Performance improvement of induction motor speed sensor‐less vector control system using an adaptive observer with an estimated flux feedback in low‐speed range

Because of various errors caused by the dead time of an inverter, temperature variation of resistances, and so on, speed estimation error is inevitable in speed sensor‐less vector control of an induction motor. In particular, the speed control loop becomes unstable at near‐zero frequencies. In order to solve these problems, this paper proposes a novel design of an adaptive observer for speed estimation. By adding a feedback loop of the error between the estimated flux and the flux command, the sensitivity of speed estimation and primary resistance identification is improved. The proposed system is analyzed and appropriate feedback gains are derived. Experimental results showed good performance in the low‐speed range. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 169(3): 33–46, 2009; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20909     

Reduction of cyclic speed change using a bandpass filter for compressor PMSM sine‐wave position sensorless drives

Position sensorless vector control has been applied to compressor drive systems using an IPMSM to realize higher efficiency. In this paper, reduction control of cyclic speed change is proposed in order to achieve improved performance, including low vibration and low acoustic noise. Designing a speed estimator by using an adaptive observer with a wide frequency band, the fundamental frequency component of the cyclic speed change is calculated by a bandpass filter. The proposed compensation method recognizing the fundamental component can reduce the cyclic speed change to an acceptable level. The principle of the compensation method is presented along with experimental results. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 169(4): 75–84, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20765     

Experimental proof of voltage‐current waveform sensor output of resin molded type for measurement of power factor and harmonics in general power distribution system

We have proposed a voltage‐current sensor of resin molded type for measurement of the power factor and harmonics. To understand the characteristics of the conventional prototype sensor and the problems of its practical use, we conducted a finite element analysis. Problems involving the cost and practical usage of the sensor were identified. Therefore, we have redesigned the prototype sensor, incorporating the current sensor designed on the basis of the FEM and a ready‐made voltage sensor. In this paper, we describe feasibility field experiments with the present sensor in a practical 6.6‐kV distribution system and show that the sensor can measure the power factor and harmonics of horizontal and vertical power line systems successfully. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(3): 1–10, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21213     

Noncritically phase matched mid-infrared generation in AgGaSe2

A tunable mid-infrared optical parametric oscillator has been demonstrated using a noncritically phase matched AgGaSe₂ crystal with pump wavelength tuning. Average power experiments have generated several hundred milliwatts of 2.63 and 3.71 μm radiation using a high-repetition-rate, multiwatt 1.54 μm pump source. Interferometric measurements of the AgGaSe₂ crystal during operation indicated only minor thermal lensing     

High‐mobility oxide TFT for circuit integration of AMOLEDs

Abstract— A high‐mobility and high‐reliability oxide thin‐film transistor (TFT) that uses In‐Sn‐Zn‐O (ITZO) as a channel material has been developed. The mobility was 30.9 cm²/V‐sec and the threshold voltage shift after 20,000 sec of a bias‐temperature‐stress (BTS) test (with a stress condition of Vg = 15 V, Vd = 15 V, and T = 50°C) was smaller than 0.1 V. In addition, a method of obtaining a stable enhancement‐type TFT, which realizes circuit integration for active‐matrix organic light‐emitting diode (AMOLED) displays has been developed.     

Flattening mechanism in thermal sprayed nickel particle impinging on flat substrate surface

The transition behavior of the splat pattern of nickel particles sprayed onto a flat substrate was investigated. Auger analysis and scanning electron microscopy observation of splats on a gold-coated substrate were examined. It was confirmed that splashing was not formed by flowing on the substrate surface from the impingement center to the periphery, but by jetting away from central disk. The etched splat surface revealed that the bottom part of the central disk of the splat solidified quite rapidly just after impingement onto the cold substrate. The splash pattern was found only in a direction perpendicular to the scratch pattern on the substrate. Therefore, it was confirmed that splashing was caused by some deterrent to the liquid flow, for example, due to effects such as poor wettability at the flow tip or initial rapid solidification of the splat. The drastic change of the splat pattern near the transition temperature seems to occur when the We number of the liquid flow coincides with some critical value. This paper originally appeared in Thermal Spray: Meeting the Challenges of the 21st Century; Proceedings of the 15th International Thermal Spray Conference, C. Coddet, Ed., ASM International, Materials Park, OH, 1998. This proceedings paper has been extensively reviewed according to the editorial policy of the Journal of Thermal Spray Technology.     

Effect of bagasse fiber on the flexural properties of biodegradable composites

Flexural modulus of the press‐molding composites made from bagasse fiber and biodegradable resin was investigated by experiment and numerical prediction with Cox's model that incorporates the compression ratio of the bagasse fiber in the cross section. The effect of the volume fraction of bagasse fiber and its length on the flexural modulus was examined. Up to 65% volume fraction in the experiment, the flexural modulus increased with increase of the volume fraction of the bagasse fiber. The numerical prediction was in good agreement with the experimental result. Above 65% volume fraction, however, the flexural modulus decreased in the experiment, while the prediction increased. It seemed that the biodegradable resin was insufficient to cover all the surface of bagasse fiber in the composite. Moreover, the decrease of the flexural modulus was found below 3 mm at the fiber length in the experimental and the same trend was shown in the numerical prediction. POLYM. COMPOS. 26:689–694, 2005. © 2005 Society of Plastics Engineers