bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance criterion sensitivity analysis of ship‐steering models with respect to shaping filter design parameters
Authors: Tugcu A. K. , Coskunoglu O. , Reid R. E. 
Published: July 2007

AbstractThe design of linear‐quadratic controllers for the steering control of ships requires the design of sway force and yaw moment disturbance shaping filters to adequately represent the statistical properties of the sea‐way. The estimated disturbance states are employed in the formulation of the optimal control law to improve the steering quality to minimize propulsion losses. In this paper a sensitivity analysis of the optimal cost criteria with respect to the shaping filter parameters is made to determine the relative importance of the filters and parameters with differing ships, cost criteria and sea‐way conditions. For simplicity of the present analysis the Kalman filter is excluded from the dynamics, i.e. all the states are assumed to be perfectly measurable. This allows the analysis to be done at the upper bound of optimal performance. The percentage deviation in the resulting optimal propulsion loss from a known deviation in the parameters is calculated. Sensitivities with respect to two different controllers, each minimizing a different performance criterion are analysed for two ship types. The results indicate that the yaw shaping filters are relatively more important for both of the ship types. It is also shown, however, that the sway shaping filter, although having no significant effect on the optimal performance of ship types such as the large tanker examined, does affect that of fine‐lined high‐speed vessels such as the container ship analysed.
Stochastic optimization for hydro‐thermal power systems
Authors: Halliburton T. S. , Sirisena H. R. 
Published: July 2007

AbstractA suboptimal stochastic optimization method for the long‐term scheduling of a hydroelectric reservoir is described. The objective of the optimization is to minimize thermal station fuel costs, in a mixed hydro‐thermal power system, over a one‐year horizon. Exact stochastic and deterministic solutions, obtained by dynamic programming (DP) for a simple one‐reservoir model, are compared. The two solutions differ significantly, indicating that deterministic solutions to the problem are inadequate. Stochastic DP is not computationally feasible for a multi‐reservoir system. A suboptimal linear feedback controller with non‐Gaussian reservoir water storages is then developed. It approximates the stochastic DP solution for one reservoir very well and is capable of extension to a multi‐reservoir version.
Numerical solution of the minimum‐time flight of a glider through a thermal by use of multiple shooting methods
Authors: Lorenz Jürgen 
Published: July 2007

AbstractThe problem of the time‐optimal flight of a glider through a given thermal is treated with the calculus of variations. The resulting two‐point boundary value problem is solved using the multiple shooting method. Solutions are obtained for various parameter values. For special values of these parameters, a branching of the solutions is observed. Additional solutions are obtained for which the control variable and the normal load factor are constrained by their maximum allowed values.
Decentralized structures for stream water quality control problems
Authors: Mahmoud Magdi S. , Hassan Mohamed F. , Saleh Saad J. 
Published: July 2007

AbstractIn this paper, the evolution of stream water quality components is described by a linear dynamic model of order seven. The model is controlled through two actions: one by changing the water discharge into the basin and another by manipulating the effluent flow rate. Computation of the decentralized gains is performed using two different multilevel structures. Results of simulating a reach of the River Nile are presented.
Phase lag and lead weighting in linear‐quadratic control
Authors: Anderson Brian D. O. , Gibson John A. , Sirisena Harsha R. 
Published: July 2007

AbstractThe effect of introducing a first order lag or lead weighting function into an otherwise conventional linear‐quadratic optimization problem is examined. Properties of the optimal compensator are derived, and the effect on robustness of the optimal system in different frequency ranges is examined.
Performance index sensitivity of optimal control systems with uncertain parameters
Authors: Ronge Peter 
Published: July 2007

