A permanent magnet synchronous motor can be controlled as a DC brushless motor, for which the position sensor is needed for detecting the rotor position. In this paper, the research on speed control system without position and speed sensors is reported, where the rotor position and speed of the motor are estimated by means of an adaptive observer. To make the state equations linear, two new state variables are introduced. Consequently, based on the Iinear control theory, an adaptive observer is designed by which the estimated speed and position are converged to real ones. The system is verified to be asymptotically stable. The operation of the system at zero speed and the effects of the mismatched parameters used in the observer are also discussed. Finally, the speed control of the system is implemented. The computer simulation and the experiments show that the system is valid.

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Three-phase diode-bridge rectifiers are used to convert the AC input into DC voltage. A large capacitor is connected as a filter on the DC side, since in most applications, a low ripple in the DC output voltage is desirable. Unbalance in the supply conditions of a three-phase diode-bridge rectifier with a DC filter capacitor gives rise to uncharacteristic harmonics on both the AC and DC sides.
This paper proposes a simplified method for calculating the uncharacteristic harmonic currents generated by the three-phase diode-bridge rectifier under unbalance, taking into account the effects of both the AC and DC side impedances. Analytical expressions for the harmonic currents are derived using the switching functions with overlap period the AC circuit theory. Therefore, the proposed method can be executed only with algebraic computation and its accuracy is quite high. The validity of the proposed method is demonstrated by comparison with the results of time simulation.

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This paper describes circuit configurations of current output type rectifer. The rectifiers with full-bridge or half-bridge, and new type rectifiers with auxiliary devices are presented. A pulsewidth modulation (PWM) strategy is employed to obtain sinusoidal input current with unity power factor. The PWM methods for each circuits are described and the circuit operations are explained. The voltage and the current waveforms in the experiments for static RL loads are shown, and the steady state characteristics are given. The circuits are compared, and the best one among the presented circuits is discussed on the switching frequency, the voltage stress of the devices, and the circuit reliability, etc.. The experiments show that the use of a double PWM method for the circuit with auxiliary devices contributes to decreasing the ripple in the sinusoidal input current wave.

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The recent development of a semiconductor device technology realizes small-size, light-weight, high performance power switching devices. But, reactive elements such as an inductor or a capacitor are still physically large and heavy. On the other hand, the improvement of high speed PWM inverter achieves high performance current control, which is applied to the active filter and so on [2] [4]. If a compact and high efficient reactive component is developed, the power converter technology may drastically change the application field.
In this paper, the concept of variable active-passive reactance (VAPAR) which consists of an inverter and passive elements is proposed. The VAPAR behaves like a two terminal reactive element and the produced active reactance component works as a passive reactive component, including in transient state.
Authors present the principle of VAPAR and two possible control schemes to realize VAPAR. Through simulations and experiments, it is verified that VAPAR shows reactive characteristics not only in steady state but also in transient state, as proposed, and basic characteristics of both control schemes are clarified.

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High frequency resonant link converters which utilize soft-switching have been focused for the purpose of downsizing or high efficiency to drive AC power machinery. Such resonant link AC/AC converters are classified to four types, that is, whether they act in voltage resonant mode or current resonant mode, and whether they include DC link or AC link. Current resonant converter has the features that the system utilizes natural commutating devices such as thyristors and does not need electrolytic capacitor for DC link.
In this paper, we propose a new DC link circuit without DC bias inductor adding a thyristor to DC link converter. This circuit has many advantages. Because of no DC inductance, it is small-sized and light-weighted and there is no possibility of abrupt releasing of DC inductor energy by commutation failure.
Further the operating characteristics are explained and the criterion of sustained resonance and the determination of circuit parameters are derived. And applying these result to the experiment, output characteristics are attained.

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A new approach to digital feedback control of PWM inverter is proposed, in which an output DB (dead beat) control is achieved with a disturbance observer. In this scheme, the state observer and disturbance observer are used, and pole placement of these two observers are chosen separately. When these observers employ the same pole placement, the system has tendency to become unstable. By selecting the different pole placement, the disturbance observer only eliminates the disturbance, and state observer only estimates the state variable of the next sampling instant.
From the view point of UPS applications, the advantages and disadvantages are discussed through simulations and experiments.

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As a basic study to realize a ski-robot in a straight downhill skiing, a posture control scheme of a two-link ski-robot is considerd in detail. First of all, we investigate vestigate about ski-robot moving on the slope approximated to two-dimension and derived the state variable equation of two-link ski-robot as minimum links, using Lagrange's equation. For the two-link ski-robot in the straight downhill, it is favorable to build up servo system which has excellent response characteristics for controlling and stabilizing. In this study, an optimal feedback control is applied to servo system of the two-link ski-robot in the stable skiing. In the stable straight downhill skiing, the center of gravity determined by the posture will be existed to a balancing position in dynamically. A simple method, by the use of a pendulum, is proposed for detecting the balancing position for the center of gravity. Furthermore, an experimental system is constructed by using a DSP (Digital Signal Processor) in the control circuit.
We show the two-link ski-robot applying the optimal feedback control has the cexcellent performance confirmed by simulation and experiment. It is clarifided that the method by use of the simple pendulum is valid for detecting the stable position for the center of gravity.

