Adaptive control-based high-performance drive system implementation of traveling-wave-type ultrasonic motor

In recent years, ultrasonic motors (USM) as new actuators have attracted special interest. Several kinds of constructions and characteristics of USMs have been reported so far. Of these USMs, a traveling wave-type USM has many characteristics such as: high torque in the low-speed range, large holding torque based upon frictional force, flexible free forms, compactness in size and low magnetic noise. In practice, an inherent mechanical resonant frequency and a velocity amplitude of USM are changed largely according to operating temperature due to frictional drive, load disturbance torque, and applied voltage levels. Therefore, it is necessary to develop a new control system which solves these items and always supplies the required power with high efficiency and high performance in the practical applications. This paper proposes mainly a new sensorless high-performance control scheme of an inverter-fed ultrasonic motor, which is based on a control system technology with two feedbacks incorporating automatic resonant frequency tracking and constant velocity amplitude control strategies. This control system is realized in terms of a high-frequency chopper and a two-phase series/parallel resonant inverter. The experimental results are demonstrated and discussed compared with the theoretical ones.     

A novel robust current control approach using adaptive line enhancer for three‐phase current‐source active power filter

An effective system control method is presented for applying a three‐phase current‐source PWM converter with a deadbeat controller to active power filters (APFs). In the shunt‐type configuration, the APF is controlled such that the current drawn by the APF from the utility is equal to the current harmonics and reactive current required for the load. To attain the time‐optimal response of the APF supply current, a two‐dimensional deadbeat control scheme is applied to APF current control. Furthermore, in order to cancel both the delay in the two‐dimensional deadbeat control scheme and the delay in DSP control strategy, an Adaptive Line Enhancer (ALE) is introduced in order to predict the desired value three sampling periods ahead. ALE has another function of bringing robustness to the deadbeat control system. Due to the ALE, settling time is made short in a transient state. On the other hand, total harmonic distortion (THD) of source currents can be minimized compared to the case where ideal identification of the controlled system can be made. The experimental results obtained from the DSP‐based APF are also reported. The compensating ability of this APF is very high in accuracy and responsiveness although the modulation frequency is rather low. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(1): 50–61, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20014     

Series resonant ZCS‐PFM DC‐DC power converter with high‐frequency high‐voltage transformer link for high‐power magnetron drive

This paper presents a single lossless inductive snubber‐assisted ZCS‐PFM series resonant DC‐DC power converter with a high‐frequency high‐voltage transformer link for industrial‐use high‐power magnetron drive. The current flowing through the active power switches rises gradually at a turned‐on transient state with the aid of a single lossless snubber inductor, and ZCS turn‐on commutation based on overlapping current can be achieved via the wide range pulse frequency modulation control scheme. The high‐frequency high‐voltage transformer primary side resonant current always becomes continuous operation mode, by electromagnetic loose coupling design of the high‐frequency high‐voltage transformer and the magnetizing inductance of the high‐frequency high‐voltage transformer. As a result, this high‐voltage power converter circuit for the magnetron can achieve a complete zero current soft switching under the condition of broad width gate voltage signals. Furthermore, this high‐voltage DC‐DC power converter circuit can regulate the output power from zero to full over audible frequency range via the two resonant frequency circuit design. Its operating performances are evaluated and discussed on the basis of the power loss analysis simulation and the experimental results from a practical point of view. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(3): 79–87, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20126     

Polyunsaturated fatty glyceride syntheses by microbial lipases

The degree of glyceride syntheses by lipase TOYO (Chromobacterium viscosum) and lipase OF (Candida cylindracea) using individual free fatty acids C_18∶1, C_18∶2, C_18∶3, C_18∶4, C_20∶4, C_20∶5 and C_22∶6 were compared. Lipase TOYO incorporated each of the fatty acids into glycerol at levels of greater than 89%. Lipase OF incorporated most of the fatty acids at levels above 70% (docosahexaenoic acid incorporation was 63%). It was concluded that these two lipases are feasible for producing glycerides from unsaturated fatty acids.     

