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71.
This paper focuses on the realization of high-performance motion control based on acceleration control. A disturbance observer is used to construct an acceleration control system. A high sampling frequency is known to be effective for improving the performance. Characteristics of acceleration control are investigated to discuss the relationship between the performance and a sampling frequency of the system. The needs for a high sampling frequency for an output are then described. Based on these considerations, a novel multirate sampling method for the acceleration control system is proposed. An output sampling period is set shorter than an input sampling period, and control calculation is executed at each output sampling period in the method. The disturbance observer is redesigned for application to the multirate system. Stability analysis is performed to verify the validity of the proposal. Feasibility of the proposed method and its influence on the performance are also verified by experimental results 相似文献
72.
Al Amin A. Shimizu K. Takenaka M. Tanemura T. Inohara R. Nishimura K. Horiuchi Y. Usami M. Takita Y. Kai Y. Aoki Y. Onaka H. Miyazaki Y. Miyahara T. Hatta T. Motoshima K. Kagimoto T. Kurobe T. Kasukawa A. Arimoto H. Tsuji S. Uetsuka H. Nakano Y. 《Photonics Technology Letters, IEEE》2007,19(10):726-728
We report a bit-rate transparent optical burst switching (OBS) router prototype using a fast 5 times 5 PLZT [(Pb,La)(Zr,Ti)O3 ] optical matrix switch. Dynamic switching in a two-wavelength, 2 times 2 OBS switch is demonstrated. Contention resolution using a tunable Mach-Zehnder interferometer wavelength converter for both 40- and 10-Gb/s bursts is demonstrated for the first time. Error-free operation was achieved for both bit rates under the same settings, as required in autonomous networks 相似文献
73.
This paper proposes an electromyographic (EMG) prosthetic hand that has five independently driven fingers, a flexion drive, and a force-magnification drive. The flexion drive allows for rapid finger motion, and the force-magnification drive allows for a firm grasp. To realize the natural feeling of control similar to that of movements with nonamputated parts, the control system includes the impedance model of human forearms and utilizes the muscle contraction level extracted from a user’s EMG signals. We experimentally verified that the maximum fingertip force of the hand exceeds 20 N, and the time required to fully close the hand by the flexion drive is 0.53 s. We also experimentally verified that in response to EMG signals, the fingers can flex smoothly and the grasping force can be modulated. Furthermore, we show that taking EMG signals as inputs makes it possible to control six operations, including ones that use the five fingers in distinctive ways. 相似文献
74.
Kenji Fukuzawa Hiroaki Tsuji Satoshi Hamaoka Mitsuhiro Shikida Shintaro Itoh Hedong Zhang 《Microsystem Technologies》2013,19(9-10):1567-1572
It is important to understand friction force in micro/nano mechanical devices both at high sliding speed and with high lateral resolution. Dual-axis friction force microscopes that can provide high lateral resolution and accuracy have been proposed; however, the sliding speed is limited by the probe scan speed. While a micro mechanical probe (MMP) with an electrostatic actuator can overcome this problem, details of probe design have not been established yet. This paper presents the principle of the mechanical design for an MMP with high force sensitivity and sufficient drive force. The dimensions of the double cantilever beam control the spring constants, resonant frequencies, and drive force. The use of an actuated MMP enables accurate friction force microscopy at high sliding speeds, which is required for the design of micro/nano mechanical devices. 相似文献
75.
Amorphous and crystallized poly(L -lactic acid) (PLLA) films were prepared and the hydrolytic degradation of the ultraviolet (UV)-treated and UV-nontreated films was investigated. This study reveals that the combination of UV and thermal treatments can produce the PLLA materials having different hydrolytic degradation profiles and that the UV-irradiation in the environment will affect the design of recycling process for PLLA articles. In an early stage, the degrees of hydrolytic degradation monitored by weight loss (Wloss), number-average molecular weight (M n), and melting temperature (T m) were higher for the UV-treated films than for the UV-nontreated films. In a late stage, the trend traced by Wloss was reversed, and the difference in the degrees of hydrolytic degradation between the UV-treated and UV-nontreated films monitored by M n and T m became smaller, with the exception of the degrees of hydrolytic degradation of the amorphous films traced by T m. Also, in the early stage, the degrees of hydrolytic degradation monitored by Wloss and M n were higher for the crystallized films than for the amorphous films. In the late stage, this trend was reversed, with the exception of the degrees of hydrolytic degradation of the UV-treated films monitored by M n. The main factors that determined the Wloss and T m were the molecular weight and initial crystallinty but not the molecular structures such as terminal CC double bonds and crosslinks. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
76.
