Showing papers by "Universiti Teknologi Malaysia published in 2000"

An improved stator flux estimation in steady state operation for direct torque control of induction machines

Abstract: The paper presents an improved stator flux estimation technique based on a voltage model with some form of low pass filtering. In voltage model-based stator flux estimation, a low-pass (LP) filter is normally used instead of a pure integrator to avoid the integration drift problem due to DC offset, noise or measurement error present in the back electromotive force (EMF). In steady state condition, the LP filter estimator will degrade the performance and efficiency of the direct torque control (DTC) drive system since it introduces magnitude and phase errors, thus resulting in an incorrect voltage vector selection. The stator flux steady state error between the LP filter and a pure integrator estimator techniques is derived and its effect on the steady state DTC drive performance is analyzed. A simple method is proposed to compensate for this error which results in a significant improvement in the steady state drive performances. Simulation based on this technique is given and it is verified by experimental results.

Radiation-induced grafting of styrene onto poly(tetrafluoroethylene) (PTFE) films. I. Effect of grafting conditions and properties of the grafted films

Abstract: Radiation-induced grafting of styrene onto poly(tetrafluoroethylene) (PTFE) films was studied by a simultaneous irradiation technique. Grafting was carried out using g-radiation from a 60 Co source at dose rates of 1.32-15.0 kGy h ˇ1 at room temperature. The effects of type of diluent, dose rate, irradiation dose, and the initial monomer concentration in the grafting solution on the degree of grafting were investigated. The degree of grafting was found to be strongly dependent upon the grafting conditions. The dependence of the initial rate of grafting on the dose rate and the initial monomer concentration in the grafting solution was found to be in the order of 0.6 and 1.7, respectively. The chemical structure and the crystallinity of the grafted PTFE films were studied by means of Fourier- transform infrared, (FTIR), electron spectroscopy for chemical analysis (ESCA) and X-ray diffractometry (XRD). # 2000 Society of Chemical Industry

LQR controller for active car suspension

Abstract: The suspension system is classified as a passive, semi-active, and active suspension, according to its ability to add or extract energy. An automotive active suspension control has been one of the favourite subjects in the automotive research area. The advantages of an automotive active suspension system have been promised for many years. The objectives of the control scheme are to improve the ride quality and handling performance within a given suspension stroke limitation. The ride quality is measured by the vertical acceleration of the vehicle body called the sprung mass. The handling performance is determined by the tyre deflection, which is the difference of position between the wheel and the road surface input. The paper analyses the aspects of passive and active suspensions and focuses on the ride quality improvement. The LQR control scheme is selected to control an actuator in an active suspension. The result shows that the ride quality can be improved using an active suspension.

Cation exchange membranes by radiation‐induced graft copolymerization of styrene onto PFA copolymer films. II. Characterization of sulfonated graft copolymer membranes

Abstract: PFA-g-polystyrene sulfonic acid membranes were prepared by simultaneous radiation-induced graft copolymerization of styrene onto poly(tetrafluoroethylene- co-perfluorovinyl ether) (PFA) film followed by sulfonation. The membrane physicochemical properties such as swelling behavior, ion exchange capacity, hydration number, and ionic conductivity were studied as a function of the degree of grafting. Thermal as well as chemical stability of the membranes was also investigated. The membrane properties were found to be mainly dependent upon the degree of grafting. The water uptake, ion exchange capacity, hydration number, and ionic conductivity of the membranes were increased, whereas the chemical stability decreased as the degree of grafting increased. The membranes showed reasonable physico-chemical properties compared to Nafion 117 membranes. However, their chemical stability has to be further improved to make them acceptable for practical use in electrochemical applications.

Proton Exchange Membranes Prepared by Simultaneous Radiation Grafting of Styrene onto Poly(tetrafluoroethylene- co-hexafluoropropylene) Films. I. Effect of Grafting Conditions

Abstract: The simultaneous radiation grafting of styrene onto poly(tetrafluoroethyl- ene-co-hexafluoropropylene) (FEP) films was studied at room temperature. The effects of grafting conditions (type of solvent, irradiation dose, dose rate, and monomer con- centration) were investigated. The degree of grafting was found to be dependent on the investigated grafting conditions. The dependence of the initial rate of grafting on the dose rate and the monomer concentration was found to be of 0.5 and 1.3 orders, respectively. The results suggest that grafting proceeds by the so-called front mecha- nism in which the grafting front starts at the surface of the film and moves internally toward the middle of the film by successive diffusion of styrene through the grafted layers. Some selected properties of the grafted films were evaluated in correlation with the degree of grafting. We found that the grafted FEP films possess good mechanical stability, which encourages their use for the preparation of proton exchange membranes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 220 -227, 2000

