Showing papers presented at "International Symposium on Industrial Electronics in 2001"
12 Jun 2001
TL;DR: The authors try to classify and analyze the conventional watermark techniques from the various points of view and find DCT-based methods have been most widely used among the transform based methods.
Abstract: In the early days, encryption and control access techniques were used to protect the ownership of media. Recently, the watermark techniques are utilized to keep the copyright of media. Digital watermarking, a concept of embedding a special pattern, uses an algorithm of inserting a watermark to protect the copyright of media. It has recently become important in various application areas. The various of watermark techniques have been proposed by many authors in the last several years. However, there are not enough analysis and comparison on the previous researches. In this paper, for the understanding of the previous works and for the future related research, the authors try to classify and analyze the conventional watermark techniques from the various points of view. Currently watermark techniques based on the transfer domain, are more popular than those of the spatial domain. DCT-based methods have been most widely used among the transform based methods. However, recently wavelet-based watermark techniques are becoming the main research topic. With wide use of the internet, effective audio and video watermarking researches are also required.
235 citations
12 Jun 2001
TL;DR: In this article, the authors present and apply the mobile robot path planning technique which integrates the artificial potential field approach with simulated annealing to mobile robots to avoid local minima.
Abstract: The artificial potential field methods provide simple and effective motion planners for practical purposes. However, there is a major problem with the artificial potential field approach. It is the formation of local minima that can trap the robot before reaching its goal. The avoidance of local minima has been an active research topic in potential field path planning. As one of the powerful techniques for escaping local minima, simulated annealing has been applied to local and global path planning. In this paper, the authors present and apply the mobile robot path planning technique which integrate the artificial potential field approach with simulated annealing to mobile robots.
158 citations
12 Jun 2001
TL;DR: In this paper, the authors proposed a novel MPPT control algorithm for a digitally implemented photovoltaic power system under rapidly changing solar radiation by inserting a test signal in the control input.
Abstract: This paper proposes a novel MPPT control algorithm for a digitally implemented photovoltaic power system under rapidly changing solar radiation. The method of the MPPT control algorithm can be classified into two categories: perturb and observe (P&O) and incremental conductance (IncCond). In comparing the P&O and IncCond algorithms, the dynamic and tracking characteristic of the IncCond algorithm is better than P&O algorithm under rapidly changing solar radiation. But in the case of digital implementation, the InCond algorithm has an error on the decision of maximum power operation point (MPOP). To solve this problem, this paper proposes a improved IncCond algorithm, which can determine the MPOP under rapidly changing solar radiation by inserting a test signal in the control input. By simulation and experimentation, the validity of the proposed control algorithm is proved.
143 citations
12 Jun 2001
TL;DR: A method which evaluates symmetry of plate corners and extracts car license plates captured from the arbitrary directions and adopts the verifier which evaluates a candidate license plate to enhance extraction rate is proposed.
Abstract: This paper proposes a method which evaluates symmetry of plate corners and extracts car license plates captured from the arbitrary directions. The generalized symmetry transform (GST) produces continuous features of symmetry between two points by combining locality constraint and reflectional symmetry. Also, we propose scan line based GST to improve time complexity of the GST significantly due to selective attention to particular distortions in case of a large searching window. The corners of a plate are detected from our modified scan line based GST with selective directions using the fact that a corner is formed by two neighboring straight lines acquired in a symmetry map of GST. However, a rotated or perspectively distorted car license plate image is very difficult for segmentation of interior characters. Image normalization by image warping is adopted to make such segmentation of license plate and later identification much easier. We also adopt the verifier which evaluates a candidate license plate to enhance extraction rate. Our experiments show that the proposed method for extracting perspectively distorted license plates is fairly reliable.
125 citations
12 Jun 2001
TL;DR: A method of applying reinforcement learning, suitable for modeling and learning various kinds of interactions in real situations, to the problem of stock price prediction of the Korean stock market is proposed.
