bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling and control of a rotary crane with a flexible joint
Authors: Yoshimoto Tadashi , Sakawa Yoshiyuki 
Published: July 2007

AbstractA dynamical model is derived for the control of a rotary crane, which has a flexible joint and makes three kinds of motion (rotation, load hoisting and boom hoisting) simultaneously. The goal is to transfer a load to a desired place in such a way that at the end of the transfer the swing of the load decays as quickly as possible. A new open‐loop plus feedback control scheme is proposed.
Optimal inventory policy with partial backordering
Authors: Wee H. M. Moses 
Published: July 2007

AbstractThis paper formulates an inventory stocking policy with partial backordering. An implicit assumption in most inventory control models is that when there is a shortage, either complete backordering or complete lost sales is assumed. Such an assumption is not always tenable in view of the different responses by customers during stockout. Others who assume a fixed ratio of backordering and lost sales encounter the complication of a non‐convex cost function. When the cost function is non‐convex, the equation formulated is unstable; hence the optimal value is rather tedious to find. In this paper the fraction of backordering and lost sales is constrained so that convexity can be assured by means of the Hessian matrix. In this way the search for the optimal solution is simplified.
A chebyshev technique applied to a controlled nuclear reactor system
Authors: Van Dooren R. 
Published: July 2007

AbstractThe optimal control of a nuclear reactor system with a single group of delayed neutrons is studied by applying a numerical method based on the expansion of the unknown functions in Chebyshev series. It is shown how the given system dynamics, the initial and final conditions and the performance index are replaced by certain approximate versions. Several practical cases are given in which different control strategies are considered.
Optimal control of linear discrete systems via hahn polynomials
Authors: Hwang Chyi , Chen Chyi‐Tsong , Shih Yen‐Ping 
Published: July 2007

AbstractThis paper presents a method of finite series expansion using Hahn polynomials for the finite time optimal control of linear discrete time systems with a quadratic performance index. The method converts the discrete two‐point boundary value Euler—Lagrange difference equations into a set of linear algebraic equations. As a result, the computation is simple and straightforward.
A multidimensional optimal stopping‐time problem, with time‐average criterion
Authors: Sun Min 
Published: July 2007

AbstractAn optimal stopping‐time problem for a diffusion process absorbed at the boundary of a bounded domain inRd(d le 1) is considered. The cost criterion is of time‐average type and may be regarded as a version of the Gittins index. We characterize the value function and construct an optimal stopping policy using dynamic programming. Two numerical algorithms are used to solve two test problems inR1andR2.
Control of a long‐line‐type plant
Authors: Szymkat Maciej , Görecki Henryk , Popek Leslaw 
Published: July 2007

AbstractThis paper presents an approach to the feedback loop controller design problem for plants described by linear partial differential equations of a long‐line type. The classical frequency domain technique called ‘the optimal modulus criterion’ is applied. The different plant cases are classified and the corresponding recurrence formulae for derivatives of the transfer function inverse are derived. The applicability of the presented technique is discussed with particular emphasis on stability and performance aspects. The conclusions for different types of controllers are illustrated with several examples. This analysis uses an originally developed computer package.
An exercise in modelling of consumption, import and export of an exhaustible resource
Authors: Sethi Suresh , Sorger Gerhard 
Published: July 2007

AbstractIn this paper we analyse a control‐theoretic model of a country possessing a finite amount of a non‐renewable resource. The country can both consume the indigenous resource and export it. Moreover, a substitute for the indigenous resource is available at a given backstop price. We obtain the optimal consumption, export and import policy for the country.
Stochastically optimal advertising policies under dynamic conditions: The ratio rule
Authors: Raman Kalyan 
Published: July 2007