XPS Studies of Radiation Grafted PTFE-g-polystyrene Sulfonic Acid Membranes

Abstract: Structural investigations of PTFE-g-polystyrene sulfonic acid membranes prepared by radiation grafting of styrene onto PTFE were conducted by X-ray photoelectron spectroscopy (XPS). The analyzed materials included original PTFE film as a reference material, grafted film, and sulfonated membrane samples having various degrees of grafting. Interest is focused on C1s, F1s, O1s, and S2p of narrow XPS spectra as the basic elemental components of the membrane. The original PTFE film was found to undergo structural changes in terms of chemical composition and shifting in binding energy induced by incorporation of sulfonated polystyrene grafts, and the amount of such changes depends on the degree of grafting. The atomic ratio of F/C was found to decrease with the increase in the degree of grafting, while that for S/C and O/C were found to increase.

Analysis and classification of heart sounds and murmurs based on the instantaneous energy and frequency estimations

Abstract: This paper proposes the use of the instantaneous energy and the frequency estimation in the classification of the heart sounds and murmurs for common heart diseases. It has been known that the present of the heart murmurs in one's heart sound indicates that there is a potential heart problem. Thus, the goal of this work is to develop a technique for detecting and classifying murmurs. Such a technique can be used as part of a heart diagnostic system. The analysis is performed based on a set of 102 data for various heart sounds. To discriminate the various heart sounds, the instantaneous energy and frequency estimation is used to estimate the features of heart sound. The techniques used to estimate the instantaneous frequency are the central finite difference frequency estimation (CFDFE) and zero crossing frequency estimation (ZCFE). From the instantaneous energy and frequency estimate, the energy and frequencies of the heart sounds are defined as the features of the heart sounds that can uniquely discriminate the various heart sounds.

Proton exchange membranes prepared by simultaneous radiation grafting of styrene onto poly(tetrafluoroethylene‐co‐hexafluoropropylene) films. II. Properties of sulfonated membranes

Abstract: Proton exchange membranes were prepared by radiation-induced grafting of styrene onto commercial poly(tetrafluoroethylene-co-hexafluoropropylene) films using a simultaneous irradiation technique followed by a sulfonation reaction. The resulting membranes were characterized by measuring their physicochemical properties such as water uptake, ion exchange capacity, hydration number, and proton conductivity as a function of the degree of grafting. The thermal properties (melting and glass transition temperatures) and thermal stability of the membrane were also investigated using differential scanning calorimetry and thermal gravimetric analysis, respectively. Membranes having degrees of grafting of 16%and above showed proton conductivity of the magnitude of 1022 V21 cm21 at room temperature, as well as thermal stability at up to 290°C under an oxygen atmosphere.

Gamma radiation-induced graft copolymerization of styrene onto poly(ethyleneterephthalate) films

Abstract: Gamma radiation-induced graft copolymerization of styrene onto poly(eth- ylene terephthalate) (PET) films was studied using simultaneous irradiation technique. The effects of grafting conditions on the degree of grafting were investigated. The grafting conditions include monomer concentration, irradiation dose, dose rate, and the type of solvent. Moreover, the effect of the addition of crosslinking agents (i.e., divinyl- benzene (DVB) and triallyl cyanurate (TAC)) having various concentrations were also investigated. The degree of grafting was found to be greatly dependent on the grafting conditions. Of the three diluents employed, methylene chloride was found to drastically enhance the degree of grafting. The order of dependence of the initial rate of grafting on the monomer concentration was found to be 2.2. The grafted PET films were identified by FTIR spectroscopy and characterized by X-ray diffraction (XRD). © 2000 John Wiley &

Issues in quality engineering research

Abstract: The field of quality has undergone significant changes as reflected by changes in its definition, paradigms, approaches, techniques, and scope of application. This paper reviews emerging trends and issues focusing on quality engineering. Changes in customer expectation have driven the changes in the technology of design and manufacturing, which is becoming more important in satisfying individual customer expectations. This also calls for special attention to the engineering aspects of quality. Brief reviews on recent advances in the prominent quality tools such as statistical process control, quality function deployment, and design of experiment are reported. General trends in quality engineering research show the tools are being enhanced, integrated, computerized and broaden their application bases, where possible opportunities for further investigation are indicated. Among others these include contributions in multiple‐response optimization, intelligent quality systems, multivariate SPC, and practical and simple guidelines for actual implementation of various tools.

Intelligent active force control of a robot arm using fuzzy logic

Abstract: The paper describes a novel and intelligent method of estimating the inertial parameter of a rigid robot arm employing an active force control (AFC) strategy with a fuzzy logic (FL) mechanism embedded in its control loop. The robustness and effectiveness of the proposed central scheme are investigated considering the trajectory track performance of the arm taking into account the application of some forms of external disturbances as the robot describes a reference trajectory given a number of initial and operating conditions. The track performance of the proposed scheme is also compared with an equivalent system employing classical proportional-derivative (PD) control.

