Joint Fault Research Articles

Robust unknown input observer for state and fault estimation in discrete-time Takagi–Sugeno systems

ABSTRACTIn this paper, a robust unknown input observer (UIO) for the joint state and fault estimation in discrete-time Takagi–Sugeno (TS) systems is presented. The proposed robust UIO, by applying the framework, leads to a less restrictive design procedure with respect to recent results found in the literature. The resulting design procedure aims at achieving a prescribed attenuation level with respect to the exogenous disturbances, while obtaining at the same time the convergence of the observer with a desired bound on the decay rate. An extension to the case of unmeasurable premise variables is also provided. Since the design conditions reduce to a set of linear matrix inequalities that can be solved efficiently using the available software, an evident advantage of the proposed approach is its simplicity. The final part of the paper presents an academic example and a real application to a multi-tank system, which exhibit clearly the performance and effectiveness of the proposed strategy.

The joint optimal filtering and fault detection for multi-rate sensor fusion under unknown inputs

In multi-sensor fusion, it is hard to guarantee that all sensors have an identical sampling rate, especially in the distributive and/or heterogeneous case. Meanwhile, stochastic noise, unknown inputs (UIs), and faults may coexist in complex environment. To this end, we propose the problem of joint optimal filtering and fault detection (FD) for multi-rate sensor fusion subject to UIs, stochastic noise with known covariance, and faults imposed on the actuator and sensors. Furthermore, the new scheme of optimal multi-rate observer (MRO) is presented and applied to detect faults. The observer parameters are determined optimally in pursuit of the UI decoupling and maximizing noise attenuation under the causality constraint due to multi-rate nature. Finally, the output estimation error of the MRO is used as a residual signal for FD via a hypothesis test in which the threshold is adaptively designed according to the MRO parameters. One numerical example is given to show the effectiveness of our proposed method.

Unbiased Minimum-Variance Filter for State and Fault Estimation of Linear Time-Varying Systems with Unknown Disturbances

This paper presents a new recursive filter to joint fault and state estimation of a linear time-varying discrete systems in the presence of unknown disturbances. The method is based on the assumption that no prior knowledge about the dynamical evolution of the fault and the disturbance is available. As the fault affects both the state and the output, but the disturbance affects only the state system. Initially, we study the particular case when the direct feedthrough matrix of the fault has full rank. In the second case, we propose an extension of the previous case by considering the direct feedthrough matrix of the fault with an arbitrary rank. The resulting filter is optimal in the sense of the unbiased minimum-variance (UMV) criteria. A numerical example is given in order to illustrate the proposed method.

Role of Rock Mass Fabric and Faulting in the Development of Block Caving Induced Surface Subsidence

Extraction of a large volume of ore during block caving can lead to the formation of significant surface subsidence. Current knowledge of the mechanisms that control subsidence development is limited as are our subsidence prediction capabilities. Mining experience suggests that, among other contributing factors, geological structures play a particularly important role in subsidence development. A conceptual modeling study has been undertaken to evaluate the significance of geological structure on surface subsidence. A hybrid finite/discrete element technique incorporating a coupled elasto-plastic fracture mechanics constitutive criterion is adopted; this allows physically realistic modeling of block caving through simulation of the transition from a continuum to a discontinuum. Numerical experiments presented emphasize the importance of joint orientation and fault location on mechanisms of subsidence development and the governing role of geological structure in defining the degree of surface subsidence asymmetry.

Influence of Joints on Ride Quality and Roughness Index

ABSTRACT Pavement joints may cause intense vibrations in moving vehicles, discomforting and even annoying drivers and passengers at times. International Roughness Index (IRI) and Present Serviceability Index (PSI) have been conventionally chosen to characterize pavement ride quality. In this paper, the increase of IRI and the decrease of PSI in the presence of concrete joints are analytically derived by using a vehicle model and considering different joint geometries. The dependence of the indices IRI and PSI on joint width, the vertical fault, and tire-road contact length, are explicitly derived. Theoretical predictions on the change of IRI agree well with the reported data. When integrated into a pavement management system, the proposed analysis can be employed to set limits on joint fault depth and to prepare joint maintenance schedules.

Influence of Joints on Ride Quality and Roughness Index

ABSTRACT Pavement joints may cause intense vibrations in moving vehicles, discomforting and even annoying drivers and passengers at times. International Roughness Index (IRI) and Present Serviceability Index (PSI) have been conventionally chosen to characterize pavement ride quality. In this paper, the increase of IRI and the decrease of PSI in the presence of concrete joints are analytically derived by using a vehicle model and considering different joint geometries. The dependence of the indices IRI and PSI on joint width, the vertical fault, and tire-road contact length, are explicitly derived. Theoretical predictions on the change of IRI agree well with the reported data. When integrated into a pavement management system, the proposed analysis can be employed to set limits on joint fault depth and to prepare joint maintenance schedules.

