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Reset control is a "simple" nonlinear control strategy that has the potential of being widely adopted and improving the performance of systems traditionally controlled with PIDs. Lack of suitable methods for proving stability, that are in line with the current industrial practice, hampers the wider acceptance of reset control. In this thesis, novel sufficient conditions for stability of reset control systems, that can be evaluated using measured frequency response function of a system to be controlled, are derived using the hybrid passivity and finite-gain framework. A method for analysing the hybrid passivity and finite-gain parameters of reset systems, that can be extended to other classes of nonlinear systems, is developed. Additionally, a variant of the “Constant in Gain Lead in Phase” reset element, that facilitates the use of the proposed method for the stability analysis, is introduced. Stability of several precision positioning systems with reset controllers, designed for different objectives, is studied to demonstrate the applicability of the proposed hybrid passivity and finite-gain approach for the stability analysis of reset control systems. Guidelines for design of reset systems such that their stability can be concluded using the hybrid passivity and finite gain method are shown. This thesis presents a new view on the stability of reset systems and addresses the need for frequency-domain tools for stability analysis of nonlinear control systems in precision mechatronics applications., Mechanical Engineering | Systems and Control

The structural responses and vibration properties such as frequencies and mode shapes are directly related to the structural mass and stiffness. Changing structural conditions will affect the structural responses and vibration properties. Structural conditions can thus be identified through measurements of structural vibration. However, certain uncertainties associated with structure models, changing ambient environmental conditions, changing loading conditions, equipment noises and various signal processing techniques used in extracting structural vibration properties, etc. is inevitable. The influences of these uncertainties on structural vibration properties might be more significant than that of the structural damage, therefore, cause false identification or result in the true structural damage not identifiable. This paper studies the applicability and reliability of a few popularly used modal identification methods including time-domain, frequency-domain and time-frequency domain methods for civil structural system identification. The results indicate that on average a 2% to 3% error tends to be yielded by using different signal processing techniques for vibration frequencies identification when the signal is not heavily noise contaminated, which should be taken into account when estimating the damage detection results. The applicability of the time-frequency domain methods to the identification of time-varying system either with sudden change or continuous variance is also discussed.

The emphasis of the book is on concepts, methods, exploration strategy and interpretation, covering material mainly applicable to general exploration of deep and shallow basins, exploration of the Earth's deep crust and propsecting for oil and gas, geothermal reservoirs and groundwater. Techniques used specifically in search of metallic sulphides are excluded. Field examples and case studies are given with the methods, not separately. The list of references has been kept to about 190 and there is a glossary and an index to subjects and place-names. Following introductory chapters on the place and role of electrical methods and the electrical properties of sedimentary rocks, there are four main sections on direct current resistivity methods, natural-source electromagnetic methods, controlled-source electromagnetic methods and the possibilities for direct detection of petroleum., The emphasis of the book is on concepts, methods, exploration strategy and interpretation, covering material mainly applicable to general exploration of deep and shallow basins, exploration of the Earth's deep crust and propsecting for oil and gas, geothermal reservoirs and groundwater. Techniques used specifically in search of metallic sulphides are excluded. Field examples and case studies are given with the methods, not separately. The list of references has been kept to about 190 and there is a glossary and an index to subjects and place-names. Following introductory chapters on the place and role of electrical methods and the electrical properties of sedimentary rocks, there are four main sections on direct current resistivity methods, natural-source electromagnetic methods, controlled-source electromagnetic methods and the possibilities for direct detection of petroleum.

The US Bureau of Mines is developing and testing geophysical methods for predicting and monitoring the flow pattern of leach solution during in situ leaching. Surface and surface-borehole time-domain electromagnetic induction (TEM), surface controlled source audio-frequency magnetotellurics (CSAMT), and surface-borehole and crosshole frequency-domain electromagnetic induction (FEM) were tested at the San Xavier experimental mine. TEM and CSAMT located brine, which simulated leach solution, replacing groundwater 160 m below surface. Seismic methods can only be used above the water table. Seismic tomography located fractured zones and water injected above the water table., The US Bureau of Mines is developing and testing geophysical methods for predicting and monitoring the flow pattern of leach solution during in situ leaching. Surface and surface-borehole time-domain electromagnetic induction (TEM), surface controlled source audio-frequency magnetotellurics (CSAMT), and surface-borehole and crosshole frequency-domain electromagnetic induction (FEM) were tested at the San Xavier experimental mine. TEM and CSAMT located brine, which simulated leach solution, replacing groundwater 160 m below surface. Seismic methods can only be used above the water table. Seismic tomography located fractured zones and water injected above the water table.

