bluuebunny/crossref_metadata_2025_split huggingface dataset:
A strategy for power system stabilization by control‐effort and response‐time minimization
Authors: Rahim A. H. M. A. , Gourishankar V. G. 
Published: July 2007

AbstractA method is described for deriving a quasi‐optimal feedback control scheme for stabilizing power systems. This is achieved by minimizing a functional which is a linear combination of response time and control effort. The transient repsonse of a power system obtained using this control strategy is found to be superior to that achieved with a controller based on a linear regulator approach. This scheme, in a slightly modified form, is easily implemented in practice. The modification does not affect the effectiveness of the scheme to control transients. Simulation results are included.
A simple design method for single‐input optimum regulators
Authors: Flower J. O. 
Published: July 2007

AbstractThis paper considers the single‐input quadratic‐cost linear‐system‐design problem. It provides a simple design procedure for establishing the feedback‐gain terms by comparison of a determinant expansion (containing the unknown gain terms) with the optimal closed‐loop polynomial for the system. This leads to a set of linear simultaneous equations, the solution of which reveals the gain terms. The procedure closely parallels the method reported by Grimble. 1It is entirely straightforward, requiring no transformation of the state variables and is particularly attractive for dealing with systems of modest order or even large‐order sparse systems.
Skimming pricing for a class of diffusion models
Authors: Rao Ram C. 
Published: July 2007

AbstractThis paper examines the optimal dynamic pricing policy of a monopolist faced with demand that follows a first‐order adjustment process. This adjustment process is assumed to capture the diffusion of a new durable good. Under these conditions the optimal policy has the structure of skimming, i.e. high initial prices followed by monotonically declining prices. This corresponds to the usual notion of a price discriminating monopolist who travels down the demand curve in order to garner all consumer surplus, but with one difference. Specifically, it is seen that when cash flows are not discounted the policy is to travel down a line that is parallel to the demand curve if demand is linear in price. If demand is of the constant elasticity type, the policy is to travel down a curve that is steeper than the demand curve. Finally, when profits are discounted, initial prices are lower than in the undiscounted case, thus increasing the rate of product diffusion initially.
A method of on‐line optimal control via moving models
Authors: Wu Wen‐Teng , Tzeng Ren‐Yih 
Published: July 2007

AbstractA method of on‐line optimal control is proposed. A control system with a quadratic performance index is investigated. The system is represented by a first‐order moving model. The difficulties involved in solving the two‐point boundary problems of the optimal control problem are avoided by the use of the proposed method. Illustrative examples are presented to show the promise that the method provides.
Insect pest eradication as a discrete non‐linear control problem
Authors: Plant Richard E. 
Published: July 2007

AbstractThe problem of eradication of an insect pest population can be viewed as a time optimal, discrete time, non‐linear control problem in which the objective is to achieve eradication as quickly as possible. We discuss the solution of a simple model problem in which eradication is carried out by means of the sterile insect technique. An algorithm for the resulting control problem is presented.
A discrete‐time optimal adaptive control law for a robot arm
Authors: Marchand Pauline A. , Lawrence Peter D. , Cherchas Dale B. 
Published: July 2007

AbstractThe equations of motion describing a robot's dynamics are coupled and non‐linear, making the design of an optimum controller difficult using classical techniques. In this work an explicit adaptive control law is proposed based on a discrete linear model for each link and on the minimization of a quadratic performance criterion for position error and total control effort. The system parameters are recursively estimated at each control step by use of least squares, with a typical sample time of 0.02 s. A computer simulation of the resulting scheme is performed to evaluate the controller. The simulation model, based on the first three links of an existing robot, includes detailed motor dynamics and treats the wrist assembly as a load mass. Simulated test paths requiring movement of the outer two links indicate that the controller adapts and that its behaviour is stable and convergent.
Robust control strategy for take‐off performance in a windshear
Authors: Chen Y. H. , Pandey S. 
Published: July 2007

