This research aims to develop a compact synchrotron dedicated for proton beam therapy using a scanning irradiation method. The effective length and magnetic uniformity of the bending magnets in the synchrotron were analyzed by 3D static magnetic field calculations. The calculation results indicate that the shape of the bending magnet satisfies the specification for beam stability. A push-pull multi-feed driven technique allows shortening the length of the FINEMET RF acceleration cavity for the synchrotron from 600mm to 450mm. The circumference of the synchrotron is 18m, which is the world's most compact size for proton beam therapy.

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Base vibration suppression is important to achieve fast and accurate positioning control for industrial machines. It is known that an active mass damper (AMD) is effective for reducing vibration. However, the effect of the AMD is limited because reducing the weight of the additional mass causes an increase in its movement range. This paper proposes an additional mass control system and a quantitative design method that considers the additional mass weight, moving range, and vibration suppression effect for reducing the size and weight of the AMD. The proposed method adds the position control result of the additional mass to the driving force command of the moving part, and it allows the moving part to assume new driving force commands. Experimental results of the assembly machine show that the proposed method can constrain the moving range of additional mass, and it can achieve the expected vibration suppression effect.

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A new structure and control method for a variable magnetic flux motor (VMFM) is proposed to achieve a high-efficiency electric vehicle (EV) motor drive under a wide range of conditions. A VFMF prototype that was designed by considering the loss was manufactured and evaluated in an experiment. The prototype demonstrated low iron loss and sufficient max torque. Thus, the prototype can provide a high efficiency drive with low output, which is frequently the case for EVs. Map control enables a wide phase angle for the vector-control drive of the VMFM under a changing magnetic flux. Thus, the VMFM provides a high-efficiency drive under a wide range of conditions.

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This paper aims at minimizing capacitor-voltage fluctuations inherent in a modular multilevel cascade inverter based on double-star chopper cell (DSCC) or a modular multilevel DSCC inverter. The inverter can drive an induction motor loaded with a quadratic-torque load. Both theoretical analysis and numerical calculation reveal that the voltage fluctuations can be minimized when the ratio of a magnetizing-current component with respect to a torque-current component in the motor current is set to unity, regardless of the motor mechanical speed. A three-phase DSCC inverter is designed and constructed to drive a 380-V, 15-kW, 50-Hz, four-pole, induction motor loaded with a quadratic torque that is proportional to a square of the motor mechanical speed. Experimental results confirm the validity of the theoretical and numerical calculations.

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We studied vibration power generation using piezoelectric elements in order to determine effective rectification methods to increase harvested energy from vibration power generation systems. First, we experimentally clarified the output characteristics of two kinds of passive rectification methods for vibration power generation systems. Then, an appropriate rectification method for various kinds of loads was studied. In order to increase the harvested power from an integrated vibration power generation system with multiple piezoelectric elements, we considered an appropriate circuit structure for connecting multiple piezoelectric elements. The effectiveness was verified experimentally.

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In this paper, a discretization error compensation method in a motor drive system by using direct torque control (DTC) is proposed. Similar to a conventional current control system, DTC allows an efficient drive and a wide range drive. Furthermore, it has the advantage that its control system can be simple and theoretically it can realize sensorless position control. Therefore, a reference flux vector calculator (RFVC) DTC is studied as a system for the ultra-high-speed drive control of permanent magnet synchronous motors (PMSMs). In high-speed drive, we revealed that a discretization error in the DTC generates an error in the instruction magnetic flux and stator magnetic flux. In addition, we revealed that current detection timing generates an error in the estimated torque and real torque. Then, we propose a compensation method to cancel the flux and torque error focusing on the phase of the stator magnetic flux and experimentally verifying its effectiveness.

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Serious defects may occur in metallic tubes used in factories and power plants owing to long-term usage. Until now, various non-destructive inspection (NDI) methods have been proposed to prevent accidents caused by deformation. However, these conventional methods require longer detection times for very long tubes. Therefore, to overcome this limitation, we propose a new detection method using electromagnetic wave propagation characteristics. In the proposed method, metallic tubes are regarded as waveguides, and we can detect defects based on the propagating electromagnetic waves. To verify this method, we conducted experiments using a vector network analyzer. As a result, we found that the proposed method is effective for detecting defects such as foreign matter and cracks, and for estimating the location and direction of the cracks. Furthermore, the proposed method is effective even if there is a bend or a branch in the metallic tubes.

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This study examines the behavior of a vehicle at a merging section in a PRT system. A vehicle arriving at a merging section must wait before entering if no vehicle is present in the other line such that it connects with a vehicle in the other line. In this merging section, an arbitrary different restriction number of waiting vehicles is given to two inflow lines, respectively. The mean queue lengths of the two inflow lines are explicitly derived.

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This letter proposes a self-excitation method for diversion of static-excitation synchronous generators such as automotive alternators. In the proposed method, a voltage doubling rectifier circuit is used to start a synchronous generator at practical rotational speed through the residual magnetism of its rotor. An experiment was performed assuming a diversion of an automotive alternator, and it was possible to configure the proposed method where only three components were added by sharing the internal components of the alternator. Finally, it was confirmed that the proposed method could generate the output voltage by the demonstration experiment at approximately 1400rpm.

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