AbstractThe solutions of optimal control problems are sensitive to the changes of parameters which can occur due to either their statistical nature or to an identification which is only approximate. To allow a reduction of this sensitivity two scalar sensitivity measures are proposed which can be incorporated into an augmented performance index. Different interpretations of the measures are given.As a first application, the problem of an insensitive feedforward control is investigated. An efficient numerical method for its solution is given. An example demonstrates not only the feasibility of this new approach but also the possible improvement in comparison to the standard optimal control procedure for problems where knowledge about system uncertainties has to be included in the design.
Traffic regulation of an underground railway transportation system by state feedback
Authors: Campion G. , Van Breusegem V. , Pinson P. , Bastin G. 
Published: July 2007

AbstractThe commonly used state‐space models for the traffic description of urban underground railway lines are not suitable for practical on‐line control. On the other hand, the proposed orginal linear formulation is very convenient for optimal state feedback control implementation. Results of simulations relative to a theoretical line as well as to the Brussels Railway lines show the benefit to be expected using this new formulation for on‐line traffic control.
Auto‐weighted minimum‐variance self‐tuning controller
Authors: Zachariah K. J. , Warwick K. 
Published: July 2007

AbstractA self‐tuning controller which automatically assigns weightings to control and set‐point following is introduced. This discrete‐time single‐input single‐output controller is based on a generalized minimum‐variance control strategy. The automatic on‐line selection of weightings is very convenient, especially when the system parameters are unknown or slowly varying with respect to time, which is generally considered to be the type of systems for which self‐tuning control is useful. This feature also enables the controller to overcome difficulties with non‐minimum phase systems.
Some remarks about open‐loop control in stochastic quasilinear systems
Authors: Socha Leslaw 
Published: July 2007

AbstractA method of obtaining the optimal control in quasilinear systems which are influenced by disturbances is presented. The analysis is carried out for second‐order stationary and non‐stationary Gaussian processes. First, the stochastic problem is changed into an equivalent deterministic problem, and next the optimal control is constructed from the maximum principle. This method is applied to the optimal temperature profile in a chemical reactor. The results are illustrated by a numerical example.
An implicit pole‐assignment self‐tuning regulator
Authors: Karam K. Z. , Warwick K. , Farsi M. 
Published: July 2007

AbstractA new self‐tuning implicit pole‐assignment algorithm is presented which, through the use of a pole compression factor and different RLS model and control structures, overcomes stability and convergence problems encountered in previously available algorithms. Computational requirements of the technique are much reduced when compared to explicit pole‐assignment schemes, whereas the inherent robustness of the strategy is retained.
Stochastic adaptive control of non‐minimum phase systems
Authors: Hersh M. A. , Zarrop M. B. 
Published: July 2007

AbstractThe explicit self‐tuning control of linear systems with constant but unknown parameters is analysed. The class of single‐input/single‐output, discrete‐time stochastic systems with coloured noise is considered without imposing a minimum‐phase condition. A stochastic approximation type of identification algorithm coupled with a general linear control law structure satisfying weak conditions is shown to lead to the required stability properties of the closed‐loop system. Similar approaches have been previously proposed for deterministic systems and for stochastic systems with uncorrelated disturbances. The specific example of a pole‐shifting algorithm is considered and it is shown that the required asymptotic behaviour is achieved under certain conditions.
Inadmissibility of siso singular observation lqg design
Authors: Halevi Y. , Palmor Z. J. 
Published: July 2007

AbstractThe widely known LQG design method for linear time invariant SISO plants may lead under certain circumstances to closed loop systems that have no stability margins; their sensitivity is infinite and the resulting system is non‐causal. We refer to such systems as inadmissible ones. This rather surprising phenomenon is analysed in the paper and is shown to be a generic property, depending on structural features of the plant, noises and criteria involved. Necessary and sufficient conditions guaranteeing admissibility of LQG design, in both the frequency and the time domains, are presented and proved. These conditions enable an a priori detection of such possible ‘traps’ in the LQG method. Although the paper focuses on LQG, some of the results are shown to be of wider applicability. It is shown that the common combination observer‐static state feedback is inadmissible if input derivatives are used by the observer. The conditions derived in the paper are used to identify suboptimal methods, developed for other purposes, by which the causality problem may be avoided. A new suboptimal method is suggested and the stability properties of suboptimal designs are discussed. In addition some apparent ambiguities regarding the stability properties of singular observation LQG designs are clarified by means of the results derived in the paper.
Non‐existence of solutions in optimal structural design
Authors: Stadler W. 
Published: July 2007

