This paper overviews a traction system for Tokaido Shinkansen trains and presents a novel silicon carbide (SiC)-applied traction system of the new generation Shinkansen train, “N700S”, which began commercial service in the summer of 2020. To achieve compactness and weight reduction, N700S's traction system aimed to take advantage of the merits of SiC devices, which have a lower power loss, higher frequency, and a higher current than Si devices, not only in the conversion system but also in the entire traction system. This weight reduction and compactness allowed for flexibility in the design of underfloor equipment of the car body and enabled the realization of a lithium-ion battery self-traction system that could operate catenary-free at low speeds in the event of a power outage. It also contributed toward achieving flexibility by the easy redesign of different configurations of trains such as 8-car or 12-car sets rather than the standard 16-car trains used for the Tokaido Shinkansen, the concept of which is referred to as the “Standardized Shinkansen train”. The continuous introduction of energy-saving Shinkansen trains including N700S has also led to a decrease in Tokaido Shinkansen's energy consumption. This is the first application of an SiC device and a lithium-ion battery to a high-speed train's traction system in the world.

Nissan has developed a 100% electrified powertrain system called e-POWER, which exhibits key features such as quick response, smooth acceleration, smooth deceleration, and quietness. The quick response and smooth acceleration can be achieved owing to the 100% electric motor drive and control strategy that has been adopted from the Nissan LEAF electric vehicle and improved further. The quietness was designed and controlled using power generation control and engine speed control. A driving mode called the e-POWER drive mode was developed using 100% electric deceleration to achieve smooth and efficient deceleration with linearity and controllability.

Solar cell systems have gained increasing attention with gradual improvements in their cost and conversion efficiency. Paint-type solar cells have been proposed. Such solar cells have several advantages, including a follow-up curved surface, free shape, and a seamless aesthetically pleasing design. In general, a solar cell is fabricated based on a series of possible configurations, and the output voltage of the solar module setup can be up to several tens of volts. In applications that involve exploiting a free shape, such devices may not provide a sufficient current. Moreover, this current may then be interrupted as a result of the small cell size or partial light blockage owing to the series construction. To address these problems, DC-DC converters based on the performance of aesthetically designed solar cells have been investigated. These components can be boosted to an easy-to-use voltage for practical daily applications. In this paper, the possibility of achieving their practical use based on a prototype is discussed based on experimental data.

A high-bandwidth current controller is necessary to suppress torque ripple. To drive motors at high speeds, the reference-value-tracking performance must be guaranteed. To ensure the reference-value-tracking performance around the Nyquist frequency, the proposed method samples reference values twice more than the conventional multirate feedforward control for a second-order system. We have previously proposed a current controller based on the perfect tracking control. However, there is still room to improve the reference value tracking performance; therefore, a new approach based on the quasi multirate feedforward current control has been proposed and applied to permanent magnet synchronous motors. The proposed method doubles the tracking points of the reference current waveform compared with the conventional methods. The enhancement of the proposed approach has been demonstrateted using simulations and experimental verifications.

This study aims to present a new two-degree-of-freedom resonant actuator and its motion control method. Accordingly, the design method for this resonant actuator that resonates using its detent force without mechanical spring is proposed. In this actuator, a centering force is generated according to the moving distance, regardless of the moving direction on the X-Y plane. Using this feature, various resonance motions on the X-Y plane can be realized. This study also proves that the reciprocating motion, elliptical motion, and scroll motion can be controlled. The results of finite element analysis support the characteristics of the proposed actuator, which were compared to the results of measurements on a prototype. Finally, the effectiveness of motion control was validated through the prototype.

