The voltage-source inverters are normally equipped with an electrolytic capacitor in their DC link. The electrolytic capacitor has several disadvantage such as increasing size, limitting converter life and reliability. Therefore, several approaches for removing the DC link capacitor have been studied. This paper proposes a new strategy of the voltage source inverter without DC link components. To restrain the current resonance caused by LC filter of AC source side, rectifier of this inverter is controlled by current closed loop with di/dt feedback (di/dt; differenciation of AC source current). To improve AC source current waveform, feedback gain of di/dt and LC parameters are investigated by calculation for a 0.75kW induction motor driven by this inverter. Both the calculated and measured waveforms of AC source currents maintain nearly sinusoidal waveforms with a unity power factor.

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This paper proposes new mathematical models with stator core (iron)-loss factor for induction motor supposed to generate precise and/or efficient torque via vector control. The proposed models take the structure that stator core-loss resistance is equivalently placed purely in parallel with stator inductance. It is shown that stator core losses consisting of eddy-current and hysteresis losses can be properly represented by the parallel resistance, especially eddy-current loss by a constant one. The models are composed of three basic vector equations in general frame of arbitrary angular frequency such as 4^th order differential equation describing motor dynamics, torque equation and energy conversion equation. These basic equations are essential for vector control design taking core-loss into consideration. The proposed models are most compact in sense of number of both of employed parameters and interior states of the motor. Compactness is an important factor for modeling and is useful for designing vector control systems.

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The paper descries a novel method to extract line segments and circular arcs from the image taken by CCD camera for object recognition. Model based matching is one of the widely used techniques of the object recognition in computer vision, and the position and orientation of the objects are decided with referring the extracted line segments and circular arcs. For the precise and stable decisions of the position and orientation, the accurate extractions of characters are required. These characters are. fast and accurately extracted in the proposed method, while its validity is confirmed in some experiments.

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This paper considers the robust stabilization of singularly perturbed systems with time-varying unknowbut-bounded uncertainties. The H_∞ control method are used to establish the stability of the closed-loop system. The construction of the stabilizing controller involves solving a certain algebraic Riccati equation with small parameter ε > 0. In order to overcome the computation difficulties caused by small parameter ε, we propose the ε-less quadratically stabilizing controller by using the results of the solution for above a algebraic Riccati equation. It is shown that if the reduced order Riccati equations have a positive definite stabilizing solution then the given uncertain linear system with the proposed controller independ of ε is quadraticaly stabilizable. To show the effectiveness of the proposed algorithm, numerical examples are included.

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With the rapid urbanization, floods have occurred in recent years because impervious surface areas have been increased. The stormwater does not infiltrate into the ground, so that the amount of stormwater exceeds the sewers capacity. In order to establish the efficient operations for the sewerage pumping facilities against flood, Rainfall Information Management Systems (RIMS) have been developed and installed into the actual wide-area sewerage system. One of main functions of RIMS is Pumping Operation Support System (POSS) including many mathematical models such as a runoff prediction model.
In this paper, a detail description of RIMS and POSS are given. The evaluation results of the performance of POSS are shown not only at off-line phase but also at on-line phase. Good results have been obtained over a year. This system is the first in the world as the on-line pumping operation support system applied to the regional sewerage and will be ranked as a big step to the real time control.

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A conventional symmetrical three-phase system can be analyzed by using a conventional Bode Diagram. However it is difficult to analyze three-phase system using rotating coordinate transformations by means of the conventional Bode Diagram. Therefore this paper proposes an extended Bode Diagram in order to analyze a high-pass filter using rotating coordinate transformations and analyze the high-pass filter using rotating coordinate transformations.

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Torsional vibration suppression control is a very important subject in a recent servo system. To overcome the torsional vibration, various control strategies have been proposed such as resonance ratio control, state feedback and Η_∞ control.
In this paper, the authors propose the method for determing optimum feedback gains applicable to the servo system employing partial state feedback compensation (PSFB compensation). This compensation is based on state feedback-based control only using measurable state variables. The performance of torsional vibration suppression control with PSFB compensation is compared to that of the resonance ratio control by means of the computer simulations and experimental results.

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In this paper, we propose a new control system that has three layers for a complicated robot. The first layer calls a Paraneuron Reinforcement Algorithm (PRA). This algorithm simulates a simple neural coupling of creature. The PRA has a self-organizing function to input signals. The second layer memorizes a state of PRA System using the Neural Network with 3 layers Back Propagation law. The third layer make a halfway target that advances to possibility of following the last target.
By using the method (3 Layers System) to motion control, a flexible control of complicated plant was made possible. But the problem is that PRA can't realize a highly precise performance.

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Electromagnetic wave emissions generated from PWM inverter and motor drive systems are rapidly increasing as switching characteristics of power switching devices used in PWM inverters are increased, and as operating frequencies of microcomputers in the motor drive controllers are also increased This paper discusses emission characteristics generated due to common mode noises which are produced by circuits having with stray capacitances between the PWM inverter frame and the motor frame. It is difficult to cope with reduction of common mode noises emissions in comparison with other differential mode noises. The emissions are analyzed by computer simulations using the method of moments, especially, for the case of emissions connected to the PWM inverter frame and motor frame by a conducting plate. The effects of cable length between the PWM inverter and motor on emissions is also examined In low frequency regions where the structure length of the drive system compromised of the PWM inverter and the motor is less than one-fourth of the electromagnetic wavelength, emissions are remarkably reduced by using a conducting plate between the PWM inverter and the motor. In high frequency regions there is hardly any reduction in emissions. Finally, the resonance phenomenon is shown to occur when cable length between the PWM inverter and the motor is equal to one half of the electromagnetic wavelength.

