Speed tracking servo control system incorporatingtraveling-wave-type ultrasonic motor and feasible evaluations

A variety of ultrasonic motors (USMs) have attracted special interest as a new type of actuator in servo motion control systems. For practical applications, the speed servo control system incorporating the ultrasonic motor developed in Japan has some special unique features. However, this system has several significant problems, such as the inherent speed ripple characteristics, the speed regulation characteristics under the condition of applied disturbance load torque, and the speed tracking characteristics. In order to solve these practical problems, some control schemes of ultrasonic-actuated motor systems have been proposed and discussed theoretically, which include fuzzy reasoning control, adaptive control, repetitive learning control, and neural-network-based learning control. However, it is considered that these control strategies mentioned above have not been sufficiently substantiated from a feasible experimental point of view. This paper presents a newly proposed precise speed tracking servo control system using the compact traveling-wave-type ultrasonic motor. Its proposed control scheme is composed of both the driving frequency control loop with the variable-gain strategy and the applied voltage control loop with the speed ripple reduction strategy of the USM. The improved speed characteristics realized by this proposed control system are demonstrated and evaluated in experiments     

Soft switching based on analysis of transient and steady-state characteristics: Application to a single-ended high-frequency inverter

A single-ended resonant-type high-frequency inverter using a static induction transistor (SIT) described in this paper can be performed as a zero current switching (ZCS) operation without dc reactor. The SIT high-frequency inverter is a low-cost one which has no transformer and it would be developed for a high-intensity ultrasonic power supply and dc-dc converter. The circuit operation regions, not only ZCS but also ZCS-ZVS (zero current switching and zero voltage switching), were elucidated in the normalized plane. The characteristics of the inverter including the power control by frequency regulation were discussed. Furthermore, the switching characteristics in the transient-state were investigated. These characteristics were substantiated on the basis of the numerical analysis and experimental results.     

Coherent structures in a fully developed stage of a non‐isothermal round jet

Direct numerical simulation (DNS) was performed for a non‐isothermal air jet with a Reynolds number of 1200 in order to reveal coherent structures of the developed jet. A fourth‐order central finite difference was applied to the simulation. An effort was also made to enable experimental visualization (dye mixing and PTV) to support the validity of the instantaneous structures by DNS. Computational results for two types of inlet profiles suggested that nozzle conditions scarcely affect the turbulence statistics and the coherent structures in a jet‐established stage. Two‐point correlations of velocity and temperature show that similar distributions denoting the temperature can be used as an indicator of a vortex. A conceptual model of a hairpin‐shaped vortex was proposed and validated by two‐point correlations and PDF analysis for vortex alignment. The hairpin‐shaped vortex stands with legs inclined downstream. The inclination angle and the tilting angle between the two legs are ?45° and 40°, respectively. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(5): 342–356, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20014     

Chaotic behavior in parametric oscillations

Parametric oscillations which occur in a nonlinear two-phase circuit with nonlinear reactors and capacitors are applied to many kinds of power devices. When the devices are operating under light load, the output voltage of these devices exhibits unstable oscillations, i.e., subharmonic oscillations, quasi-periodic oscillations or chaotic oscillations. This paper analyzes the abnormal oscillations and confirms the validity of the analysis experimentally. In this paper, new circuit equations are presented that can be applied to the analysis of a two-phase nonlinear circuit in which reactor saturation curves are sharp. It is clarified by this analysis that the parametric oscillations of the circuit which contains reactors of moderate saturation characteristics become subharmonic or quasi-periodic with the existence of resistances of the power supply side. Also, when the nonlinearity of the reactors in the circuit is sharp, the parametric oscillations may change into chaotic oscillations in addition to the aforementioned oscillations.     

A 2.5-ns clock access, 250-MHz, 256-Mb SDRAM with synchronousmirror delay

A 256-Mb SDRAM (245.7 mm²) has been developed using (1) a high cell occupation ratio (60.2%) array design for chip size reduction and a high yield, (2) a prefetched pipeline scheme (PPS) using a first-in first-out (FIFO) buffer with parallel serial converter for 250-MHz clock frequency operation, and (3) a synchronous mirror delay (SMD) circuit for 2.5-ns clock access and low standby current     

Ultrasonic motor-actuated direct drive positioning servo control system using fuzzy-reasoning controller

This paper describes a traveling-wave ultrasonic motor (USM)-actuated positioning servo driver, suitable for direct-drive motion systems, which incorporates a fuzzy-reasoning software controller with speed and position-variable feedback schemes. The experimental results of this USM position servo driver operating at two-phase high-frequency resonant inverter are illustrated and evaluated using a one-axis servo motion drive system. The results show that the new system using a compact USM that incorporates a microprocessor-based two-input and one-output fuzzy-reasoning controller is cost effective and suitable for special purposes in the industrial, medical, automotive, space and consumer fields.     

Release behavior from hydrogen‐bonded polymer gels prepared by pressurization

Our previous research showed that a simple ultra‐high‐pressure process made poly(vinyl alcohol) (PVA) solution into a macrogel and nanoparticles. To investigate the release properties of PVA hydrogels prepared by the ultra‐high‐pressure treatment, we prepared hydrogels containing model drugs by pressurizing a PVA solution with Alfa‐G Hesperidin or Oil Blue N as a water‐soluble or an oil‐soluble model drug, respectively. In the case of the oil‐soluble drug, an oil‐in‐water emulsion, Oil Blue N containing dodecane in a PVA solution, was used by homogenization before pressurization. The average diameter and the diameter distribution of oil droplets before and after the ultra‐high‐pressure treatment were almost the same. However, the PVA hydrogel prepared at 10,000 atm for 10 min exhibited the slowest release rate of model drugs. Thus, we found that the release rates of the model drugs from the PVA hydrogels were controlled by the degree of crosslinking in the resulting gels, which was determined from the operation parameters of the ultra‐high‐pressure treatment, such as the pressure, time, and concentration of the PVA solution. Therefore, an ultra‐high‐pressure process is promising for drug‐carrier development because of the nonharmful simple preparation process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Silicon Wafer Surface-Temperature Monitoring System for Plasma Etching Process

A thermoreflectance temperature measuring system was developed with the aim to realize monitoring of the silicon wafer surface temperature during plasma etching. The thermoreflectance detects variations in temperature through changes in optical reflectance. To overcome such difficulties as low sensitivity and limitation in installation space and position for in situ measurements, the differential thermoreflectance utilizing two orthogonal polarizations was introduced. Noise such as fluctuations in the incident beam intensity or changes of loss in the optical path would affect both polarizations equally and would not affect the measurement. The large angle of incidence of the beam allows measurement to be performed from outside the viewing ports of existing plasma etching process chambers through the gap between the plasma electrode and the silicon wafer. In this article, an off-line measurement result is presented, with results for bare wafers as well as for wafers with metal depositions. A prototype system developed for tests in plasma etching facilities in a production line is described.