, carried out for understanding the role of sulfur exposure in mixed disulfides in dethiolation process, evidenced that the sulfur exposure is important for the rate but not for determining the kind of reaction (substitution or dethiolation). Our data underline the contribution of SH/SS exchanges to determine levels of various thiols as reduced and oxidized species in human plasma. © 2007 Wiley‐Liss, Inc.