AbstractThere has been considerable debate among marketing researchers about the optimality of popularly used advertising policies. In particular, the ratio rule has aroused much interest. This paper analyses its optimality under the expected profit maximization criterion for a general class of models. The optimality of the ratio rule extends to the stochastic case provided that the conditions which ensure its optimality for the deterministic case are enlarged by an additional restriction. This additional restriction has the effect of transforming the stochastic evolution of goodwill and sales to log‐normal processes. Advertising dynamics, the nature of the response function and unexplained error variance all interact to determine whether the ratio rule is exactly optimal, approximately optimal or not optimal at all.
Approximate parallel controllers for discrete stochastic weakly coupled linear systems
Authors: Shen Xuemin , Gajic Zoran 
Published: July 2007

AbstractThe global Kalman filter of linear weakly coupled discrete systems is exactly decomposed into separate reduced‐order local filters via the use of a decoupling transformation. The approximate parallel controllers, up to an arbitrary degree of accuracy, are derived by approximating coefficients of the optimal control law. The proposed method allows parallel processing of information and reduces both off‐line and on‐line computational requirements. A real‐world example demonstrates the efficiency of the proposed method.
On mimo optimal preview tracking control for known trajectory models
Authors: Pak H. A. , Shieh R. 
Published: July 2007

AbstractA class of discrete time feedforward tracking controllers is presented for linear multivariable plants subjected to time‐varying exogenous inputs with known models. The controller design is based on linear quadratic optimization techniques and the augmented system approach. The optimal controllers use state feedback for regulation purposes. For the tracking objective the future set‐points along the reference trajectory vector are used. Necessary and sufficient conditions for the existence of an optimal feedforward solution are presented in terms of the relationships between the eigenvalues of the closed‐loop system and those of the trajectory models. For illustration a numerical example is included which is based on a dual‐stage positioning carriage modelled as a linear multivariable plant.
An algorithm for optimal scheduling of a class of cascade water supply systems
Authors: Brdys M. A. 
Published: July 2007

AbstractThe problem of determining overall optimized control schedules for a class of cascade water supply systems containing only fixed speed pumps is examined. The system control is by nature an on‐off type. The optimal scheduling problem can be formulated as dynamical optimal control problems with purely discrete symbols, discrete controls and also with continuous intermediate variables interrelated in a highly non‐linear way. An efficient problem solver is proposed. Its high efficiency is achieved by exploiting, through a suitable decomposition, certain structural properties of the problem. Lagrange relaxation is applied in order to break down the time structure of discrete control variables. The decomposition also enables consideration of mixed integer optimization on purely static grounds. The dynamical optimization constitutes only that part of the solver which deals with entirely continuous variables. There is a duality gap in the problem. However, certain, but not complete, information obtained through solving the dual problem (dual optimal information) is close to that which corresponds to the true (primal) optimal solution. This is an important property of the scheduling problem, which together with the problem structure creates a basis for the solver design.
Robust pole assignment in a specified region using output feedback
Authors: Oh Myungho , Gu Da‐Wei , Spurgeon Sarah K. 
Published: July 2007

AbstractAn output feedback pole assignment method is presented which seeks to achieve a robust solution where the assigned poles are as insensitive as possible to perturbations in the closed‐loop system. The freedom available to obtain a robust solution is realized by assigning poles not to exact locations but within specified regions of the complex plane. The problem is formulated as a non‐linear programming problem with a set of non‐linear constraints of matrix‐valued functions as well as a set of linear constraints. A numerical algorithm is presented in two forms and the results obtained are compared with those generated from other algorithms for a series of test examples taken from the literature.
Decomposition method for solving kalman filter gains in singularly perturbed systems
Authors: Shen Xuemin , Rao Ming , Ying Yiqun 
Published: July 2007

AbstractIn this paper a decomposition method is introduced for the solution of the optimal Kalman filter gains in singularly perturbed systems by solving two reduced‐order linear equations. The decomposition is achieved via the use of the Chang transformation, which is applied to the Hamiltonian matrix of the singularity perturbed Kalman filter. Since the decoupling transformation can be obtained up to an arbitrary degree of accuracy at very low cost, this approach produces an efficient numerical method for obtaining the Kalman filter gains. A numerical example is given to demonstrate the efficiency of the method.
Autopilot design using mixed H2 and H∞ optimal control
Authors: Sparks Andrew , Yeh Hsi‐Han , Banda Siva 
Published: July 2007