AbstractA robust control strategy has been designed for an aircraft during take‐off. The effects of different windshear intensities have been analysed for one‐ and two‐dimensional models. The robust control is designed to tolerate windshear regardless of its variations. The only information the control utilizes is the upper‐bound value of the allowable control magnitude.
Boundary feedback control of a vibrating beam subject to a displacement constraint
Authors: Sloss J. M. , Adali S. , Sadek I. S. , Bruch J. C. 
Published: July 2007

AbstractThe problem of controlling the dynamic response of a beam by means of boundary feedback is solved. The control is applied at one of the supports of the beam by means of a torque actuator in order to keep the maximum deflection within specified bounds. Since the location and time of the maximum deflection depend on the control itself, the feedback is determined by the solution of a min‐max problem. The theory is illustrated by a numerical example involving an impulsively loaded beam, and the effectiveness of the proposed control is studied numerically.
On the approximate identification of the leading coefficient of a linear elliptic equation by output error and equation error minimization
Authors: Crosta Giovanni 
Published: July 2007

AbstractBy definition, the approximate solution to the (finite‐dimensional) identification problem is a minimizing element of either cost function. The output error is minimized by two methods: finite difference‐discretized gradient (FD‐DZG) and finite element—discrete gradient (FE‐DG). The equation error is minimized by a DZG method. Two‐sided constraints are applied.With reference to an example of polynomial type in a rectangular domain, some tests are carried out in which the role of several parameters, including data noise, is investigated. Most computational results pertaining to the output error are interpreted according to: (a) sensitivity analysis; (b) an error estimate, which compares FD‐DZG to FD‐DG; and (c) a dynamical system model of the algorithm.An optimal uniform initial value of the unknown coefficient is found which yields a computed solution very close to the reference solution, regardless of domain discretization and output error minimization method. The superior noise immunity of FE‐DG over FD‐DZG is demonstrated. The results obtained from equation error minimization are less satisfactory.
Robust parameter estimation for fuel cost models in economic operation of electric power systems
Authors: Al Gobaisi Darwish M. K. , Bajpai A. C. , Singh P. N. P. 
Published: July 2007

AbstractThis paper is focused on optimal parameter estimation of fuel cost models intended for economic scheduling of electric power systems. The common approaches of least squares and conventional weighted least squares may not be appropriate for situations involving non‐normally distributed measurement errors. Techniques of robust parameter estimation, in particular the iteratively reweighted least‐squares estimator, offer an attractive option in these situations.The paper discusses the theoretical aspects of this powerful technique and presents computational experience with a number of popular choices of weighting functions. A comparative evaluation of the parameter estimates obtained is carried out in terms of both accuracy of the estimates and their effects on economic scheduling strategies.
Time‐optimal control for robotic manipulators
Authors: Chernousko F. L. , Akulenko L. D. , Bolotnik N. N. 
Published: July 2007

AbstractOptimal control methods present an efficient approach to construct controls of robotic manipulators. Much recent research has been devoted to different problems of optimal control for industrial robots. In this paper we give a brief survey of work done in this field and present some new results on optimization of robotic motions. Manipulation robots governed by electromechanical drives are considered. We obtain open‐loop and feedback time‐optimal controls for robotic motions using both analytical and numerical methods. The results show that optimal controls can lead to a considerable improvement in the time taken for transport operations performed by robots.
Minimum energy controllers with inequality constraints on output variances
Authors: Hsieh C. , Skelton R. E. , Damra F. M. 
Published: July 2007

AbstractWe consider the design of control systems to minimize the input energy subject to output variance inequality constraints. Necessary and sufficient conditions are developed for state feedback, measurement feedback and dynamic controllers. We find that all these problems are equivalent to LQ problems with a diagonal output weighting matrixQ, whereQhas some interesting properties which reflect the importance of each constraint. An algorithm which iteratively selects the weightQis given. Similar results are also derived for the dual problem where input variance inequality constraints are desired. All these results can be applied to the deterministic case with inequality constraints on theL∞,‐norm of the outputs.
Extended horizon self‐tuning control of a pulsed liquid‐liquid extraction column
Authors: Najim K. , Irving E. 
Published: July 2007

