Showing papers in "Sadhana-academy Proceedings in Engineering Sciences in 1997"
TL;DR: In this paper, an experimental study of orthogonal cutting was conducted on the edge trimming of unidirectional and multi-directional graphite/epoxy composites with polycrystalline diamond tools.
Abstract: The current focus of manufacturing research on fibre-reinforced plastics (FRP) is composed of the search for efficient processing techniques capable of providing high quality machined surfaces. Very limited work has been performed to identify the influence of manufacturing processes like edge-trimming and drilling on material performance. Recent reports suggest that process-induced damage may affect the mechanical behaviour of FRP materials. Therefore an experimental study of orthogonal cutting was conducted on the edge trimming of unidirectional and multi-directional graphite/epoxy composites with polycrystalline diamond tools. The effects of tool geometry and operating conditions were evaluated from an analysis of chip formation, cutting force, and machined surface topography. All aspects of material removal were found to be primarily dependent on fibre orientation. Discontinuous chip formation was noted throughout this study, regardless of machining parameters. Three distinct mechanisms in the edge trimming of fibre-reinforced composite material including a combination of cutting, shearing, and fracture along the fibre/matrix interface were observed. An investigation conducted on the compression, flexural and impact strength of graphite/epoxy composites machined by both traditional and non-traditional techniques, confirms that manufacturing characteristics may not only affect bulk properties but also influence the initiation and propagation of failure.
80 citations
TL;DR: A new algorithm is presented that combines backward dynamic programming for solving low level subproblems and interleaved conjugate gradient method for solving the high level problem and significantly improves algorithm convergence and solution quality.
Abstract: Scheduling is a key factor for manufacturing productivity. Effective scheduling can improve on-time delivery, reduce inventory, cut lead times, and improve the utilization of bottleneck resources. Because of the combinatorial nature of scheduling problems, it is often difficult to find optimal schedules, especially within a limited amount of computation time. Production schedules therefore are usually generated by using heuristics in practice. However, it is very difficult to evaluate the quality of these schedules, and the consistency of performance may also be an issue. In this paper, near-optimal solution methodologies for job shop scheduling are examined. The problem is formulated as integer optimization with a “separable” structure. The requirement of on-time delivery and low work-in-process inventory is modelled as a goal to minimize a weighted part tardiness and earliness penalty function. Lagrangian relaxation is used to decompose the problem into individual part subproblems with intuitive appeal. By iteratively solving these subproblems and updating the Lagrangian multipliers at the high level, near-optimal schedules are obtained with a lower bound provided as a byproduct. This paper reviews a few selected methods for solving subproblems and for updating multipliers. Based on the insights obtained, a new algorithm is presented that combines backward dynamic programming for solving low level subproblems and interleaved conjugate gradient method for solving the high level problem. The new method significantly improves algorithm convergence and solution quality. Numerical testing shows that the method is practical for job shop scheduling in industries.
72 citations
TL;DR: The actor-critic algorithm of Barto and others for simulation-based optimization of Markov decision processes is cast as a two time scale stochastic approximation.
Abstract: The actor-critic algorithm of Barto and others for simulation-based optimization of Markov decision processes is cast as a two time scale stochastic approximation. Convergence analysis, approximation issues and an example are studied.
39 citations
TL;DR: The technique of space vector pulsewidth modulation (SVM) is reviewed and the basic principle of SVM is derived and is compared with sinetriangle PWM.
Abstract: The technique of space vector pulsewidth modulation (SVM) is reviewed. The basic principle of SVM is derived and is compared with sine-triangle PWM. Operation in the overmodulation range is explained. Extension of SVM to other inverter-motor combinations such as three level inverters and split phase motors are discussed.
35 citations
TL;DR: A comprehensive account of the state-of-the-art on types of construction of the motor, closed loop controllers in position, speed and current/torque control and recent trends in inverters, sensors etc. are given in this paper.
