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Industrial Electronics, 1998. Proceedings. ISIE '98. IEEE International Symposium on

Date 7-10 July 1998

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  • IEEE International Symposium on Industrial Electronics [front matter]

    Page(s): 0_2
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  • Contents

    Page(s): v - xvii
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    Freely Available from IEEE
  • Author's index

    Page(s): 0_4 - 0_7
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    Freely Available from IEEE
  • VLSI analog multiplier/divider circuit

    Page(s): 493 - 496 vol.2
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    Intelligent systems require signal processing which can be done quickly and accurately. The commonly used digital approach has many advantages, but some disadvantages as well. Analog signal processing is in many cases much simpler, faster, and easier for performing parallel processing. In this paper a new accurate CMOS multiplier/divider circuit is presented. Contrary to previous solutions, which use the square law formula for MOS transistors operation, in the strong inversion mode, the multiplier/divider circuits employ MOS transistor characteristics in the subthreshold conduction mode. It is shown that the circuit generates very accurate results. With some modification, the basic circuit can also be used as a four-quadrant multiplier, which may operate for both positive and negative input signals. The circuit itself may have many applications such as multiplier, divider, signal squaring, square root calculations, frequency modulation, frequency doubling, etc. Most importantly it can be used for analog signal processing in many intelligent systems of industrial electronics View full abstract»

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  • Quasi-sliding technique of smooth ratio changing for inverters

    Page(s): 535 - 539 vol.2
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    A novel technique of quasi-sliding modulation has been applied to the scheme of asymmetrical pulsewidth modulation (PWM) for three-phase voltage source inverter with minimum number of switch commutations. It is based on a direct description of pulse patterns of line-to-line output voltage of inverter in the function of operating frequency of adjustable-voltage adjustable-frequency drive system. To provide smooth continuous shock-less variation of voltage waveform special signals with sliding width are formed step by-step near the center of 60° clock intervals of line voltage. The scheme of modulation presented combines properties of both scalar and vector principles of PWM. It has been given examples of determination on control parameters for inverter with low switching frequency. It has been described also in general form process of gradual transition from PWM to square-voltage at the maximum output frequency of rated control mode View full abstract»

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  • Using a fault detecting circuit for parallel connected DC/DC converters

    Page(s): 359 - 362 vol.2
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    In applications that demand high power consumption, there is a trend to use several standard DC/DC power converters working in parallel. The goal of this work is to develop a fault detecting scheme for every individual module in such parallel system. Together with the fault detecting scheme, a control circuit is used in order to achieve a proper response of the system in the presence of faults. To evaluate the behavior of the fault detection scheme, simulation and laboratory tests were made with one single buck power converter. Experimental results are given that validate the scheme View full abstract»

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  • Business data modelling and forecasting with the use of fuzzy neural networks

    Page(s): 396 - 401 vol.2
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    The first goal of this paper is to briefly present a methodology for complex system modelling which can utilize both quantitative (numerical) and qualitative (linguistic, fuzzy) types of knowledge which usually contribute to the description of the behaviour of the system. This methodology is based on fuzzy neural networks. An inference and forecasting engine designed with the use of the proposed fuzzy neural network is also presented. The second goal of this paper is the application of the proposed methodology to modelling of the data describing the level of sales in relation to the changes of a leading indicator. The data is typical of that arising in business forecasting View full abstract»

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  • Model of a laser-frequency measuring device

    Page(s): 639 - 642 vol.2
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    The authors propose a triple frequency phase range finder in this paper. By utilising three close frequencies, the instrument is able to determine ranges with absolute high precision. At the transmitter, the three frequencies are modulated with a laser beam and the resultant signal propagated. This composite signal (three frequencies modulating a laser beam) is ultimately reflected at the target. On reception, phase measuring circuits determine the phase changes/differences suffered by the individual frequencies and eventually the range is calculated. Because the oscillators may suffer frequency instabilities at times, several readings of the same range are taken before the average is taken to ensure high accuracy. The main advantage of the instrument is that the distance is calculated almost instantaneously without any extra calculations View full abstract»

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  • Crew operation scheduling using state selection method and relaxation search method

