A. Abdul-Ameer

Machine Tool Axis Dynamics

Abstract The independent axis dynamics of machine tools that employ long slender lead screws, bearings, and workpiece saddles, mounted on supporting slides, will be considered. Distributed-lumped parameter techniques will be used for system analysis and in the model formulation procedures. Realizations that encompass combined torsional and tension loading will be incorporated. Specific, integrated, distributed-lumped machine tool configurations will be derived and described in block diagram form. Simulation studies illustrating the dynamic signature of a machine tool axis drive, when operated at various feed rates, together with the measured results will be presented. The effect of changes in the effective lead-screw length on the workpiece surface finish will be commented on.

Warship propulsion system control

The modelling of a dual gas turbine, single-shaft transmission drive, for a naval propulsion system, is considered. Owing to the spatial dispersion of the arrangement, a distributed–lumped parameter approach to the dynamic analysis problem is necessary. This enables the relatively concentrated assemblies to be included as lumped, pointwise representations and the propulsion shaft to be incorporated as a dispersed inertia and stiffness element. A multivariable, least effort controller design strategy is employed to achieve the regulation required. The performance of the closed-loop system following reference input and load disturbances is evaluated and the drive shaft speed and twist angle response transients are computed.

Winder control using a Ward-Leonard system

An electrically driven winder for a deep shaft mine is considered. The system comprises a two stage Ward-Leonard motor-generator set, a winding drum, head and reduction gear and a braking unit, for which a linear model is derived. A minimum control effort regulation strategy is proposed enabling the simultaneous regulation of the motor speed and armature current. The computed responses for the system are presented for open and closed loop conditions. The effectiveness of the system when following particular, demanded speed requirements is investigated. The control energy dissipation and regenerative braking performance of the system are commented upon.

High-speed rotor-shaft systems and whirling identification

Abstract The transverse vibrations of shaft-rotor systems are considered. Interconnected assemblies of distributed parameter, compliant shafts, pointwise lumped rotor, and isentropic bearing units, are investigated. Analysis methods for shaft-rotor systems are formulated from the truncated, series expansion, of the rotor model, impedance matrix elements. Frequency domain evaluation of the determinant of the matrix model, enabling accurate validation, is incorporated. An illustrative application for a high speed, turbo-charger rotor system model is presented. Critical whirling speed conditions are identified. Alternative, established whirling speed evaluation techniques are investigated. Analysis, modelling accuracy, and the computational integrity of the procedures employed are emphasized.

Gas pipeline modelling and control

The distributed parameter modelling of the gas flow through long pipelines is considered. Procedures which incorporate the gas stream energy storage, the pipeline frictional resistance and pressure attenuation characteristics are introduced. The pipeline input–output, transfer function, pressure and volume flow representations are formulated. An optimum, least effort, closed loop regulation strategy is proposed. Frequency response techniques are invoked enabling the derivation of simple, robust control algorithms. Confirmation of the results obtained, from the transient response computation of the outputs following input reference and load disturbance changes, are presented. The accuracy and novelty of the approach presented is commented upon.

Energy-efficient gas pipeline transportation

Gas transportation via long pipelines is considered. Distributed parameter, dynamic modelling with series and shunt energy dissipation and gas stream, equivalent capacitance and inductance effects are proposed. Hybrid analysis techniques, wherein both the distributed and the lumped, concentrated elements of the pipeline system are included in the overall model, are advocated. Constrained optimisation procedures, with the introduction of the Hamiltonian function to minimise the pipeline, inflow–outflow difference, are invoked thereby promoting impedance matching and the energy-efficient transportation of the specified, gas volume flow rate. Illustrative application studies are outlined thereby validating the analytical methods employed and the determination of the optimum, pipeline exit resistance.

The transverse vibration of high-speed rolls

The transverse, dynamic deflection of high-speed, wide-faced, composite tubular rolls is investigated. General procedures are proposed enabling the analysis of inter-connected units comprising both distributed parameter and rigid, pointwise models. Modelling methods, eliminating intermediate variables are employed facilitating the realisation of an overall system, input–output representation. Illustrative studies, detailing the analysis and evaluation process are presented. A high-speed, paper making machine, table roll application is considered. Whirling conditions and the effect of this problem on sheet quality and manufacturing output is commented upon.

Modelling of fluid power transmission systems

The mathematical modelling of fluid power transmission systems involves solving a system of differential equations and addressing the problems generated by transient pressure propagation. The main difficulties in modelling pressurised, fluid pipelines arise from the complex interactions involving boundary conditions, reflections and non-linear behaviour. This paper presents a new method of modelling pipeline systems that provides an accurate transient response of the system incorporating a frequency-dependent fluid friction term. The modelling method employed is based upon distributed-lumped parameter modelling techniques which enable the inclusion of a wide variety of non-linear effects. The model comprises a distributed element representing the pressure and flow rate through out the length of the pipeline and a lumped element that represents the boundary conditions at the pipeline exit. The simulation results for the system are compared with experimental data validating thereby the analytical procedures proposed.

Ventilation system airflow dynamics

Abstract Ventilation system airways comprising ducting and ventilation shafts of various lengths and diameters are considered. Conventional modelling methods for these systems, for automatic control purposes are commented upon. Analytical techniques which combine the distributed and relatively lumped parameter properties, of spatially dispersed systems, are introduced. General, distributed, and lumped realizations and structures are devised for the components, for typical ventilation system configurations. The formulation of multivariable, integrated, distributed parameter, hybrid models, for spatially dispersed ventilation systems comprising the transmission, energy storage, and dissipation elements, are proposed. Transfer function derivation methods enabling the airflow transients, at strategic system locations to be predicted, are presented. Typical application studies are outlined.