Abstract: This paper deals with the latest developments in Permanent Magnet Brushless DC (PMBLDC) motor drives. A comprehensive account of the state-of-the-art on types of construction of the motor, closed loop controllers in position, speed and current/torque control and recent trends in inverters, sensors etc. are given. Techniques for mechanical sensors elimination are discussed in detail. Special efforts made to reduce torque ripples, noise and vibrations are described. The impact of microelectronics through integrated chips used in the control of PMBLDC motor drives is given. The increasing applications of this drive due to improved performance and its cost reduction are also enlisted.
34 citations
TL;DR: In this paper, the authors highlight the important results of the investigations on Electrochemical Discharge Machining (ECDM) conducted by the author and his coresearchers and show how ECD can be very conveniently used for micro-welding operation without using any sophisticated arrangement.
Abstract: This paper highlights the important results of the investigations on Electrochemical Discharge Machining (ECDM) conducted by the author and his coresearchers. It has been found that “switching phenomenon” plays a crucial role in spark generation and not the straightforward breakdown of the non-conducting vapour blanket. The mechanism of spark generation has been understood reasonably well and inductance in the circuit has emerged as an important process parameter from the investigations. This information has been effectively used to improve the process capability of ECDM by a substantial amount. It has also been shown how ECD can be very conveniently used for micro-welding operation without using any sophisticated arrangement.
34 citations
TL;DR: In this paper, the authors identify and discuss eight performance measures for generic business processes, including lead time, customer service, dependability, quality, flexibility, cost, capacity, and asset utilization.
Abstract: A manufacturing enterprise is a collection of interrelated, flexible, optimized business processes delivering value to the customers through high quality products and services, faster than competition. This view of an enterprise enables one to consider the entire business system including the suppliers, product development, manufacturing, logistics, distribution, and retailing and to smoothen out the interfaces between them. Performance measures and performance measurement are important for monitoring, control and management. We identify and discuss eight performance measures for generic business processes. These include lead time, customer service, dependability, quality, flexibility, cost, capacity, and asset utilization.
32 citations
TL;DR: In this paper, the authors deal with the basic principles, which may help in identifying its diagnostic ability, the scope of its diagnostic capabilities, the instrumentation in vogue for its monitoring and the state-of-the-art of the monitoring techniques and programs.
Abstract: Vibration is an effective tool in detecting and diagnosing some of the incipient failures of machines and equipment. The present paper deals with the basic principles, which may help in identifying its diagnostic ability, the scope of its diagnostic capabilities, the instrumentation in vogue for its monitoring and the state-of-the-art of the monitoring techniques and programs. A few case studies are also given to illustrate how machine troubles/failures are diagnosed with the help of vibration signatures.
24 citations
TL;DR: The Hamming scan is made to operate on the Kronecker or Chinese product of two sequences with best-known discrimination values, so that one can go to large lengths and yet get good results in affordable time, and suggest the superiority of the ternary sequences.
Abstract: The problem of obtaining long sequences with finite alphabet and peaky aperiodic auto-correlation is important in the context of radar, sonar and system identification and is called the coded waveform design problem, or simply the signal design problem in this limited context. It is good to remember that there are other signal design problems in coding theory and digital communication. It is viewed as a problem of optimization. An algorithm based on two operational ideas is developed. From the earlier experience of using the eugenic algorithm for the problem of waveform design, it was realised that rather than random but multiple mutations, all the first-order mutations should be examined to pick up the best one. This is called Hamming scan, which has the advantage of being locally complete, rather than random. The conventional genetic algorithm for non-local optimization leaves out the anabolic role of chemistry of allowing quick growth of complexity. Here, the Hamming scan is made to operate on the Kronecker or Chinese product of two sequences with best-known discrimination values, so that one can go to large lengths and yet get good results in affordable time. The details of the ternary pulse compression sequences obtained are given. They suggest the superiority of the ternary sequences.
22 citations
TL;DR: In this paper, a comprehensive review of the past and recent developments in the area of single-phase power factor correction (PFC) techniques is provided, and the motivation for the research in this area, and manifold directions into which the research has gained impetus, are clearly brought out.
