Moisture measurements play an important role in many material preparations and industrial processes. Microwave techniques have been used for several decades for such measurements. Shortcomings associated with the method have been addressed. Graphical solutions used hitherto to obtain the permittivity from waveguide measurements have been replaced by computer programs. The accuracy of measurement have been improved by the development of waveguide standards and the implementation of calibration procedures. Permittivity measurements in through and short circuited rectangular waveguides are reported on a wide range of solid, granular and liquid materials important to the food industry. Techniques to suppress standing wave effects have enabled accurate plane wave measurements of permittivity. For bulk materials, new measurement probes have been developed for on line measurements and associated with these probes lower cost instrumentation has been considered. The· main outcome of the study is the improvement in permittivity measurements of sample quantities of material. Moisture measurements in bulk materials have been facilitated by novel non invasive probes.

This thesis addresses the growing "divergence" in the field of surface metrology through the presentation of a practical system for unification. A technical and economic review of applied surface metrology is presented, highlighting the problems associated with the many advances in instrumentation - particularly in light of the growing industrial dependence on surface metrology. This background serves as the basis for the development of a scheme whereby surface specification, instrumentation, and analysis can be concisely and completely defined and, more importantly, controlled. Several technical aspects of surface metrology are addressed in the development of the scheme. First the topic of specification and reference geometries is addressed, where it is argued that least squares methods should provide the most stable basis for assessment. Stylus/radius convolution and the associated wavelength transmissions are also considered and experimental investigations are undertaken as to describe their influences on measured data sets. The treatment of unwanted asperities is investigated and a new, robust algorithm developed and presented. The study of wavelength limitation approaches concludes that a sub-set of current methods is technologically acceptable and therefore economically attractive. A review of parameterization concentrates on a means for selecting a "unified" set of parameters and guidelines for the incorporation of future parameters. Finally, it is shown that the this proposed scheme addresses the underlying divergence in surface metrology in a manner which is practical in the context of application, technically justified in the context of standardization, and extensible in the context of further research.

No description available.

No description available.

This thesis addresses a comprehensive approach to understanding the time-varying thermal errors in machine tools. Errors in machine tools are generally classified as being time or spatial dependent. Thermal errors are strongly dependent on the continuously changing operating conditions of a machine and its surrounding environment. Uniform temperature rises or stable temperature gradients, which produce time-invariant thermal errors, are considered to be rare in ordinary shop floor environments. Difficulties in analysing time-varying thermal errors are that, first of all, the temperature distribution within the components of a machine should be evaluated, and secondly, the distribution is continuously changing with time. These difficulties can be overcome by introducing a point-wise description method with three thermal parameters. From the theoretical analysis of simple machine elements such as bars, beams and cylinders, and extensive finite-element simulation data for a straightedge subject to room temperature variations, three thermal parameters, i. e. time-delay, time-constant and gain, were identified to obtain a precise description of the thermal deformation of a point of a machine body. Time-delay is dependent largely on thermal diffusivity, and the heat transfer mechanism. The time-constant is governed by heat capacity, heat transfer mechanism and body size. Gain, on the other hand, is determined by the thermal expansion coefficient, heat transfer mechanism and mechanical constraint. The three thermal parameters, in turn, imply that thermal deformation of a point in a body can be described by a simple first- order differential equation. Regarding their dependence on the heat transfer mechanism, a more refined description requires a time-varying linear first-order differential equation. Such an equation can be applied to each point of interest of a machine body. The final form of modelling, using the parameters, is a state-space equation gathering the governing equations for the points of interest. By adopting the point-wise discrete modelling method, we can overcome the difficulty of the spatial distribution of the temperature. Indeed, the calibration of a machine tool is usually performed at discrete points. The completion of this approach was made by presenting the methods by which the three thermal parameters can be evaluated. The first method employs analytical tools based on simplifying assumptions about the shape and boundary conditions of machine components. The second method was to apply numerical techniques to complex machine components. Because there are many drawbacks in theoretical approaches, experimental techniques are essential to complement them. The three thermal parameters can be easily identified using popular parameter identification techniques which can be applied to time-varying cases by their recursive forms. The techniques described were applied to modelling the thermal errors in a single-point diamond turning research machine. It was found that the dominant error component was spindle axial growth. The predictive model for the time-constant was shown to be in agreement with both the machine and with the scaled physical model rig.

Knowledge of the accuracies of air bearing spindles in the sub-micrometre to nanometre range is required for the design, commissioning and operation of ultra-precise machine tools, measurement systems and other machines employing high precision rotational motion. In order to verify the dynamic performance of a spindle, measurement is required of its error motions in the unwanted five degrees of freedom (one axial, two tilts and two radial motions). Presentation of these error motions (eg in the form of polar charts) can then be used to provide critical spindle metrology data including total, asynchronous and average error motion rosette profiles and their average and peak values. This thesis describes a metrology system based on optical interferometry for measuring such unwanted error motions in three degrees of freedom involving motion along the spindle axis (axial rectilinear displacement and tilts about orthogonal axes), incurred with rotation of a precision air spindle over its specified speed-range. The system is not sensitive to orthoaxial translations which may be measured using alternative methods. Possible alternative techniques for measuring any of the degrees of freedom include an array of proximity sensors, (one for each translational degree of freedom and a further one for each of the other rotational degrees of freedom), to measure the run-out of an artefact. Proximity sensors based upon capacitive or optical fibre back-scatter techniques each offer the required single degree-of-freedom non-contacting capability and bandwidth. In the current work, a Fizeau interferometer is used to monitor the motion of the spindle of a vertical axis ultra-precision facing machine using a test-artefact. This is a mirror with less than one fringe departure from planarity from which interferogram. fringe-patterns are captured, digitised and analysed synchronously as the spindle rotates. The issue of the prediction of the dynamic form and motions of the observed interferograrn arises and the earlier theory is extended to optimise the set-up, including provision of automatic servo- alignment of the optical axis with the axis of the spindle. Measurement interferograrn data is sampled at selected angular incremental positions of spindle-rotation and image processing techniques used to filter the fringe pattern, enabling measurement of spindle tilt and axial displacement. Issues of sampling with respect to the anticipated spatial angular frequency of the spindle run-out are considered with respect to the speed/frequency capability of data-acquisition and processing arrangements. Essentially, with a spindle rotating at typical machining speeds of 300- 3000 rev/min, for consistent error motions, the resolution of an error plot is principally a function of observational time. It is foreseen that the system will be applicable in research and production-support in ultra-precision machining production processes and in rotational metrology.

Two different factors involved in the measurement of photogrammetric plates have been studied. A novel interferometer designed to monitor the position of a microscope stage, to be used to measure photogrammetric plates, has been built. The prototype instrument is able to give the position of the stage with a maximum error of less than 200nm. An algorithm has been developed for a motor driven x-y microscope that is able to search a photographic plate automatically for targets, and record their positions. In a trial survey this system was able to measure the positions of the targets on the plates with an uncertainty of approximately 2gm. This result is comparable with the precision that a human operator could achieve using the same equipment, but without the fatigue effect associated with visual observation. Virtually no human interaction is necessary for the system to function.

No description available.

No description available.

No description available.