AbstractThis paper describes the application of an extended horizon self‐tuning control to a liquid‐liquid extraction column. The work forms part of an industrial collaborative project. The control law is derived from plant output prediction over several steps with the assumption that beyond a certain horizon the control increments become constant.This technique is used to control the hydrodynamics of a liquid‐liquid extraction column. The purpose of control is to maintain the column in its optimal behaviour zone, which corresponds to a specific hydrodynamic operation defined as a limit between two operating regimes. The measure of the conductivity gives information on the hydrodynamic behaviour of the column and has been selected as a control variable. The pulse frequency was also selected as a control variable.A single input‐output linear discrete model with time‐varying parameters was adopted to model the complex dynamics of the column. The model parameters are recursively estimated by a constant trace estimation algorithm. Some modifications have been introduced to improve the robustness of this estimation algorithm.Experiments carried out show that the presented algorithm has excellent control properties.
Maximum principles applied to a model of consumer brand choice
Authors: Ferreira Josa A. Soeiro 
Published: July 2007

AbstractThis paper presents an application of the maximum principle and the generalized maximum principle (a recent extension of that principle) to a discrete‐time model of consumer choice behaviour. The model includes two brands in a market and uses a non‐stationary first‐order Markov chain. The optimization is carried out by algorithms based on the above mentioned principles. These algorithms are described, and their performances are discussed and compared both with and without fulfilment of the directional convexity property.
An optimal dynamic output feedback controller for a flexible spacecraft
Authors: Sreenatha A. G. , Bhat M. Seetharama , Shrivastava S. K. 
Published: July 2007

AbstractThe design of a low‐order dynamic output feedback controller for a flexible spacecraft is carried out using modified linear quadratic Gaussian (LQG) theory. The necessary conditions for optimization are given. The linear equations governing a flexible spacecraft with a central rigid body and two sun‐tracking solar panels are presented. The parameters of the Solar Electric Propulsion Spacecraft (SEPS) are selected for analysis and simulation. The optimal gains for the dynamic controller are estimated using an iterative algorithm. The sequential procedure which assures convergence is selected. The initial gains which stabilize the system are chosen on the basis of the principle of a PD controller. A third‐order controller for pitch, roll and yaw axes of the 18th‐order system, which includes sensor and actuator dynamics, is designed. Numerical simulations carried out to ascertain the performance of the controller show the performance to be satisfactory.
Sequential rank‐one/rank‐two updates for quasi‐newton differential dynamic programming
Authors: Rakshit A. , Sen S. 
Published: July 2007

AbstractThis communication presents computational results with a variant of differential dynamic programming. The class of methods is motivated by quasi‐Newton methods and constructs quadratic approximations by using stagewise gradients. We compare two methods of updating the approximations: the first is based on the symmetric Broyden update and the second is a sequential rank‐one/rank‐two update. Our computational results suggest that the latter is a practical and efficient algorithm for discrete‐time optimal control.
Optimal response in siso ripple‐free deadbeat systems
Authors: Sebakhy O. A. , Assiri J. A. 
Published: July 2007

AbstractThe ripple‐free deadbeat control problem for SISO plants subjected to arbitrary reference signals is considered. The trade‐off between the settling time and the integral square error between the system output and reference signal is investigated. Given a specific order of the controller, it is shown how to design an optimal ripple‐free deadbeat controller. An illustrative example is presented to show the feasibility of the proposed algorithm.
Optimal pole assignment into specified regions and its application to rotating mechanical systems
Authors: Kim Jong‐Sun , Lee Chong‐Won 
Published: July 2007