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We have proposed two design methods of AC/DC thyristor converter current control systems with MRAC (Model Reference Adaptive Control). To linearize the input/output relation of the systems, we dealt with the constant term of the model in different ways. In the first method, we made a linear transformation of the control input, while in the second one, neglected the constant term and compensated modeling error by integral adaptation. Computer simulations and experiments have shown that the control performances of the MRAC systems are much better than that of PI controllers. But in the first one, as the variable vector is not persistently spanning, the convergence rate of estimated parameters is not as high as expected. The second one has better dynamic characteristics but its stability has not been proved in theory.
This paper suggests a new design method in which the constant term is considered as a deterministic disturbance. The feature of this method is: by introducing an equality equation which makes the term of disturbances unobservable apparently, we can eliminate the effect of disturbances, and can use the existing adaptive control scheme without disturbances whose stability has been theoretically proved. Computer simulations and experiments show that the new method can obtain better responses than the old ones.

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The paper describes a workspace force controller based on disturbance observer. In the multi-degrees-of-freedom robot, either joint space or workspace is selected to construct the disturbance observer. In case the disturbance observer is constructed in the joint space, the total stability of motion controller is independent of the configuration of robot. In the workspace observer-based motion controller, however, the total stability depends on the configuration of robot.
In the paper, the differences between the joint space observer and the workspace observer are shown from a viewpoint of the stability. Furthermore, the decoupling control strategy is discussed in the workspace. First, the observer-based system is analyzed in one-degree-of-freedom system. Secondly, we explain a basic structure of workspace motion controller based on the joint space observer and the workspace observer. Then the stability of each motion controller is considered. Several numerical results are also shown to confirm the theoretical analysis of the observer-based motion controller.

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This paper deals with a kind of cellular robotic system (CEBOT-Cellular Robot), called Self Organizing Manipulator System (SOMS). In this system the configuration of the manipulator can be changed according to the given task. A new type of cells is designed, which the signal bus and power lines are made inside the cell. We use two manipulators to assemble, disassemble, and reassemble cellular manipulator by cooperation of the manipulators. When a task is given, the system analyzes the task and generates the structure of the cellular manipulator. The assembly work of the cellular manipulator is divided into modular subtasks. The system generates the macro command for each subtask based on the database. The collision avoidance is considered for planning the cooperation work by using the collision database which was calculated before hand. The simulation results and the experiments illustrate validity of the proposed system.

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A discrete-time learning control for robotic manipulators is studied from a viewpoint of zeros of a control system. The signal used for learning is a position signal of each joint detected by a pulse encoder. Firstly, we show that when sampling period is small, the learning is unstable because of an unstable zero of the system. Secondly, we show that we can stabilize the learning control system with small sampling period by using a low pass filter, and also show that a tracking error converges not to zero but to a certain value in that case. Finally, experimental results on the trajectory control of robotic manipulators using the discrete-time learning control are shown. These experimental results agree well with the analytical ones.

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A 70 MW class superconducting generator has been developed under an eight year program since FY 1988 as one of the MOON LIGHT PROJECTS conducted by MITI.
This paper summarizes the experimental results of a superconducting model coil using a rotating cryostat. The test setup is designed to verify performances of the model coil under actual centrifugal force and helium conditions of the 70 MW class superconducting generator.
The current carrying characteristics of the model coil were tested at the rated rotating speed of 3, 600 rpm. Furthermore the rotating speed was changed from 300 rpm to 3, 600 rpm to verify the effect of rotation. The tested quench current was approximately the same as the static test value. High stability of the model coil under severe flux change was also verified. These results verify that the superconductor, coil supporting structure and cooling method applied to the model coil are suitable for superconducting generators.

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A distinctive feature on speed controls of synchronous motor is that the steady state speed error can always be reduced to zero as long as the stator frequency can precisely be identified. However, the problem of stepping-out in both steady and dynamic states is inevitable and, in usual, the so called closed control system has been constituted. Thus, if any open loop control (OLC) system without rotor position sensors can be constituted in pursuing to overcome the problem, it is quite desirable for extendind the application areas of OLC.
First, voltage source drive (VSD) and current source drive (CSD) are compared for OLC and it is made clear that CSD is more profitable for the constitution of OLC than VSD is. However, CSD has the following features. (i) Large torque is generated in the low speed range. (ii) The voltage of synchronous motor becomes excessively high in the high speed range. (iii) The dynamic characteristic is not good. (vi) The current of synchronous motor is large in the light load.
Second, we show a new control method which the torque of synchronous motor is proportional to the angle between rotor position and stator current vector and use lead-lag compensation. The torque transfer function becomes constant using this control method. As a result, the good characteristics are obtained.

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This paper describes H^∞ robust control design for a magnetic suspension system of double flexible beam which simplifies both an elastic rotor and body in a magnetic bearing system. A magnetic bearing requires feedback control since it is inevitably unstable. Moreover, it is desirable that the controller guarantees robust stability at presence of a variety of uncertainties; errors of parameters, neglected nonlinearities, or unmodeled dynamics.
At first, the magnetic suspension system is introduced. Next, its linearized model with disturbance terms as unmodeled uncertainties is formulated in a state space form. In order to deal with the uncertainties, the generalized plant is constructed from LQ differential game theoretic point of view, which involves weighting matrices for state variables and control input and frequency weighting functions for uncertainty models. Then the control systems are designed with both H^∞ control and PID control, which are implemented by a digital controller using a digital signal processor. Finally, several experiments are made for the evaluation of the control performance, where the proposed control is compared with PID control.

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In Institute for Posts and Telecommunications Policy, a postal transportation system has been studied. This system would make use of linear induction motor (LIM)-driven vehicles for conveying mail between post offices in the Tokyo metropolitan area. The system would connect the main post offices in the Tokyo area with tunnels circularly constructed underground and transport mail using linear induction motor-driven vehicles. In this study, it is found that if vehicle weight were reduced climbing capabitity could be considerably improved. Accordingly, the potential for reducing the LIM weight mounted vehicles have been explored, and a prototype light-weight LIM has been manufactured. This paper report on the light-weight LIM produced and its characteristics.

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