Attenuation of Sound and Temperature Caused by Faulted Distribution Cable Joints

This paper briefly describes the products and effects resulting from the failure of distribution cable joints in a manhole. Lab tests reproducing the field conditions have been performed to characterize two specific aspects: the maximum sound level and the air temperature rise during a cable joint fault. Since the effects could be hazardous for workers, a special device has been designed to reduce the sound and air temperature values to safe levels.

Effect of Concrete Mix Consolidation on Joint Faulting and Load Transfer Efficiency

Six jointed reinforced concrete pavement and one jointed plain concrete pavement test sections on US-69 in Miami County, Kansas, constructed in 1979 have been surveyed annually for faulting for the past 9 years. Falling weight deflectometer tests were conducted in 1995 to assess the load transfer efficiency of the joints. The results show that, in general, as the original concrete density increases due to improved consolidation, the rate of increase of the joint fault depth decreases at doweled joints at a given pavement age. The occurrence of joint faulting is much more severe when load transfer devices are not present; this was observed even for the pavement section built on a nonerodible subbase. Improved consolidation sometimes appeared to help improve load transfer, resulting in a lower rate of faulting. Thus, the mandatory density requirement of 98 percent rodded unit weight, which has been in effect since 1980, has undoubtedly led to better joint performance for concrete pavements in Kansas.

Effect of Concrete Mix Consolidation on Joint Faulting and Load Transfer Efficiency

Six jointed reinforced concrete pavement and one jointed plain concrete pavement test sections on US-69 in Miami County, Kansas, constructed in 1979 have been surveyed annually for faulting for the past 9 years. Falling weight deflectometer tests were conducted in 1995 to assess the load transfer efficiency of the joints. The results show that, in general, as the original concrete density increases due to improved consolidation, the rate of increase of the joint fault depth decreases at doweled joints at a given pavement age. The occurrence of joint faulting is much more severe when load transfer devices are not present; this was observed even for the pavement section built on a nonerodible subbase. Improved consolidation sometimes appeared to help improve load transfer, resulting in a lower rate of faulting. Thus, the mandatory density requirement of 98 percent rodded unit weight, which has been in effect since 1980, has undoubtedly led to better joint performance for concrete pavements in Kansas.

Single and joint fault plane solutions for microearthquakes in South Iceland

We obtain fault plane solutions for a swarm of twelve events and two single events ranging in magnitude between −0.3 and 3.1. The events were recorded by a local network in South Iceland, consisting of eight three-component stations with approximately 30 km between the stations. For events larger than M L −1 the solutions are well constrained. The non-uniqueness of the fault plane solutions increases with diminishing magnitude. To enhance the uniqueness of the fault plane solutions for the earthquake swarm, we search for mechanisms with a common fault plane but possibly varying slip directions in that plane. Data for all the events are consistent with faulting on a common plane. Relative location of the events shows that they all occurred less than 11 m from a single plane. Fault plane solutions for all the analysed events of the swarm, as well as the two single events, are consistent with strike-slip-dominated faulting on faults striking roughly north-south. The results are in agreement with the strikes of mapped surface fractures and focal mechanisms of larger earthquakes in the area. This indicates that the microseismicity is related to the same pattern of regional deformation as the major earthquakes in South Iceland.

The evolution of the South Hunsrück and Taunus Borderzone

The main fabric development of the South Hunsrück and Taunus Borderzone (HTB) occurred during Late Variscan homoaxial backfolding of an Early Variscan stack of thrust sheets in a narrow WSW-ENE trending zone, several hundred kilometres long. Rotation and uplift of the southern Rhenohercynian Zone was accompanied by the subsidence of the southward adjacent, northernmost parts of the Saxothuringian Zone, and the development of the Saar-Nahe Basin.During the latest Carboniferous changing stress conditions gave rise to the development of normal faults along the HTB and an extensive tholeiitic and rhyolitic volcanism. Contemporaneous uplift of the Hunsrück is reflected by coarse elastics in the Saar-Nahe Basin. Subsequently the HTB became covered by latest Carboniferous, Early Permian and Mesozoic sediments. Cretaceous uplift of the Rhenish Shield caused their erosion.The faultzone separating the Rhenohercynian Hunsrück and Taunus from the Permo-Carboniferous Saar-Nahe Basin is characterised by reverse and normal faults. Conjugate shear, indicated by slickensides on steep oblique fracture planes, as well as slight folding and small scale thrusting in post-Variscan sediments, may be attributed to compressional foreland deformation, reactivating Variscan joint fabrics and fault systems. Timing of these deformations is ambiguous and could partly be related to dextral shear during the Cenozoic subsidence of the Rhine Graben.Cenozoic sediments of the Upper Rhine graben overstep the northeastern parts of the HTB. Seismic investigations indicate that the HTB is associated with a system of southeast hading listric planes, extending beneath the Moho. Occasional dip-slip earthquakes occur along these fractures.