Abstract: This paper provides a comprehensive review of the past and recent developments in the area of single-phase power factor correction (PFC) techniques. The motivation for the research in this area, and the manifold directions into which the research has gained impetus, are clearly brought out. The various PFC techniques are broadly classified into (1) passive, (2) active, and (3) active-passive PFC techniques. The active PFC techniques, based on the output dynamics, are further classified into (1) conventional techniques which have slow output dynamics and (2) techniques with fast output dynamics. The critical issues within each PFC technique are discussed in detail. An extensive list of references is also provided at the end.
20 citations
TL;DR: The first is approximation of the functional associated with the variational formulation via epi-convergence, replacing the edge set with a function, and a fast algorithm for minimizing the approximate functional is provided.
Abstract: Many edge detection techniques exhibit scale-dependent distortion of edges. We develop two ideas, which may also be of independent interest, to produce sharp edge localization at all scales. The first is approximation of the functional associated with the variational formulation via epi-convergence, replacing the edge set with a function. We provide a fast algorithm for minimizing the approximate functional. The second is to scale parameters and data to focus the edges. The resulting edge detector is a singular perturbation of a coupled pair of partial differential equations, yielding an elegant structure, suitable for digital or analog parallel implementation on mesh-connected arrays.
IBM1
TL;DR: In this article, the authors focus on the vital role that quantitative modelling techniques such as those founded in Operations Research and Industrial Engineering can play in reengineering supply chains, and illustrate such use by surveying current industrial practice and introducing real world examples based on their practical experience in solving supply chain and reengineering problems.
Abstract: The first-wave of reengineering, during the first half of the nineties, focused on making organizational changes and used primarilyinformation models of supply chains to integrate business processes.Quantitative models are expected to have a significant impact in the second-wave of reengineering through the deployment of performance and optimization models, economic analysis, and decision support systems. In this paper, we focus on the vital role that quantitative modelling techniques such as those founded in Operations Research and Industrial Engineering can play in reengineering supply chains. These quantitative models can extend the business process reengineering concepts to provide a concurrent reengineering framework for modelling the supply chain processes, identifying reengineering opportunities, evaluating design alternatives, guiding the selection of the best alternative, and deploying tools to implement the design. We illustrate such use by surveying current industrial practice and introducing real world examples based on our practical experience in solving supply chain and reengineering problems.
TL;DR: The emphasis of the survey is on simulation methodology and event scheduling, which forms the core of any simulation package or environment.
Abstract: Discrete event simulation has been widely used to model and evaluate computer and engineering systems and has been an on-going area of research and development. This paper presents an overview of the field. It covers specifications of discrete event systems, simulation methodology, simulation languages, data structures for event management, and front and backend support in simulation packages including random number generation and resource management. The emphasis of the survey is on simulation methodology and event scheduling, which forms the core of any simulation package or environment.
TL;DR: In this article, the literature on non-burning, non-circular jets is reviewed and recent studies on noncircular jet flames are discussed with focus on the work conducted in the author's laboratory.
Abstract: Gas jets from noncircular exits entrain more air from surroundings than jets from circular exits of equivalent area. Because the mixing rate of fuel and air governs the combustion and pollutant emission of diffusion flames and partially premixed flames, noncircular geometries offer a passive control of the flame characteristics. In this paper, the literature on nonburning, noncircular jets is reviewed and recent studies on noncircular jet flames are discussed with focus on the work conducted in the author’s laboratory.
TL;DR: A comprehensive review of the advances made in vector control or field orientation as applied to high performance AC motor drives is presented in this paper, where a substantial updated bibliography is included for those who are interested in keeping track of the present state-of-the-art and working further in this area.
Abstract: This paper attempts to present a comprehensive review of the advances made in vector control or field orientation as applied to high performanceac motor drives. Brief application survey, machine models ind-q representation, implementation issues with inverters and cycloconverters, parameter effects etc for both induction and synchronous motor vector control are dealt with and sample results from studies on them are presented. The latest advance on this control like direct torque control (DTC) has been briefly discussed. A substantial updated bibliography, though by no means complete, is included for those who are interested in keeping track of the present state-of-the-art and working further in this area.
