In order to design a system for assisting the car-allocation when the electric power's service was requested in emergency, we made a commander's thought process clear at first.
As the result, we recognized that his knowledge was classified under a quantitative and an algorithmic one, and we proposed a concrete way to realize the systematization of them.
Then we developed “The Expert System for Assisting Car-Allocation in emergency” that judged which car was the most adequate and watched automatically the arrival time of cars almost similarly to a commander did.
After field works, we confirmed that this system came up to our expectations.

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For pulsed power systems such as lasers and accelerators, semiconductor switches with their longer service life have been actively developed as replacements for thyratrons. The MOS-driven thyristors are suitable for pulsed power applications because they have the high-power handling and fast turn-on capabilities. The MOS Assisted Gate-triggered Thyristor (MAGT), especially designed for pulsed power, is a promising candidate in this field.
This paper presents the results of an investigation into the performance of MAGTs. Using a pulse forming network (PFN), the pulse switching characteristics and the dynamic resistance characteristics during the current flow were investigated. A maximum current density of 21.8kA/cm² and di/dt of 106kA/ μs/cm² with 1, 550 V anode voltage on a single shot basis were obtained. Furthermore, a life test with 10⁹ shots at a high repetition rate showed no degradation in the observed characteristics. Based on these experimental results, a carrier flow model of MAGT during turn-on process was proposed and the turn-on mechanism was considered.

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Converters or rectifiers using semiconductor switching devices generate harmonics caused by the behavior of switching. Harmonic currents generated by a rectifier are almost constant even if a source impedance varies, because the impedance on the dc side is much larger than the source impedance on the ac side. Therefore, the equivalent circuit of the rectifier can be considered as an ideal current source for harmonics. However, the theoretical derivation of the equivalent circuit has not been reported as long as the authors know.
In this paper, some problems of the conventional equivalent circuit are pointed out, and a new equivalent circuit of the rectifier for harmonics which can solve the problems of the convenional equivalent circuit is derived theoretically. As a result, the applicable limitation of the new equivalent circuit is revealed quantitatively. To clarify the validity of the new equivalent circuit, it is appied to the analysis of anti-resonance between the source impedance and the LC filter connected on the ac side of a rectifier. An accurate explanation of the harmonic amplification in the source is done by using the new equivalent circuit proposed in this paper.

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In this paper, a novel version of the dual voltage converter is presented with improved voltage regulation and enabling a wide range of voltage control by using self-turn-off devices (power transistors) instead of diodes. Further, this system operates with unity displacement factor. We have obtained the analytical expressions of this circuits. The results is, however, quite complex. We could calculate values of the voltage and current waveforms by using computer. The calculated values are essentially in agreement with experimental values.
Experimentally, an ideal load characteristic with null voltage regulation was obtained by the conduction angle control for power transistors. Further, a wide range of voltage from 220V to 39V was obtained.
A disadvantage for this system is the requirement for snubber circuits with a larger value of capacitor in order to suppress the surge voltages at turn-off periodes.

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Magnetically levitated vehicle, using the electro-dynamic suspension and the linear motor, draw public attention as a promising high speed transport system in the forthcoming generation.
The operation of these vehicles should be automatic from start to stop. Accurate and comfortable positioning is indispensable to get a fine adjustment between the vehicle and platform doors. However, it is very difficult to regulate the speed and position of the vehicle, especially with large inertia, at the same time.
This paper describes the fuzzy set theory based speed and position controls. The fuzzy logic uses the velocity and position errors as input signals and issues an acceleration reference. Positioning accuracie is kept within 3_??_4cm by adopting the proposed system.

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The Universal Field Oriented (UFO) controller operating in the airgap flux reference frame is applied to a current regulated PWM induction motor drive. Inside the induction motor, voltages induced in center tapped windings are used to sense directly the airgap flux position and amplitude. Field orientation is realized without any additional calculations requiring machine parameters. In steady state, the resulting Direct Universal Field Oriented (DUFO) controller is not affected by detuning errors and can operate during flux weakening up to the theoretical limits of the drive. The DUFO drive has an excellent dynamic performance even under strongly detuned conditions.
Furthermore, due to its high degree of generality the UFO controller is fully compatible with direct and indirect field orientation. As a consequence, it is feasible to switch over to Indirect Universal Field Orientation (IUFO) at low speed. The latter expands the use of the high performance induction motor drive down to standstill.

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This paper describes how to construct the digital control system including the observer which estimates disturbance torque and volocity.
First, the digital observer is designed based on the digital model which includes 0 order hold. Next, as a pre-process to construct the digital control system, bilinear transformation model and feedfoward model are prepared. And, the total digital control system is constructed. By the pole allocation, the stability of this system can be evaluated.
Next, we propose new methods with respect to the order of calculation of the digital controller and the initialization of the observer. Finally, the experimental results are shown.

