This paper describes a the position sensorless vector control system for PMSM in the inverter overmodulation drive. Operating PMSM in the inverter overmodulation range achieves a fast torque response and widens the high-speed drive region of PMSM. However, in the overmodulation range of the inverter, harmonics voltage/current affect not only the closed loop current control system but also the position/speed estimation system and then become unstable in the worst case. To solve this problem, the authors propose a position sensorless control system with harmonic estimator to compensate for the harmonics components.

In this paper, focusing on the position estimator, the effectiveness of the proposed system is demonstrated by discussion about the problem of the conventional system and is evaluated by several experiments.

This paper is organized as follows. First, the problems of the conventional position estimation methods in the overmodulation range are described. Next, two approaches for improving position estimation in the overmodulation range are compared. Lastly, the effectiveness of the proposed method is confirmed through several experiments.

This paper presents a new sensorless vector control method for permanent-magnet synchronous motors (PMSMs) that employs discrete-time high-frequency voltage injection. The frequency range of the injected voltage is almost the same as that of the pulse width modulation (PWM) carrier of the voltage command. This allows high-speed phase estimation and a high-performance drive, and possibly low acoustic noise caused by the injected voltage. The high-frequency current corresponding to the injected voltage is analyzed in discrete time. Conventional phase estimation methods that employ continuous-time voltage injection are reconstructed by means of the analyses. The reconstructed methods are characterized by high-speed phase estimation, high-performance drive, and high robustness against motor parameter variation. The usefulness of the proposed method is verified through extensive experiments.

Galvano scanners are used as laser beam scanners in laser drilling machines. The mirror of the galvano scanner has vibration modes not only in a rotational direction but also in an inclined direction. Vibration in an inclined direction causes an error in the positioning of the laser spot in the direction perpendicular to the position. In multiple steps of motion, vibration is excited by an unbalanced moment of the mirror, thus degrading the positional accuracy. This paper proposes a feedforward input design method to reduce vibration in the inclined direction. The effectiveness of the proposed method is shown by simulation.

As a simple sensorless vector control method for permanent-magnet synchronous motors (PMSMs), a power-factor-based vector control (PFVC) method has been reported. This method has the attractive characteristics that three functions such as current limit, efficiency and sensorless drive can be performed simultaneously in a simple manner. However, it was developed under the assumption that there is no practical voltage limit, and that it cannot be applied over the rated speed. This paper proposes a new PFVC method that allows PMSMs to be driven even over the rated speed under application of a practical voltage limit, while keeping the desired characteristics. The effectiveness and usefulness of the proposed method are verified through extensive experiments.

In this paper, a new hybrid-excited motor is proposed. Its unique feature is that it has no field exciting coil, despite being a type of bypass yoke core (BYC) hybrid-excited synchronous motor. Based on finite element analysis (FEA), the following facts are clarified. Since the stator coil magnetomotive force (MMF) and claw poles rotate at the same speed and in the same direction, they are motionless relative to each other. Since the claw poles are located at one of its ends near the BYC surface with a gap, it receives immovable magnetization by the stator coil MMF through the BYC; then the claw poles can supply a magnetic field flux via the BYC. This flux via the BYC increases the total torque, because its torque is added the two other torque components: the permanent magnet torque and claw poles reluctance torque. In addition, the magnetic polarity and the amount of the flux of the claw poles can be varied by controlling the armature current phase angle.

This paper presents a new method of determining the causes of faults by using decision tree analysis. These days, the high economic growth in Japan has led to a rapid increase in the number of customers receiving high voltages (i.e., > 50kW electric facilities). Therefore, the maintenance of these facilities has become important from a power quality point of view, and electric facilities for private use install an insulation level monitoring device to detect the leakage current from an electrical fault. The insulation level monitoring device detects the leakage current based on threshold current of 50mA. Usually, faults are detected by combining analytical elements of the threshold or majority decision method. However, these methods cannot achieve high accuracy without the optimal threshold being defined.

In this paper, we propose a new method for determining the causes of faults by using decision tree analysis with an insulation level monitoring device. We compared the differences in the accuracy among the threshold method, majority decision method, and decision tree analysis. We found that decision tree analysis can determine the optimal threshold to classify the fault cause. By repeating this method in multiple stages, the optimal threshold of each fault cause can be determined more accurately.

In this paper, we propose a modeling method for an engine combustion system by applying the approximated Gaussian process regression. We model not only the output behavior of the combustion system, but also the uncertainty evaluation for the output estimation. The experimental results show that the proposed method achieves almost the same level of modeling accuracy, while more efficiently reducing the computational cost than previous methods. Finally, we applied the constructed models and their uncertainty evaluations to control input design. For given desired outputs, we find the corresponding inputs of the engine system using the models and their uncertainty evaluations.

There are two types of the transformers in a contactless power transfer system: solenoid type (H-shaped) and circular type transformers. These two types of transformers are not compatible because their magnetic field structures are different. An Hc type transformer that is compatible with both transformer types has been proposed. The Hc type receiver adds a central magnetic pole by dividing the winding coil of the H-shaped receiver. The Hc type receiver can change the magnetic field structure by changing the connections of the divided windings and can receive power from both types of transmitters. In this study, we conducted a circuit analysis and evaluated the performance of the Hc type transformer.

This paper describes a design method for the inductor of a vehicle. The number of air gaps and their positions affect the magnetic characteristics of the inductor. This paper clarifies the effect of the air gap distribution. Based on the result, a design strategy for the air gap distribution is proposed.

Multi-degree-of-freedom (multi-DOF) actuators have been developed for the fields of robotics and industrial machinery. However, evaluation methods for the multi-DOF actuators have not been proposed. In order to evaluate the characteristics of the actuators, an evaluation method based on a torque equation and singular value decomposition is proposed. The evaluation method can be used to evaluate the torque characteristics using a torque area that is composed of an absolute torque and its direction. Finally, the static torque characteristics of some previously developed multi-DOF actuators are evaluated using the proposed evaluation method.

A wind power generator system without a control circuit that uses a three-phase voltage-doubling rectifier circuit was proposed previously. The proposed generator system can achieve maximum power output of wind turbines. In this letter, the validity of the proposed generator system is shown by the results of a comparative simulation of the generation characteristics of the proposed control-circuit-less method and the MPPT control method.