AbstractRecently, much effort has been expended in establishing the well‐posedness of optimal structural design problems. Experience indicates, however, that awareness of the non‐existence of a solution may also be beneficial and can eliminate time wasted in searching for non‐existing numerical or analytical optima. Two standard approaches to non‐existence proofs are presented: the construction of suitable sequences and the use of necessary conditions — both within the context of contradiction proofs. The methods are illustrated with examples from optimal structural design ranging from the minimum weight design of an axially loaded rod to that of axisymmetrically loaded shells of revolution. It is shown that the causes of non‐existence can be the choice of function space, boundary conditions, and a discontinuous dependence on parameters, among others. Some possible guidelines for a successful formulation of well‐posedness in structural design are included.
An adaptive filter for dynamic positioning
Authors: Gourishankar V. G. , Trybus L. , Rink R. E. 
Published: July 2007

AbstractAn adaptive filter is developed to estimate the low frequency (LF) drift and high frequency (HF) wave‐induced oscillations of a floating vessel. The parameters of the HF model depend on the weather and must be updated. By applying a singular perturbation approximation, we decompose the filtering problem into two separate LF and HF designs. This results in an LF Kalman filter and an HF parameter estimator. The parameter estimator is implemented as an extended Kalman‐filter‐type robust algorithm. To some extent, our approach provides a bridge between existing dynamic positioning filter synthesis techniques. Simulation results are included.
Optimal hydrothermal load flow: Formulation and a successive approximation solution for fixed head systems
Authors: El‐Hawary M. E. , Rao R. S. , Christensen G. S. 
Published: July 2007

AbstractThis paper deals with the optimal load flow problem in a fixed‐head hydrothermal electric power system. Equality constraints on the volume of water available for active power generation at the hydro plants as well as inequality constraints on the reactive power generation at the voltage controlled buses are imposed. Conditions for optimal load flow are derived and a successive approximation algorithm for solving the optimal generation schedule is developed. Computer implementation of the algorithm is discussed, and the results obtained from the computer solution of test systems are presented.
Neighbouring extremals of dynamic optimization problems with parameter variations
Authors: Lee A. Y. , Bryson A. E. 
Published: July 2007

AbstractNeighbouring extremals of dynamic optimization problems with a known parameter vector θ and an unknown parameter vector π are considered in this paper. The parameter vector π and the control are to be optimally determined to minimize a cost functional with a given θ. With some simplifications, the neighbouring extremal problem is reduced to one of solving a linear, time‐varying, two‐point boundary value problem with integral path equality constraints. A modified backward sweep method is used to solve this problem. Example problems are solved to illustrate the validity and usefulness of the solution technique.
Decentralized control for multimachine power systems
Authors: Lu Qiang , Lu Jin , Gao Jixang , Lee Gordon K. F. 
Published: July 2007

AbstractA new approach to solve the problem of designing decentralized optimal controllers for large‐scale power systems is proposed. The control law that results from the design is a decentralized one; accordingly, each subsystem is controlled only by its own variables. In using the proposed scheme, the cost functional for each subsystem is minimized, and the interacting effects between the subsystems are not ignored in deriving the control strategy. As a result, the application of the control scheme proposed by this paper provides optimality even if the subsystems are very strongly coupled. Results of investigation into the decentralized optimal control of a 10‐machine system are satisfactory.
Optimal maintenance of a system of machines with weakest‐link‐dependent performance
Authors: Teo K. L. , Wong K. H. , Goh C. J. 
Published: July 2007