    Page(s): 726 - 731 vol.2
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    Railway crew operation scheduling is a problem in that the schedule of crews is scheduled according to a train timetable, whilst satisfying constraints such as working hours, rest hours etc. The authors propose a method which is made up of two phases: an initial scheduling phase; and a modification phase. In the first phase, the state selection method is used to satisfy the meal break constraint and knowledge for satisfying the meal break constraint is created. In the modification phase, a relaxation search method is created to dissolve other constraint violations. Exchange rules for dissolving constraint violation are created. This method is applied to a real rail timetable in order to show its usefulness View full abstract»

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  • Face recognition in a heterogeneous population

    Page(s): 594 - 599 vol.2
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    Face recognition technology has many and varied applications, ranging from document verification to crowd surveillance. The use of face recognition technology in access control is, due to its nonintrusive nature, extremely promising. Most face location and segmentation algorithms proposed in the literature have very limited capabilities, with most not able to find a face which is either rotated or scaled. A novel segmentation algorithm which attempts to overcome these restrictions was developed and used in this study. The Eigenface approach (Karhunen-Loeve transform) has been shown to work extremely well when used to extract feature vectors from a face image. It was found to be the most promising of all the published methods and was therefore used. Most face recognition papers in the open literature have generally used Caucasian faces to test their algorithms, no special mention is made of the other population groups. The effect of a heterogeneous population on face recognition is therefore something of an unknown quantity. It is the aim of this paper to investigate the performance of the developed face recognition system, with emphasis on the effect of a heterogeneous population View full abstract»

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  • Computer assisted seed identification

    Page(s): 589 - 593 vol.2
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    In this paper the author presents SIS, a computer assisted seed identification system developed by the CSIR. SIS assists seed analysts to identify unknown seeds. SIS uses digital image processing as a front end to an expert system connected to a comprehensive database containing feature vectors describing previously trained seeds to identify unknown seeds View full abstract»

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  • Inspection- and repair robots for waste water pipes a challenge to sensorics and locomotion

    Page(s): 476 - 478 vol.2
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    Sewerage is a very large and important infrastructure in the water industry. Because around 20% of the municipal pipe network is estimated to be significantly damaged, it is of high priority to inspect, maintain and repair public sewers. During recent years mobile robots have been developed to inspect but also to repair the pipes. To navigate through the hostile environment, they are generally only equipped with video cameras and connected to the outside world via an umbilical cord which transmits the image information. The tethered robots are tele-operated from a remote service station placed at the end of a maintenance shaft. These pipe robots are commonly wheeled systems especially adapted to withstand the adverse conditions of the waste pipe environment. In this paper the actual state of the art in the field of mobile robots for repair and inspection of sewerage is given and the possible improvements of the next generation of robots caused by developments of the sensors, the material, the tele-operation techniques and the locomotion principles are reported. This will allow the robots to increase their capabilities and to enlarge the application areas to pipes with smaller diameters and pipes in industrial plants View full abstract»

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  • Methods of logical functions decomposition for LUT-based FPGA

    Page(s): 487 - 492 vol.2
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    The increasing popularity of the field programmable gate array (FPGA) has generated a great deal of interest for FPGA design problems. Due to the fact that FPGAs are mainly characterized both by high integration rate and “reprogrammability”, they are useful for complex image processing. However, fast processing is not possible without parallel processing; also traditional integration methods are not sufficient enough. Thus, one possible way is to adapt the processing algorithm to the FPGA architecture and to avoid general methods of schematic description, allowing an easily implantation, but not an optimum partitioning-routing. With this aim, we tried to minimize the number of CLBs (configurable logic block) in the FPGA, to integrate logical functions (addition, multiplication, comparison etc.) dedicated to segmentation, classification, as well as filtering operations. This is done by expressing the whole “architecture-function to integrate” as Boolean constraints View full abstract»

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  • Reluctance synchronous machine drive for hybrid electric vehicle