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This paper presents an excellent speed control scheme for the induction motor drive. The quick torque control of an induction motor is used to provide better torque characteristics. PLL technique based on PID feedback of phase difference is employed to provide extremely accurate speed regulation and the four quadrant operation is obtained by the exchange of PLL control for the constant torque control. Besides, the disturbance is estimated by the disturbance observer and its feedback eliminates the disturbance effect on speed. The system combines the advantage of the quick torque control and the precise speed regulation of PLL technique, and the insensitivity to disturbance by disturbance compensation.
An analytical model of the drive system is developed and phase plane analysis is used to evaluate effects of gain coefficients on PID feedback of phase difference and to predict the system behavior. An experimental model using a 2.2kW induction motor is built and tested. Experimental results are presented to verify the predicted system behavior.

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The paper describes an adaptive force controller. In general force controller, force response depends on unknown parameters of the environment which the manipulator contacts. In case the target environment is hard, the force response of common system is oscillatory. To obtain stable force response which is independent of environment, it is necessary to adjust control gain according to the environment.
In the proposed method, a disturbance observer is applied to each joint and the total disturbance effects are canceled out in joint space. In the observer-based manipulator, full dynamics including the environment is cleared up and the workspace force controller is constructed without any disturbance effect. Then the least-squares estimator of unknown parameters of environment is also introduced to adjust the control gain. Several experimental results are shown to verify the proposed force controller.

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An efficient finite element method, the sliding element method, is proposed for dynamic analysis of the electromagnetic field in electric machines. It handles motion in a convenient way by using independent and unconnected meshes which may be freely translated or rotated. The unconnected fields solutions are coupled together at the contact interface following the constrained variational principle and by using Lagrange multipliers, which ensures complete electromagnetic continuity between the unconnected fields solutions at the contact interface. An innovative implementation is also proposed for the calculation of the Lagrange multipliers using the finite difference scheme and the virtual thin element model. The adapted periodicity condition for the contact interface is also developed from the classical periodicity condition in order to reduce the analysis domain. The sliding element method is first validated by checking the electromagnetic continuity throughout the coupling interface and the effects of the periodicity conditions in an application to a magnetostatic problem for a simple model of a one pole pitch motor. A time varying problem is also examined with the same model and the results obtained at quasi stationary state are compared with those computed by the up-wind finite element method.

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In this paper, mutual magnetic forces between two permanent magnets which have no pole piece or york are discussed using equivalent current sheets around the magnets are discussed and two important results are obtained. The first result is two decrease methods of unwanted horizontal or lateral unstable stiffness in case of vertical repulsion configurations. The second one deals with 45-degree direction stiffness, which is shown to be zero, using a wo parallel straight sheets model. At first, a very simple two parallel currents model is used. This simple model gives us very impotant insight into the magnetic forces. Yonnet's theorem about magnetic force stifiness is applied to two above-mentioned results, showing correcctness of the analyses. Finally, several numeric examples from published papers are shown.

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The linear induction motor (LIM) has been used as the driving device of urban transit vehicle with maximum speed of about 70km/h in Canada and Japan. The relation between the efficiency or the kW/kVA and the length of primary member of LIM are analyzed by using many design examples satisfied the specifications of rated speed of 11m/s, thrust of 11kN, mechanical clearance of 12mm and line to line voltage of three-phase of 1, 100V. The efficiency increases with motor length and saturates with length to the value of about 0.8. The small increase of efficiency requires extremely increase of motor length in the region above the efficiency of about 0.75. The other side, the LIM with relative low efficiency of about 0.65 can be realized with compact size of 1.6m. Both of the use of copper secondary conductor and the shortening of mechanical clearance are used but they are a little effective to improve characteristics of efficiency and kW/kVA.

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Intra-Aortic Balloon Pump (IABP) is an effective device for support of the circulation. However, the small size of the IABP is required in the related fields.
This paper proposes new small-sized IABP which is driven a Linear Pulse Motor (LPM) instead of the air-driven as the driving source. In generally, the LPM has advantages of high thrust/input power and good controllability. The developed LPM for IABP drive has high thrust/input power of 19.9 newtons/watt, it is also has kinetic thrust of 270 newtons at the range of speed from 100 to 140mm/s. IABP using the LPM has extremely simple constitution. As the result of the mock testing, the IABP using a LPM can be obtained not only same performance with the ordinary air-driven IABP, but the mass of the IABP will be reduce of half-size of the ordinary one.

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High power and high rotational speed motors are required in machine tools and turbomolecular pumps. Bearingless motors, which have another set of windings in stator slots to produce radial forces, have been proposed by the authors. The machine has four-pole windings for torque production, and two-pole windings for radial force production. In this paper, bearingless motors with a non-salient pole rotor are analyzed. Inductance functions are derived assuming MMFs are sinusoidal. Both the rotor and stator surfaces are also assumed to be smooth. Mutual inductances between four-and two-pole windings are expressed as functions of rotor radial displacements. Radial forces are derived in relation to these inductances and winding currents. An induction machine type bearingless motor was built to confirm these equations and demonstrate performances of bearingless motors.

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