TL;DR: In this article, a general technique for the analysis of time-period nonlinear dynamical systems is presented based on the fact that all quasilinear periodic systems can be replaced by similar systems whose linear parts are time invariant via the well-known Liapunov-Floquet (L-F) transformation.
Abstract: In this study, a general technique for the analysis of time-period nonlinear dynamical systems is presented. The method is based on the fact that all quasilinear periodic systems can be replaced by similar systems whose linear parts are time invariant via the well-known Liapunov-Floquet (L-F) transformation. A general procedure for the computation of L-F transformation in terms of Chebyshev polynomials is outlined. Once the transformation has been applied, a periodic orbit in original coordinates has a fixed point representation in the transformed coordinates. The stability and bifurcation analysis of the transformed equations are studied by employing thetime-dependent normal form theory and time-dependent centre manifold reduction. For the two examples considered, the three generic codimension-one bifurcations, viz, Hopf, flip and tangent, are analysed. The methodology is semi-analytic in nature and provides a quantitative measure of stability even under critical conditions. Unlike the perturbation or averaging techniques, this method is applicable even to those systems where the periodic term in the linear part does not contain a small parameter or a generating solution does not exist due to the absence of the time-invariant term in the linear part.
TL;DR: In this paper, the authors present an outline of the research done in the area of facility layout and discrete material handling system design and present an algorithm which aids in solving the combined pick-up/drop-off point location and material handling flowpath problem.
Abstract: The paper presents an outline of the research done in the area of facility layout and discrete material handling system design. The objective of this paper is to observe the trend in the literature in the area of manufacturing system design and predict the direction of future research in this area. The paper attempts to link the areas of facility layout design and material flow network design. A methodology for solving the integrated design problem is presented. An algorithm which aids in solving the combined pick-up/drop-off point location and material handling flowpath problem is outlined.
TL;DR: A review of the state-of-the-art and recent developments in Switched Reluctance Motor (SRM) drives can be found in this article, where the authors briefly discuss the historical background and the basic operating principles of the motor.
Abstract: The objective of this paper is to review the state-of-the-art and recent developments in Switched Reluctance Motor (SRM) drives. The interest for improved performance and reliability has motivated many SRM advances in the recent years. Even after almost 30 years of research in SRM, which might appear to be the simplest of all machines, there remain critical issues to be explored to gain deeper insight into the SRM technology. The paper briefly discusses the historical background and the basic operating principles of the motor. The topics discussed include the current state of research in converter topologies, control algorithms, torque ripple, noise, and sensorless operation. Recent advances in the field of SRMs indicates that they will have an increasing influence in the area of variable speed drives in the coming decades.
TL;DR: By exploiting three unique characteristics of confined swirling incompressible flows (i.e., centrifugal acceleration, internal separation or recirculation zones near the axis, and bistability) of multi-phase flows, a number of vortex machines have been developed as mentioned in this paper.
Abstract: By exploiting three unique characteristics of confined swirling incompressible flows — centrifugal acceleration, internal separation or recirculation zones near the axis, andbistability (i.e. rarefied and condensed stable states) of multi-phase flows — we developed several innovativevortex machines which will revolutionize mechanical technologies in a variety of industries. The machines utilizing these features include:Vortex Engine, Vortex Thruster, Vortex Suction Device, Vortex Chemical Reactor, Bubbling Centrifuge andVortex Mill. As a specific example, we describe here in some detail the development of a liquid piston engine, including analysis of its hydrodynamic and thermodynamic features. We have designed a laboratory ‘cold’ model and performed detailed experimental, theoretical and numerical analyses to study the role of the controlling parameters and are now ready to test a ‘hot’ model. In addition, we mention a few other vortex technologies of interest to us.
