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21.
Fengyang Tan Hiroyuki Yamato Takeo Koyama 《Journal of Marine Science and Technology》2002,6(3):148-157
In our first report, a method to deal with the nonlinearity of saturation was proposed. A method of dealing with nonlinearity
in equations of motion is proposed in this paper. The nonlinear equations of motion are expressed as variations of linear
equations of motion. The nonlinear equations can be linearized around a specific point with a tangential plane or line. Accordingly,
nonlinear equations effective in a certain domain can be obtained by variations in this tangential line. A control system
with varying elements can be designed using the general H
∞ control theory. As an example, we present a speed and heading changing system for large vessels at low speeds during berthing
maneuvers, where the equation will vary during motion. The nonlinearity of the equations is caused by the speeds. The control
system is essentially designed to be robust in disturbance and noise. In this example, the saturation in the propeller is
also considered using the method proposed in the first report. The results show that the method proposed in this paper is
effective.
Received: February 20, 2001 / Accepted: December 11, 2001 相似文献
22.
Tadanori Yamaguchi 《国际交通安全学会研究报告》2018,42(4):190-196
In Cambodia, a rider's license is not required for motorcycles below 125?cc. and 73% of traffic accident fatalities among persons aged 15–19?years involve unlicensed riders. Motorcycle riding differs from automobile driving in that motorcycle riding reflects the rider's skill to a much greater degree, so unskilled riding is much more highly correlated with accidents. Going forward, in addition to gaining knowledge from traffic safety education, motorcycle riders should also learn basic specific motorcycle techniques. In particular, having riders learn and practice the three key tasks in motorcycle riding (breaking, leaning, and exiting) is effective at curbing the number of motorcycle accidents. In a new initiative aimed at improving riding skill, university students, instructors, and police officers were given practical riding instruction on a course using pylons. Program participants were able to learn riding techniques in an enjoyable setting, while seeing the potential for becoming motorcycle riding role models. 相似文献
23.
H. Yamaguchi S.-I. Doi N. Iwama Y. Hayashi 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1993,22(5):299-308
The improvements of ride comfort and vehicle maneuverability in the vehicle design can be achieved by using an active suspension. However, the problems in such a control are the complex control logic because of the control laws incompatible with the improvements of ride comfort and maneuverability, and the cost increase because of various sensors to be attached. Therefore, we examined the control abilities of ride comfort and maneuverability on a unique control law using frequency shaped LQ, and controlled the characteristic of the contact between tire and road without a road displacement sensor 相似文献
24.
This research proposes a new offshore wind energy generation system that uses a tension leg platform (TLP) and describes experiments performed on a TLP type wind turbine in both waves and wind. The following conclusions can be made from the results of this research. 1) In the case of coexisting wave-wind fields, the wind effect stabilizes the pitch motion. 2) The wind effect decreases vibration of the mooring lines when waves and wind coexist. In particular, the springing (2nd or 3rd order force) also decreases in this field. 3) It can be estimated that the reduction in the rate of generation of electrical power can be up to about 6% as a result of the heel angle. In addition, the annual amount of electricity generated was estimated along with the utilization factor based on the experimental results. 相似文献
25.
Hajime Yamaguchi Hiroharu Kato Kazuyuki Matsuda 《Journal of Marine Science and Technology》1996,1(4):198-208
Sound pressure distribution around a monotone sound source was measured inside a marine propeller cavitation tunnel and compared
with the calculated result by a two-dimensional boundary element method. The measured sound pressure distribution showed some
peaks due to the reflection effect of the tunnel test section boundary. As the frequency increased, the sound pressure distribution
became more complicated, showing more peaks. The tunnel reverberant effect should be taken into account when the noise data
measured in the tunnel are converted into full-scale values. In the boundary element method calculation, the boundary condition
at the acrylic observation window of the tunnel was examined in detail. The calculated sound pressure distribution pattern
in the tunnel transverse section agreed well with the measured distribution when a reasonable boundary condition was adopted.
The boundary element method is an effective method for theoretically predicting the acoustic field inside the cavitation tunnel
if the precise boundary condition is adopted. 相似文献
26.
Akihisa Konno Kazuaki Wakabayashi Hajime Yamaguchi Masatsugu Maeda Norio Ishii Shunji Soejima Koyu Kimura 《Journal of Marine Science and Technology》2002,6(4):181-192
The bursting phenomenon of tip vortex cavitation of a propeller sometimes causes severe high-frequency vibration, but its
mechanism has not yet been elucidated. In this study, we carried out model experiments by changing the propellers, wake distributions,
thrust coefficients, and cavitation numbers parametrically, examined the bursting phenomenon with a high-speed video camera,
and measured the pressure fluctuations caused by the phenomenon. We also measured flow distribution around the tip vortex.
As a result, we found that in the bursting phenomenon, large pressure fluctuations occurred twice, and that they strongly
depended on the wake distribution. Two means were suggested to suppress the bursting phenomenon, other than changing the wake
distribution: stabilizing tip vortex cavitation or reducing the cavity volume.