AbstractAn autopilot for a transport aircraft is designed using mixed H2 and H∞ optimal control. The control law design technique allows real parameter uncertainty to be accounted for in the design process. The autopilot consists of an inner loop that controls aircraft heading in response to external commands and an outer loop that tracks a localizer beam so that the aircraft is properly aligned with the runway for landing. The problem formulation and the robust control law design technique allow a wide range of performance and robustness requirements to be met. Analysis of the closed‐loop system shows the controller performance and robustness for a number of flight conditions through two separate approach profiles.
Existence of optimal control for non‐linear systems with an implicit derivative
Authors: Dauer J. P. , Balachandran K. 
Published: July 2007

AbstractThe existence of an optimal control for non‐linear systems having an implicit derivative with quadratic performance is proved. The results are established through the notions of condensing map and measure of non‐compactness of a set and using a fixed point theorem due to Sadovskii.
Numerical solution of time‐delayed optimal control problems with terminal inequality constraints
Authors: Lee Llan Y. 
Published: July 2007

AbstractIn this short communication we consider an approximation scheme for solving time‐delayed optimal control problems with terminal inequality constraints. Time‐delayed problems are characterized by variables x(t ‐ τ) with a time‐delayed argument. In our scheme we use a Páde approximation to determine a differential relation for y(t), an augmented state that represents x(t ‐ τ). Terminal inequality constraints, if they exist, are converted to equality constraints via Valentine‐type unknown parameters. The merit of this approach is that existing, well‐developed optimization algorithms may be used to solve the transformed problems. Two linear/non‐linear time‐delayed optimal control problems are solved to establish its usefulness.
Stability of distributed estimators for linear stochastic systems
Authors: McCullough Claire L. , Birdwell J. D. , Lenhart S. M. 
Published: July 2007

AbstractIn this paper we examine the stability of estimators on the infinite time horizon in the case where mismatch exists between the true system and the system model assumed by the filters. A counterexample is given to show that standard stability requirements on the true system and the filters are not sufficient to guarantee that covariance of the error between the actual state and the estimate remains finite in the limit. Sufficient conditions for uniformly bounded error covariance are presented and in a special case, necessary and sufficient conditions are given. These will ensure that a filter is implementable and will remain stable over the infinite time horizon. We also show that an asymptotically stable system will not necessarily have finite state covariance in the limit as t → ∞, and give the necessary and sufficient conditions to assure boundedness of the covariance.
Identification of rudder—yaw and rudder—roll steering models by using recursive prediction error techniques
Authors: Zhou Wei‐Wu , Cherchas Dale B. , Calisal Sander 
Published: July 2007

AbstractLinear and non‐linear recursive prediction error (RPE) methods have been employed for the purpose of identification of the dynamics of ship rudder—yaw and —roll motions. The evaluations of the goodness of model structures have been carried out by comparing simulated outputs from the identified model with real measurements. In the linear case Nomoto's first‐order model has been initially considered for the transfer functions between rudder—yaw and —sway, with a second‐order model for rudder—roll with coupling effects considered only between sway—yaw and —roll. Identification results have shown that such a model is not appropriate. Changing the model to second‐order between rudder—sway and —yaw and further considering the coupling effects between roll angle—sway and —yaw shows that a significant improvement is achieved, while the coupling effect between yaw and roll appears negligible. In the nonlinear case effects due to various non‐linear terms have been studied with the non‐linear RPE algorithm.
Further development of an approximate loop transfer recovery methodology for fixed order dynamic compensator design
Authors: Byrns Edward V. , Calise Anthony J. 
Published: July 2007

