The A variety of switched-mode high voltage DC power supplies using voltage-fed type or current-fed type high-frequency transformer resonant inverters using MOS gate bipolar power transistors; IGBTs have been recently developed so far for a medical-use X-ray high power generator. In general, the high voltage high power X-ray generator using voltage-fed high frequency inverter with a high voltage transformer link has to meet some performances such as (i) short rising period in start transient of X-ray tube voltage (ii) no overshoot transient response in tube voltage, (iii) minimized voltage ripple in periodic steady-state under extremely wide load variations and filament heater current fluctuation conditions of the X-ray tube.
This paper presents two lossless inductor snubber-assisted series resonant zero current soft switching high-frequency inverter using a diode-capacitor ladder type voltage multiplier called Cockcroft-Walton circuit, which is effectively implemented for a high DC voltage X-ray power generator. This DC high voltage generator which incorporates pulse frequency modulated series resonant inverter using IGBT power module packages is based on the operation principle of zero current soft switching commutation scheme under discontinuous resonant current and continuous resonant current transition modes. This series capacitor compensated for transformer resonant power converter with a high frequency transformer linked voltage boost multiplier can efficiently work a novel selectively-changed dual mode PFM control scheme in order to improve the start transient and steady-state response characteristics and can completely achieve stable zero current soft switching commutation tube filament current dependent for wide load parameter setting values with the aid of two lossless inductor snubbers. It is proved on the basis of simulation and experimental results in which a simple and low cost control implementation based on selectively-changed dual-mode PFM for high-voltage X-ray DC-DC power converter with a voltage multiplier strategy has some specified voltage pattern tracking voltage response performances under rapid rising time and no overshoot in start transient tube voltage as well as the minimized steady-state voltage ripple in tube voltage.

抄録全体を表示

A 4H-SiC pin diode with improved termination named mesa JTE has been developed and a high blocking voltage of 6.2kV and a low V_F of 4.7V at 100A/cm² have been achieved. A developed diode has an excellent trade-off between the blocking voltage and on-state voltage superior to the trade-off limit of the commercialized Si pin diodes. By evaluation of forward characteristics, a developed diode has 5 to 10 times lower differential resistance than that of a commercialized 4.5kV Si diode.

抄録全体を表示

This paper proposes a new circuit configuration for a position-sensorless drive system using an interior permanent magnet synchronous motor (IPM motor) rated at 3.7kW. The configuration can decrease the number of the sample and hold circuits to four, though fourteen sample and hold circuits are required for the conventional system. In addition, the configuration makes it efficient to detect current variations. It is shown experimentally that the drive system has good position estimation characteristics with absolute and relative errors within ±2 deg and ±0.5 deg in electrical angle, respectively. Moreover, the position control response is improved by adding current control loops to the position-sensorless drive system.

抄録全体を表示

A novel controller based on the Sliding Mode (SM) approach is designed for controlling a permanent magnet synchronous motor (PMSM) in a servo drive. After analyzing the classical SM controller, changes are made in the controller design such that its performance is substantially improved. To improve the controller performance in steady state (zero error positioning) an integral block is added to the controller resulting in a new controller configuration, which we call Sliding Mode Integral (SMI) controller. The new controller is tuned based on the results from parameter identification of the motor and the working machine. To cope with model parameter variations, especially unpredictable friction changes, gain scheduling and fuzzy based adaptive techniques are used in the control algorithm. Experiments and simulations are carried out and their results show a high performance control. The new controller offers very good tracking; it is highly robust, reaches the final position very fast and has a large stall torque. Furthermore the application of the SM ensures reduction of the system order by one. For comparison, the new controller's performance is compared with that of a PI controller. From the experimental results it is obvious the superiority of the new proposed controller.

抄録全体を表示

Regarding environmental and energy issues, increasing importance has been placed on energy saving in various systems. To save energy, it would be desirable if the total efficiency of various types of equipment were increased.Recently, a hybrid electric vehicle (HEV) and an electric vehicle (EV) have been developed. The use of new technologies will eventually lead to the realization of the new- generation vehicle with high efficiency.
One new technology is the variable-speed drive over a wide range of speeds. The motor driving systems of the EV or the HEV must operate in the variable-speed range of up to 1:5. This has created the need for a high-efficiency motor that is capable of operation over a wide speed range.
In this paper, we describe the concept of a novel permanent magnet reluctance motor (PRM) and discuss its characteristics. We developed the PRM, which has the capability of operating over a wide speed range with high efficiency. The PRM has a rotor with a salient pole, which generates magnetic anisotropy. In addition, the permanent magnets embedded in the rotor core counter the q-axis flux by the armature reaction. Then, the power density and the power factor increase. The PRM produces reluctance torque and torque by permanent magnet (PM) flux. The reluctance torque is 1 to 2 times larger than the PM torque. When the PRM operates over a constant-power speed range, the field component of the current will be regulated to maintain a constant voltage. The output power of the developed PRM is 8 to 250kW. It is clarified that the PRM operates at a wide variable-speed range (1:5) with high efficiency (92-97%).
It is concluded that the PRM has high performance over a wide constant-power speed range. In addition, the PRM is constructed using a small PM, so that we can solve the problem of cost. Thus, the PRM is a superior machine that is suited for variable-speed drive applications.