Abstract: Recently, numerous investigations for stock price prediction and portfolio management using machine learning have been trying to develop efficient mechanical trading systems. But these systems have a limitation in that they are mainly based on the supervised learning which is not so adequate for learning problems with long-term goals and delayed rewards. This paper proposes a method of applying reinforcement learning, suitable for modeling and learning various kinds of interactions in real situations, to the problem of stock price prediction. The stock price prediction problem is considered as Markov process which can be optimized by reinforcement learning based algorithm. TD(0), a reinforcement learning algorithm which learns only from experiences, is adopted and function approximation by an artificial neural network is performed to learn the values of states each of which corresponds to a stock price trend at a given time. An experimental result based on the Korean stock market is presented to evaluate the performance of the proposed method.
99 citations
12 Jun 2001
TL;DR: This paper attempts to introduce a new modulation algorithm for matrix power converters, with an alternative PWM strategy, regardless of type of input and output (AC or DC), and also the number ofinput and output phases, by using suitable toggling matrix switches, such that favorable output patterns are achieved.
Abstract: In this paper, the authors attempt to introduce a new modulation algorithm for matrix power converters, with an alternative PWM strategy, regardless of type of input and output (AC or DC), and also the number of input and output phases, by using suitable toggling matrix switches, such that favorable output patterns are achieved (with variable amplitudes and frequency). The switch functions in such a converter ensure that the switches do not short-circuit the voltage sources, and do not open-circuit the current sources, thus yielding continuous currents at output terminals. Also if the number of input-phases are equal or less than the number of output-phases, then continuous current is available at input terminals. The advantage of this approach is that it can be developed for any kind of matrix converter. It is illustrated that, even under unbalanced and highly distorted input voltage waveforms, the output waveforms are reasonably clean and balanced. Here, the topology of a DC to single-phase AC power converter and single-phase to three-phase AC/AC power converter are presented.
74 citations
12 Jun 2001
TL;DR: In this paper, a new PID (proportional, integral and differential) control scheme based on the feedback of averaged derivatives to realize a noise-tolerable differential control with its application to the load frequency control in the power system.
Abstract: This paper presents a new PID (proportional, integral and differential) control scheme based on the feedback of averaged derivatives to realize a noise-tolerable differential control with its application to the load frequency control in the power system. It is well known that the LFC (load frequency control) is exposed to the quite noisy environment. The noisy environment has made it difficult to adopt the differential feedback loop since the derivatives of the signals deteriorated by high frequency noise causes the system instability. This paper proposed a new PID control scheme adopting averaged derivative of the signal as the differential feedback signal in order to remove the effects of high frequency noise. This study deals with an application of the average differential feedback to the LFC problem in the power systems. The proposed control scheme has been tested for the load frequency control of power systems.
68 citations
12 Jun 2001
TL;DR: In this paper, the authors proposed that torque ripple in the commutation period of a brushless DC motor is inevitable, even if the current control is successful, and analyzed the causes of commutation torque.
Abstract: Torque ripple generated in the commutation period is the main drawback of the brushless DC (BLDC) motor, which deteriorates its precision. Many methods to solve this problem have been studied. In many control methods, torque ripple reduction was considered at the point of current control, which means that if current can be controlled properly, the BLDC motor does not produce any torque ripple. In this paper, the authors propose that torque ripple in the commutation period of a BLDC motor is inevitable, even if the current control is successful. A torque model, considered with decaying phase back EMF, is introduced and the causes of commutation torque are analyzed. The influence of commutation time on torque ripple and the relationship between commutation time and speed are introduced. This paper deals with torque ripple reduction of a BLDC motor from the viewpoint of commutation time and gives a theoretical background to reduce it.
66 citations
12 Jun 2001
TL;DR: Fuzzy versions of two measures that are used for evaluating each association rule in the field of data mining are shown and it is shown that the direct use of confidence as a certainty grade is not always appropriate from the viewpoint of classification performance.