Part II. Properties of the grafted and sulfonated membranes

Abstract: The physical and chemical properties of polystyrene grafted and sulfonated polytetrafluoroethylene (PTFE-graft-PSSA) membranes prepared by radiation-induced grafting of styrene onto commercial PTFE films using simultaneous irradiation technique followed by a sulfonation reaction are evaluated. The investigated properties include water uptake, ion exchange capacity, hydration number and ionic conductivity. All properties are correlated with the amount of grafted polystyrene (degree of grafting). The thermal stability of the membrane evaluated by thermal gravimetric analysis (TGA) is compared with that of original and grafted PTFE films. The membrane surface structural properties are analysed by electron spectroscopy for chemical analysis (ESCA). Membranes having degrees of grafting of 18%and above show a good combination of physical and chemical properties that allow them to be proposed for use as proton conducting membranes, provided that they have sufficient chemical and mechanical stability.

Cation Exchange Membranes by Radiation-Induced Graft Copolymerization of Styrene onto PFA Copolymer Films. III. Thermal Stability of the Membranes

Abstract: Thermal stability of cation exchange, PFA-g-polystyrene sulfonic acid membranes prepared by radiation-induced graft copolymerization of styrene onto PFA films followed by sulfonation was studied by thermal gravimetric analysis (TGA) and oven heat treatment. The tested samples included original and grafted PFA films as reference materials. All the membranes showed multistep decomposition patterns due to dehydration, desulfonation, dearomatization, and decomposition of the PFA matrix. Investigations of the individual decomposition behaviors showed that the weight loss strongly depends upon the degree of grafting. However, the decomposition temperatures were found to be independent of the degree of grafting. The loss in some selected membrane properties such as ion exchange capacity and water uptake was found to be function of the degree of grafting, temperature, and the time of heat treatment.

Parallel Huffman decoder with an optimized look up table option on FPGA

Abstract: Compression is very important for systems with limited channel bandwidth and/or limited storage size. One of the main components in image/video compression is variable length coding (VLC). This paper discusses one of the most popular VLC technique known as Huffman coding. A real time hardware parallel Huffman decoder has been successfully designed and implemented using 50,000 gate FPGA (FLEX10K20 from Altera). The parallelism is exploited in the design to achieve the high frame rate such as in JPEG and MPEG implementation. Using a parallel technique, a codeword is guaranteed to be processed within a single clock cycle. The codeword to be processed is matched with the one stored in a look up table (LUT). A LUT is needed during the coding and decoding process. In order to save memory cost, an optimized LUT is suggested. This paper does not intend to complete an optimized operating speed design, but instead only concentrates on producing a workable real-time decoder design.

FPGA implementation of RSA public-key cryptographic coprocessor

Abstract: The hardware implementation of the RSA algorithm for public-key cryptography is presented. The algorithm is dependent on the computation of modular exponentials. Critical to this computation is a fast implementation of modular multiplications. A high-performance systolic array architecture for modular multiplication based on the algorithm of Montgomery (1985) is proposed. The design is targeted for implementation in reconfigurable logic, which can yield custom-hardware performance yet maintains all the flexibility of software-based systems. Reconfigurable computing allows the designer to respond, in the prototyping stage, to flaws discovered in implementation or to changes in standards or data formats. We report the issues involved in the preliminary design of the prototype to be fabricated in Altera FLEX10KE series FPGA mounted on a PCI card.

Wear Behavior of PVD and CVD Coated Carbide Tools when Face Milling Inconel 718

Abstract: The wear behavior of two types of coated cemented carbide tools has been studied when face milling a nickel-based superalloy Inconel 718. PVD-TiN and CVD-TiCN+Al2O3 tools were used. It was found that the coatings were detached after only five seconds of cutting. An attrition type wear mechanism associated with workpiece material adhesion was observed which eventually led to severe chipping, flaking, plastic deformation and cracking. It was noted that the coatings had no significant effect on tool performance under the cutting conditions tested. Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

Implementation of pipelined data encryption standard (DES) using Altera CPLD

Abstract: The paper presents a pipelined data encryption standard (DES) architecture design implemented in Altera CPLD. The architecture contains three main parts, DES module, pipeline module and control unit module. A four-segment pipeline is used in this architecture to burst the throughput of the DES. Although the processing time for a single encryption operation is still the same; but with more encryption operations, this pipelined DES can increase significantly the throughput. Altera Hardware Description Language (AHDL) is used to implement the pipelined DES design.