抄録全体を表示

This paper describes a control strategy to realize grasping and cooperative motion in multiple mobile manipulators. In the general approach, the stable grasping motion is well realized, but the emergent motion such as the obstacle avoidance motion and the collision avoidance motion among the robots are not taken into account in the cooperative motion of multiple mobile manipulators. In the practical application, however, the above issue is important to realize an adaptive and sophisticated motion. The proposed approach introduces the null space motion based on the grasping matrix and the absolute position of target object in the grasping motion of the manipulator. In this case, each motion of mobile manipulator is given independently of the grasping and the cooperative motion, and the emergent motion is determined arbitrary. This is one of the remarkable features of the proposed strategy. Several numerical and experimental results show the validity of the proposed approach.

抄録全体を表示

This paper proposes an anti-windup starting-time control strategy for a First-Order-Plus-Dead-Time Model.The PID controller with Proporional-Band (PB) displays much smoother set-point tracking performance.However, the desirable small value of PB will cause the inferiorority of stability performance.On the other hand, Two-Degree-Of-Freedom (T-DOF) control system is very appropriate to employ tracking and stability performance independently.For a T-DOF, if input saturation is considered, it will restrict the closed-loop performance due to the reference model should satisfy the linear range for a stationary condition.This paper focuses on the characteristics of PB and T-DOF simultaneously for a starting-time of plant.The proposed method has been successfully in computer simulations and experiments applied to an extruder temperature control system despite disturbances under the switching point for the control algorithm.

抄録全体を表示

A swinging leg of a biped robot landing, impact force usually occurs between the sole and the ground, and then it causes instability of the gait. The paper describes the advantages of adopting redundant legs to the robot in order to conquer the difficulty, and proposes a novel way of the motion control for the redundant legged biped robot.
In general, each leg of a conventional biped robot consists of 3 joints, namely, hip, knee and ankle in the sagittal plane. On the other hand, the proposed robot has been added extra joints, and thereby has redundancy in terms of degrees-of-freedom. Since the redundant leg can select its arbitrary posture, regardless of the tip position, the structure enables to move the position of the center of mass (COM) of the leg independently. The impact force is suppressed by controlling the COM acceleration of the landing leg. In order to achieve the decoupled motions between the tip and the COM, the unified decoupling controller is introduced. The controller includes three types of the disturbance observers together, and both desired motions are realized consequently. The validity of the proposed approach is confirmed in physical experimental results.

抄録全体を表示

In recent years, a resonant snubber to minimize switching power losses and EMI noises have attracted special interest for the voltage-fed soft switching sinewave PWM inverters and active rectifiers. The authors have discussed the performance evaluations on lower noise and high efficiency for two switch auxiliary resonant DC link snubber assisted three-phase voltage-fed soft switching PWM inverter. It was proved that cost effective three phase soft switching inverter treated here is able to improve both efficiency and EMI noise. However, some practical problems to be improved have recognized for the soft-switching three phase PWM inverter treated here from a practical point of view. This three phase soft-switching inverter with two switch type auxiliary resonant DC link snubber has significant disadvantages of DC busline link voltage reduction for the existence of the zero voltage mode transition period as well as the larger size and physical volume of electrolytic capacitor incorporated into the resonant DC link snubber. The additional technology to minimize the busline DC link zero voltage period in order to overcome the practical problems mentioned above is newly proposed in this paper. From experimental and simulation viewpoints, the modified version of this soft-switching inverter is discussed and evaluated for the DC busline voltage utilization factor as compared with the previously developed one.

抄録全体を表示

This paper focuses on a stator-core and rotor-core losses compensation technique devoted to a direct field-oriented control system of an induction motor incorporating parameter identification. The fundamental control algorithm is based on direct field orientation, which essentially requires rotor flux estimation using several motor parameters and detection of line currents and a rotor position. In order to suppress the flux estimation error caused by parameter mismatches, the magnetizing inductance and the rotor resistance are identified insensitively to the stator resistance by utilizing instantaneous reactive power. However, due to a model mismatch associated with the stator-core loss and rotor-core loss, neither the field orientation nor the parameter identification can be achieved as is expected, which mainly results in degradation of flux and torque control accuracy. This paper describes characteristics of the motor parameters precisely measured under various operating conditions, the influence of both stator-core loss resistance and rotor-core loss resistance on the field orientation and the parameter identification, and a compensation technique to obtain higher controllability than conventional field-oriented control techniques. Effectiveness of the proposed technique has been examined through experimental tests as well as computer simulations, and the absolute accuracy and linearity of the motor torque has been improved as a result.