Abstract: Association rules are frequently used for describing association (i.e., co-occurrence) among attribute values in the field of data mining. When an attribute is continuous (i.e., real-valued) such as height, length and weight, its domain is usually discretized into several intervals. Fuzzy rules are recognized as a convenient tool for handling continuous attributes in a human understandable manner. When we use fuzzy rules, the domain of each continuous attribute is discretized into several fuzzy sets. A linguistic label is usually associated with each fuzzy set especially when linguistic interpretations of fuzzy rules are required. In this paper, we first fuzzify the concept of association rules. That is, we show fuzzy versions of two measures (i.e., confidence and support) that are used for evaluating each association rule in the field of data mining. Then we illustrate these two measures of fuzzy rules for function approximation and pattern classification problems. Finally we examine the relation between the classification performance of fuzzy rules and the definition of their certainty grades through computer simulations. Simulation results show that the direct use of confidence as a certainty grade is not always appropriate from the viewpoint of classification performance.
64 citations
12 Jun 2001
TL;DR: In this article, the authors proposed a medium voltage adjustable speed drive that consists of a twelve-pulse diode rectifier and a three-level neutral point clamped inverter using high voltage IGBTs.
Abstract: This paper presents a solution to allow simple and risk-free retrofit of existing fixed speed induction motors with medium voltage adjustable speed drives to achieve attractive energy savings. The presented medium voltage adjustable speed drive consists of a twelve-pulse diode rectifier and a three-level neutral point clamped inverter using high-voltage IGBTs. Innovative features of the drive include series-connection of high-voltage IGBTs. The motor control is based on field-oriented vector control and an optimized PWM modulator, so that switching losses and current harmonics are minimized. An EMC-sinusoidal output filter is available to retrofit existing fixed speed motors with adjustable speed drive converter without incurring overvoltage stress on the winding insulation system, changes on the motors, the mechanical couplings, or the motor feeder cables, excitation of motor critical speed, or reduction in shaft power. Experimental and field results are also presented to confirm the proposed topology and related energy savings.
64 citations
12 Jun 2001
TL;DR: The results show that the proposed watermarking algorithm has excellent robustness against various watermark attacks with the high quality of the watermarked image.
Abstract: In this paper, we propose an effective watermarking algorithm for copyright protection. This is a blind watermarking which can confirm the copyright without the original image. The original image is transformed using wavelet transform and flags are created with the secret key. The secret key is the thing we need to extract the flags and compare the extracted flags with the original flags that are created during the watermark embedding procedure. To criticize the robustness of this scheme we compared the extracted flag with the original flag after several attacks such as JPEG compression, collusion, resize and noise addition. The results show that the proposed watermarking algorithm has excellent robustness against various watermark attacks with the high quality of the watermarked image.
12 Jun 2001
TL;DR: In this article, the authors investigated power converter topologies and presented control techniques for a photovoltaic power system with parallel operation, where instantaneous power sharing control is used to achieve the current distribution and ensure a fast dynamic response, an adjustable load sharing capability and eliminate the circulation current.
Abstract: This paper investigates power converter topologies and presents control techniques for a photovoltaic power system with parallel operation. Instantaneous power sharing control is used to achieve the current distribution and ensure a fast dynamic response, an adjustable load sharing capability and eliminate the circulation current. The system controller is based on a DSP to simplify the circuit and it is easy to modify the system. A modified method of tracking the photovoltaic maximum power points (MPPs) and forcing the system to operate close to these points is presented. Simulation and experimental results are presented to verify the proposed system performance.
12 Jun 2001
TL;DR: In this article, a simple nonlinear control method for pipeline inspection gauge (PIG) flow in a natural gas pipeline is introduced, where the PIG is controlled using the amount of bypass flow across its body.
