Active Suspension Control; Performance Comparisons Using Control Laws Applied to a Full Vehicle Model

Based on a mathematical model of an actively suspended vehicle, the effects of the following issues in deriving the control laws are studied:

(a)representation of the ground surface as integrated or filtered white noise.

(b)cross-correlation between left and right track inputs.

(c)wheelbase time delay between front and rear inputs.

The third of these issues is shown to be by far the most important. Considerable improvements at the rear suspension can be obtained if the control law includes the information that the rear input is simply a delayed version of the front input. Effectively this provides feedforward terms in the control law for the rear actuator. For the full state feedback case, these improvements are indicated by reductions in the rear body acceleration and rear dynamic tyre load of around 20% and 40% respectively with no increase in suspension working space.     

Semi-Active Attitude and Vibration Control

The paper discusses the attitude and vibration control of a passenger car on the basis of a full vehicle model. The analysis presented consists of two parts: (I) The introduction of a newly developed semi-active anti-roll/pitch system, (ii) An example of an actively suspended full vehicle model using a simple control strategy to improve ride comfort. The attitude control using semi-actively generated compensation forces prevents the car from rolling in curves and pitching during braking or accelerating. The strength of the system is the small energy consumption. The performance of the combination of both attitude and vibration control can compete with a fully active suspension system.     

Full scale measurements at magnus

The environmental and structural monitoring system on Magnus tower was designed making use of experience from previous monitoring systems on West Sole, Forties and Buchan. The paper describes the measuring systems adopted together with their calibration procedures and independent checks.

The major results in terms of environmental conditions and platform response are discussed. They are compared with the Forties results and standard design procedures. Deterministic and spectral extreme conditions are considered. Where applicable, comparisons are made with other published results.

Finally, the principal conclusions of the measurement programme are presented and discussed. These refer particularly to structural dynamics, coefficients for the Morison equation and appropriate methods of application of wave loading to a deep water structure.     

Estimation of fatigue damage and extreme response for a jack-up platform

Results from four different methods for stochastic dynamic response analysis of a proposed jack-up platform are compared. This structure exhibits both significant dynamic amplification and non-linear transfer of sea elevation into load effects. Both estimation of extreme response and fatigue damage are considered. The most complex procedure based on time-domain simulation and step-by-step integration is employed as a benchmark for assessment of three simplified methods. The simplifications consist of various types of linearization in conjunction with transfer function approximations. Applicability of the methods to structures with increasingly non-linear behaviour and dynamic amplification is briefly discussed.     

Rule-based optimization of midship structures

A rule-based overall design methodology for midship structures of small inland waterways vessels is presented. It is shown how the designer, under conflicting requirements, can select the optimum design by using a combined objective function with priority factors assigned to individual design criteria. The concept of optimization, in large-scale structural design problems, is extended to the local members (the stiffening elements) of the ship structure, so that the stiffeners can be specified by their actual dimensions instead of section moduli. The effects of price-structure (labour rate to material price ratio) and the choice of type of stiffener on design are investigated. Standard sections and optimized fabricated sections are taken as the alternative options for selecting the stiffeners. Conversion of exact mathematical optimum solutions into production-oriented designs is also demonstrated in a series of practical applications of the proposed method.     

Approximate procedures for planning public transit systems: A review and some examples

The approximate analytical models of public transit systems are reviewed. First, the derivation and formation of the standard model form is presented. Once the model is explained in general terms some practical planning applications are considered and evaluated. The model type presents an invaluable tool to the transit planner but a few operational problems need to be considered. Further benefits to the planning professionals would be realized if researchers were to devote more effort to sensitivity analysis as a means of determining which system parameters have the greatest impact upon the operation of the transit system.     

Carbon flux in ice–ocean–plankton systems of the Bellingshausen Sea during a period of ice retreat

Most analyses of marine microbial systems in the seasonally ice covered areas of the Southern Ocean have been based on data from the major embayment areas of the Ross and Weddell Seas. In this study data were collected at stations covering a range of regimes from full ice cover through to open water in the Bellingshausen Sea. A major feature of the production system was a rapid retreat of the ice-edge, which uncoupled the marginal ice zone from a phytoplankton bloom which remained associated with a frontal system. This bloom was maintained, and probably initiated, in an unusual environment generated by the interaction between the marginal ice zone and the front. Size-based analyses of the microbial system were derived for ice-covered, recently ice-covered and open water sites. Estimates of standing stocks and key rate processes were combined to produce a single food web network for each station. The under-ice system was one of low production and low recycling but apparently high retention. As the ice retreated the microbial systems to the north began to develop, but these were constrained by grazing pressure. The bloom in the area appeared to be sustained even though estimated losses were far higher than production, although the high sedimentation losses expected were not observed. The carbon flow networks are discussed in relation to the environmental changes and the interaction of the marginal ice zone and the frontal system appears crucial to the phytoplankton. Microzooplankton grazing is implicated as a major controlling factor. The local microbial dynamics are strongly influenced by material which was produced at an earlier time and somewhere else in the Southern Ocean.     

The privatization of United Kingdom seaports

The background is described to U.K. port administration and the implementation of the Conservative Goverment's privatization policy is reivewed. The objectives of privatization and the ways in which it has been achieved with trust and municipal port authorities are discussed. The paper goes on to discuss the difficulties encountered in privatizing statutory undertakings and concludes by examining the benefits port managers claim have arisen from the introduction of teh policy.     

Recent trends in ship conversion: an overview

A survey of more than 250 ship conversions between 1980 and 1990 is presented. Conversions are defined as jumboizations of hulls, changes of missions of ship with or without major structural changes, and major reconstruction of cruise liners and passenger ferries. From reports publishd in maritime journals, a database has been established, allowing for analysis of various ratios, principal particulars, and mission changes. Whenever available, evolution of conversion cost and duration over time as well as age, country of build, and converting shipyard are considered. Conclusions are drawn from comparisons of our database with the world fleet. Finally trends in the ship conversion market are discussed.