Remote Sensing as Tool for Interpreting Structural Geology in Appalachians: ABSTRACT

The science of remote sensing of the earth's surface with special cameras and other instruments that measure reflectance and/or emission of energy in the electromagnetic spectrum has had nearly exponential growth since the early 1940s. Since the mid-1950s scientists and engineers gradually have become aware of and interested in utilizing remote sensor technology in the natural sciences. This technology, developed principally from classified military projects, has been used only in unclassified civilian projects in natural sciences and earth resource fields during the past decade. Applications of remote sensing that have been advanced and tested include geologic use of Gemini and Apollo satellite photography, Nimbus AVCS (advanced vidicon camera system) and thermal infrare scanner data, as well as data from a number of aerial systems. Remote sensor systems which have received attention in geology and allied disciplines are: (1) black and white (B/W) photography (panchromatic and infrared), (2) color and color infrared (IR) photography, (3) multiband (MB) photography, (4) thermal infrared (TIR) scanner images, (5) multispectral scanner (MSS) images (from near-ultraviolet to far-thermal infrared), (6) side-looking radar (SLAR or SLR) images, and (7) passive microwave scanner (PMS) images. Several of these systems have been tested from aircraft and spacecraft over parts of the Appalachians and adjacent regions. Remote sensing image data (ground observations, etc.) have provided useful information related to regional structures such as joint patterns, drainage patterns, fault traces, and rock types. The application of geologic remote sensing is in its infancy, however, and these tests are not meant to imply that remote sensing is or will be a panacea for all the problems of Appalachian structural geology, but surely a combination of selected sensing systems can provide additional information for a well-balanced scientific approach to the problems of the Appalachians. Remote sensors provide synoptic views of large areas and of conditions that cannot be perceived either by the unaided eye or by field observations. These include surface distributions of heat, moisture, open water, and vegatative vigor differences, all of which are useful to the geologist. End_of_Article - Last_Page 2108------------

Geology of the Harold D. Roberts Tunnel, Colorado: Station 468+49 to East Portal

The Harold D. Roberts Tunnel is a 23.3-mile water-diversion tunnel that extends through the western part of the Front Range between Grant and Dillon, Colorado. This report concerns the geology of the southeastern segment of the tunnel, which is partly in the Montezuma stock—a Laramide quartz monzonite pluton—but is mainly in Precambrian basement rocks. The Precambrian metamorphic rocks consist of relatively thick, complexly folded units of amphibolite, migmatite, microcline gneiss, and biotite gneiss. These rocks were invaded by plutons of Boulder Creek Granite and Silver Plume Granite, regarded as syntectonic and late tectonic, respectively, in relation to Precambrian deformation and metamorphism. Most of the basement rocks are distinctly foliated. Laramide deformation resulted in elevation of the core of the Front Range along northward-trending marginal upthrusts and in development of the Front Range mineral belt, a broad northeast-trending zone of strike-slip faults, veins, and igneous intrusions that extends diagonally across the range. The Montezuma stock was emplaced approximately at the junction of the mineral belt with the western margin of the range relatively late in the deformation. The stock is massive and shows little indication of flow fabric. Analysis of fault data obtained in the tunnel indicates two complementary sets of strike-slip faults, trending northeast and northwest, apparently related to wrench-fault movement along the mineral belt. Minor faults are randomly oriented but tend to be concentrated in north-trending dip-slip sets approximately parallel to the marginal upthrusts. The fracture pattern in the Montezuma stock conforms to the regional fault pattern. The major joint sets and fault sets are parallel to one another and probably formed concurrently. The fracture pattern in the Precambrian rocks is unlike that in the Montezuma stock. Minor faulting was controlled largely by the rock fabric. Joints bear no obvious relation to the faults or rock fabric and are believed to have formed mainly later than the faults. The anomalous rupture pattern in the foliated basement rocks is attributed to their anisotropy and to a probable transition from pseudoductile to brittle behavior as the core of the range was uplifted.

Joint System and Fault System of Granites in the West of the Matsumoto Basin, Nagano Prefecture

Joint System and Fault System of Granites in the West of the Matsumoto Basin, Nagano Prefecture