A hybrid intelligent active force controller for robot arms using evolutionary neural networks

Abstract: In this paper, we propose a hybrid intelligent parameter estimator for the active force control (AFC) scheme which utilizes evolutionary computation (EC) and artificial neural networks (ANN) to control a rigid robot arm. The EC part of the algorithm composes of a hybrid genetic algorithm (GA) and an evolutionary program (EP). The development of the controller is divided into two stages. In the first stage, which is performed off-line, the proposed EC algorithm is employed to evolve a pool of ANN structures until they converge to an optimum structure. The population is divided into different groups according to their fitness. The elitist group will not undergo any operation, while the second group, i.e. stronger group, undergoes the EP operation. Hence, the behavioral link between the parent and their offspring can be maintained. The weaker group undergoes a GA operation since their behaviors need to be changed more effectively in order to produce better offspring. In the second stage, the evolved ANN obtained from the first stage, which represent the optimum ANN structural design, is used to design the on-line intelligent parameter estimator to estimate the inertia matrix of the robot arm for the AFC controller. In this on-line stage, the ANN parameters, i.e. the weights and biases, are further trained using live data and back-propagation until a satisfactory result is obtained. The effectiveness of the proposed scheme is demonstrated through a simulation study performed on a two link planar manipulator operating in a horizontal plane. An external load is introduced to the manipulator to study the effectiveness of the proposed scheme.

A modified approach for load flow analysis of integrated AC-DC power systems

Abstract: High voltage direct current (HVDC) power distribution systems have been extensively used in modern transmission system. The major concern of the HVDC transmission is the loadflow in the system. This paper is dealing with the development of loadflow solution for a HVDC link in a power system. The loadflow solution is based on the fast decoupled method which needs some iteration to obtain the result. The paper exposed us to the integration of HVDC link with an AC power system. Variables of the direct current link which have been chosen for simulation are the converter terminal DC voltages, converter transformer tap ratios, firing angle of the rectifier and current in the HVDC link. An algorithm has been developed to solve the HVDC link power system loadflow and the algorithm has been tested on the IEEE test system.

Implementation of two dimensional forward DCT and inverse DCT using FPGA

Abstract: This paper describes the (field programmable gate array) FPGA implementation of two dimensional forward and inverse discrete cosine transform (2D-DCT and 2D-IDCT) using the 100 K gate ALTERA FLEX10K100 FPGA/CPLD. The architecture used in both 2D-DCT and 2D-IDCT is based on the conventional row-column decomposition method. The use of a fast algorithm and distributed arithmetic (DA) technique to implement the DCT and IDCT greatly reduces the hardware complexity.

Consolidation Characteristics of Lime Stabilised Soil

Abstract: Soft clay is always associated with settlement and consolidation. Stabilisation of soft clay with lime as bearing stratum is an alternative to replacement of that material. The compression and consolidation characteristics of the stabilised material need to be fully understood for design purposes. This paper presents the results of study on the consolidation characteristics in terms of compressibility, rate of consolidation and the permeability characteristics of both unstabilised and lime stabilised soil samples using Oedometer test. Oedometer specimens of 50 mm diameter and 20 mm height were tested with respect to age at 0,7, 14 and 28 days and effective stress at 0, 200, 400, 800 and 1600 kPa. Three soil types were selected and studied in this project; they are Tapah Kaolin, Sungai Buloh clay and UTM clay. From the test results, it is discovered that lime stabilisation improved the consolidation characteristics and reduced the settlement of unstabilised clay with age especially after stabilisation phase is achieved, i.e., after the age of 14 days.

Market-based approach for multi-team robot cooperation

Abstract: The scalability of market-based approaches in multi-robot system coordination enables an assigned task to be decomposed into subcomponents achievable by individuals or subteams within the team. However, in some potential multi-robot system applications, particularly search and rescue operations, this can involve deployment of multiple teams of robots from different parties to work side by side. Each team of robots is independently managed by its operator. A loose collaboration among teams of robots is needed to increase the efficiency of a task completion. This work presents a variant architecture of multi-robot systems using Contract Net Protocol to address the coordination among multiple teams of robots. The system is named a multi-team robot system. It places emphasis on a team's data security in communication where each team operates on a respective communication network while maintaining their collaboration. The method of task coordination is explained in detail and verified on a physical mobile robot platform.

Prediction of salt contamination on high voltage insulators in rainy season using regression technique

Abstract: The severity of contamination on the high voltage insulator surfaces is the significant factor in determining the level of outdoor insulation and in choosing the types of insulators. In the equatorial region, the most dangerous kind of contamination is salt contamination. A regression technique has been used to develop a modified equivalent salt deposit density (ESDD) mathematical model with respect to meteorological conditions. This model provides a useful way for predicting contamination level and for determining frequency of washing the insulators in a given contaminated area.