The equation of brushless dc motors is nonlinear, to which linear control theories are difficult to apply. In this paper, firstly, a disturbance observer to estimate rotor positions is proposed. By assuming the non-linear term of the e. m. f. as a kind of disturbance, the model of the brushless dc motors becomes a linear one so that the disturbance observer can be applied. Secondly, a velocity estimator using the e. m. f. estimated by the disturbance observer is proposed. The observer and estimator are 2nd-order systems. Thus they are simple and easy for tuning. Their pole assignments and influences of parameter deviations are also discussed. The experimental results show that the proposed method is valid.

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For sufficient transportation capacity and passengers comfort and convenience, it is very important to design the suitable lift systems (e. g., the appropriate number of cages, velocity, capacity etc.) using a model which describes real elevator movements.
The procedure used in conventional design calculations for office buildings is to determine the transportation capacity for the up-peak traffic situation using a, simple passengers arrival model.
This paper presents a new design calculations using balanced traffic model, which can deal with the elevetor movements considering passengers arrival rate. As some performance indexes to evaluate the quality of service can be calculated by using this model, lift system designers can determine the appropriate lift facilities as to satisfy their goals. The validity of the propsed model is also shown by comparing with the measured data in real lift systems.

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This paper proposes a new hybrid vector control scheme for induction motor without velocity and position sensors. It has the following interesting and distinguished features. It is a completely seamless hybrid of indirect and direct orientation schemes and indirect one is quite new and simple. Employed field orientation is pure rotor flux orientation. Field orientation scheme requires neither velocity nor position estimation at all. Estimates of both rotor and stator fluxes can be obtained. It is completely free from variation of rotor electrical parameters in most of operation cases. Instant estimate of rotor velocity for speed control is available. Extensive numerical experiments are carried out in order to examine torque response with constant velocity in both of motoring and regenerating operations, torque response in four-quadrant operation with variable velocity, and speed response to variable command in which maximum and minimum values are 500 and 1 (rad/s) respectively, acceleration and deceleration are ±400 (rad/s²). Result of the experiments shows possibility of high potential usefulness of proposed hybrid scheme.

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The PWM methods of parallel connected current fed type inverter for increasing the capacity of a inverter with sinusoidal outputs have been investigated. The main circuit configuration of this type inverter is very simple. Only one rectifier is used for supplying the dc power to two unit inverters, and the ac output terminals of each unit inverter are directly connected in parallel without any transformers. Since it is very important to balance the dc currents, the large dc reactors are usually connected in the dc input terminals of each unit inverter.
In this paper, the new PWM method which allows a great reduction in the DC reactor is proposed. This PWM method is based on closed-loop regulation of the ac current vector. The suitable current vector is carefully selected to reduce the distortion of the output current waveform Then, the closed-loop control of balancing the currents of the dc reactors is achieved at the same time by measuring the difference of the reactor current.
This paper describes the configuration of main circuit, the principle of balance control of the dc currents, the design of control circuit. Moreover, the feasibility of proposed PWM method is confirmed by some experimental results using a small test system.

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In this paper, we present a new design method of model following digital PID controller for multivariable system. The dynamic characteristic of the system is expressed by the step response of the system, then the optimal PID parameter which minimizes the error integral of the step response between the control system and reference model is obtained by using the matrix computation.
The derived algorithm can be implemented through a simple and systematically applied to the PI, I-PD, PI-PD type controller.
We show a numerical simulation result by the propose method and apply the method to a temperature control system to show the effectiveness.

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This paper presents a novel high-speed and high-precision positioning control of a servo drive system. The controller comprises a two-degrees-of-freedom position control system by using a mode switching control to ensure the fine positioning without overshoot in the position response. In this proposed system, since the position response strongly depends on the initial motor velocity at the mode switching, the optimal initial velocity which realizes the specified positioning accuracy is analytically examined. In addition, a fuzzy inference-based control parameter tuning of feedforward coefficient is proposed to obtain the initial velocity.
The proposed control scheme has a distinct feature that the control gain scheduling is not required and the same control performance can be always achieved under arbitrary position command amplitude. Experimental results using a prototype show the effectiveness of the proposed control.

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This paper proposes a drive system for a three-phase hybrid (HB) stepping motor, combining sensorless closed-loop control with conventional open-loop control. It is characterized by the sophisticated control providing both prevention of pulling out from synchronism and suppression of rotor natural oscillation, without any position sensor attached to the motor shaft. Switching technique in chopper control is described, which can enlarge a speed range controllable in the sensorless closedloop control. Moreover, starting and stopping sequences are developed to reduce mechanical natural oscillation caused in transient state. Finally, the proposed drive system is compared with a conventional constant-current open-loop drive system experimentally. It is shown that the proposed drive system can perform a switchover from the starting to the sensorless closed-loop operation within 20ms, and can reduce the natural oscillation caused just after positioning.

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The generation of harmonics and their subsequent propagation into power line is a topic of increasing concern to power supply authorities. To prevent the obstacles on the power system, Unity-Power-Factor PWM converter is going to apply to AC-DC power conversion circuit. However, PWM converter, especially at single phase circuit, has some serious defects, that is low frequency ripple current which flows into the battery connected to the DC output or low frequency ripple voltage which appears on the DC output capacitor. Especially, in case of the batteries are connected with the DC output, the low frequency ripple current flows into the battery and cause power loss on the battery. The power loss cause high temperature of the battery and shortens the life of it. To accomplish the reduction of the low frequency ripple current, the authors have been proposed a novel topology of the PWM rectifier and reported its operation principles.
In this paper, the operation limit influenced by the circuit parameters, especially capacitance of the input capacitor, is discussed. It is shown that the operation limit can be estimated based on the calculation of the ripple energy that is stored in the input capacitors. By adopting the ripple energy expression on both the input capacitor and the DC output, the limitation for the DC ripple reduction can be clearly expressed. The calculated results agree well with that of the experimental results. The proposed calculation technique is useful for the practical design of the proposed PWM converter.