Bilateral control is a remote-control technique that can transmit the reaction force received by a slave as feedback to its master. However, it poses several problems; hence, bilateral control using functional electrical stimulation (FES) has been proposed as a solution. Generally, in bilateral control, position synchronization and establishing the force action-reaction are considered the control targets for an acceptable force sense transmission. In this study, bilateral control using FES based on a dynamic model is proposed to achieve position synchronization and force action-reaction. The approximation of the relationship between the stimulus value and the exerted torque by the dynamic model is expected to simplify the creation of inverse models and improve the force control performance. The results obtained through comparison with other methods indicated that the proposed method reduced the angle and torque tracking errors between the master and slave. The results also revealed that the proposed bilateral control system achieved highly accurate position synchronization and force action-reaction in bilateral control using FES.

This paper presents a cooperative optimization-based autonomous parameter design method for cascade-structure feedback (FB) controllers used in industrial precision servo systems. Designing fine parameters for a cascade-structure FB controller that realizes a wide control bandwidth is a nonconvex optimization problem owing to the nonlinear relations between the parameters. In conventional parameter design methods based on nonlinear optimization techniques, the obtained parameters strongly depend on the initial point, which requires considerable labor for trial and error-based initial point setting in industry. This paper aims to eliminate such annoyance in cascade-structure FB controller design by using the cooperative optimization technique with a simple initial parameter setting method. The effectiveness of the proposed method is verified through an example FB controller design for a galvanometer scanner, compared to a sequential quadratic programming-based parameter optimization method.

In recent years, it is required to extend the operation regions of induction motors (IMs) even at low-speed in regenerating while maintaining a high control performance. Conventional rotor speed estimation methods using an adaptive flux observer are unstable at low-speed in regenerating, particularly near the zero frequency. In this paper, we propose a simultaneous estimation method of the rotor speed and the stator resistance to improve the control performance of the speed-sensorless vector control of IMs. In addition, we prove that the proposed estimation method is stable even at low-speed in regenerating. Furthermore, the effectiveness of the proposed method is demonstrated experimentally.

Recently, permanent magnet synchronous motor (PMSM) drive systems without the rotor position sensor are widely used as actuators in many applications. However, in the case of a pulsating load such as the compressors, the rotational speed of the motors is fluctuated and the drive system is vibrated due to the pulsating load torque. In this paper, we propose a new method to reduce the rotational speed pulsation. This method can seamlessly change the vibration suppression control and the high efficiency control. The simulation results indicate that the proposed method is very effective and practical.

In recent years, more than half of the electric power generated in the country is being consumed by motors. Therefore, high performance motors are desired especially for industrial applications. In addition, it is desirable to reduce motor size. Recently, motors called axial gap type have been proposed and researched to achieve both high torque and small size. Axial gap motors are generally suitable for applications requiring flat shape such as a disk. Conventional axial gap motors frequently employ Nd sintered permanent magnets (PMs) to achieve high torque. However, axial gap motors with Nd sintered PMs are not very efficient at high rotational speed due to the eddy current loss arising in the PM. Axial gap motors that use ferrite PMs have also been proposed, but torque density is low. In this paper, an axial gap motor using Nd bonded PMs is proposed to achieve high efficiency in the high-speed and high-torque region. The proposed axial gap motor using Nd bonded PM is compared with other axial gap motors employing Nd sintered PM and ferrite PM through 3D-FEA and experiments. Consequently, it was found that the Nd bonded PM is more effective in enhancing the efficiency of an axial gap motor in the high-speed and high-torque region, compared with Nd sintered PM and ferrite PM.

This paper presents a control scheme for smooth torque production in permanent-magnet synchronous motor drives. The proposed control scheme consists of two techniques: a feedforward compensation for torque ripple minimization and an online parameter estimation technique for harmonic fluxes. The feedforward compensation is constructed on a position-sensorless vector control system and generates voltage commands to suppress torque ripples. The command calculation process requires the parameters of the harmonic fluxes; therefore, the proposed control scheme includes their estimator and calculates them from detected current information. These techniques are simpler than existing ones and can be implemented on a computational device with a small amount of calculation load. The proposed control scheme is verified by performing simulations and experiments.