    Page(s): 367 - 372 vol.2
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    The reluctance synchronous machine drive is amazingly not mentioned in literature as a possible alternative drive for electric vehicle propulsion. The paper describes the use of a small, compact reluctance synchronous machine drive for a series hybrid electric vehicle. The advantages and disadvantages of this drive compared to other drives are highlighted. It is shown that a finite element optimum designed flux barrier rotor reluctance synchronous machine has good torque density and efficiency. The machine is current angle-controlled for maximum torque per ampere or minimum kVA. This ensures that the machine is operated reasonably close to optimal efficiency for all loads. The simple drive controller together with an optimum layout three-phase IGBT inverter forms a compact power controller for the vehicle. The calculated and measured results of the reluctance synchronous machine drive system for the electric vehicle are given. The 28 kW peak reluctance synchronous machine is used to drive the front wheels of a sedan, series hybrid electric vehicle through a differential with a gear ratio of 4.5:1. Simulation results show, amongst others, that with the single RSM drive generating a peak torque of 120 Nm, the 1445 kg vehicle accelerates from 0-80 km/h in 25.5 seconds. The maximum speed is 120 km/h View full abstract»

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  • Fine active calibration of camera position/orientation through pattern recognition

    Page(s): 657 - 662 vol.2
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    Precise information on an object, which is obtained through pattern recognition, is fused into an active calibration process. The calibration process can be classified into two modes, i.e., passive and active calibration. Passive calibration is possible by using images of calibration grids pre-located at a reference position with fixed size, while active calibration is performed using images of real objects, which are to be manipulated. In most active calibration processes, either based upon a line-correspondence scheme or upon a point-correspondence scheme, clear images of the object are required. Even with uncontaminated images, there exist errors in estimating the position and orientation of a camera due to lens distortion and limited number of pixels, as well as inherent errors due to the perspective model of a camera. These problems are being tackled in various ways since there is no simple and solid approach. In this paper, precise position and shape information of an object, which is obtained by a pattern recognition procedure, is integrated into the calibration process based upon a point-correspondence scheme to improve the accuracy in estimating the position/orientation of a camera. Experiments are performed to show the improvement in this accuracy View full abstract»

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  • A resonant turn-off snubber for high power IGBT converters

    Page(s): 519 - 523 vol.2
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    This paper presents a resonant active turn-off snubber for high power IGBT power converter applications. The main feature of this snubber is that the maximum current rating of the auxiliary switching devices is small compared to that of the main switches. Comparing the costs of the snubber elements, to the benefits of the snubber makes it an extremely attractive option for reducing switching losses and EMI in high power converters. The snubber components can be combined into a single module which can be fitted to an existing converter without any modifications to the control method or basic structure of the converter. The basic operation of the snubber is described and theoretically analyzed. An experimental version of the snubber is evaluated on an 80 kVA phase-arm. A reduction of 72% in the effective turn-off losses was measured. The effect of the snubber on the sources of EMI namely the magnetic and electric fields near the converter are also investigated View full abstract»

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  • A new graphic method for stability analysis of speed sensorless FO controlled induction motor drives working at low speed in regenerative mode

    Page(s): 380 - 384 vol.2
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    In this paper, a graphic method to analyze, on the torque versus speed plane, the stability of a speed sensorless field oriented (FO) controlled induction motor drive is proposed. A decoupling control is used to generate the voltage commands from the current commands instead of the traditional current regulators. The speed is estimated using a Luenberger speed observer, that has been simplified taking into account the decoupling control equations. Special attention is given to the stability of the drive operation at low speed, in regenerative mode. This makes the proposed method interesting when the sensorless drive control has to be designed, for example, for electric vehicles applications. The proposed method has been simulated and the results obtained are shown in this paper View full abstract»

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  • An induction furnace employing a 100 kHz MOSFET full-bridge current-source load-resonant inverter

    Page(s): 530 - 534 vol.2
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    An induction furnace using a current-source, full-bridge load-resonant MOSFET inverter suitable for melting small amounts of precious metal (gold and platinum) is presented. Melting times of 25 seconds were achieved at a power level of approximately 900 watts. A parallel resonant topology was employed to resonate at 100 kHz. The full-bridge or H-bridge output stage was used to provide power input to the load in two quadrants. Two important reasons for utilising the current-fed, full-bridge topology in this application are: (1) it has an inherent short-circuit protection capability; and (2) it has a simple design structure, using few components, which has been proved to be advantageous over the other inverter topologies. The induction-heating load is driven at its resonant frequency, by the inverter. This ensures maximum efficiency and power transfer, with zero voltage switching. A simple but effective gate drive and control timing circuit was applied. The compact layout of the inverter suppressed ringing between parasitic lead-inductance connections and the drain-source capacitance of the MOSFETs. The induction furnace operates effectively in open loop throughout the heating cycle. The performance was tested on a 100 kHz prototype, rated at approximately 1 kW. An analysis and experimental results are presented View full abstract»

