The purpose of this paper is to establish a design process of photovoltaic (PV) systems and to develop a system which gives comprehensive support to design PV systems in Japan.
In this paper, first of all, a knowledge about a design process of PV systems is acquired from existing PV systems and supplemented by interviews with expert engineers. Secondly, the knowledge is systematically represented as a knowledge base and incorporated into an expert system on a personal computer.
The expert system covers various configurations of PV systems. Data bases and programs which are necessary for designing PV systems are incorporated into it. This makes a design of PV systems possible, when no climate data are observed at the place where a PV system will be installed.
Several examples confirm that the expert system is effective in the design of PV systems. It should contribute to a wide spread of PV systems in the future.

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The dynamic tracking system of a video tape recorder (VTR) uses a moving-coil head actuator. The head fluctuates at the mechanical resonant frequency which is higher than fundamental drive frequency, so damping of mechanical resonance is important.
In voltage drive, short-circuit damping effectively reduces the Q factor of resonance. However, voltage-displacement sensitivity varies with the coil's resistance. On the other hand, in current drive, short circuit damping is not effective, but current-displacement sensitivity does not vary with the coil's resistance.
In order to obtain fine tracking, both the Q factor and the sensitivity variation need to be reduced. Consequently, a capacitor damping is proposed in which the actuator is short-circuited by a capacitor. This damping method is expected to have the following characteristics: a) current drive around the fundamental drive frequency, and b) voltage drive at frequency around the mechanical resonance.
The sensitivity variation of the proposed circuit with respect to load resistance, as well as the frequency response of an actuator driven by this circuit, have been investigated by using an equivalent circuit and circuit simulation program, SPICE. The experimental results confirm that the Q factor and the sensitivity variation have both been reduced.

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In this paper, the overall control for high performance AC drives for robotic applications using fuzzy logic is presented. The controller is based on the rotor flux field orientation. To estimate the rotor flux irrespectively of the motor parameters changes (i.e. the stator and rotor resistances variations due to the temperature variations), the estimation is based on two different types of estimators adapting the rotor resistance using a fuzzy logic technique. The controller robustness capability in the case of the inertia variations and of the load torque disturbances is achieved by means of the combination of a fuzzy logic controller and a classical PI controller in the speed loop. The simulation results show excellent performance in any working conditions.

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Levitation force between permanent magnets and a high T_c superconductor (HTSC) is analyzed numerically based on the critical state model. Size and combination of the magnets are examined to obtain the large levitation force. An axisymmetric code is applied to the evaluation of basic properties of the levitation force, and a thin plate approximation code is applied to the analysis of a partial model of a flywheel. There are the size of the magnets and the magnetic field configuration to obtain the maximum levitation force for a given size of the HTSC. Obtained results will be useful to design the flywheel system with HTSC.

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In commercializing the superconducting maglev system it is important to reduce the cost, especially that of ground coils installed all along the guideway. The ground coils designed for Yamanashi test track under construction are composed of both eight-shaped null-flux coils for EDS (Electro-Dynamic Suspension) and double-layered armature coils of LSM (Linear Synchronous Motor). The former reduces the magnetic drag of the running resistance, and the latter reduces the electromagnetic fluctuation in the superconducting coils. Besides, the eight-shaped coils can generate propulsion force by being connected to the power supply. This system can generate levitation force, guidance force and propulsion force by the same ground coils. Therefore this system is expected to save the cost of ground coils, number of which are decreased. In this paper we present the principle and analytical formula of the combined propulsion, levitation and guidance system (PLG system), including one for angles. In addition, using numerical examples, the characteristics of this system are expressed.

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Large eddy current is induced at high speed in a slub type rail of a electromagnetically levitated train. The eddy current causes magnetic drag force and decreases attracting force between the magnet and the rail.
In this paper, magnetic drag force in a system, which has magnetic rails made of laminated iron sheets, was studied theoretically and experimentally, and the following results were obtained:
(1) Magnetic drag force in a system with a laminated iron rail was measured using a rotary disc type apparatus. Calculated values were simulated with 2-dimensional finite element method. The calculated values of magnetic drag force were approximately equal to the measured values, and the difference between the calculated and the measured values was within 10%. This result shows that the theory is reasonable.
(2) The ratio of magnetic drag force to magnetic attracting force of a slub type rail is about a few %. It was confirmed that the ratio of a laminated rail in this paper was less than 0.3% and that adoption of laminated rails is effective.
(3) The magnetic flux density in the air gap between the magnet and the laminated iron rail does not decrease at high speed of 170km/h. This indicates that the attracting force is constant even at high speed and therefore stable levitation charcteristics will be obtained.