Abstract: This paper introduces a simple nonlinear control method for pipeline inspection gauge (PIG) flow in a natural gas pipeline. The PIG is controlled using the amount of bypass flow across its body. The dynamic behavior of the PIG depends on the different pressure across its body and the bypass flow through it. The system dynamics includes: dynamics of driving gas flow behind the PIG, dynamics of expelled gas in front of the PIG, dynamics of bypass flow and dynamics of the PIG. The method of characteristics (MOC) and Runge-Kutta method are used to solve the dynamics of flow. To control the PIG velocity, a simple nonlinear controller is proposed based on the back-stepping method. The closed loop system is stable in the sense of Lyapunov stability. To derive such a controller, three system parameters should be measured: the PIG position, its velocity and the velocity of bypass flow across the PIG body. To show the effectiveness of the proposed controller, the simulation has been done with three cases: the PIG starts to move at its launcher, the PIG arrives at its receiver and the PIG restarts after stopping in the pipeline. The simulation results show that the proposed controller can be used for controlling the PIG velocity with good performance when it runs in the natural gas pipeline.
12 Jun 2001
TL;DR: A new control protocol, LnCP (Living network Control Protocol), targeted at low implementation cost networking system in a home environment and based on a multi-master system and uses a peer-to-peer communication model.
Abstract: This paper proposes a new control protocol, LnCP (Living network Control Protocol), targeted at low implementation cost networking system in a home environment. The protocol is based on a multi-master system and uses a peer-to-peer communication model. The protocol assumed single bus therefore the appliances can be attached to the bus anywhere if the power lines are employed as the network bus. Home appliances linked via LnCP are controlled and monitored at remote place. Every device communicates with each other in packet unit, which has variable length so that the protocol can deal with the devices having the diverse room of RAM resource. The bytes number of the packet header is also variable in order that the new function can be added in the future. The minimum hardware requirements to implement the protocol are 8-bit processing microcomputer including built-in UART, 17 bytes of volatile memory and a few bytes of nonvolatile memory. Therefore it may be embedded in low-cost microcontrollers that are employed in white goods such as refrigerators, washing machines, micro oven ranges and even light switches.
12 Jun 2001
TL;DR: In this article, a nonlinear dynamic boiler model of 300 MW power unit is given which is derived from a mass and energy balance relationship, the parameters of the model can be obtained from the physical dimensions and characteristics of the boiler.
Abstract: The nonlinear dynamic boiler model of 300 MW power unit is given which is derived from a mass and energy balance relationship. The parameters of the model can be obtained from the physical dimensions and characteristics of the boiler. The inputs of the model are feedwater valve position, steam valve position, fuel valve position, and feedwater temperature, the outputs of the model are drum pressure, water level, main steam flow. The model can be used for synthesis of model-based control algorithms of a boiler system. It can also be used for setting up a real-time simulator for testing a new boiler control system and operator training.
12 Jun 2001
TL;DR: A high-speed high-resolution vision system for the inspection of large TFT LCD is proposed and developed and can obtain image information through line scan cameras rather than expensive high- resolution area cameras.
Abstract: As the resolution and size of the TFT LCD are becoming higher and larger, respectively, its inspection system is required to have high resolution to detect dirt, impurities, cracks, etc. Also, in order to reduce the cost to inspect TFT LCD, the inspection time must be reduced. One of the most important subsystems in the TFT LCD inspection system is a vision system. But existing vision systems are insufficient to perform inspection tasks for a large TFT LCD during a short time. A high-speed high-resolution vision system for the inspection of large TFT LCD is proposed and developed in this paper. In order to have desired resolution over a large area, the proposed vision system can obtain image information through line scan cameras rather than expensive high-resolution area cameras. In order to reduce task time, this vision system consists of four high-performance digital signal processors (DSP). A parallel architecture and a pipeline algorithm are developed to reduce time to process image data of multiple line scan cameras. Based on these architectures and algorithm, an appropriate task will be assigned to each DSP, which results in reducing image-processing time. Through a PCI bus, the developed vision system can be connected to a personal computer (PC) that can provide a convenient user interface. Some experiments that show the performance of the developed vision system will be performed.
12 Jun 2001
TL;DR: In this paper, the authors apply a recently developed energy-based controller design technique to generate a new family of nonlinear controllers for switched power converters, which do not rely on the systems inversion, hence they can directly regulate the output signal, which as is well-known is a non-minimum phase output.