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Mixed-μ system of levitation consists of a magnetic flux source and materials of both μ>μ₀ and μ<μ₀, for example permanent magnet, iron and high-temperature bulk superconductors. Because of the diamagnetism of bulk superconductors located between the permanent magnet and iron, two-dimensional stability is realized without active control. We have already calculated the levitation and guidance characteristics using the two-dimensional FEM (finite element method). However it is difficult to obtain the optimum sizes of each elements and gap length.
In this paper the relation of the two-dimensional stability of three components, i.e. permanent magnets, iron and high-temperature bulk superconductors, of the mixed-μ system is found. And the appearance mechanism of two-dimensional stability is explained. It reveals that the relative position of the corner of the iron with respect to the one of the superconductor determines the two-dimensional stability.

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This paper proposes a restart method for an induction motor drive system without speed sensor after power supply interruption, when the motor shaft is rotaring under the action of disturbance torque. This method is based on the characteristic of the induction motor impedance, which is resonant for a frequency corresponding to the angular rotor speed. Positive feedback is used in the proposed method, in order to excite the natural frequency of the system and the speed information is extracted from the resonant stator cuurent. Since high speed ACR are not required, this method can be implemented using a low cost processor.
The validity of the proposed method is verified by simulation and experiments, using a standard 5.5kW induction motor.

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When the cage bars of induction motor are skewed, the potential difference is induced between the cage bars and core. Therefore, the cross current losses occur as a result of cross currents flowed through cores and cause reducing the machine efficiency. In order to calculate the cross current losses, it is essential to evaluate the potential distribution on the cage bars and the actual cross resistances between the cage bars.
This paper states about method of computing the cross current losses taking account of not only the construction data of the armature and the rotor, but also the actual cross resistance between the cage bars.

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This paper presents a novel analysis of a self-regulated, self-excited, brushless three-phase synchronous generator, which includes the effect of core losses. The core losses are modeled by equivalent core loss resistances connected to additional windings on the generator's magnetic coupling model. A magnetic circuit is drawn from the magnetic coupling model, and an electrical equivalent circuit of the generator is derived by utilizing a duality between the magnetic and electric circuits. Using this equivalent circuit, the generator's steady-state performance is theoretically predicted, and the results are verified through experiment. In addition, the power losses during power generation are analyzed quantitatively. The proposed analysis takes into account of the nonlinearity of the exciting impedances due to magnetic saturation.

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High dv/dt rate at switching of IGBTs become source of EMI noise. For this problem, various methods that makes low dv/dt rate by using soft switching circuit are proposing. In this paper, a novel snubber circuit with passive energy recovery for soft switching inverter is proposed. This novel circuit uses a capacitor which makes zero voltage switching to both upper and lower IGBTs, and a transformer which regenerates the snubber energy. And this paper describes the EMI noise from the novel soft switching circuit. From results of experiment and analysis, we clarified that radiational noise is not reduced by making low dv/dt rate of only IGBT. Radiational noise generates from resonant current flowing through the soft switching circuit and IGBT. This resonant current don't flow trough the conventional hard switching circuit. So, we indicate the reducing methods of radiational noise that the reducing the resonant current by using saturation type reactor and RC snubber with snubber diodes. The effect of the methods has been verified by experimental and simulational results.

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Recently trains raise speed and reduce the motor vehicle ratio. It is needed, therefore, to utilize adhesion force more effectively. Although several. anti-slip readhesion control methods have been developed, it has become clear that slip and readhesion repeat under strict adhesion conditions as far as they rely on the conventional concept of readhesion control. So we thought about the reason why conventional anti-slip control methods cause slip/readhesion reiteration under strict adhesion condition and have developed a new control method “Anti-slip Readhesion Control Method with Presumed Adhesion Force”. We confirmed in running tests that we can prevent slip/readhesion reiteration and stably control motor currents even under strict or rapidly changing adhesion conditions by using the newly developed control method.

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A superconducting magnetically-levitated system is now tested at the Yamanashi Test Line. It is important to obatin a certain level of magnetic damping so as to improve the dynamic characteristics of the system. We have therefore proposed a magnetic damping method using an inductive power collection system and analysed its characteristics assuming a side wall electrodynamic suspension system. The principle of this method is based on the fact that levitation force varies with the phase angle of the induced current in the power collection coils. We can obtain damping force by changing the phase angle in proportion to the velocity of vehicle vibration. We investigated the force which can be used for damping, and evaluated its magnitude and availability by a numerical example. In this example, the vertical force of 3.5kN was obtained per bogie, and a half of this force can be utilized by changing the phase angle up to π/6.

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This paper discusses a control method of a three-phase four-wire instantaneous-reactive-power compensator. This method is based on a balanced time-variant conductance circuit model. The compensator controls the line currents so as to equate instantaneously the currents of the conductance model. The zero-sequence current of the line can be eliminated without using an energy storage component in the compensator. This control strategy is verified by simulation study.

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The authors have proposed that ΔΣ modulator is effectively applied to an inverter system with PWM pattern generating scheme. The major features of ΔΣAE modulator is the inherent nature of spread spectrum and simple configuration. On the other hand, ΔΣ modulator can be considered as a sort of error amplifier. Using proposed ΔΣ modulator, an automatic amplitude control function will be realized. In this paper, an automatic amplitude control performance of ΔΣ modulated voltage source inverter is described. The results of computer simulation and FFT analysis indicate that output influence due to DC source variation are effectively reduced by ΔΣ modulator. Furthermore, a possibility of system design simplification is described in this paper.

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