This paper proposes a new high speed robust tracking control system based on both “Zero Phase Error Tracking” (ZPET) control system and robust servo system for an optical disk recording system. In the optical disk recording systems (for example CD-R), the tracking servo system must have the complete tracking response whose error is less than 0.1 [μm] for an amplitude of 100 [μm] of reference input signal. However, its detecting signal is only a tracking error. For this purpose, this paper proposes a new estimation method of the reference input signal by using only tracking error, and realizes the high speed robust tracking servo system with ZPET control. Moreover, this paper considers the saturation of controller output. The experimental and simulation results point out that the proposed system has a quick and precise tracking response.

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The combining of the outputs of two inverters using inter-phase reactors is a widely used method for supplying large a. c. drives rated at more than several thousands kW. Certain drawbacks are associated with this method, such as high acoustic noise and high losses due to the inter-phase reactors.
To overcome this problem, in this paper, a new low acoustic noise and high efficiency drive system using an open-winding a. c. motor and two space vector modulated inverters, is proposed. This configuration consists of a 3-level inverter with switching at once every cycle and a 2-level inverter of about 1kHz switching frequency, connected respectively to the opposite terminals of the open-winding motor. With the proposed configuration, good current waveforms and high efficiency can be obtained.

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This paper presents a perturbation and observation method with a capacitance estimation for the maximum power point tracking (MPPT) in a photovoltaic power system. Usually, by increasing or decreasing the duty ratio of power switching devices, the maximum power point is tracked. The variation of duty ratio is determined by considering the circuit parameters. However, it is well known that actual capacitance of an electrolytic capacitor in parallel with the photovoltaic array has 50% tolerance of its nominal value and also the capacitor degrades its value as time passes. If the variation of duty ratio is determined by its nominal value, the performance of MPPT may be degraded. Therefore, we must use the actual capacitance in order to improve the MPPT performance. In our system, we adapt the model reference adaptive system to estimate the capacitance, then we can obtain the accurate capacitance and correct the variation of duty ratio by the estimated value. As a result, we may obtain the high performance of MPPT. Experimental results show that the proposed method can track the maximum power point stably instead of the variation of capacitance using a newly developed inverter using Buck-boost chopper circuits.

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A cost effective high-efficiency, simple, low noise voltage-source type single-ended quasi-resonant high frequency inverter using a single power semiconductor switching device and its modified circuit topologies are commonly applied for consumer induction heated rice cooker with a warmer function, cooking heater and microwave oven. This paper presents some comparative performance evaluations of each generation IGBT and MCT (MOS Controlled Thyristor) incorporated into the typical voltage-source quasi-resonant inverter operating under zero voltage soft switching transition mode. New generation IGBT has been improved for consumer power applications in order to reduce the conduction loss which is based on the lowered saturation voltage characteristics due to the latest IGBT. The comparative steady-state characteristics of some sample power-semiconductor switching devices of each generation IGBT are demonstrated on the basis of the simplest single-ended quasi-resonant inverter circuit operating under a condition of zero voltage soft switching commutation principle. In addition, the power losses and temperature performance analysis of the latest IGBT are discussed and evaluated as compared with previously-developed IGBTs. Finally, the further reduced saturation voltage and conduction loss characteristics of MCT which are more suitable for consumer utilizations are presented in comparison with the conventional IGBT.

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This paper proposes a new unified method for identifying equivalent stator core-loss resistance of AC motors, which can be applied to both of induction and synchronous motors. In order to make the AC motors exhibit high performance such as precise torque generation and/or efficient energy transmission, stator core-loss cannot be neglected in designing vector control systems. It is common to model stator core-loss in magnetic circuit as loss caused by equivalent resistance in electrical circuit. One of the best mathematical models for controlling AC motors with core loss is a kind of parallel-type model that succeeds in modeling both eddy-current and hysteresis losses. The newly proposed method succeeds in identifying separately and simultaneously two kinds of equivalent coreloss resistances on the model corresponding to eddy-current and hysteresis losses. The practical usefulness of the method is evaluated and confirmed through experiments using two induction motors of 5.5 and 2.0(kW) having relatively high core losses and a permanent magnet synchronous motor of 750(W) having relatively low core losses.

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This paper proposes a damping method of rotor natural vibration in three-phase hybrid stepping motors, in which optimal commutation signals are calculated from the period of the natural vibration measured by detecting the motor voltages. Moreover, an acceleration and deceleration pattern is derived from a simple model of the rotor vibration, to suppress undesirable transient oscillation in acceleration. deceleration, and positioning operations. An experimental drive system has been implemented and tested to confirm the effectiveness and versatility of the proposed method. Some experimental results show that the experimental system can damp the rotor natural vibration even if the rotor inertia varies. Comparing with the conventional pattern, it is confirmed that the proposed pattern has great contribution to damp the undesirable transient oscillations.

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In this paper, we analyze the conditions when surge voltage peaks higher than 2 p. u (2 times the inverter DC link voltage) occur at the induction motor terminals fed by PWM inverters. These overvoltages can reach 3 p. u or more and posse a threat for the motor insulation. Experimental results and simulations are used to study the dependence of voltage at the motor terminals from the application conditions (cable and motor parameters). Anew algorithm for correction of the PWM, which reduce the motor terminal peak voltage under 2 p. u, is proposed and tested successfully in different PWM schemes. Further more a method for calculation of the minimum allowed short time intervals between two consecutive pulses, is given and its results are confirmed from the experiment. Advantages of the new proposed PWM correction method are that it can be implemented at no additional costs, independently from the PWM mode (Sinusoidal PWM, Space Vector PWM, Discrete PWM) used_??_ and without changing the performance of the drive. The application of this method improves the switching reliability of the drive.