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A novel solid state ballast, which operates in the MHz-range frequency, is presented in this paper. A circuit composed of a voltage-source half-bridge inverter, a distributed constant line, and a parallel LC resonant circuit has been developed for this purpose. The HID (High Intensity Discharge) lamp is connected to the output terminal of the inverter through the distributed constant line. Here, since the length of the line is adjusted to 1/4 of the propagation wavelength λ(λ/4 condition), the output voltage of the voltage-source inverter can be converted to a current source on the load side. Therefore, the ballast can supply not only high voltage to the HID lamp for initiating discharge but also stable current to it during discharge condition. The modification of the proposed circuit is also presented in order to expand the operating frequency without increasing the undesirable harmonic current. The experimental results from a prototype system verify the theoretical procedure.

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We have been studying the aplication of permanent magnet synchronous motor (PMSM) for railway vehicle traction in order to reduce the weight and size of direct drive traction motor. As a part of this study establishing a current control system of PMSM suitable for railway vehicle traction should be investigated.
In this paper we discuss about designing method of current control system mentioned above and suggest a method which is available under the condition of railway vehicle traction, low switching frequency and long digital calculating period. Next we investigate how to decide current response time constant T_d and reach a conclusion that it is about 10ms is appropriate under some assumed condition. Then we checked this current control system for railway vehicle traction through experiments and studies of influence of parameter changing. Consequently we can recognize the current control system has satisfactory performance for railway vehicle traction.

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A mathematical model and an optimal control system of hot-blast stove process are described. A precise mathematical simulation model of the hot-blast stove was developed and the accuracy of the model has been confirmed. An optimal control system of the thermal conditions of the hot-blast stoves in staggered parallel operation was also developed. By the use of the multivariable optimal regulator and the feedforward compensations for the change of the aimed blast temperature and blast volume, the system is able to control the hot blast temperature and the brick temperature efficiently.
The system has been applied to Kashima works. The variations of the blast temperature and the silica brick temperature have been decreased. The ultimate low heat level operations have been realized and the thermal efficiency furthermore has been raised by about 1%.

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This paper proposes a new type magnetic suspension system in which the electromagnet is magnetized by an AC current. The basic idea is a feedback of difference between the exciting current and the applied voltage. The feedback signal is applied to a power amplifier through two phase sifters and a band pass filter. The usefulness is established by the experiments of magnetic suspension. The main merit of this system is that the stable suspension is achieved without a displacement sensor and without a self-sensing controller.

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In order to improve the performance of a permanent magnet type of retarder, which is used as auxiliary braking system of heavy vehicles, the dc steady state flux and eddy current distributions should be analyzed.
In this paper, the method of do steady state eddy current analysis using a moving coordinate system, in which the dc steady state flux and eddy current distributions are directly obtained without time iteration, is described. The 2-D and 3-D eddy current analysis of the permanent magnet type of retarder at high speed is carried out. The results, such as the flux distribution and the braking torque, obtained from the analysis and experiment are compared with each other. It is shown that the stable flux and eddy current distributions without spurious oscillations can be obtained by using a moving coordinate system at high Peclet number, and 3-D analysis should be carried out because the result obtained by 2-D analysis is much different from those obtained by 3-D analysis and experiment.

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Takasaki-Nagano section, a part of Hokuriku Shinkansen was opened in October, 1997, just before Nagano Winter Olympics. Hokuriku Shinkansen has been electrified by 30kV a. c. commercial frequency AT feeding system.
As for the commercial frequency, Japan is divided into two zones: the western part of Japan is a 60Hz zone and its eastern part is a 50Hz zone. Two different power frequencies exist in Hokuriku Shinkansen which passes power frequency borders between different electric power companies. Therefore, in case of a contact fault between two different power frequencies, a beat-formed large fault current will flow, which should be immediately detected and cut off.
At present, a distance relay and an AC ΔI type relay are used as protective relays for a feeding circuit of Shinkansen lines. However, it was experimentally made clear that those relays do not operate by a beat-formed fault current which appears in the case of a contact fault between two different power frequencies. For this reason, we have developed and put to practical use a protective relay for a contact fault between two different frequencies, which operates by detecting 55Hz component peculiar to the current caused by the contact fault and also detecting power frequency of an opponent traction substation.
They have been installed at a frequency-bordered sectioning post and at traction substations which sandwich the sectioning post.

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A superconducting (SC) magnetically levitated (Maglev) transportation system has been developed in Japan and various experiments have been done in the new test line at Yamanashi prefecture. Although the superconducting electrodynamic suspension (EDS) system has the advantage of stable levitation without active control, various electromagnetic or mechanical disturbances can cause the change of gap length and the displacement or oscillation of the bogie. In this system, the severest disturbance is SC coil quenching. Therefore it is important to show the running characteristics of the Maglev train and to increase the stability in this case. We developed three dimensional numerical simulation program for the Maglev train. Using this program, running simulation of the train for Yamanashi new test track was undertaken in the case of SC coil quenching. Because of the damping characteristics of the EDS system, influence of the coil quenching is smaller at a higher speed. In the train model, electromagnetic spring strength of the EDS system is larger than mechanical spring of the secondary suspension system connecting a bogie and cabins. Therefore influence of the quenching is only seen in the cabins connected to the quenched bogie. Demagnetization of the SC coil quenching is considered to increase the stability of the train. Although this method is useful to decrease large guidance force, lateral displacement, yaw and roll angle of the bogie, vertical displacement and pitch angle become large.

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