Conventional position sensorless control methods for a permanent magnet synchronous motor (PMSM) in a low-speed region suffer from some disadvantages such as too much electromagnetic noise, the need for rotor saliency, and so on. On the other hand, a position sensorless method that introduces an induced voltage caused by magnetic saturation (IVMS) has already been reported(14). IVMS can be detected by an open phase of a PMSM using a block commutation drive, and it changes depending on the rotor position. The position sensor-less drive is achieved by detecting the IVMS. This method needs no rotor saliency and or harmonic injection. However, this technique has a disadvantage. Because the IVMS is a very small voltage, it is eliminated by a reversal direction electromotive force (EMF). It is difficult to achieve a reversal rotation drive in a low-speed region. To solve this problem, we introduce a PWM pulse shift to the low-speed region. With this method, both the normal and reversal direction IVMSs can be detected and the bidirectional drive is achieved. We implemented this method by using a 16-bit microcomputer and an FPGA with a 20kHz carrier frequency. Moreover, excellent drive performance in the low-speed region was obtained in the experiments.
The optical image stabilizer (OIS) system using a voice coil motor (VCM) has recently been widely adopted in digital cameras to minimize blurring and provide image stabilization. Since customers buying digital cameras with an OIS are concerned with the noise level in addition to the primary performance, camera manufacturers have been making efforts to reduce acoustical noise. This paper proposes an electromagnetic-structural-acoustic coupled analysis method that uses the FEM; measurements were carried out for verification. The proposed method was used to redesign the cover structure of the VCM to reduce acoustical noise.
This paper proposes a new sensorless vector control method for energy-efficient and wide-speed-range drives of sensorless permanent-magnet synchronous motors. The proposed method has the following features: 1) current limitation. 2) high efficiency, 3) wide-speed-range drive under voltage limit. These features are realized in a very simple manner and can perform adaptively in all sensorless driving modes including motoring/regenerating and steady/transient states. The usefulness of the proposed method is verified by extensive experiments.
Ultra-high-speed motors over 1,000,000rpm have been developed for high-speed compressors and electric turbo-chargers, and these motors demand a higher frequency and sinusoidal current waveform over 10kHz. For example, a three-phase inverter with above 100-kHz switching operation is needed to supply these motors with a 10kHz sinusoidal current waveform. A circuit implementation of a high-frequency-switching three-phase PWM inverter is applied by separating heat sinks. Therefore, this paper focuses on a three-phase inverter using a Si-MOSFETs and SiC-SBD to realize switching operation above 100kHz and discusses both the loss analysis and thermal resistance. Moreover, a laboratory system of the three-phase PWM inverter focused on a cooling structure is produced with separating heat sinks. Finally the experimental results for 300-kHz switching operation rated at 300V and 3.2kVA are presented to verify the separating heat sinks structure.
To improve the active safety of a vehicle, advanced vehicle dynamics control is required. A lateral tire force sensor (LTFS) can directly measure the lateral force that is acting upon a tire. In this study, the measure performance of the LTFS was quantified on the basis of the measurement period, time delay, and resolution changes due to quantization error and jitter. The effectiveness of the acceleration error correction method is verified by simulation and experiment. A novel yaw-rate control method using an LTFS and yaw moment observer is proposed, the method is verified by simulation and by actual implementation on an experimental electric vehicle.
During peak seasons, Shinkansen station platforms are considerably congested because many passengers stay in queues to board a train. It is essential to estimate effective countermeasures so that passengers can board and alight from trains smoothly and trains can depart without delays. In order to estimate the countermeasures in advance, we have developed a multi-agent simulator, in which not only a passenger but also the baggage is expressed as an agent. In this paper, we present the structure of the simulator and show the results of numerical analysis for several different types of passenger alignments and the influence of platform screens to the times of boarding and alighting.
In this report, we adopt metal cores made of amorphous metal (2605SA1, Metglas, Inc) to minimize the iron loss in electrical motors, and compare the efficiency improvement with that obtained with electrical steel cores. First, we measured the iron loss of the cores by the improved exciting current method and the H coil method and found that the iron loss of the amorphous metal core is about one-fifth that of the electrical steel core. Then we built 11kW output motors with each type of core and compared the efficiencies. The efficiency improvement with the amorphous metal cores is 1.5% at the rated power and speed.
This paper presents a manual train operation assistance method for limiting braking power to avoid regeneration cancellation and to save train operation energy. This assistance system consists of on-board computers and interface devices. The braking assistance command is generated from a “dictionary” prepared to increase regenerated energy without any extension of train running time. In order to consider the power limitation and resolve assistance operation problems in terms of the operation delay time, this method was evaluated on a revenue service line. This paper proposes a “best effort method” for energy-saving train operation that does not use the conditions of other trains since train drivers cannot obtain information on the actual status of other trains in present railway systems. On-track tests showed that the power-limiting brake was effective on energy-saving for a train operation. The practical problem of the man machine interface for driver assistance was also intensively studied.
This paper presents a method for analyzing the settling response to the deterioration of ball bearings, such as fretting damage, of a galvanometer scanner. A galvanometer scanner is a type of swaying motor used in laser-drilling machines. It is able to position a laser at more than 2400 points per second with a positioning error of less than 3μm. Analysis of the settling response is important to the precise positioning of galvanometer scanners. The settling response of the galvanometer scanner was decoupled into each vibration-mode component through Prony analysis. This experimental modal analysis method was used to detect modal parameters from the time series data. The vibration modes from the pole-zero configuration of a closed-loop system where normalized frequencies was near the first torsion mode were caused by changing the frequency response characteristics of the controlled object. A galvanometer scanner with fretting damage to its ball bearings was analyzed using this method, and the relationship between the position error of the settling responses and the deterioration of the ball bearings was quantified by focusing on the initial amplitudes of the overdamping modes.
In this study, we evaluate the losses of a 1-MW-class induction motor at the inverter feeding. We propose a loss calculation method using the resistivity of the bars based on an expression of the motor characteristic and measured results. Then, we separate the losses into no-load iron loss, stray load loss, and time-harmonic loss by the inverter feeding. The results show that the measured and corresponding calculated losses agree well. Then, it is clarified that the secondary harmonic loss is especially large. In addition, we reveal that the time-harmonic losses are caused by the magnetic flux of the carrier harmonics, which passes through the surfaces of the secondary bars by a calculation considering the carrier-harmonic currents.
Our research focuses on the bio-signal and multimedia signal processing. Especially, we focus on the brain machine or computer interface, KANSEI analysis, objective evaluation for riding comfort, taste, how to feel, like/dislike, interests, sleepiness, fast face tracing, emotional detection and detecting the sounds direction of array.