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Ray trace based radio propagation prediction in urban environments has been recognized as a remarkable method today. It provides a more accurate prediction than other methods such as empirical statistic models. But this method requires 3D city model database and it takes much time to execute simulation, so it is not easy to apply this method for large cities. This paper presents GIS (Geographical Information System) based radio propagation simulator using ray trace method. This system generates a 3D city model automatically from 2D digital maps stored in GIS. The generated city model is managed using hierarchical bounding volume to effective collision test between rays and buildings. Simulation results such as propagation paths and power levels of receivers are shown over the 3D city model. It helps users to analyze the simulation results and also to predict power delay profile. Based on the experimental results using an actual digital map, the effectiveness of this system is totally discussed from the viewpoint of practical usage.

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One of the the important issues to drive bipedal robot is a limit of joint actuator. In case of a high-speed walking motion or the motion with heavy load, motor torque is saturated. To address this issue, this paper proposes a control strategy to avoid the torque saturation.
First, the walking pattern is generated according to the requred walking speed. Then the exaggerated torque is calcurated from the final torque reference and the estimated disturbance torque. Second, the generated walking pattern is modified so that the motor torque is not saturated.
The effectiveness of the proposed algorithm is confirmed by several results of simulation and experiment.

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In Hard Disk Drives, a digital control system is usually applied because of the dispersively recorded positioning signal on the disk, so, to improve head positioning accuracy, it is necessary to make the sampling frequency high using conventional methods. However, it is very difficult to increase the sampling frequency, because of the decrease in capacity of the Hard Disk Drive. So, to solve this problem, a method of improving a head positioning accuracy without making the sampling frequency high is proposed in this paper. In the proposed method, a control signal to the Voice Coil Motor is changed in the sampling period. Furthermore, by setting both the changing time allocation and the gain of the control signal to the optimum, the phase delay by discretization is improved and stimulation of the resonance mode of the Voice Coil Motor is avoided. The proposed method does not require an alteration to hardware at all, and is easily applicable to massproduction simply by changing the control program. The validity of the proposed method was confirmed by numerical and experimental results using a miniature 2.5-inch Hard Disk Drive.

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This paper describes a three-phase AC-DC converter using world-wide PFC (Power Factor Correction) circuit and soft switching full bridge type DC-DC converters. The feature of our new PFC circuit is unity power factor and low harmonics distortion of the input currents, high efficiency and low impressed voltage on the semiconductors. Furthermore, we indicate a method to improve the efficiency and the output voltage ripple at the switching transient of the DC-DC converter using phase shift control. According to the experimental results, the PFC circuit can be applied the semiconductors with the rating voltage 600V at the input voltage AC200V or AC400V. In addition, the input power factor, the efficiency, and the output voltage ripple of the AC-DC converter are good value.

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In our previous paper, we proposed a new sensorless elimination method for position control of an Interior Permanent Magne (IPM) motor, in which we utilize carrier frequency component current of PWM inverter as the motor position informatio source. In this paper we propose a new position estimation diagram and shows the experimental system together with the control results of the new position control method. With this control scheme, the motor speed has been successfully controlled from zero speed to 1, 400rpm (1.4 times rated speed) without mechanical sensor.

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Visual servo is the eye-in-hand robot system directly using real time visual information for control. In this paper, we propose a novel visual servoing system with Motion Observer (MOB) based Feature Prediction. The position of the target object cannot be directly observed. Motion Observer is designed using a minimum order observer and is useful for high performance servoing. We show the effectiveness of the proposed method is shown through simulations and experiments.

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As economic development, urbanization and population growth continue in the developing countries, the urban heat island (UHI) has been attributed to causing such problems as energy shortages, air pollution, and living condition deterioration in those countries. UHI is just now beginning to be researched in large cities in those countries. This paper illustrates an integrated approach. It utilizes both GPS mobile observation techniques and automatic ground monitoring stations as the most direct, easy-to-implement and cost-effective way to monitor and measure UHI in developing countries. As a part of the Core Research Project for Environmental Science Technology, funded by JSTC, we have been experimenting with our proposed monitoring systems since 1997, analyzing data collected from Shanghai, the largest commercial and industrial city in China.
Results indicate the proposed monitoring systems are valuable for making climatic observations and collecting data. They also shed light on an application of advanced observation techniques on UM research in developing countries.

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Traffic flow surveillance systems are used to maintain comfortable driving and road safety. In this paper, we propose a traffic flow surveillance method using a spatio-temporal image processing that provides low cost traffic flow classification and can be applied to systems that are equipped with numerous cameras. This method uses the DTT method, which transforms spatio-temporal images into 2-D data (DTT image) on a directional-temporal plane, and creates an edge-directional histogram of the DTT image. Using the histogram as input signals, the traffic flow is classified into five patterns (Normalcy, Traffic congestion, Heavy traffic congestion, Stop, and Low speed) through a neural network. To create teaching data for the neural network, we used the data obtained by shifting the histograms for standard patterns and by making computer graphics images. Experimental results show the effectiveness of the method. In addition, we describe a low cost system, which is equipped with intelligent cameras that have simple image processing functions, using the proposed method.

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Taking into account the iron loss, a vector control method is proposed to compensate the torque accuracy. An efficiency maximizing control method of this system is also presented by changing the flux command. The effectiveness of the proposed system has been verified by digital simulation.

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