An investigation is presented, using digital-camera image analyses and ultrasonic wave velocity determinations, of crack propagation on the surface and in the interior, respectively, of coal cores, induced by microwave energy, in order to evaluate the potential of formation microwave heating treatment (FMHT) for de-gassing coalbed methane and for coal fracturing. The study uses seven bituminous coal cores obtained from Fugou mine, Shanxi province and 24 natural core cores from Xinbei mine, Ganshu province, China. The results indicate that the microwave-induced fractures increase with increased heating time, the crack propagation is related to the distribution of receptive mineralogical components, and the microwave energy breaks up the core when the heating time and power are 210 s and 2 kW, respectively. The coal density, bulk modulus and shear modulus, and the P- and S-wave velocity in the coal cores decrease after microwave treatment. The amplitude and domain of the P- and S-wave frequency spectra of the coal cores decrease after microwave heating. Vertical and horizontal designs for a heating process to de-gas coalbeds with or without microwaves are provided., 61 refs., An investigation is presented, using digital-camera image analyses and ultrasonic wave velocity determinations, of crack propagation on the surface and in the interior, respectively, of coal cores, induced by microwave energy, in order to evaluate the potential of formation microwave heating treatment (FMHT) for de-gassing coalbed methane and for coal fracturing. The study uses seven bituminous coal cores obtained from Fugou mine, Shanxi province and 24 natural core cores from Xinbei mine, Ganshu province, China. The results indicate that the microwave-induced fractures increase with increased heating time, the crack propagation is related to the distribution of receptive mineralogical components, and the microwave energy breaks up the core when the heating time and power are 210 s and 2 kW, respectively. The coal density, bulk modulus and shear modulus, and the P- and S-wave velocity in the coal cores decrease after microwave treatment. The amplitude and domain of the P- and S-wave frequency spectra of the coal cores decrease after microwave heating. Vertical and horizontal designs for a heating process to de-gas coalbeds with or without microwaves are provided.

The theoretical basis for electromagnetic induction exploration is presented and analytical solutions of Maxwell's equations are given for shapes of bodies that permit precise solutions, includsing spheres, spheroids, cylinders and discs. The results are compared to show what parts of the field behaviour are independent of the shape of the body, so that generalisations about interpretation of electromagnetic induction mineral surveys can be drawn. Both time-domain and frequency-domain behaviour are examined, and reasons for greater effectiveness of time-domain methods discussed., The theoretical basis for electromagnetic induction exploration is presented and analytical solutions of Maxwell's equations are given for shapes of bodies that permit precise solutions, includsing spheres, spheroids, cylinders and discs. The results are compared to show what parts of the field behaviour are independent of the shape of the body, so that generalisations about interpretation of electromagnetic induction mineral surveys can be drawn. Both time-domain and frequency-domain behaviour are examined, and reasons for greater effectiveness of time-domain methods discussed.

The behaviour of electromagnetic fields in frequency and time domains in a layered medium is investigated. Analyses of apparent resistivity curves in two-, three- and four-layered media are made for various modifications of electromagnetic soundings and the relation between the behaviour of the apparent resistivity curves and parameters of geoelectrical section is explored in depth. Case histories involving the application of transient soundings for the solution of geothermal problems and problems in petroleum geology are described and examples of determination of the oil (or gas) and water contact are given., The behaviour of electromagnetic fields in frequency and time domains in a layered medium is investigated. Analyses of apparent resistivity curves in two-, three- and four-layered media are made for various modifications of electromagnetic soundings and the relation between the behaviour of the apparent resistivity curves and parameters of geoelectrical section is explored in depth. Case histories involving the application of transient soundings for the solution of geothermal problems and problems in petroleum geology are described and examples of determination of the oil (or gas) and water contact are given.

Measurement and extraction, using a spectrum analyser, of frequency-domain characteristic parameters (frequency band range of interference and frequency distribution) of the interface voltage on a security-monitoring system device's power line under normal working conditions are described. Using an orthogonal experimental design method based on finite difference time-domain analyses of a multiple-conductor transmission line, as exemplified by a power line and two signal lines in parallel (S- and L-terminal representing two terminal sides of the transmission line), the optimal electromagnetic interference parameters of the security-monitoring signal line were: length of transmission line 90 m, distance between power and signal line 50 cm, distance between two signal lines 2 mm, distance between transmission line and ground 10 cm, and load of terminal side of transmission line 10 ohms. Comparison of optimised and MATLAB simulation results indicates that, after optimisation, the electromagnetic interference voltage of the security-monitoring signal line was reduced by at least 34.2%., Measurement and extraction, using a spectrum analyser, of frequency-domain characteristic parameters (frequency band range of interference and frequency distribution) of the interface voltage on a security-monitoring system device's power line under normal working conditions are described. Using an orthogonal experimental design method based on finite difference time-domain analyses of a multiple-conductor transmission line, as exemplified by a power line and two signal lines in parallel (S- and L-terminal representing two terminal sides of the transmission line), the optimal electromagnetic interference parameters of the security-monitoring signal line were: length of transmission line 90 m, distance between power and signal line 50 cm, distance between two signal lines 2 mm, distance between transmission line and ground 10 cm, and load of terminal side of transmission line 10 ohms. Comparison of optimised and MATLAB simulation results indicates that, after optimisation, the electromagnetic interference voltage of the security-monitoring signal line was reduced by at least 34.2%.

