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The primary aim of this thesis is to develop a novel procedure for an intelligent automatic diagnostic condition monitoring system for rolling element bearings. The applicability of this procedure is demonstrated by its implementation in a particular electric motor drive system. The novel bearing condition diagnostic procedure developed involves three stages combining the merits of advanced signal processing techniques, feature extraction methods and artificial neural networks. This procedure is the effective combination of these techniques and methods in a holistic approach to the rolling element bearing problem which provides the novelty in this thesis. Maintenance costs account for an extremely large proportion of the operating costs of machinery. In addition, machine breakdowns and consequent downtime can severely affect the productivity of factories and the safety of products. It is therefore becoming increasingly important for industries to monitor their equipment systematically in order to reduce the number of breakdowns and to avoid unnecessary costs and delays caused by repair. The rolling element bearing is an extremely widespread component in industrial rotating machinery and a large number of problems arise from faulty bearings. Therefore, proper monitoring of bearing condition is highly cost-effective in reducing operating cost. The advanced signal processing techniques used here are bispectral-based and wavelet-based analyses. The bispectral-based procedures examined are the bis-pectrum, the bicoherence, the bispectrum diagonal slice, the bicoherence diagonal slice, the summed bispectrum and the summed bicoherence. The wavelet-based procedure uses the Morlet wavelet. These methods greatly enhance the ability of an automated diagnostic process by linking the increased capability for signal analysis to the predictive capability of artificial neural networks. The bearing monitoring scheme based on bispectral analysis is shown to provide greater insight into the structure of bearing vibration signals and to offer more diagnostic information than conventional power spectral analysis. The wavelet analysis provides a multi-resolution, time-frequency approach to extract information from the bearing vibration signatures. In order to effectively interpret the wavelet map, the time-frequency domain is used instead of the time-scale domain by plotting the associated time trace and power spectrum.

This thesis presents three reluctance machines with flux assistance. These machines provide alternative novel geometries that provide high efficiencies with a reduction in the ampere turns in the armature windings for torque production, lowering armature winding switching losses and reducing the power electronic rating. The Dual Stack Variable Reluctance Machine is a switched reluctance variant of the homopolar inductor alternator topology. The Single Stack Variable Reluctance Machine is a simplification of the Dual Stack machine. Both machines use a toroidal field winding to provide additional flux. The methods of connecting armature coils on each stator pole to utilise the armature flux and the choice of power electronic circuitry are important. Testing shows that such machines favour unipolar excitation with single coil per pole for the armature windings. Use of the field winding in series with the armature windings improves torque production. The Dual Stack Variable Reluctance Machine can have the mechanical angular displacement between the two stator stacks varied to provide an improved back emf waveshape for smoother torque production. The Single Stack Variable Reluctance Machine has parasitic and axial air gaps that pose interesting design issues (e.g. end thrust). Magnets can be placed in steel sections where flux is unidirectional. An ideal candidate for magnet insertion is the Flux Switching Motor. A Permanent Magnet Flux Switching Motor has been built that replaces the field windings with ferrite magnets. The Permanent Magnet Flux Switching Motor achieves efficiencies of over 80%. It adds no additional cost to the fan application as cost savings in lower temperature rated thermoplastics offsets the cost of magnets. A prototyping circuit incorporating a novel micro-processor program to alter the commutation timings as the machine operates has been designed to allow fast optimisation of each machine for minimum input power.

Vibratory bowl feeders are widely used in automation processes for the storage, feeding and orientation of identical components for presentation to workstations or other mechanical handling devices. The investigation described here has been directed at modelling the dynamiC behaviour of vibratory bowl feeders, both to improve understanding of their behaviour, and to facilitate improvements in their design. The work undertaken has involved the following stages: i) A numerical model for the prediction of the eigenvalues and eigenvectors of the bowl feeder was developed, modelling the structure as a lumped parameter eight degree-of-freedom system; ii) The natural frequencies and mode shapes predicted by the model were compared with those obtained from experimental modal analysis. There was good agreement for the first three natural frequencies. Differences in the higher frequency modes indicated an overconstrained model which could be accounted for by the flexural vibration of the bowl; iii) A numerical model of the forced response of a bowl feeder when driven by a harmonic excitation was developed using a spreadsheet package, and verified experimentally; iv) The spreadsheet package was developed further, varying the geometric parameters of the bowl and springs over specified ranges. Changes in spring angles were investigated experimentally to verify the predicted values; v) A customised design tool was developed using the spreadsheet package to enable engineers to investigate the behaviour of different configuration feeders; vi) An investigation of the causes of dead-spots was undertaken. These were shown to be due to the asymmetrical arrangement of the springs and electromagnetic coil relative to each other; and vii) Solutions proposed to the problem of dead-spots were the use of four spring banks instead of three, and the specification of an annular shaped pole piece for the electromagnetic coil.

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Friction in fluid Journal. Bearings is usually investigated by measuring the torque which appears on a bearing whilst a shaft is rotated inside it. The bearing is supported hydrostatically which would allow it to rotate freely if otherwise un restricted. Motion of the bearing is restricted by tension gauges which indicate the frictional force which they are resisting. The work described in this thesis is concerned with a new method of measuring frictional torque In journal bearings. The method consists of driving a shaft up to a given speed inside a fixed bearing and then permitting it to decelerate freely. The decelerations are timed electronically and almost instantaneous deceleration rates are obtained. From these deceleration rates and known polar moment of Inertia, the frictional torque in the bearing can be found for given speeds. The method has been found to be very reliable and also has wider application with other rotating systems.

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No description available.