Switching characteristics of the power semiconducter device, IGBT were tested and discussed through the structure of IGBT as well as the circuit simulation. The IGBT has been considered as a very useful device because of its small input power and low on-resistance which is recently applied on power conversion systems.
Under these circumstances its switching characteristics should be recognized presicely and the principles to application on the real circuits are also necessary. It was made clear that the electric ocsillation or voltage spike across the device would occur by the stray inductances located at the lead wires and sometimes that would be harmful.

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The speed sensorless vector control systems have been developed under the sensitiveness of the temperature variations of the secondary resistance. The conventional compensation way is somewhat difficult in the sensorless drive system to calculate the secondary resistance, because of the necessity of the rotor speed.
This paper proposes a secondary resistance calculation method for speed sensorless drive systems, which doesn't need the variable of the rotor speed. The secondary resistance is obtained directly from characteristic equations. It is impossible under the steady state but the equations can be solved under non sinusoidal voltage supplied motor. Therefore, on-line calculation of the secondary resistance is possible in the PWM inverter drive system, and it can apply to the sensorless drive which makes free from the secondary resistance variation.
The effectiveness of the proposed method was verified by some digital simulations and experimental results. By using this method, the compensation for the secondary resistance variations is realized. In this paper, the influence of the variations of the primary resistance, the leakage inductance and the mutual inductance are also investigated.

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In application fields of a 2-mass resonant system, control theory-based various techniques by using feedforward/feedback control have been proposed to achieve the high performance motion control. Although these schemes are effective to suppress the resonant vibration, they are quite sensitive to system parameters because the design of such controllers basically relies on system mechanical parameters.
This paper presents a disturbance observer-based novel mechanical parameter measurement scheme of 2-mass resonant system. In the proposed measurement, the load inertia and the torsional constant of the resonant system can be measured by using error components of the estimated disturbance torque due to setting errors of the parameters in the observer. This measurement algorithm has a distinctive feature that no additional tool but the observer is required for the parameter measurement. The effectiveness of the proposed measurement scheme is verified by experimental results which are obtained by a prototype.

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This paper newly proposes a simple and robust robot motion control method using the robust velocity controller. The robust velocity controller is based on H^∞ control theory, and it is called H^∞ velocity controller. H^∞ velocity controller based motion control method is completely equivalent to the robust acceleration control method using H^∞ acceleration controller, but it has simpler structure. Therefore, the proposed system can realize a fine robot motion control easily. In order to confirm the validity of the proposed method, this paper realizes the hybrid control of position and force for multi-joint robot manipulator. Further, this paper also proposes the simple realization of hybrid control considering the attitude of robot manipulator. This system realizes the hybrid control of position and force of robot manipulator while keeping the perpendicular attitude to the target environment. The experimental results in this paper show that the proposed system have the desired force and position response to the target environment.

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Reductione of the noise emitted from the automobile alternator has recently become a serious issue, especially in relationship to the improvement of the amenity of driving. In order to design a quiet automobile alternator, a designer needs to anticipate all important resonant frequencies of the alternator stator. We intend to simulate the electromagnetic vibration behavior of the stator using finite element method. The results obtained are applicable to alternator design for the reduction of noise.

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Reduction of machine size increases the number of harmonic components which appear in the magnetic fields on induction motors. For practical design, it is necessary to estimate these harmonic components. This paper describes a method to analyze harmonic fields on induction motors, considering higher harmonics in the secondary current. The method consists of two parts. One is the magnetic field calculating part done by a 2D-finite element method considering rotor rotation, and the other is the harmonics analyzing part done by considering space and time harmonic components using the former results.
Dependence of periodicity in the magnetic fields on driving conditions is discussed. Then the relationship between the analysis period, the method of mesh division, and the periodicity is clarified for calculating magnetic fields. From the comparison between calculated and experimental results, the proposed method is shown to be appropriate and useful for quantitative estimation of harmonic components on induction motors.

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In recent years, distortion of power source voltage waveform has become noticeable, as electrical appliances with rectifier circuits have been widely used. Connecting capacitor induction motor (CRM) to such distorted supply, or controlling CRM by simple controller with switching device such as triacs, harmonic voltage is supplied to CRM. In that case, CRM produces electromagnetic vibrations caused by not only the fundamental voltage but also time-harmonic voltages in the distorted voltage. In addition, CRM produces electromagnetic vibration due to backward magnetic field. Thus, it is difficult to clarify the relationship between electromagnetic vibration of CRM and harmonic voltages.
In this paper, the causes of the electromagnetic vibration of CRM operating under distorted wave supply voltage are discussed. First, a general equation of dominant electromagnetic force waves is shown considering not only forward magnetic fields but also backward magnetic fields. Using the general equation, causes of dominant electromagnetic vibration are clarified. Next, by means of discussing in details of some examples of the dominant vibration, the relationship between the vibration and harmonic voltages becomes evident. Furthermore, the relationship between the vibration and backward magnetic field is clarified.