AbstractThis paper further develops a methodology for designing fixed order compensators. The formulation uses an approximate loop transfer recovery (LTR) method to achieve performance and stability subject to a disturbance and unstructured uncertainty at either the plant input or the plant output. The approximate LTR methodology has the advantage that the quadratic performance index weighting matrices are uniquely defined. To reduce sensitivity to real parameter uncertainty, the performance index is modified to include a penalty on the closed‐loop sensitivity dynamics. The formulation avoids the explicit introduction of sensitivity states into the performance index and thus does not increase the overall dimension of the problem. An example design for the coupled mass benchmark control problem is provided to demonstrate this methodology.
New performance bounds of continuous‐time LQ systems with uncertain parameters
Authors: Zhang X. F. , Luo J. S. , Johnson A. 
Published: July 2007

AbstractIn this short communication we present new upper and lower performance bounds of LQ (linear—quadratic) systems with time‐varying parametric uncertainties. These new performance bounds improve on those proposed by Wang and Kuo by giving more accurate measures of performance robustness. We use the same example as that used by Wang and Kuo to show that the improvements are substantial.
Discrete time lq design from the viewpoint of the inverse optimal regulator
Authors: Mehdi D. , Darouach M. , Zasadzinski M. 
Published: July 2007

AbstractIn this communication a new design method for the discrete‐time LQ regulator based on the solution of the inverse optimal regulator is presented. The main feature of the method is that it requires no Riccati solution in addition to having a number of tuning parameters which help to shape a desirable response of the closed‐loop system.
An application of optimal control theory to the trajectory tracking of rigid robot manipulators
Authors: Grabbe M. T. , Dawson D. M. 
Published: July 2007

AbstractIn this paper optimal control theory is applied to the trajectory tracking problem for a rigid robot manipulator. First a stability result is developed showing the relationship between optimal control theory and the global exponential stability of a class of second‐order non‐linear systems. Next this class of nonlinear systems is shown to contain the trajectory tracking error dynamics for a rigid robot manipulator when using a modified computed torque controller with an auxiliary input. Finally the stability result is applied to the tracking error dynamics to determine the auxiliary input to the robot controller. The result is a non‐linear feedback control law which provides exponentially stable position and velocity tracking for a rigid robot manipulator without complete feedback linearization of the robot dynamics.
Analysis of optimal controls for a mathematical model of tumour anti‐angiogenesis
Authors: Ledzewicz U. , Schättler H. 
Published: July 2007

AbstractAnti‐angiogenic therapy is a novel treatment approach for cancer that aims at preventing a tumour from developing its own blood supply system that it needs for growth. In this paper we consider a mathematical model where the endogenous stimulation term in the dynamics is taken proportional to the number of endothelial cells. This system is an example from a class of mathematical models for anti‐angiogenic treatment that were derived from a biologically validated model by Hahnfeldt, Panigrahy, Folkman and Hlatky. The problem how to schedule a given amount of angiogenic inhibitors to achieve a maximum reduction in the primary cancer volume is considered as an optimal control problem and it is shown that optimal controls are bang‐bang of the type 0a0 with 0 denoting a trajectory corresponding to no treatment andaa trajectory with treatment at maximum dose along that all inhibitors are being exhausted. Copyright © 2007 John Wiley & Sons, Ltd.
Influence of fiber orientation on high stress wear behavior of sisal fiber‐reinforced epoxy composites
Authors: Chand Navin , Dwivedi U. K. 
Published: July 2007