抄録全体を表示

This paper presents methods to determine the operational impedance of rotating machines by Fourier Transformation of the voltage and current measured when a step (or pulse) voltage is applied to the two stator winding terminals. These standstill tests using a small-capacity DC power supply unit are tentatively named the DC Testing Method. We also describe in detail the case using a DC power source with ripple and the case in which a step (or pulse) voltage is applied with current flowing. These methods are applied to a 5.5kW squirrel-cage induction motor having semi-closed rotor slots. The validity of the proposed prediction methods is demonstrated by comparing the calculated and measured speed characteristics of the tested induction machine.

抄録全体を表示

This papaer describes the magnetic properties of wound-core type three-phasetransformer. In the analysis, magnetization characteristics are approximated by a Fourier-series, and it is assumed that the eddy current factor is proportional to the time-varying magnetic flux. Moreover harmonic balance method where the zero-phase-sequence and third harmonic components of flux density are taken into consider is used.
From the results of numerical analysis, the influences of operating flux density, dimension ratio and construction of the core on the magnetic properties of wound-core type three-phase transformer are discussed. The results of the analysis were confirmed by the experiments. The results obtained will be useful in the design of wound-core type three-phase transformer.

抄録全体を表示

This paper proposes a novel three-phase power distribution system feeding trapezoidal voltages to various power electronic loads with diode rectifier front-ends. The network distributes trapezoidal voltages generated by synchronous superposition of wave-shaping voltages onto sinusoidal voltages available from a utility power grid. The power distribution by the trapezoidal voltages allows reducing harmonics of the line currents without electronic switching devices because of a spontaneously widened conduction period of the current waveforms. The reduction of the harmonic currents also contributes to improve total power factor at the load input terminals and efficiency of the power transmission cables. Since the diodes of the rectifiers successively commutate the trapezoidal waves during periods of their flat parts, not only total harmonic distortion of the currents is improved, but also voltage ripple across the dc-buses of the rectifiers can effectively be reduced with less filter capacitors. In addition, the system offers an uninterruptible power supply function by immediately changing its outputs from the wave-shaping voltages to the trapezoidal voltages when interruption occurs in the power grid. In this paper, a prototype of the system is experimentally examined from various angles of operating characteristics and test results are presented to prove feasibility of the proposed system.

抄録全体を表示

This paper shows a novel design method of MAGNAGAP Linear Motor (MLM) which is a type of inductor linear motor. The MLM has several disadvantages of the shortage of thrust and the increase in cogging force with thrust. First, in order to improve the maximum thrust and the motor constant, the design method proposes optimum armature structure which may be calculated with a new presented design approach, halbach magnet array and trapezoid shaped inductor teeth. Then, in order to reduce the cogging force without decreasing in the maximum thrust and the motor constant, the design method proposes armature structure which may cancel the cogging force. Finally, in order to verify the effectiveness of the design method quantitatively, the characteristics of a prototype MLM are measured.

抄録全体を表示

A measurement system of the high voltage power line without using an expensive insulation has been developed. The equipment is directly attached to the power line and floated in the air to insulate from the ground. In this paper, a ±5 V dual outputs power supply for the floating measurement system is presented. The power supply obtains energy from the current in the high voltage power line using an induction coil. The AC voltage induced by the coil is greatly changed from several volts to several hundred volts by the current in the high voltage power line and by the load of the power. Then, the AC voltage is roughly converted around 5 V by an AC-DC converter in order to absorb this large fluctuation of the AC input voltage. After that, the regulated ±5 V is supplied by a dual output DC-DC converter.
By using the proposed power supply, it is confirmed that, the floating measurement system can monitor the signal of the power line current ranging from 50 to 300 A. The excellent characteristics are obtained by the steady-state and transient experiments of the proposed power supply.

抄録全体を表示

This paper proposes to paste non-magnetic materials on the rotor surface of a cylindrical brushless DC motor and to use the model including the extended e.m.f. for sensorless control. In the proposed method, the inductance changes depending on the rotor position because of eddy currents, which flow on the non-magnetic material at high frequency. The rotor position can be estimated at standstill and at low speeds. The simulation results show that the proposed method is very useful.

抄録全体を表示

A single-phase voltage-doubler rectifier using pump circuits is presented. This can be operated in the switching states for pumping action to pump twice the peak supply voltage onto the output capacitor and for forcing the input current to follow its sinusoidal reference in the vicinity of a zero crossing of the supply. The arrangement tested, using two dual-switch power modules with IGBTs and a controller for output voltage regulation, is implemented to investigate the operation. The experimental results confirm that the input current can be waveshaped sinusoidally with a near-unity power factor under the output voltage duplication.

抄録全体を表示