TL;DR: A review of the progress in flexible AC transmission system (FACTS) controllers is presented in this paper, where a generalized description of FACTS controllers is also presented, as well as a general description of the system.
Abstract: With the availability of high power semiconductor switches with turn-off capability, voltage source converter based controllers for power transmission system applications have become a reality. Prototypes of some second generation Flexible AC Transmission System (FACTS) controllers like TCSC and STATCON have been installed. This paper presents a review of the progress in FACTS. A generalized description of FACTS controllers is also presented.
TL;DR: In this article, the authors present a critical review of the major modelling paradigms, namely, CSG, B-Rep, non-manifold, and voxel models.
Abstract: The next generation manufacturing technologies will draw on new developments in geometric modelling. Based on a comprehensive analysis of the desiderata of next generation geometric modellers, we present a critical review of the major modelling paradigms, namely, CSG, B-Rep, non-manifold, and voxel models. We present arguments to support the view that voxel-based modellers have attributes that make it the representation scheme of choice in meeting the emerging requirements of geometric modelling.
TL;DR: In this paper, the authors present a comprehensive state-of-the-art of the recent advances in simulation of power electronic converter systems, including various methods of modelling, circuit analysis approaches, numerical techniques etc.
Abstract: This paper presents a comprehensive state-of-the-art of the recent advances in simulation of power electronic converter systems. Knowing the importance of simulation, this paper reviews the various methods of modelling, circuit analysis approaches, numerical techniques etc. Several general purpose simulators and dedicated power electronic simulators have been discussed. A few demonstrative examples of simulation of power electronic converters by using different simulators are provided. Practical difficulties in simulation, challenges, new developments and scope for future work are also discussed.
TL;DR: In this paper, the authors discuss the complexities associated with a broad product line are complexities related to design, forecasting, coordination, and operations, and discuss some of these important issues.
Abstract: With the increase in the drive towards greater customer satisfaction, there has been a proliferation in the variety of products offered by manufacturers. Variety provides considerable choice to customers and encourages manufacturers to modularize their product lines. However, associated with a broad product line are complexities related to design, forecasting, coordination and operations. In this paper, we discuss some of these important issues.
TL;DR: Some recent results in single-product, capacitated production-inventory systems in discrete time are presented, considering periodic demand, and multiple stages — serial, distribution and assembly.
Abstract: We present here some recent results in single-product, capacitated production-inventory systems in discrete time. The key results are: (1) structure of optimal policy for single stage systems; (2) analysing via a shortfall process; (3) using simulation to optimize; (4) an approximation using tail probabilities. We consider periodic demand, and multiple stages — serial, distribution and assembly. Related topics of re-entrant flow shops, lead time quotation and value of information are also discussed briefly.
TL;DR: The manufacturing capabilities available impact the scope of design, while design for manufacturing ensures the economic success of the products as mentioned in this paper, which is very closely related to the design of the product.
Abstract: Manufacturing and design are very closely related. The manufacturing capabilities available impact the scope of design, while design for manufacturing ensures the economic success of the products.
TL;DR: A brief review of modernac motor traction drives, powered from 25 kV power frequencyac supply, employing voltage source inverters, current source inverter, and induction and synchronous motors have been discussed.
Abstract: The paper presents a brief review of modernac motor traction drives, powered from 25 kV power frequencyac supply. Drives employing voltage source inverters, current source inverters, and induction and synchronous motors have been discussed.
TL;DR: The proposed matrix partitioning method independently generates Cholesky factorizations of each part, and reduces the complexity to that of solving generally, a dense linear system involving several rank one updates of the identity matrix.
Abstract: We consider here a linear programming problem whose rows of the constraint matrix can be partitioned into two parts. Such natural partitions exist in several special linear programs, including the assignment problem, the transportation problem, the generalized upper-bounded variable problem, the block diagonal linear program; and can also be used to induce sparsity patterns in Cholesky factorizations. In this paper, we propose a matrix partitioning method for interior point algorithms. The proposed method independently generates Cholesky factorizations of each part, and reduces the complexity to that of solving generally, a dense linear system involving several rank one updates of the identity matrix. Here, we propose solving this linear system by an inductive use of the Sherman-Morrison-Woodbury formula. The proposed method is easily implemented on a vector, parallel machine as well as on a distributed system. Such partitioning methods have been popular in the context of the simplex method, where the special structure of the basis matrix is exploited.