Abstract: The problem of regulating the output voltage of switched power converters has attracted the attention of many control researchers for several years now. Besides its practical relevance in modern power systems for satellites, noncivilian, industrial and consumer electronic applications, these systems are an interesting theoretical case study because they are switched devices whose averaged dynamics are described by a bilinear second order non-minimum phase system with saturated input and highly uncertain parameters-the load resistance and the input voltage. In this paper, the authors apply a recently developed energy-based controller design technique to generate a new family of nonlinear controllers for switched power converters. In contrast to other schemes reported in the literature, their controllers do not rely on the systems inversion, hence they can directly regulate the output signal, which as is well-known is a nonminimum phase output. Furthermore, the control laws are simple static state feedback.
12 Jun 2001
TL;DR: A modular and object-oriented approach for the PC-based open robot control system, which can reconfigure the control system in various production environments, is investigated and the performance of thePC-ORC is examined.
Abstract: An open architecture manufacturing system pursues integrated manufacturing components on a single platform. Therefore, a particular component can be easily added and/or replaced. In this paper, a modular and object-oriented approach for the PC-based open robot control system is investigated. A standard reference model for controlling robots, which consists of a hardware platform, an operating system module, and various application software modules, is first proposed. Then, a PC-based open robot control (PC-ORC) system, which can reconfigure the control system in various production environments, is developed. The PC-ORC is constructed based upon the object-oriented method. Hence, it allows an easy implementation and modification of various modules. The PC-ORC consists of basic software, application objects, and additional hardware devices on a PC platform. Finally, by applying the proposed PC-ORC to a SCARA robot, the performance of the PC-ORC is examined.
12 Jun 2001
TL;DR: This paper addresses real-time DC motor speed and position control using the low-cost TMS320C31 digital signal processing starter kit with the improvement of system outputs as expected with a PID controller, with actual system outputs matching theoretical calculations.
Abstract: This paper addresses real-time DC motor speed and position control using the low-cost TMS320C31 digital signal processing starter kit (DSK). A PID controller is designed using MATLAB functions to generate a set of coefficients associated with a desired controller's characteristics. The controller coefficients are then included in an assembly language program that implements the PID controller. Code Explorer is used to load and run the PID controller to achieve real-time control. Furthermore, the PID parameters can be adjusted while the motor is running, so that online adjustment is achieved. This avoids shutting-down the system, re-assembling and re-compiling the source code each time the PID parameters are adjusted. Both speed and position control are investigated on a DC motor system with speed feedback and position feedback. Results show the improvement of system outputs as expected with a PID controller, with actual system outputs matching theoretical calculations.
12 Jun 2001
TL;DR: The IEEE 802.11 wireless LAN is used to extend a Profibus-DP network to connect mobile devices such as mobile robots and automated guided vehicles (AGV) to a fieldbus in order to satisfy real-time requirements on data communication.
Abstract: This paper focuses on a method to connect mobile devices such as mobile robots and automated guided vehicles (AGV) to a fieldbus. In this paper, the IEEE 802.11 wireless LAN is used to extend a Profibus-DP network for the mobile devices. In order to integrate these two networks, a protocol converter is developed that consists of two processes-master process of Profibus-DP and virtual master process of IEEE 802.11-and a transmission buffer. Furthermore, a virtual polling algorithm is developed at the protocol converter in order to satisfy real-time requirements on data communication.
12 Jun 2001
TL;DR: This paper aims to approximate more correctly the lane of an actual road by applying the least-mean square method with the fault-removed edge information for curve fitting.
Abstract: A lane detection based on a road model or feature needs correct acquisition of information on the lane in an image. It is inefficient to implement a lane detection algorithm through the full range of an image when it is applied to a real road in real time because of the calculation time. This paper defines two search ranges of detecting a lane in a road. First is the searching mode that searches the lane without any prior information of a road. Second is recognition mode, which is able to reduce the size and change the position of a searching range by predicting the position of a lane through the acquired information in a previous frame. It is allowed to extract accurately and efficiently the edge candidate points of a lane without any unnecessary searching. By means of inverse perspective transform that removes the perspective effect on the edge candidate points, we transform the edge candidate information in the image coordinate system (ICS) into the plane-view image in the world coordinate system (WCS). We define a linear approximation filter and remove faulty edge candidate points by using it. This paper aims to approximate more correctly the lane of an actual road by applying the least-mean square method with the fault-removed edge information for curve fitting.