AbstractThis paper considers the maintenance policy of a system of machines whose deterioration is dependent on the machines' quality states and maintenance efforts. The return of the system of machines, however, is dependent only on the machine with the lowest quality state. This becomes a realistic feature when the machines are arranged in series as part of an assembly line production. This feature also gives rise to an unconventional optimization problem with an interesting theoretical challenge. The problem is subsequently formulated as a constrained optimal control problem. It is first shown that the problem admits an optimal control. Then, by using the control parametrization approach, an efficient computational scheme is devised for solving the problem.
Real‐time computation of feedback controls for constrained optimal control problems. part 1: Neighbouring extremals
Authors: Pesch Hans Josef 
Published: July 2007

AbstractA numerical method is developed for the real‐time computation of neighbouring optimal feedback controls for constrained optimal control problems. The first part of this paper presents the theory of neighbouring extremals. Besides a survey of the theory of neighbouring extremals, special emphasis is laid on the inclusion of complex constraints, e.g. state and control variable inequality constraints and discontinuities of the system equations at interior points. The numerical treatment of these constraints is particularly emphasized. The linearization of all necessary conditions of optimal control theory leads to a linear, mulitpoint, boundary value problem with linear jump conditions that is especially well suited for numerical treatment.
On the design of active suspension incorporating human sensitivity to vibration
Authors: Lee Allan Y. , Salman Mutasim A. 
Published: July 2007

AbstractThe human sensitivity to vertical acceleration at various frequencies is incorporated in the design of active suspension by using the linear quadratic regulator (LQR) control method with a frequency‐shaped cost functional. With this method, a decrease in vertical acceleration of the sprung mass is achieved over the range of frequencies that causes maximum discomfort to the human passenger.
Numerical method for the solution of the singular riccati matrix
Authors: Subrahmanyam M. B. 
Published: July 2007

AbstractA computational scheme is presented for the solution of the Riccati matrix associated with time‐varying quadratic regulation. It is shown that the local truncation error of the algorithm is at most O(Δt3) where Δt is the interval of computation. The main contribution of this short communication is to demonstrate that the scheme yields the solution even in the face of singularities. Higher‐order formulae are useful when the sensitivity of the Riccati matrix to error is large.
Servo controller design based on frequency‐dependent error
Authors: Furuta Katsuhisa , Suenaga Osamu 
Published: July 2007

AbstractVariables to be controlled are usually taken from measured outputs. They may be filtered and the regulation of frequency‐dependent error has been considered in the design of robust controllers. Anderson considered the frequency‐dependent linear‐quadratic (LQ) problem. The frequency‐dependent weight he considered is restricted to the phase lag and lead type. This paper considers not only regulation of general frequency‐dependent errors but also a servo controller tracking to a given reference signal in the presence of disturbances. The control law is determined either on the basis of the quadratic criterion function or by pole assignment in a region. The control law to assign poles in a region is derived from one designed for the corresponding discrete‐time system obtained by bilinear transformation.
Stochastic adaptive control of a class of non‐minimum‐phase systems
Authors: Chan C. Y. , Sirisena H. R. 
Published: July 2007

AbstractThis paper presents a computationally efficient pole‐zero placement adaptive controller for linear discrete stochastic systems with coloured noise. The systems are assumed to be open‐loop stable, but not necessarily minimum phase. It is shown that the algorithm asymptotically achieves the required properties of the closed‐loop system.
Applications of the exterior penalty method in constrained optimal control problems
Authors: Xing An‐Qing , Wang Chung‐Lie 
Published: July 2007

AbstractThis paper gives a theoretical analysis of the applications of the exterior penalty method in continuous‐time non‐linear programs and constrained optimal control problems. As an example, the Cauchy Inequality in the continuous case is proved. Also, the exterior penalty method is used to treat constrained optimal control problems. It is proved, under suitable assumptions, that a constrained optimal control problem can be solved by performing a sequence of unconstrained optimal control problems, and the constrained solution to the constrained optimal control problem can be obtained as the limit of the solutions to the sequence of unconstrained optimal control problems. In using the exterior penalty method to solve constrained optimal control problems it is usually assumed that each of the modified unconstrained optimal control problems has at least one solution. An existence theorem for these problems is also given.
Finite‐dimensional approximation for optimal fixed‐order compensation of distributed parameter systems
Authors: Bernstein Dennis S. , Rosen I. Gary 
Published: July 2007