TL;DR: A detailed understanding of the wear mechanisms leading to material removal would allow for the design of efficient machining processes for producing ceramic surfaces of high quality as discussed by the authors, as well as a complete understanding of wear mechanisms in a particular finishing process can be found in the literature.
Abstract: Ceramic materials are finished primarily by abrasive machining processes such as grinding, lapping, and polishing. In grinding, the abrasives typically are bonded in a grinding wheel and brought into contact with the ceramic surface at relatively high sliding speeds. In lapping and polishing, the ceramic is pressed against a polishing block with the abrasives suspended in between them in the form of a slurry. The material removal process here resembles three-body wear. In all these processes, the mechanical action of the abrasive can be thought of as the repeated application of relatively sharp sliding indenters to the ceramic surface. Under these conditions, a small number of mechanisms dominate the material removal process. These are brittle fracture due to crack systems oriented both parallel (lateral) and perpendicular (radial/median) to the free surface, ductile cutting with the formation of thin ribbon-like chips, and chemically assisted wear in the presence of a reactant that is enhanced by the mechanical action (tribochemical reaction). The relative role of each of these mechanisms in a particular finishing process can be related to the load applied to an abrasive particle, the sliding speed of the particle, and the presence of a chemical reactant. These wear mechanisms also cause damage to the near ceramic surface in the form of microcracking, residual stress, plastic deformation, and surface roughness which together determine the strength and performance of the finished component. A complete understanding of the wear mechanisms leading to material removal would allow for the design of efficient machining processes for producing ceramic surfaces of high quality.
TL;DR: This paper reviews the evolution of off-line quality engineering methods with respect to one or more quality criteria, and presents some recent results.
Abstract: This paper reviews the evolution of off-line quality engineering methods with respect to one or more quality criteria, and presents some recent results. The fundamental premises that justify the use of robust product/process design are established with an illustrative example. The use of designed experiments to model quality criteria and their optimization is briefly reviewed. The fact that most design-for-quality problems involve multiple quality criteria motivates the development of multiobjective optimization techniques for robust parameter design. Two situations are considered: one in which response surface models for the quality characteristics can be obtained using regression and considered over a continuous factor space, and one in which the problem scenario and the experiment permit only discrete parameter settings for the design factors. In the former scenario, a multiobjective optimization technique based on the reference-point method is presented; this technique also incorporates an inference mechanism to deal with uncertainty in the response surface models caused by finite, noisy data. In the discrete-factors scenario, an efficient method to reduce computational complexity for a class of models is presented.
TL;DR: In this paper, non-equilibrium fluid mechanics and thermodynamics of two-phase vapour-droplet and gas-particle flow are considered, and a new theory of nucleation in steam turbines is developed that reproduces many aspects of measured droplet size spectra which cannot be explained by any available steady flow theories.
Abstract: Non-equilibrium fluid mechanics and thermodynamics of two-phase vapour-droplet and gas-particle flow are considered. Formation of the droplets as well as their subsequent interaction with the vapour are discussed. A new theory of nucleation in steam turbines is developed that reproduces many aspects of measured droplet size spectra which cannot be explained by any available steady-flow theories. (Steam turbines are responsible for 80% of global electricity production and the presence of moisture significantly reduces turbine efficiency costing 50 million pounds per annum in UK alone.) Fluid dynamic interactions discussed include flow instabilities induced by condensation, condensation wave theory, relaxation gas dynamics for vapour-droplet flow, thermal choking due to non-equilibrium condensation, the structure of shock waves and their development through unsteady processes, and jump conditions and the interpretation of total pressure in two-phase flows.