12 Jun 2001
TL;DR: In the modeling of interleaved dual boost converter operating in the discontinuous current mode, a state-space averaging technique is used and various steady-state performance expressions are derived.
Abstract: The modeling of interleaved dual boost converter operating in the discontinuous current mode is presented in this paper. In the modeling of the converter system, a state-space averaging technique is used. Various steady-state performance expressions are derived. Simulation studies are carried out in the MATLAB environment. A prototype converter system is built for experimental studies. Simulation and experimental results are compared to validate the modeling process.
12 Jun 2001
TL;DR: A knowledge-based product recommender system that gathers the user's requirements on a particular product by questioning the user and consulting its knowledge base to find the items that best meet the users' requirement.
Abstract: This paper deals the design and implementation of product recommender system on a Internet shopping mall. In e-commerce application, sometimes potential buyers may be interested in receiving recommendations about what to purchase. The mainstream of an automated recommender system is collaborative filtering. In this paper, we present a knowledge-based product recommender system. The knowledge base of product domain and inference engine is implemented by JESS (Java expert system shell) and Java servlet. The system gathers the user's requirements on a particular product by questioning the user and consulting its knowledge base to find the items that best meet the user's requirement. For the recommender system, the design of product knowledge base are discussed. As a sample implementation, a cellular phone recommender system is built where the system tries to find a phone model that best meets the user's requirements.
12 Jun 2001
TL;DR: In this paper, a flame image processing and analysis system has been developed for optimal coal firing of thermal power plant, especially for low NO/sub x/ and safe operation, aiming at gaining the relationship between burner flame image and emissions of NO and unburned carbon in a furnace, through which this system quantitatively determines the conditions of combustion on individual burners.
Abstract: The flame image processing and analysis system has been developed for optimal coal firing of thermal power plant, especially for low NO/sub x/ and safe operation. We aimed at gaining the relationship between burner flame image and emissions of NO/sub x/ and unburned carbon in a furnace by utilizing the flame image processing methods, through which this system quantitatively determines the conditions of combustion on the individual burners. For the first step of development, its possibility test was undertaken with a bench furnace. The test proceeded to the second step with a pilot furnace, through which the system was observed to be effective for evaluating the combustion conditions monitoring and burner maintenance.
12 Jun 2001
TL;DR: A novel measurement method for determining line impedance using an inverter circuit is proposed in this paper, in which the line inductance can be measured relatively accurately and the resistance includes the circuit loss.
Abstract: In order to tackle the problem of harmonic elements in a distribution line system, it is important that we are able to measure the impedance of the distribution line in a simple way. In addition, it is desirable that we make the measurement without service interruption. The line impedance could be measured by a technique derived from fundamental measurement theory, in which only passive elements such as inductors or resistors are used. However, as the voltage and/or current being measured increases, the size of inductor or resistor would also need to be increased, so it would be very difficult for such a measurement system to be implemented. Under such circumstances, a novel measurement method for determining line impedance using an inverter circuit is proposed in this paper. In the case where we are determining the resistance, the result that we obtain also includes the circuit loss, so this needs to be measured in advance and subtracted from the result. In the case where we are determining the inductance, the line inductance can be measured relatively accurately.
12 Jun 2001
TL;DR: In this paper, a 2 wheeled welding mobile robot with seam tracking sensor touched on welding line is developed, where the motion control is realized in the view of keeping constant welding velocity and precise seam line even though the target welding line was on straight or curved one.