AbstractThis paper considers a pole assignment problem to cluster all poles of a closed‐loop system into some specified regions by introducing the complex state for systems having an isotropic property and by using the Riccati equation. The algebraic relations for the distribution of the eigenvalues of a complex matrix are used in order to cluster the poles into specified regions, which guarantees the relative stability margin, e.g. uniform damping or uniform damping ratio. The proposed scheme is essentially a combination of the pole assignment approach and linear quadratic design, taking the advantages of both. A block modal control method—an extension of recursive pole assignment—is also developed for the vibration control of rotating systems by clustering the forward and backward modes in order. Vibration control simulations with an isotropic rotor—bearing system, a magnetic bearing system and a rotating circular disc are treated in order to demonstrate the advantages of the proposed method.
Multivariable routh‐approximant model reduction method in the time domain
Authors: Ramakrishnan J. V. , Rao S. Vittal , Koval L. R. 
Published: July 2007

AbstractThe time‐domain Routh‐approximant method for model reduction of large‐scale systems is modified and enhanced in this paper. A new transformation matrix that overcomes a limitation of earlier work is proposed. This feature greatly enhances the multivariable method. Some interesting results on symmetry properties are developed in conjunction with a structure example. A sufficiency condition of stability of the reduced‐order model is identified. The response of the reduced‐order model traces the original system very well. Thus the Routh method offers promise for application in the suboptimal control of large space structures, given its inherent simplicity.
A dynamic net present value rule in a financial adjustment cost model
Authors: Kort Peter M. 
Published: July 2007

AbstractA dynamic model of a self‐financing firm is presented in which a convex adjustment cost function is incorporated. The horizon date is assumed to be infinite. It turns out that the concept of ‘net present value of marginal investment’ is a useful tool to develop the firm's optimal investment policy. When this net present value is positive, negative or zero, it is optimal for the firm to fix the investment rate at its maximum level, minimum level or equilibrium level respectively.
A constrained H∞ smooth optimization technique
Authors: Fisher M. E. , Moore J. B. , Teo K. L. 
Published: July 2007

AbstractIn H∞ optimal control the cost function is the maximum singular value of a transfer function matrix over a frequency range. The optimization is over all stabilizing controllers. In constrained H∞ control the controllers typically have a fixed structure, perhaps conveniently parametrized in terms of a parameter vector. Also, there may be functional constraints involving singular values representing, for example, robustness requirements. Such problems are usually cast as non‐smooth optimization problems.In this paper we consider a general class of constrained H∞ optimization problems and show that these problems can be approximated by a sequence of smooth optimization problems. Thus each of the approximate problems is readily solvable by standard optimization software packages such as those available in the NAG or IMSL library. The proposed approach via smooth optimization is simple in terms of mathematical content, easy to implement and computationally efficient.
The optimal control problem for the vidale‐wolfe advertising model revisited
Authors: Ferreyra Guillermo 
Published: July 2007

AbstractThe optimal control problem for the Vidale‐Wolfe advertising model with unbounded controls is reformulated rigorously. It is shown that even though the optimal control is a measure of bounded variation, there exist physically realizable approximations to it. These smoother controls converge to the optimal control together with the induced trajectories and costs. Also, closed‐form expressions are given for the optimal state trajectories and the induced costs.
Design of a field voltage controller for a synchronous generator using feedback linearization
Authors: Mielczarski Wladyslaw , Zajaczkowski Antoni M. 
Published: July 2007

AbstractThe problem of non‐linear field voltage controller synthesis for a synchronous generator is considered. The theory of feedback linearization of non‐linear systems is applied and the existence of a linearizing feedback controller for the improved reduced‐order three‐dimensional model of a generator is proved. Simulation results for the proposed non‐linear controller, which includes a non‐linear observer and two systems based on an automatic voltage regulator and a power system stabilizer, are presented.
Comparison of two methods for the design of active suspension systems
Authors: De Jager A. G. 
Published: July 2007

