Sensorless Vector Control of Induction Motors Using Minimum Dimensional Flux D‐State Observer with Instantaneous Speed Estimation

This paper proposes a new sensorless vector control method for induction motors using a minimum dimensional flux D‐state observer with instantaneous speed estimation. First, the D‐state observer with a new design rule of constant observer gains is established in a different way. Second, a new speed estimator using flux estimates produced by the observer is established on the basis of the fundamental relationship between the rotor flux and the slip frequency. Speed estimates are reused in the observer as feedback. Characteristic analyses and the usefulness of the proposed vector control method are verified by simulations.     

Observability for bilinear systems

Since the observability for bilinear systems is affected by the input, this paper defines three kinds of observability for bilinear systems ; namely (1) observability with some input, (2) observability with any input, (3) observability with unknown input. The necessary and sufficient condition for the observability with some input and sufficient conditions for the observability with any input and with unknown input for discrete bilinear systems are derived respectively and the effects of the input are clarified     

New Simple High‐Quality Torque Control for Permanent‐Magnet Synchronous Motors: Compensating for Torque Ripple Caused by Nonsinusoidal Back EMF

This paper proposes a new and simple torque‐sensorless torque control method for permanent‐magnet synchronous motors (PMSMs) with nonsinusoidal back EMF. The method suppresses the sixth and/or 12th harmonic torque ripples caused by the back EMF in a feedforward manner even at high speeds; it consists of two subordinate methods for compensation command generation and command‐tracking current control. The first subordinate method generates compensation current commands to cancel the torque ripples based on a mathematical model of PMSMs. The second method controls the stator current to track a current command containing both fundamental and compensatory components. In conjunction with the current control, a dedicated disturbance observer that employs a digital speed‐varying band‐pass filter as a disturbance filter is also proposed. The effectiveness and usefulness of the proposed method were verified through extensive experiments.     

Three‐Phase Current Control by Dynamic Reconstruction of Undetected Currents for AC Motor Drives

This paper proposes new three‐phase current control methods for AC motor drives, which detects only a phase current from among three‐phase currents. The first proposed method first detects a phase current, and then estimates the two‐phase current in the stationary reference frame using the detected single phase current. The second proposed method first detects a phase current, then synthesizes the two‐phase quasi‐current in the dq rotating reference frame, and finally produces two‐phase current estimates by extracting the positive‐phase component from the quasi‐current. The third proposed method produces two‐phase current estimates by filtering out the negative‐phase component from the quasi‐current. This paper presents the principles and detailed characteristic analyses of the proposed methods and validates them on the basis of extensive experiments.     

A New Self‐Tuning Power‐Factor‐Based Vector Control Method for Efficient Wide‐Speed Range Sensorless Drive of Permanent‐Magnet Synchronous Motors

As a simple sensorless vector control method for permanent‐magnet synchronous motor (PMSMs), a power‐factor‐based vector control (PFVC) method has been reported. This method has the attractive characteristics that three functions such as current limit, efficiency and sensorless drive can be performed simultaneously in a simple manner. However, it was developed under the assumption that there is no practical voltage limit, and that it cannot be applied over the rated speed. This paper proposes a new PFVC method that allows PMSMs to be driven even over the rated speed under application of a practical voltage limit, while keeping the desired characteristics. The effectiveness and usefulness of the proposed method are verified through extensive experiments.     

基于多样性的风景论 为了实现环境多样性、社会(生活方式)多样性、文化(风景)多样性

以自己45年来的学术研究、造园教育、大学运营和社会工作为基础,从环境、社会(生活方式)以及文化(风景)三个方面深刻论述了风景园林的多样性,探索了21世纪风景园林的发展方向。主要内容包括:明治神宫内外苑工程的"多样性"和"统一性"、社丛中的"科学的多样性原理"与人林分离的"造园技术"、"国际生物多样性年2010"与"里山计划"、提供人的多样性与多种空间的世界的造园史、基于安定性的风景论以及面向可持续发展的地球社会的环境学。     

Properties of sensitivity and complementary sensitivity functions in single-input single-output digital control systems

Sensitivity and complementary sensitivity functions play a key role in feedback control system design. This paper is concerned with the relation between the sampling period and the properties of these functions in digital control systems. Some integral constraints and the lower bounds of the H ^∞-norm are derived, which show that the feedback performance for the unstable plant with the stable digital compensator can be improved as the sampling period goes to zero.     

Changes in Chemical Constituents of Kiwifruit During Post-Harvest Ripening

Kiwifruit (Actinidia chinensis Planch, Hayward cultivar) were ripened at 20°C under a stream of water-vapor saturated air containing 5 ppm ethylene gas. A remarkable rapid softening in the texture and rising of the soluble solids were observed in 24 hr. The total acidity, starch and amylose content decreased during ripening. Both fructose and glucose increased from 2.7% to 5.0% after 5 days of ripening. Sucrose content increased from 0.45% to 2.22% on the second day, then decreased to 1.19% after 5 days. No significant change in chlorophyll and total solids were observed throughout the experiment. There were stepwise decreases in the L and b_L values during ripening. The ascorbic acid content decreased from 210 to 190 mg per 100g fresh fruit after 5 days of ripening.     

Mesenchymal stem cells-derived extracellular vesicles as ‘natural’ drug delivery system for tissue regeneration

Mesenchymal stem cells (MSCs) have abilities to mediate tissue protection through mechanisms of anti-apoptosis, anti-oxidative stress and anti-fibrosis as well as tissue regeneration through mechanisms of cell proliferation, differentiation and angiogenesis. These effects by MSCs are mediated by a variety of factors, including growth factors, cytokines and extracellular vesicles (EVs). Among these factors, EVs, containing proteins, mRNA and microRNAs (miRNA), may carry their contents into distant tissues with high stability. Therefore, the treatment with MSC-derived EVs may be promising as ‘natural’ drug delivery systems (DDS). Especially, the treatment of MSC-derived EVs with the manipulation of specific miRNAs expression has been reported to be beneficial under a variety of diseases and tissue injuries. The overexpression of specific miRNAs in the EVs might be through pre-loading method using the gene editing system by plasmid vector or post-loading method to load miRNA mimics into EVs by electroporation or calcium chloride-mediated transfection. Despite current several challenges for clinical use, it should open the next era of regenerative medicine for a variety of diseases. In this article, we highlight the therapeutic potential of MSC-derived EVs as ‘natural’ DDS and current challenges.     

Parametrization of stabilizing controllers for multivariable servo systems with two degrees of freedom

A necessary and sufficient condition for the existence of a servo controller is derived using the fractional representation approach for the plant, whose measured variables are not necessarily coincident with its controlled outputs. An independent parametrization of the servo controllers and the attainable transfer characteristics is proposed. The possible classes of all controllers with integrity in the error channel or measured output channel is also clarified using the derived parametrization.