AbstractSisal fiber‐reinforced epoxy composites having three different fiber orientations, namely LL, LT, TT mentioned in the text were prepared and tested for their high stress abrasive wear behavior. Effect of fiber orientation, sliding distance, and load on abrasive wear of sisal–epoxy composites have been determined. Wear data of composites have been compared with the pure epoxy. Incorporation of fibers decreases the wear rate of epoxy resin, which varies with the fiber orientation. Wear rate in case of TT composite is found minimum as compared to other two composites. Wear rate follows the following trend, WTT < WLT < WLL. Owing to minimum exposed area of fiber to the sliding asperities, lowest wear rate occurs in the case of TT composite. Increase of load and sliding distance increases the wear volume in all the composites, because of the progressive loss of material. Wear mechanism has been discussed by using SEM micrographs of the worn surfaces. POLYM. COMPOS., 28:437–441, 2007. © 2007 Society of Plastics Engineers.
Fluorinated aramid fiber reinforced polypropylene composites and their characterization
Authors: Maity J. , Jacob C. , Das C.K. , Kharitonov A.P. , Singh R.P. , Alam S. 
Published: July 2007

AbstractPolymer fibers are one of the main substances used for the reinforcement of plastic composites. Surface modification of aramid fiber was performed by direct fluorination. The crystallinity and the decomposition temperature of the modified fiber were increased. Scanning electron microscope shows that the roughness increases in the modified fiber. Composites were prepared by using modified and unmodified fibers. It was shown that the mechanical and thermal properties increase for modified fiber reinforcing composites. To reduce the fiber degradation or breakdown, composites were prepared by solution casting method. POLYM. COMPOS., 28:462–469, 2007. © 2007 Society of Plastics Engineers
Melting and crystallization behavior of polyhedral oligomeric silsesquioxane‐capped poly(ε‐caprolactone)
Authors: Ni Yong , Zheng Sixun 
Published: July 2007

AbstractIn this study, we investigated the melting and crystallization behavior of polyhedral oligomeric silsesquioxane (POSS)‐capped poly(ε‐caprolactone) PCL with various lengths of PCL chains by means of X‐ray diffraction and differential scanning calorimetry. This organic–inorganic macromolecule possesses a tadpole‐like structure in which the bulky POSS cage is the “head” whereas PCL chain the “tail”. The novel organic–inorganic association result in the significant alterations in the melting and crystallization behavior of PCL. The POSS‐terminated PCL displayed the enhanced equilibrium melting points compared to the control PCL. Both the overall crystallization rate and the spherulitic growth rate of the POSS‐terminated PCLs increased with increasing the concentration of POSS (or with decreasing length of PCL chain in the hybrids). The analysis of Avrami equation shows that the crystallization of the POSS‐terminated PCL preferentially followed the mechanism of spherulitic growth with instantaneous nuclei. It is found that the folding free energy of surface for the POSS‐terminated PCLs decreased with increasing the concentration of POSS. It is found that the folding free energy of surface for the POSS‐terminated PCLs decreased with increasing the concentration of POSS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2201–2214, 2007
Silica nanoparticle dispersions in homopolymer versus block copolymer
Authors: Lan Qiang , Francis Lorraine F. , Bates Frank S. 
Published: July 2007

AbstractSilica nanoparticles (17 ± 4 nm in diameter) were modified by grafting polystyrene chains to the surfaces using atom transfer radical polymerization (ATRP). The molecular weight of the grafted chains ranged from 8 to 48 kDa. These modified nanoparticles were mixed in solution with poly(styrene) homopolymer (18–120 kDa) and symmetric poly(styrene‐b‐butadiene) (PS‐PB) diblock copolymer (34–465 kDa) and the states of dispersion in the dried composites were characterized by transmission electron microscopy (TEM). In the so‐called wet brush limit, when the graft molecular weight equals or exceeds the matrix value, the silica particles form a uniform random dispersion in poly(styrene). Increasing the homopolymer matrix, molecular weight above the graft value results in particle clustering and macroscopic‐phase separation. Mixtures of the lamellar forming block copolymer and nanoparticles exhibit a very different trend, with particle clustering at the lower PS‐PB molecular weights and dispersion at the highest value. This latter finding is rationalized on the basis of packing constraints associated with lamellar order and the effective particle dimensions, and the degree of solvation at ordering, both of which favor higher molecular weight block copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2284–2299, 2007