摘要:

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

ISSN:0143-2087    

DOI:10.1002/oca.4660060202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

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‐rese

ISSN:0143-2087    

DOI:10.1002/oca.4660060203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractThis paper presents the optimal behaviour of a landlord. A dynamical model is introduced for the deterioration of housing quality with periodic maintenance, and the optimal policy is investigated for maximizing the landlord's profit with respect to the construction time, the initial quality and the maintenance investment.

ISSN:0143-2087    

DOI:10.1002/oca.4660060204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractSailplanes, when launched, need to extract energy from vertical motion of the air. The usual procedure is to circle and climb in vertical currents of limited spatial dimension (‘thermals’) under cumulus clouds and thereafter to exchange the gained height into distance by gliding out to the next cumulus cloud. While doing so, sailplane pilots will often encounter larger‐scale regions where the atmosphere moves in a vertical direction. Until recently the optimal strategy in such situations was assumed to be to fly slower through regions with upward moving air and faster through regions with downward moving air. Only a few years ago it was discovered both in theory, from energy considerations, as well as in practice, by contest pilots, that in some circumstances more energy could be extracted from the atmosphere when the loadfactor, i.e., the total aerodynamic lifting force on the wings divided by the weight, was varied. The research reported in this paper was set up to investigate this phenomenon. To that end a simple dynamic model is assumed for the sailplane, and the optimization problem is formulated as an optimal control problem with terminal constraints. This optimal control problem is solved numerically for a number of different widths and strengths of the vertical currents encountered. The computer program used for this purpose is a rather general continuous optimal control program based on the use of (conjugate) gradients in function space and a projection operation to account for the terminal constr

ISSN:0143-2087    

DOI:10.1002/oca.4660060205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

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 val

ISSN:0143-2087    

DOI:10.1002/oca.4660060206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractIn the design of surfaces which absorb waves, the impedance boundary condition is used as an effective means of diminishing the reflection. In this paper, we use the geometrical optics method to approximate the optimal impedance value which minimizes the reflected field for the scalar wave equation with a monochromatic source. Our treatment yields good results for optimal impedance in the asymptoticity region of the geometrical optics solution.

ISSN:0143-2087    

DOI:10.1002/oca.4660060207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractThe feasibility of applying disturbance‐accommodating control (DAC) techniques to the problem of steering control of a large tanker in a seaway is examined. A performance criterion representative of propulsion losses related to steering is used as a basis for the design of course‐keeping controllers. The development of disturbance state models to take advantage of the short‐term regularity of the seaway within a DAC framework is presented. Comparisons are made between the performance resulting from the DAC approach and previous LQG approaches to the problem using computer simulation results. On this basis, it is shown that controller design within a DAC framework may be a viable alternative to existing Kalman filter estimation/control schemes used in autopilot d

ISSN:0143-2087    

DOI:10.1002/oca.4660060208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

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.

ISSN:0143-2087    

DOI:10.1002/oca.4660060209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

ISSN:0143-2087    

DOI:10.1002/oca.4660060211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

ISSN:0143-2087    

DOI:10.1002/oca.4660060213

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY