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A Second-Order Sliding Mode Controller for Active Suspension Systems
Shigehiro Toyama,Fujio Ikeda,Yoshio Sorimachi 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
This paper presents a second-order sliding mode controller for active suspension systems. The proposed controller, which occurs a limit cycle as the second-order sliding mode, is designed by the integral sliding mode control theory with the twisting algorithm. With the block diagram algebra, the proposed control system can be converted into a nonlinear feedback system consisting of a linear transfer function and a nonlinear element. For the nonlinear system, the describing function method can approximately lead the existence condition for an ideal limit cycle at desired frequency with desired amplitude. Satisfying the existence condition, the proposed controller could almost occur the desired limit cycle in the vicinity of the switching surface, instead of the perfect sliding mode for the conventional sliding mode control theory. As a result, deterioration of the control efforts due to the chattering in high frequency range, such as the ride comfort or the road holding performance, could be suppressed, since the control input could be smooth. An indicator of the robustness against the perturbation of the plant was led from a view of the existence condition in the Nyquist’s plot. Finally, simulation results show the effectiveness of the proposed controller.
Shigehiro Morooka,Seita Tsuda,Makoto Ohsaki 한국공간구조학회 2009 한국공간구조학회지 Vol.9 No.4
The seismic responses of small-scale spatial frames such as school gymnasiums are usually evaluated using static analysis, although time-history analysis should be carried out to fully incorporate the dynamic responses of the structures against seismic motions. In this study, advanced static analysis procedures are presented for school gymnasiums that will improve the performance evaluation against seismic motions. The seismic loads are approximated by equivalent static loads corresponding to the two performance levels; i.e., Levels 1 and 2 defined by the Japanese building standard. The importance of utilizing the eigenmode in the load pattern is discussed. Simple static analysis procedures are presented for evaluation of maximum vertical acceleration. It is shown that the static analysis for Level 2 input significantly underestimates the responses by dynamic analysis; however, the inelastic responses for Level 2 are shown to be successfully evaluated using the equivalent linearization that is similar to the “method based on calculation of limit strength” for building frames in Japan. 학교체육관과 같은 소 규모 공간구조물의 지진응답은 본래 지진동에 대한 동적응답을 시각이력해석에 의해 검증해야 하지만 통상은 정적해석에 의해 평가하고 있다. 본 연구에서는 학교 체육관의 내진성능평가를 가능하게 하는 정적해석의 진행수순을 나타내기로 한다. 지진하중은 2개의 성능 레벨 즉, 일본의 건축기준법에 정의되어 있는 레벨 1과 2에 대응하는 등가인 정적하중으로 근사한다. 또한, 재하 패턴으로서 고유모드형을 사용하는 것에 대한 중요성을 논의하고, 정적해석의 간단한 순서에 의해 최대연직방향가속도를 평가할 수 있는 것을 나타낸다. 아울러, 레벨 2의 입력에 의한 정적해석은 동적해석으로 얻어진 응답치를 과소평가하지만, 일본의 중층구조에 사용되는 “극한내력계산법”에 근사한 등가선형화 기법에 의해 레벨 2의 입력에 대한 탄소성응답이 가능하다는 것을 나타내고자 한다.
Research and development of new magnetic filter for high gradient magnetic separation
Shigehiro Nishijima,Naoki Nomura,Fumihito Mishima 한국초전도저온학회 2023 한국초전도저온공학회논문지 Vol.25 No.3
We have been developing a new magnetic filter so that small sized paramagnetic substances can be separated even in a low magnetic field (lower than 2T). The developed filter is a packed ferromagnetic filament with a triangular cross section. The filament has a diameter of 120 μm and a length of 3 mm, and is mechanically packed with a volume ratio of 17.6%. Using this filter, a magnetic separation experiment of hematite was carried out using a superconducting magnet at the field of 2T. Similarly, magnetic separation was performed using a conventional magnetic filter. It became clear that the separation efficiency of newly developed filter is high as that of conventional mesh filter. The smaller sized hematite (<3μm) could be separated though conventional mesh filter could not separate.
Status of Tea Production and Pest Control in Japan
Shigehiro Kodomari 한국차학회 1998 한국차학회지 Vol.4 No.1
Japan, the total area of planted tea covers abort 52,700 hectares(in 1996) and the total annual production is about 88,700 tons. The greatest tea-producing region is Shizuoka prefecture, it has about 46% of the total tea production in Japan. There are several kinds of tea made in Japan is mostly green tea; it is non-fermented. Tea is harvested two or three times in a year. The first crop is plucked in late April to mid-May. The first harvested tea is the best quality and most valuable. The second crop is plucked in mid-late June and the third crop in early August, but recently the latter harvest is suspended. Nitrogen-, phosphate, and potassium-fertilizers of 540, 180 and 270㎏/hectare as pure ingredients of N, P and K, respectivly, are applied to the field annually in five split applications. There are many kinds of insect pests and diseases in tea fields of Japan. Nowadays the control of these insect pests and diseases depends on chemicals. These chemicals are tested with regard not only to their effectiveness against the pests but also residual toxicity and tainting which may give some influence to the quality of made tea. Then, the prohibited period of harvest after application is set up at all chemicals used at tea fields. But, it is desirable that the use of chemicals are minimized, as tea is an important drink for us and as the environment should be protected from pollution by chemicals. Therefore, non-chemical control methods are being studied, and some methods are already in practice.
Adaptive Torque Demand Control of SI Engine with a Continuous Variable Valve Train
Shigehiro Sugihira,Noriaki Sato,Hiromitsu Ohmori 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
In recent years, integrated vehicle control system has been designed based on the information of torque. There-fore, engine is teated as the actuator generating torque and necessity of controlling engine torque has been increased. This paper describes adaptive torque demand control of SI(Spark Ignition) engine with continuous variable valve lift which is based on STC(Self Tuning Control).
Properties and Structure of High Frequency Soft Magnetic Nano-composite Films
Shigehiro Ohnuma,Hiroshi Masumoto 한국자기학회 2011 Journal of Magnetics Vol.16 No.4
Metal-insulator type, nano-granular soft magnetic films have been reviewed from the viewpoint of high frequency magnetic materials. The formation of nano-granular structure is related to the magnitude of heat of formation of intergranule materials. Variation of the ratio of granule phase to intergranule phase in the film is found to produce various characteristics in the magnetic properties of the film. The HRTEM observation reveals that neighboring granules in the film with above 60 at.% Co, contact at considerable points and the films show soft magnetic properties which are explainable in terms of the random anisotropy model for nanocrystalline materials. Addition of Ni group elements in Co-O based films enhances their anisotropy field up to 400 Oe and they exhibit excellent frequency response of permeability. Also, large electromagnetic noise suppression effect is demonstrated as one of their potential applications.