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This paper describes a multi-winding transformer as a plasma initiator in tokamak devices and the application to the design of poloidal field coil power supply system. The scale of tokamak device has been considerably increased based on some experimentally obtained scalings of a energy confinement, because the plasma performance has been improved with the current and size parameters. Since large tokamaks require the hybrid functional poloidal field coil system, the each coil power supplies must prepare the high voltage generation circuit for the plasma breakdown, and it causes increase in the number of current interrupters, disconnectors and the resisters. Therefore, the plasma position and shape control tend to be difficult especially in the start-up phase of the discharge. The plasma initiator proposed in this paper makes the plasma initiation circuit to be simple by unification of the high voltage generation circuit. It has similar ampere-turn and permeance distribution with the tokamak device and produces the magnetic field necessary for plasma breakdown. An application to FER tokamak proposed by JAERI is also presented.

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Development of a solenoid which was used for the high-speed solenoidvalve with a 1 ms switching time is discussed in this paper.
First, by using the mathematical model, we quantitatively studied the effects of design particu lars, such as the dimensions of the solenoids and the number of turns of coil, on the switching time. Next, we investigated the suitable and comprehensive conditions that would satisfy given specifications under the various limitations inherent in the solenoid valve's operation.
Finally we manufactured the solenoid valves in accordance with the effective methods for performing fast switching, and evaluated their performance.

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The wind power generator system has been widely studied. Most of these system, however, are constructed by voltage source inverter and synchronous or induction machine. In these system, chopper circuit to maintain direct current voltage constantly of CVCF inverter is needed, because induced electromotive force is varied widely by the change of wind velocity. In addition, capacity of generator and inverter must be larger than maximum supply capability. These problems cause increasing mechanical loss or size of AC generator.
In this paper, wind power system using a wound rotor-induction machine are discussed. In this system, capacity of inverter and generator can be reduced to half by controlling the rotation speed of generator. Above all, by using current source inverter, this system supplies three-phase electric power with constant voltage and sinusoidal waveforms.
This paper describes the principle and performance characteristics of system. Experimental result of the testing machine shows that this method is useful for decreasing mechanical loss and the size of system.

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It is difficult to model a discrete system than a continuous system. Recently, a great number of applications of Petri nets to the design and the analysis of discrete systems have been reported. However, a common problem in its applications is that the required computer memories and the computation times increase explosively in accordance with the increase in the number of systems' components. Some methods to divide or to reduce Petrinets have been proposed to solve this problem. Although the liveness and boundedness of Petri nets are held in the divided or reduced Petri nets, the reachability problem can not be solved by these methods.
In this paper, we propose another method to model discrete systems by Petri nets with place invariants. Sequential control system will be described as a typical kind of discrete systems, and its structural characteristics will be used in modeling. Each component of a sequential control system will be modeled by a sub Petri net with place invariants. There are many components in one sequential control system, but each one is not necessarily complicated. Most sub Petri nets do not have so many places or transitions. It is also well known that a Petri net with place invariants is bounded and can be live by being put sufficient tokens into its initial marking. Besides, the reachability problem is not so difficult to solve in a small sub Petri net. Further, we define an activating relation to combine two or more sub Petri nets. And, some rules to reduce conflicts among enabled transitions will be described for simulations.

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This paper presents a method for constructing a cost estimation system in the design stage for sheet metal parts. For estimating the cost of the parts, settings of the manufacturing process should be known. Since decision of experts on the settings depends heavily on the individual parts, a method of estimating the cost of parts using the past cases is effective.
The input of this system is CAD data of parts. The system extracts Sheet Thickness Features (STFs) from the CAD data. The STFs extracted from each projecting plane are indexed, and the cost estimation is done using the cases retrieved with the indices.

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