The application of optimal controls with constrained derivatives to the roll stabilisation of ships
Başlık:
The application of optimal controls with constrained derivatives to the roll stabilisation of ships
Yazar:
Ameen, Yashwant K., author.
ISBN:
9780438057777
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (284 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: T. R.F Nonweiler.
Özet:
This thesis describes the results of a study of a novel type of controller for fin stabilisers. Formulation of the control problem for roll stabilisation leads to a deterministic tine-optimal problem and the synthesis of a sub-optimal controller in the presence of random sea disturbance by simulating the problem on a hybrid computer and analyzing the behavior of the deterministic solution. The design of the deterministic time-optimal controller is considered to be a special case of the optimal control problem in which the control variables and their derivatives of any order are bounded for a general system and a general performance criterion. The general optimal control problem is reformulated and solved as an unified problem in the calculus of variations. This leads to the definition of the optimal control over a hierarchy of intervals which are adjoined by suitable junction conditions. From the general solution, a specific solution is developed for time-optimal problems in which the control system is linear and this is then applied to the stabiliser control problem. By means of the reversed time technique, a minimum-time controller is synthesised in a form which may be exploited for practical purposes. An elegant and powerful technique for analogue simulation of a fully developed wind-generated sea is presented. The sea state is assumed to be defined by Neumann unidirectional wave height and slope spectra. It is shown that these spectra are equivalent to the output spectra of certain systems with white noise inputs. As neither the systems nor their white noise inputs are physically realisable, suitable approximants ere required. Pseudo-random binary signals are proposed as white noise approximants and their characteristics are described. A class of systems with outputs having the desired spectral properties is also proposed and the system parameters are optimised so that their output spectra match the Neumann spectra. Typical analogue computer realisations are given, together with records of wave height and slope. A detailed design procedure is illustrated for a specific controller whose action is represented by a switching portrait. The controller characteristics are determined by certain control coefficients which are optimised in order to achieve optimum roll stabilisation. It is seen that the optimum values of these coefficients are comparable to those estimated from the deterministic solution. Computed values and typical simulation records of the stabiliser performance are presented, and the results indicate that the minimum-time controller may be superior to a conventional controller of similar specifications. The dissertation is concluded with a general discussion and the scope for further research.
Notlar:
School code: 0547
Mevcut:*
Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684636.1) | 684636-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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