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The paper deals with the analysis of a superconducting linear synchronous motor propulsion of a maglev vehicle of Japan Railway. A dq-axis analysis is made with taking account of the space harmonic fields that the superconducting magnets (SCMs) produce. The relative angle, which is an electrical angle between the three-phase axis and the dq axis, used as a variable of a dq transformation matrix is readily determined by observing the fundamental component of the flux linkages of the LSM windings by formulating in Fourier series expression. The propulsion force is formulated in terms of both three-phase and dq0 variables. The calculated results are shown for the two types of LSM winding configuration, i. e., the configuration of 120-degree coil pitch with single layer and the configuration of 240-degree coil pitch with double layers. The propulsion force coefficient, which is defined as a ratio of the propulsion force to the armature current in q-axis, can fluctuate with time according to the configuration of the LSM windings. And the coefficient is shown to have fluctuations even for the 240-degree coil pitch configuration due to the difference between the positions of the two winding layers. It is suggested that selecting the number of poles of SCMs as an even number may be the effective measure to flatten the pulsated propulsion force coefficient.

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For exciting superconducting magnets has been used conventional power supply and power leads. This way has some problems: heat leak into the cryogenic part, occurrence of Joule loss in the power leads, etc. To overcome such problems, the use of superconducting magnetic flux pump has been studied. The magnetic flux pump can serve a permanent current mode switch and power leads to supply large current in superconducting magnets. However, the design method of the flux pump has not been known well. Therefore, we have developed a small size magnetic flux pump for analysis purposes to investigate its characteristics and actual performance when exciting a superconducting magnet. Furthermore, we have theoretically and experimentally examined the method to improve performances of the flux pump. As a result, we derived some important design parameters. This paper also gives a comparison between theoretical simulation and experimental results for the case of single and series-connected flux pump devices, respectively. Further it is clarified that the series- and parallel- connection of the flux pump can improve performances.

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This paper describes a position sensorless brushless dc motor drive system, in which an interior permanent magnet (IPM) motor is used as a synchronous motor. It is characterized by the position-sensing technique based on current detection of the free wheeling diodes. A three-phase voltage-source inverter with the conducting interval of 120 degrees in each phase is employed in the drive system. Reluctance torque plays an important role in producing torque of the IPM motor, having q-axis inductance larger than d-axis inductance, so that the control of i_d=0 can not achieve the highest motor efficiency.
The characteristic analyses of the position detection and the commutation overlapping angle are done, in which the saliency of the motor and harmonics of the back electromotive force are taken into consideration. It is shown that the detection angle and the commutation leading angle tend to lead with increase of the load torque, while the phase angle of the fundamental armature current lags by half of commutation overlapping angle. As the result, the total leading angle of the fundamental armature current exists near the optimal one which can attain the highest efficiency. The experimental results shows that higher efficiency is achieved at the rated speed without special phase angle control in relation to the load torque.

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Soft-switching phase-shifted PWM converters have been attracted much attention because of their low switching losses, constant frequency operation and simple control. However, a circulating current flows through the transformer and the primary bridge circuit during the freewheeling interval, resulting in relatively high current stresses for the transformer and switching devices compared with those of conventional hard-switching PWM converters.
This paper presents an improved soft-switching PWM DC-DC converter which can substantially reduce the circulating current by employing a tapped inductor for output low-pass filter. The principle of operation and the role of the tapped inductor are illustrated. The effectiveness of the tapped inductor is evaluated through simulating analysis. Moreover, a 500W-100kHz prototype converter is implemented to demonstrate the excellent performances of both low switching and low conduction losses.

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This paper proposes a linear robust control scheme for robotic trajectory tracking based on the H_∞ control theory. The controller consists of a model-based linear robust controller, and it does not employ inverse dynamic computation, hence once the controller has been obtained, computational burden for H_∞ controller is relatively small, because the H_∞ controller is linear and time invariant and the computational burden is only matrix vector multiplications. Further, the control input is continuous. Therefore, the H_∞ controller is suitable for realization of real-time model-based robust control.
At first, our experimental manipulator is introduced. Then, the dynamics and model uncertainties of the robot system including actuator are discussed. Dynamic couplings and the gravity forces are treated as the real structured uncertainties. Then, setting up the control objectives in H_∞ synthesis framework, an H_∞ controller is designed with the static constant scaling matrix D to achieve robust performance of the closed-loop system by small gain theorem. Finally, we show the effectiveness of proposed linear robust H_∞ control scheme for a robot manipulator with experimental results.

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