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  • On an automated signature verification system

    Page(s): 600 - 604 vol.2
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    An online signature verification system is discussed and an overview of the different elements of the system is given. The point is made that even systems that boast very reliable performance should be carefully designed in order to operate effectively in practice View full abstract»

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  • Optimal ordering method for coupling point production control system

    Page(s): 568 - 572 vol.2
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    In the coupling point production system (CPPS), inventories are concentrated at the position where supply lead time and demand lead time are equal. Inventory and production planning are made at this position. This position is defined as the “coupling point” (CP). In a CPPS, different products may have the same coupling point on the same production line. The authors propose an optimal ordering method (OOM for CPPS) to prevent running out of stock and to limit re-order quantities. This new method has been applied to a window frame manufacturing process successfully View full abstract»

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  • PC based number plate recognition system

    Page(s): 605 - 610 vol.2
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    A PC based number plate recognition system is presented. Digital gray-level images of cars are thresholded using the Niblack algorithm, which was found to outperform all binarization techniques previously used in similar systems. A simple yet highly effective rule-based algorithm detects the position and size of number plates. Characters are segmented from the thresholded plate using blob-colouring, and passed as 15×15 pixel bitmaps to a neural network based optical character recognition (OCR) system. A novel dimension reduction technique reduces the neural network inputs from 225 to 50 features. Six small networks in parallel are used, each recognising six characters. The system can recognize single and double line plates under varying lighting conditions and slight rotation. Successful recognition of complete registration plates is about 86.1% View full abstract»

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  • Scheduling of cogeneration facilities operating under the real-time pricing agreement

    Page(s): 390 - 395 vol.2
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    South Africa's largest electricity supply industry (ESI), Eskom, has introduced a pilot project aimed at developing and introducing a real-time pricing (RTP) tariff to its customers. The potential electricity cost savings that this tariff will have on the cogeneration industry is modelled. The purpose of this study is to add more insight into the basic concepts surrounding the scheduling of cogeneration. The system configuration is discussed and simplified. The schematic model configuration show the model's input-output characteristics. The model consists of an energy and cost fraction section. After modelling the generation and steam shifting operations, the cost of electrical energy due to the implementation of the RTP tariff structure is calculated from the model. This cost is compared with the cost of energy after optimal Nightsave (Eskom's two-part demand and energy tariff) scheduling is carried out. The advantages that the RTP tariff holds for industries with cogeneration facilities is also discussed View full abstract»

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  • An automated system for core loss measurement and characterization: a useful tool for high frequency magnetic components design

    Page(s): 540 - 545 vol.2
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    This paper describes an automated measurement system for core loss characterization in high frequency magnetic components. This system can accomplish these aims, within specified magnetic induction and frequency ranges, and at different temperatures, with high accuracy, due to the techniques used in the acquisition and computation of the waveforms involved in loss calculation. The core loss characterization, obtained by fitting the core loss density (per unit volume) versus frequency and magnetic induction, permits the use of an equation, which is a very useful tool for the design optimization of high frequency magnetic components, such as transformers and inductors for switched mode power supplies View full abstract»

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  • Quasi-resonant circuit DC-link inverter using a zero average current error control algorithm

    Page(s): 456 - 461 vol.2
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    A full-bridge bi-level inverter using a quasiresonant circuit DC-link to implement soft-switching is presented in this paper. It is demonstrated that the zero average current error algorithm digital time control can provide a suitable interface between the quasi-resonant circuit DC link and the inverter. Experimental results for a low power single-phase current-controlled inverter are documented, including quasi-resonant circuit waveforms, inverter waveforms and electromagnetic interference spectral characteristics View full abstract»

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  • A ZVS clamping mode-current-fed push-pull DC-DC converter

    Page(s): 617 - 621 vol.2
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    This paper introduces a new technique to recover the energy trapped in the leakage inductor of the current-fed push-pull converter, by means of an active clamping mode circuit. Theoretical analysis and experimental results, taken from a 800 W/40 kHz are presented in the paper. The studied converter also features ZVS (zero voltage switching) in all switches, preserving all the main properties of the original circuit. As a result, the efficiency is improved and the electromagnetic disturbances are minimized View full abstract»

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