An overview of fault monitoring and diagnosis in mining equipment

Proper detection and diagnosis of failing system components is crucial to efficient mining operations. However, the harsh mining environment offers special challenges to these types of actions. The atmosphere is damp, dirty, and potentially explosive, and equipment is located in confined areas far from shop facilities. These conditions, coupled with the increasing cost of downtime and complexity of mining equipment, have forced researchers and operators to investigate alternatives for improving equipment maintainability. This paper surveys monitoring and diagnosis technologies that offer opportunities for improving equipment availability in mining. Expert systems, model-based approaches, and neural nets are each discussed in the context of fault detection and diagnosis. The paper concludes with a comparative discussion summarizing the advantages and disadvantages of each     

Assembly of amino-terminal fibronectin dimers into the extracellular matrix

Fibronectin is a dimeric adhesion molecule that consists of three types of repeating modules. Adherent cells bind soluble fibronectin and incorporate it into insoluble fibrils in the extracellular matrix. The amino-terminal 70-kDa portion of fibronectin mediates binding to the cell surface, but amino-terminal fragments do not accumulate in the extracellular matrix. The ninth type I and first type III modules, the cell adhesion region, and the cysteines that form the interchain disulfide bonds have also been implicated in matrix assembly. To further define which regions of fibronectin are essential for matrix assembly, we generated a dimeric protein (d70 kDa) in which the 70-kDa amino terminus is directly linked to the last 51 amino acids of fibronectin, which contain the cysteines involved in interchain disulfide bonding. d70 kDa bound to cells and accumulated in the extracellular matrix. Incorporation of d70 kDa into the extracellular matrix was dependent upon protein synthesis; in cycloheximide-treated cultures that lacked a pre-existing matrix, d70 kDa accumulated in the extracellular matrix only in the presence of intact fibronectin. Monomeric 70-kDa protein was not incorporated into the matrix in the presence or absence of cycloheximide. These data indicate that fibronectin molecules containing only the amino-terminal 70-kDa region and the carboxyl-terminal 51 amino acids can become assembled into the extracellular matrix.     

Alternatives for assessing the electrical integrity of inductionmotors

The use of periodic inspection methods for early detection of motor deterioration is addressed. Two alternatives to traditional procedures that are appropriate for detecting stator-winding deterioration in three-phase induction motors of the sizes commonly found in the process industries are presented. The use of an effective-negative-sequence impedance as a predictor of incipient failure is recommended     

Design of versatile eIRA codes for parallel decoders

In this paper we propose a semi-random technique for the generation of a class of eIRA codes (a popular class of irregular LDPC codes that can be encoded in linear time) suited to partially parallel decoder implementations. The suggested technique tries to avoid both low-weight codewords and nearcodewords, which limit the performance of the belief propagation decoder. Its effectiveness is verified by comparison with literature results. The obtained codes are versatile, in terms of code-rate and block length, and they are characterized by a low error floor.     

An on-line method to detect incipient failure of turn insulation inrandom-wound motors

Induction motors used in various mining industry applications fail frequently because they are subjected to severe operating conditions. Periodic test procedures are inappropriate for many installations and the cramped and hazardous mining environment makes unscheduled motor replacements difficult and time-consuming to perform. An online detector of insulation degradation is proposed and demonstrated analytically and experimentally. This detector, termed the effective negative-sequence impedance, is computed from the voltage and current phasors at the motor terminals. It can be used frequently, even continuously, and does not interfere with normal motor operation. With this detector, motor replacements can be scheduled, thereby reducing production downtime associated with emergency maintenance actions     

On-line control strategies to minimize peak loads on mine conveyornetworks using surge units with variable discharging capability

Control of peak loads on gathering belts in mine conveyor systems can result in substantial reductions in power consumption as well as savings in capital and maintenance costs for the conveyor equipment. This paper first extends an existing control approach involving dynamic adjustment of feeder discharge rates to the case where the differences in transit times between section feeders and the gathering belts where the flows converge are small. It is shown that multiple units should be considered simultaneously when determining control actions, and a dynamic programming approach is given for determining the optimal control policy in such a situation. Subsequently, the application of this approach is considered for longwall mines where flow from the longwall is not controlled, but the discharge rates of continuous miner section feeders are adjusted in real-time to prevent belt overloading while minimizing any production constraint on the continuous miner units. This application requires special treatment for the highly variable material flow pattern produced by longwalls. The practical utility of these approaches is evaluated through detailed simulation studies. These studies are used to estimate the magnitude of savings in energy, capital, and maintenance costs     

Detection of AC machine winding deterioration using electricallyexcited vibrations

Presented in this paper is a theoretical review of the relationships that should exist between electrical winding parameters and the mechanical vibration of AC machine elements under normal and faulted operating conditions. Also included are data from an experimental study that relate stator vibration and bearing vibration to selected winding faults in a synchronous machine. Consideration of these results indicates a significant relationship between electrical deterioration and mechanical vibration and, thus, provides the motivation for additional study and a basis for future applications     

Numerical Schubert Calculus

We develop numerical homotopy algorithms for solving systems of polynomial equations arising from the classical Schubert calculus. These homotopies are optimal in that generically no paths diverge. For problems defined by hypersurface Schubert conditions we give two algorithms based on extrinsic deformations of the Grassmannian: one is derived from a Gröbner basis for the Plücker ideal of the Grassmannian and the other from a SAGBI basis for its projective coordinate ring. The more general case of special Schubert conditions is solved by delicate intrinsic deformations, called Pieri homotopies, which first arose in the study of enumerative geometry over the real numbers. Computational results are presented and applications to control theory are discussed.     

An efficient class of direct search surrogate methods for solving expensive optimization problems with CPU-time-related functions

In this paper, we characterize a new class of computationally expensive optimization problems and introduce an approach for solving them. In this class of problems, objective function values may be directly related to the computational time required to obtain them, so that, as the optimal solution is approached, the computational time required to evaluate the objective is significantly less than at points farther away from the solution. This is motivated by an application in which each objective function evaluation requires both a numerical fluid dynamics simulation and an image registration process, and the goal is to find the parameter values of a predetermined reference image by comparing the flow dynamics from the numerical simulation and the reference image through the image comparison process. In designing an approach to numerically solve the more general class of problems in an efficient way, we make use of surrogates based on CPU times of previously evaluated points, rather than their function values, all within the search step framework of mesh adaptive direct search algorithms. Because of the expected positive correlation between function values and their CPU times, a time cutoff parameter is added to the objective function evaluation to allow its termination during the comparison process if the computational time exceeds a specified threshold. The approach was tested using the NOMADm and DACE MATLAB? software packages, and results are presented.