Maximum torque per flux control strategy used for high-speed operations causes instability in direct-torque-controlled IPMSM drives. Therefore, some reference calculation methods in direct torque control have been reported for high-speed operations. This paper compares the features of controls using each calculation method and considers the influence of inductance variation in simulations and experiments.

Pumps are commonly used to supply and distribute water as the basic facilities in domestic water and sewage service businesses, which have aging facilities, have a shortage of experienced technical personnel, are experincing a dire financial situation, and so on. Since pump failure has a significant impact on plant operation, online monitoring technology is expected to improve the efficiency of diagnosis and inspection. This paper proposes a method for quantifying pump performance to monitor pump degradation by using online monitoring data accumulated with a supervisory control and data acquisition (SCADA) system. The proposed method estimates the performance of each pump from the measured values at the confluence of pipes with the least-squares method and respective on-off signals. From the viewpoint of practicality, the accuracy and usefulness of the proposed method were evaluated by the data acquired from the actual water supply system and the results generated by computational simulation.

Railway operating companies must prepare rolling stock schedules to realize train operations during a timetable revision. Companies create a roster, which includes a series of trains to be considered by the particular rolling stock with inspection interval constraints. In some Japanese railway lines, splitting and combining operations are often used to adjust the transportation capacity flexibly. However, shunting operations of splitting and combining are necessary under such operational conditions. These operations are labor-intensive and time-consuming, necessitating a reduction in the amount of splitting and combining. In this paper, we present a rolling stock scheduling based on a mixed integer linear programming model to reduce the amount of splitting and combining. Computational experimental results are presented based on real instances of several railway lines in Japan, indicating the computational effectiveness of the methodology.

Robust stable feedback (FB) controller design against plant perturbation is crucial for industrial servo systems. However, since the controller parameter design generally requires expert skills and/or considerable labor by engineers, an autonomous controller design technology would be promising. This paper presents an efficient autonomous design method that optimizes the parameters of a cascade structure FB controller to achieve robust stabilization. Conventionally, robust stabilization is realized by imposing stability constraints on all the perturbed plant model sets in a parameter optimization problem. As a result, the design time would be much longer owing to the complicated optimization problem. The proposed method makes the parameter optimization considering robust stability more efficient than the conventional method, by simplifying the stability constraint definition and optimizing the specified circle radius for the stability constraint based on a bisection method. The effectiveness of the proposed method is evaluated through an example FB controller design for a laboratory galvanometer scanner.

A new equivalent circuit model based on flux linkages is proposed for a permanent magnet synchronous motor (PMSM), in which the dependence of the amplitude-modulation-ratio is introduced into an inductance connected in series with an iron loss resistance to accurately consider iron losses due to carrier harmonics in a wide speed range. Additionally, the stator end-winding leakage inductance is considered in the equivalent circuit. The effectiveness of the proposed equivalent circuit model was verified by applying it to the PMSM with concentrated winding fed by pulse-width modulation inverters in the overmodulation region.

We have been studying the application of amorphous metal with low loss to axial gap motors. However, because radial gap motors are used extensively, we are also considering a motor structure involving the application of amorphous metal to radial gap motors. In this study, we analyzed and evaluated an IPM motor to evaluate the improvement in efficiency caused by the use of amorphous metal for the entire stator cores. Creating an efficiency map of the prototype and comparing the efficiencies confirmed a significant improvement in efficiency in the low torque and high frequency bands.

Recently, iron-based amorphous metals have attracted increasing attention as suitable materials for high-efficiency motors. As a preliminaly step of research, we report the results of manufacturing iron-based amorphous cores and silicon steel cores for fan motors and comparing the motor performance depending on the cores. The load test shows that the efficiency of the iron-based amorphous core exceeded the silicon steel core at each rotation speed from 1000 to 6000min^-1. In particular, at 6000min^-1, the efficiency was higher by 10% or more when the iron-based amorphous core was used at 0.15Nm or less. Moreover, it was shown that high efficiency can be achieved by adopting an amorphous core, and that the performance changes depending on the operating conditions.

In this paper, a new type of variable-flux permanent magnet (PM) motor, named the “flux-modulating consequent pole motor (FCM)”, is proposed. The FCM is a combination of a flux-modulating (FM) motor and a consequent-pole PM motor. The torque of the FCM can be generated from both the FM and PM motors without resulting in an unbalanced magnetic force (UMF). The effects of pole combinations of the FM and PM motors on the electromagnetic performance of the FCM were investigated through finite element analysis and experiments. The results thus obtained show that the winding factors of the FM and PM motors affect on the open-circuit flux linkage and flux-regulation capability of the FCM.

In the magnetic-head positioning control system of a hard disk drive (HDD) for a data center, the disturbances caused by the cooling fans in the storage box have large gains at high frequencies. Therefore, the control system must have low gains of the sensitivity function at high frequencies so that the control system rejects these disturbances. To achieve this, we employed a resonant filter that can decrease the gain of the sensitivity function beyond the servo bandwidth or the mechanical resonant frequencies. In this paper, we proposed a design method for the resonant filter of a dual-stage actuator system in the HDD. Using the proposed method, we implement the resonant filter at high frequencies and provide comparison with the conventional design method. The design results with the HDDs for data centers show that the proposed method rejects the fan-induced disturbances at high frequencies. In addition, the designed control system can handle variations in the mechanical characteristics well with robust performance.

This paper proposes a new and general construction method for orthogonal matrices used in orthogonal transformations. The proposed method allows the decomposition and independent control of the fundamental and harmonic components contained in the multiphase signals of even-multiphase AC motors.

Our research focuses on the real-world haptics, imitation learning, functional electrical stimulation, and hydraulic actuators.