Numerical fluid simulations around a propeller in noncavitating, unsteady conditions were also conducted, and the strength
of the tip vortex along the circumference and its derivative were examined. As a result, the phenomena were parameterized
by the time derivative of the strength of the tip vortex, and if it was higher than a threshold value, the tip vortex cavitation
burst. Therefore, it is possible to predict the occurrence of the bursting phenomenon by numerical analysis.
Received: November 6, 2001 / Accepted: January 24, 2002 相似文献
27.
Dan Walker Neil Bose Hajime Yamaguchi Stephen J. Jones 《Journal of Marine Science and Technology》1997,2(1):12-20
Hydrodynamic loads on a propeller blocked with simulated ice were studied using a cavitation tunnel. Comparative predictions were made using a panel method. The propeller was a model of the Canadian Coast Guard's R-class icebreake propeller, and the ice block was simulated using a solid blockage. Experimental results show the open water performance of the propeller, its performance behind a blockage, and the effects of cavitation in these conditions, as well as the loading on the simulated ice block. Panel method predictions were made of the time series propeller performance in the blocked flow. Cavitation during propellerice interaction resulted in a reduction of mean suction load on the ice block. Block load measurements indicated an increase in the oscillation about the mean value of the loads, with a variation in the phase of the loading with respect to blade position as compared with the non-cavitating results. Comparisons of panel method results with the measured block loads support the reliability of the dynamic measurements.List of symbols
D
propeller diameter
-
F
block drag load
-
K
T
thrust coefficient,T/(n
2
D
4)
-
K
B
block load coefficient,F/(n
2
D
4)
-
K
Q
torque coefficient,Q/(n
2
D
5)
-
Q
propeller torque
-
T
propeller thrust
-
n
propeller rotational speed
-
J
propeller advance coefficientV
A/(nD)
-
P
A
ambient pressure at propeller
-
P
ATM
atmospheric pressure
-
P
V
vapour pressure of water
-
V
A
propeller advance speed
-
dissolved gas content
-
s
saturated dissolved gas content at atmospheric pressure
-
o
open water propeller efficiency
-
cavitation number, (P
A
–P
V
)/(0.5(nD)2)
-
density of water 相似文献
28.
Ryuichi Shibasaki Takashi Usami Masahiko Furuichi Hiroyuki Teranishi Hironori Kato 《Maritime Policy and Management》2018,45(4):543-566
This study focuses on the expected impact of Northern Sea Route (NSR) usage and the Panama Canal (PC) expansion on liquefied natural gas (LNG) imports of Asian countries, from not only the macroeconomic viewpoint but also diversification of the supplying countries. First, the amounts saved from shipping costs due to these events are estimated, based on scenarios on the navigable period of the NSR, transit fee of the NSR considering the exchange rate between the Russian ruble and US dollar, and bunker fuel price. Second, a spatial general equilibrium model based on macroeconomic theory is applied to predict changes in LNG trade patterns and measure economic impacts due to the reduction of shipping costs. Finally, the impacts of NSR usage as well as the PC expansion on LNG imports of Asian countries are discussed based on the calculations. The results show that diversification of supplying countries for LNG imports can be observed, especially in Japan, the largest LNG importer in the world, and other Asian countries are secondarily affected by changes in Japan’s import pattern, with limited impacts on these countries’ national economies. 相似文献
29.
Masuru Sugai Hiroyuki Yamaguchi Masanori Miyashita Takaji Umeno Katsuhiro Asano 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1999,32(4):299-312
In this paper, we propose a new control strategy for an antilock braking system (ABS) to maintain the braking force at maximum. The popularization of the ABS that prevents the wheels from locking has resulted in an improvement of the vehicle stability and shortening of the braking distance. Further improvement is anticipated if the maximization of the braking force is realized. We found an interesting phenomenon in which the characteristics of the resonance system composed of the vehicle body and the wheel and road surface reflects the slip condition of the road surface. Using this phenomenon, we realized a control method for maintaining the maximum value of the braking force. 相似文献
30.
Yoshihisa Takekoshi Takafumi Kawamura Hajime Yamaguchi Masatsugu Maeda Norio Ishii Koyu Kimura Tadashi Taketani Akihiko Fujii 《Journal of Marine Science and Technology》2005,10(2):70-81
A new method for designing propeller blade sections is presented. A vortex lattice method is used to evaluate the performance and the time-dependent pressure distribution on the blade surface in a non-uniform flow, while efficient optimization algorithms are used to modify the blade sections. Two different designs were carried out in this study. The first was a design to realize a target pressure distribution in a rotating three-dimensional flow. A two-dimensional wing theory was used to obtain the target pressure distribution. The predicted increase in efficiency and the reduction in the cavity volume were confirmed by model experiments. The second was a design to maximize the propeller efficiency. By this method, the propeller efficiency was improved by 1.2% under the constrains of constant thrust and a prescribed margin for face cavitation. 相似文献