AbstractThe design of controllers for active suspension systems can be formulated as an optimal control problem. The main objective of the controller is to isolate parts of the system from vibrations in other parts. Additional constraints are limited suspension travel, limited actuator force and good track‐holding capability. The objective and the constraints can be used in the formulation of an optimality criterion.Two criteria are examined, with the corresponding LQ and H∞ control design methods. The methods are compared with respect to their ability to generate a controller that achieves the best performance. For the LQ method three controllers with different structures were generated.To illustrate the use of the design methods, controllers have been designed for a simple but typical suspension system. For this system the controllers based on a quadratic norm perform comparably but the controllers based on output feedback are less robust. The H∞ controller did not perform well for this problem when the same weighting functions were used to generate the controller as for the LQ method. Use of the H∞ design method therefore requires careful tuning of the weighting functions. Use of the standard functions is inappropriate.
Optimal open/closed‐loop control of a rayleigh beam
Authors: Esfandiari Ramin S. , Sadek Ibrahim S. 
Published: July 2007

AbstractOptimal open/closed‐loop control of a Rayleigh beam relative to a specified performance measure is investigated. A method to suppress the undesired transient beam vibrations is proposed and utilized to obtain numerical results for different problem parameters. With the assumption of a prescribed closed‐loop control law, the Fourier‐type open‐loop optimal control law is derived in closed form through minimization of the performance measure via a calculus‐of‐variations technique. Numerical results presented in graphical form indicate that a feedback control mechanism may be effectively utilized in the presence of an open‐loop control.
Optimal control of the penicillin G fed‐batch fermentation: An analysis of the model of heijnen et al.
Authors: van Impe Jan F. , Nicolaï Bart M. , Vanrolleghem Peter A. , Spriet Jan A. , De Moor Bart , Vandewalle Joos 
Published: July 2007

AbstractThis paper presents the application of optimal control theory in determining the optimal feed rate profile for the penicillin G fed‐batch fermentation, using a mathematical model based on balancing methods. Since this model does not fulfil all requisites for standard optimal control, we propose a sequence of new models — that converges to the original one in a smooth way — to which the standard techniques are applicable. The unusual optimization of some initial conditions is included. We then state the conjecture that allows us to obtain the optimal control for the original model. The enormous gains in production and the vanishing of the characteristic biphasic behaviour through feed rate profile optimization raise some questions concerning the validity of this model. In this way this optimal control study can prove to be very useful for model discrimination purposes. Furthermore, mathematical and microbial insights lead to the construction of a suboptimal heuristic strategy — which we show to be a limiting case of the optimal scheme — that can serve as a basis for the development of robust, model‐independent, optimal adaptive control schemes.
A numerical algorithm for singular optimal control synthesis using continuation methods
Authors: Chen Yaobin , Huang Jian 
Published: July 2007

AbstractThis paper presents an efficient computational method for the synthesis of singular optimal control problems. The proposed numerical procedure consists of two phases. In the first phase the original singular optimal control problem is converted into a non‐singular one by adding to the performance index a perturbed (or weighted) energy term. The resultant boundary value problem can easily be solved for an appropriately large value of the perturbation parameter. In the second phase the solution obtained from the first phase is refined in a systematic manner based on continuation methods (imbedding methods or homotopy methods) until the optimal (or suboptimal) solution to the original problem is achieved. One of the major advantages of the proposed algorithm is that the resultant two‐point boundary value problem need be solved just once for a properly large perturbation parameter and the refinement of the solution is accomplished by solving a set of initial value problems sequentially and/or in parallel as the perturbation parameter goes to zero. The proposed algorithm is therefore computationally efficient and applicable to a large class of optimal control problems with various boundary conditions (e.g. fixed and free terminal time). The practicability of the method is demonstrated by computer simulations on an example problem.