Visualization of Knoop Indentation Damage of Silicon Nitride by Plasma Etching

A visualizing technique for indentation damage of ceramics was developed. Plasma etching was used to enhance the view of cracks and the subsurface microcracking crush zone following Knoop indentation of hot pressed Si₃N₄. The microcracking zone was readily identified from the surface view of the indented surface as a grain-falling-off region (GFOR), defined as a region in which grains were removed by preferential etching using CF₄ gas, followed by ultrasonic cleaning. A fissure-like opening corresponding to the indentation cracks was also observed. It is inferred that the formation of the GFOR region and the fissure-like opening were caused by the etching/cleaning treatment. Meanwhile, the etching on a section which included diagonals of the impression provided a section view of the microcracking zone.     

Optical sensing of materials movements occurring at a plant surface with a probe beam

Optical sensing of materials movements across a plant surface with a probe beam is reported. It is based on monitoring of deflection of a probe beam passing through a vicinity of the plant surface. The deflection of the probe beam was caused by concentration gradients of chemical species involved in the materials moments in physiological activities of the plant. Typha angustifolia L. was used as a model plant. The beam deflection at different locations of both leaves and roots in respiration process were monitored and compared. It is found that deflection signals changed with time and locations. Experimental results showed that the beam deflection method could be used for noninvasive sensing and monitoring of materials movements across the plant surface.     

Dual-Mode Time-Sharing Sinewave-Modulation Soft Switching Boost Full-Bridge One-Stage Power Conditioner Without Electrolytic Capacitor DC Link

This paper is aimed at presenting a novel system topology and control scheme of a selective dual-mode pulse-modulated high-efficiency single-phase sinewave power-conversion circuit for the new energy generation and storage applications. This power-conversion system is composed of a time-sharing-operated sinewave-absolute-modulation boost chopper with a bypass diode in the first power conditioning and processing stage and time-sharing sinewave partially pulse-modulated full-bridge inverter in the second stage. The proposed power conditioner is operated by a selective time-sharing dual-mode pulse pattern signal processing control scheme without electrolytic capacitor dc link. The unique operating principle of the two-power conditioning and processing stages with sectional time-sharing dual-mode partial sinewave-modulation scheme is described and discussed with a design example. In addition, this paper proposes also a sinewave tracking voltage controlled soft switching pulsewidth-modulation boost chopper with a bypass-diode loop, which includes a passive auxiliary edge-resonant snubber. The new conceptual operating principle and the control implementation of this novel power conditioner are presented and evaluated through experimental and simulation results     

A High-Frequency Resonant Inverter Using Current-Vector Control Scheme and Its Performance Evaluations

The authors introduce a new configuration of resonant-type high-frequency inverter having inherent fast control response of the output power and variable-voltage variable-frequency (VVVF) capability. The circuit is composed of a parallel combination of two series-resonant inverters with common input and output terminals. Both inverter units are operated at synchronous frequency and with an adjustable phase difference from 0° to 180°, allowing control of the output power from full to null power, respectively. Operation of this inverter is explained and computer-simulated operating waveforms and characteristic curves are shown in terms of normalized control variables and circuit parameters. A prototype inverter using Power MOSFET modules has been originally tested with a high-frequency induction heating and melting load to demonstrate experimentally the proposed control principle and the steady-state inverter performances under parallel tuned load conditions.     

Mechanical and magnetic properties of Ni-Co dispersed Al2O3 nanocomposites

Effects of the fabrication processing on the microstructure and properties of composites were investigated. High-density Ni-Co dispersed-Al₂O₃ (Al₂O₃/Ni-Co) composites were obtained by hydrogen reduction and consolidated using hot pressing and pulse electric current sintering (PECS) of Al₂O₃, Ni(NO₃)₂·6H₂O and Co(NO₃)₂·6H₂O powder mixtures. Microstructural investigations of the hot-pressed composite fabricated using again wet/dry ball-milled powder mixture after calcination revealed that fine Ni-Co particles, about 145 nm in diameter, dispersed homogeneously at the matrix grain boundaries. In particular, fine microstructure of dispersion with the average size of 90 nm was realized for the specimen consolidated by PECS method. High strength of over 1 GPa and hardness of 19 GPa were measured for the nanocomposites prepared from the again ball-milled powder mixture. The ferromagnetism of nano-sized Ni-Co contributes to the magnetic properties of the composites. A change in the coercive force with dispersion size was observed. Also, the extent of magnetic response by an applied stress was strongly influenced by the size of Ni-Co particles. The relations between microstructure and mechanical as well as magnetic properties are discussed.