AbstractIn controlling distributed parameter systems it is often desirable to obtain low‐order, finite‐dimensional controllers in order to minimize real‐time computational requirements. Standard approaches to this problem employ model/controller reduction techniques in conjunction with LQG theory. In this paper we consider the finite‐dimensional approximation of the infinite‐dimensional Bernstein/Hyland optimal projection theory. Our approach yields fixed‐finite‐order controllers which are optimal with respect to high‐order, approximating, finite‐dimensional plant models. We illustrate the technique by computing a sequence of first‐order controllers for one‐dimensional, single‐input/single‐output parabolic (heat/diffusion) and hereditary systems using a spline‐based, Ritz‐Galerkin, finite element approximation. Our numerical studies indicate convergence of the feedback gains with less than 2% performance degradation over full‐order LQG controllers for the parabolic system and 10% degradation for the hereditary system.
Structural and robust optimality of discrete‐time optimal regulators
Authors: Mirza Kais Baker , Basha Akiel E. 
Published: July 2007

AbstractThe following problem is discussed: given an optimal control law for a linear, discrete‐time, single‐input system with respect to some quadratic cost, determine the necessary and sufficient condition whereby this control law remains optimal in the presence of small plant parameter variations. This condition is derived and expressed in terms of the loop transfer function of the optimal system, its Nyquist plot and the transfer function from the input to the controlled variables associated with the weighting matrix.
Optimal slidesmanship in conferences with unpredictable chairmen
Authors: Hartl Richard F. , Jørgensen Steffen 
Published: July 2007

AbstractConference attendance is an area of scientific endeavour that can be very rewarding to its skilled practitioners. However, the inexperienced conference attendee (speaker) may not be aware of the rules of the game and runs a risk of making disastrous mistakes.In this paper we are concerned with slidesmanship and wish to design optimal policies for a slidesman who must decide on such questions as the number of slides to prepare, the timing of the slides and at what time to terminate the presentation. We suggest that the slidesman is facing a forgetful audience as well as an unpredicatable chairman.
On‐line optimal terrain‐tracking system
Authors: Lee Sung Mhan , Bien Zeungnam , Park Seung O. 
Published: July 2007

AbstractThe problem of on‐line optimal tracking control is considered for an aircraft terrain‐following system. An on‐line optimal control law which reflects the non‐linear airborne vehicle dynamics with bounded control input is obtained by using a pointwise optimization technique called optimal decision strategy. The stability of the resulting system is also discussed. To demonstrate the feasibility and effectiveness of the proposed scheme, simulations have been performed for a realistic terrain‐following system.
Design of a low‐sensitivity, minimum norm and structurally constrained control law using eigenstructure assignment
Authors: Burrows Simon P. , Patton Ron J. 
Published: July 2007

AbstractThe freedom for eigenvalue assignment in specified areas of the complex plane and of the scope for placing the corresponding eigenvectors is utilized to form an analytical gradient‐based optimization problem which may be used to determine a low‐sensitivity eigenvalue assignment with a structurally constrained and low‐norm linear gain matrix. Examples are used to compare the properties of such optimized controllers with those obtained using single‐objective design techniques.
On stable full‐order and reduced‐order LQG controllers
Authors: Halevi Yoram , Bernstein Dennis S. , Haddad Wassim M. 
Published: July 2007

AbstractThe problem of deriving a suboptimal LQG controller which is internally stable is considered. In the case where the controller is internally unstable a procedure is given for modifying the optimization parameters, i.e. the state weighting matrix and/or the process noise intensity. Sufficient conditions for controller stability of appropriately modified optimization problems are given for both the full‐order and reduced‐order cases. A final tuning procedure is then used to minimize the deviation from the original LQG problem.