Vodhanel R.S. Elrefaie A.F. Iqbal M.Z. Wagner R.E. Gimlett J.L. Tsuji S. 《Lightwave Technology, Journal of》1990,8(9):1379-1386
A comparison is presented of the performance of amplitude-shift-keying (ASK), frequency-shift keying (FSK), and differential-phase-shift-keying (DPSK) lightwave systems which operate at 10 Gb/s with directly modulated 1550-nm distributed feedback (DFB) laser transmitters and conventional 1310-nm dispersion-optimized fiber. Computer modeling techniques were used to accurately simulate the amplitude modulation response and the frequency modulation response of DBF lasers. The system performance is evaluated from simulated eye patterns for both direct and heterodyne detection. With the narrow-optical spectral widths of these signal formats, fiber chromatic dispersion limits up to 70 km were obtained for transmission at 1550-nm using conventional 1310-nm optimized fiber 相似文献
77.
For the purpose of developing liquid crystalline microactuators, the transient behaviors of a nematic liquid crystal between two parallel plates have been computed for various parameters such as applied voltage, the gap between the plates, and the twist and tilt angles at the plates. The Leslie-Ericksen theory has been selected as a constitutive equation. The twist angle has an effect on the induced velocity profiles; for example, the induced flow is planar at the twist angle of 0°, while the flow has an out-of-plane component when the twist angle is not 0°. Transient behaviors of shear stress acting on the plates, the flowrate, and the maximum values of the velocity, and the tilt angle between the plates have been reported. In addition, we have investigated the effects of the applied voltage, the gap between the plates, and the tilt angle at the plates on the above-mentioned values. We can develop microactuators with arbitrary characteristics by suitably controlling the applied voltage, the size of the actuators, and the director anchoring conditions. 相似文献
78.
Poly(L ‐lactic acid) (PLLA), poly(ε‐caprolactone) (PCL), and their films without or blended with 50 wt% poly(ethylene glycol) (PEG) were prepared by solution casting. Porous films were obtained by water‐extraction of PEG from solution‐cast phase‐separated PLLA‐blend‐PCL‐blend‐PEG films. The effects of PLLA/PCL ratio on the morphology of the porous films and the effects of PLLA/PCL ratio and pores on the physical properties and biodegradability of the films were investigated. The pore size of the blend films decreased with increasing PLLA/PCL ratio. Polymer blending and pore formation gave biodegradable PLLA‐blend‐PCL materials with a wide variety of tensile properties with Young's modulus in the range of 0.07–1.4 GPa and elongation at break in the range 3–380%. Pore formation markedly increased the PLLA crystallinity of porous films, except for low PLLA/PCL ratio. Polymer blending as well as pore formation enhanced the enzymatic degradation of biodegradable polyester blends. Copyright © 2006 Society of Chemical Industry 相似文献
79.
Y Tominaga T Nakatsu S Kusachi M Murakami S Toyonaga K Yamamoto T Watanabe I Sano K Mashima T Tsuji 《Canadian Metallurgical Quarterly》1997,47(6):545-551
Sociodemographic differences between rural and urban clients with severe mental illness (SMI) are explored using approaches which extend research in this area beyond limitations found in the few existing studies. Sixteen hundred adult clients from 18 Wisconsin counties are classified according to the degree of rurality of their counties of residence, using two definitions: a dichotomous metropolitan-non-metropolitan grouping and population density. There are significant differences between rural and urban clients for age, gender, and marital status, but not education or income. Young (18-35 years), unmarried males are more likely to live in more densely populated counties. Older (65 and older) women who are currently or previously married are more likely to live in less densely populated counties. 相似文献
80.
A stationary packed bed of cohesionless particles is set up in a vertical pipe for the fundamental study of plug conveying. The effect of flow acceleration or deceleration on the pressure drop of the plug is investigated first. It is found that the pressure drop increases due to the flow acceleration and vice versa. Next, the following three kinds of experiments were made for the study of friction characteristics: 1. Friction between the plug and moving wall without air flow, 2. Friction between the plug and wall with downward air flow, 3. Friction between the plug and wall with upward air flow. The results are compared with the theory established in powder mechanics. The state of stress being of the active or passive case is discussed. Finally the problem of particles raining down from the back of the plug is studied. It is shown that the air velocity necessary to support the particles can be calculated based on a simple analysis of pressure distribution around the particles. 相似文献