The relative sensitivities of the active and reactive components of a harmonic field are considered as well as that of transient fields to changes in the resistivity and dimensions of a conducting body. It is shown that the active and reactive components of a harmonic field have different resolving capabilities and, as such, different signal/noise ratios. The resolving capabilities of time and frequency domain techniques are compared in both high and low frequency ends of the spectrum, as well as early and late stages of the transient. The useful signal and the "geologic noise" are approximated by two conducting bodies immersed in an otherwise non-conducting medium., The relative sensitivities of the active and reactive components of a harmonic field are considered as well as that of transient fields to changes in the resistivity and dimensions of a conducting body. It is shown that the active and reactive components of a harmonic field have different resolving capabilities and, as such, different signal/noise ratios. The resolving capabilities of time and frequency domain techniques are compared in both high and low frequency ends of the spectrum, as well as early and late stages of the transient. The useful signal and the "geologic noise" are approximated by two conducting bodies immersed in an otherwise non-conducting medium.

Studies have determined that both gradient and dipole-dipole arrays may produce a rather strong electromagnetic (EM) coupling effect under certain conditions. Variations in these apparent effects are closely correlated with changes of surface current density and also influenced by topographic relief. It has been shown by theoretical calculations and model studies that response curves of frequency effects of EM coupling in logarithmic coordinates have distinctive features of sectional linearisation. This can provide a basic method to correct approximately EM coupling. Compared with methods being used inside and outside China, the suggested correction method has the advantage of wide application. This has been already proven by a few field examples., Studies have determined that both gradient and dipole-dipole arrays may produce a rather strong electromagnetic (EM) coupling effect under certain conditions. Variations in these apparent effects are closely correlated with changes of surface current density and also influenced by topographic relief. It has been shown by theoretical calculations and model studies that response curves of frequency effects of EM coupling in logarithmic coordinates have distinctive features of sectional linearisation. This can provide a basic method to correct approximately EM coupling. Compared with methods being used inside and outside China, the suggested correction method has the advantage of wide application. This has been already proven by a few field examples.

Computer simulation of low-frequency electromagnetic digital data acquisition in the presence of natural field noise demonstrates several important limitations and considerations. Without a remote reference noise removal scheme, it is difficult to obtain an adequate ratio of signal to noise below 0.1 Hz for frequency-domain processing and below 0.3 Hz base frequency for time-domain processing for a typical source receiver configuration. A digital high-pass filter substantially facilitates rejection of natural field noise above these frequencies; however, at lower frequencies where much longer stacking times are required, it becomes ineffective. Use of a remote reference to subtract natural field noise extends these low-frequency limits by one decade, but the remote reference technique is limited by the resolution and dynamic range of the instrumentation. Gathering data in short segments so that natural field drift can be offset for each segment allows a higher gain setting to minimize dynamic range problems. The analysis is also applicable to the induced polarization technique in which similar problems arise at low frequencies in the presence of telluric noise., Computer simulation of low-frequency electromagnetic digital data acquisition in the presence of natural field noise demonstrates several important limitations and considerations. Without a remote reference noise removal scheme, it is difficult to obtain an adequate ratio of signal to noise below 0.1 Hz for frequency-domain processing and below 0.3 Hz base frequency for time-domain processing for a typical source receiver configuration. A digital high-pass filter substantially facilitates rejection of natural field noise above these frequencies; however, at lower frequencies where much longer stacking times are required, it becomes ineffective. Use of a remote reference to subtract natural field noise extends these low-frequency limits by one decade, but the remote reference technique is limited by the resolution and dynamic range of the instrumentation. Gathering data in short segments so that natural field drift can be offset for each segment allows a higher gain setting to minimize dynamic range problems. The analysis is also applicable to the induced polarization technique in which similar problems arise at low frequencies in the presence of telluric noise.

Frequency domain techniques for manipulating gravity and magnetic data are reviewed, with brief descriptions of the following operations: high, low and bandpass frequency filtering; first and second vertical derivatives; upwards and downwards continuation; reduction to pole; and pseudo-gravity. The application of these techniques to Irish gravity data is briefly described using published results as examples. Aeromagnetic data for the Irish Midlands has been processed and filtered in the frequency domain to produce bandpass filtered, strike filtered and pseudo-gravity maps. These maps are used as a basis for a geological interpretation which confirms the existence of a trough-block structure for the subsurface interface between the Carboniferous and underlying units. The effect of deeper structures can also be seen, as can intrusive bodies such as those at Glenamaddy and near Navan., Frequency domain techniques for manipulating gravity and magnetic data are reviewed, with brief descriptions of the following operations: high, low and bandpass frequency filtering; first and second vertical derivatives; upwards and downwards continuation; reduction to pole; and pseudo-gravity. The application of these techniques to Irish gravity data is briefly described using published results as examples. Aeromagnetic data for the Irish Midlands has been processed and filtered in the frequency domain to produce bandpass filtered, strike filtered and pseudo-gravity maps. These maps are used as a basis for a geological interpretation which confirms the existence of a trough-block structure for the subsurface interface between the Carboniferous and underlying units. The effect of deeper structures can also be seen, as can intrusive bodies such as those at Glenamaddy and near Navan.