Abstract: This paper describes development results of a 2 wheeled welding mobile robot with seam tracking sensor touched on welding line. The motion control is realized in the view of keeping constant welding velocity and precise seam line even though the target welding line is on straight or curved one. The body position and direction are controlled by using signal errors between two potentiometer type of touched sensors attached on torch slider and body side. In turning motion, the body and torch slider are controlled by using the kinematic mathematical model related with two motions of body turning and torch sliding. The straight locomotion is controlled according to 11 control patterns obtained from displacements between seam tracking sensor and body positioning sensor. The effectiveness is proven through the experimental results for arc welding machine.
12 Jun 2001
TL;DR: In this article, the backlight inverter used in a laptop computer is investigated and the results of the comparison with input-output and brightness-efficiency characteristics show the possibilities of lower profile and high efficiency in back light inverters.
Abstract: Modern display panels are large and thin, and require a high voltage for the lamp. As the market demand for large display screens is increases, inverters needs to be small, high-powered, and very efficient. The backlight inverter used in a laptop computer is investigated in this paper. It has been difficult for the electromagnetic transformer in the inverter to obtain a high efficiency and compact profile. In this study, a piezoelectric transformer (PT) is used and it is shown that it reduces the loss and volume compared to the standard electromagnetic transformer. The results of the comparison with input-output and brightness-efficiency characteristics show the possibilities of lower profile and high efficiency in backlight inverters.
12 Jun 2001
TL;DR: In this article, the robust speed control of a PMSM using sliding mode control with load torque estimation is presented, where the load disturbance is detected by the observer of an unknown and inaccessible input, and is compensated by the feedforward current.
Abstract: Field-oriented control has made permanent magnet synchronous motor drives possible for the high performance applications. With a high-performance field oriented control system, the torque and flux producing components of the stator current are decoupled so that the independent torque and flux controls are possible as in DC motors. Thus, a high quality control of the stator current vector is essential for the successful implementation of the field-oriented control since the current controller has a direct influence on the drive performance. The current control schemes for a voltage source inverter-fed PMSM drive can be classified as hysteresis control, ramp comparison control, synchronous frame proportional-integral (PI) control, and predictive control. Among them, the predictive control is known to give a superior performance. However, this control scheme requires the information on the machine parameters and operation conditions with the sufficient accuracy, and cannot give a satisfactory response under parameter mismatch. To overcome such a limitation, the robust speed control of a PMSM using sliding mode control with load torque estimation is presented. The load disturbance is detected by the observer of an unknown and inaccessible input, and is compensated by the feedforward current. The proposed control schemes are applied to PMSM driven by a three-phase voltage-fed PWM inverter and the effectiveness is verified through the comparative simulations.
12 Jun 2001
TL;DR: The paper presents a seam tracking controller of high speed rotating arc sensor developed by a microprocessor based system that is proven through the experimental results for several kinds of welding condition.
Abstract: The paper presents a seam tracking controller of high speed rotating arc sensor developed by a microprocessor based system. The seam tracking algorithm is based on the average current value at each interval region of four phase points on one relating cycle. To remove the noise effect for the measured current, the area during one rotating cycle is separated into four regions of front, rear, left and light. The average values at each region are calculated, using the regional current values and a low pass filter incorporating the moving average and exponential smoothing methods are adopted. The effectiveness is proven through the experimental results for several kinds of welding condition.
12 Jun 2001
TL;DR: In this article, a single-phase bi-directional AC/DC converter based on neutral point diode clamped configuration is proposed to draw a clean sinusoidal line current with nearly unity input power factor and to achieve DC bus voltage regulation.
Abstract: A single-phase bi-directional AC/DC converter based on neutral point diode clamped configuration is proposed to draw a clean sinusoidal line current with nearly unity input power factor and to achieve DC bus voltage regulation. Based on the neutral point diode clamped scheme, the voltage stress of the power devices is clamped to half DC bus voltage instead of full DC link voltage in the conventional half and full bridge PWM rectifier. The line current command tracking, voltage regulation and balanced neutral point voltage are performed by the inner loop current controller, the outer loop voltage controller and voltage balance compensator, respectively. To generate a three-level PWM pattern on the AC terminal of the AC/DC converter, a region detector of the mains voltage is employed. The effectiveness of the proposed control scheme is confirmed by the experimental results.