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821.
There are many filtering methods that can be used for the initial alignment of an integrated inertial navigation system. This paper discussed the use of GPS, but focused on two kinds of filters for the initial alignment of an integrated strapdown inertial navigation system (SINS). One method is based on the Kalman filter (KF), and the other is based on the robust filter. Simulation results showed that the filter provides a quick transient response and a little more accurate estimate than KF, given substantial process noise or unknown noise statistics. So the robust filter is an effective and useful method for initial alignment of SINS. This research should make the use of SINS more popular, and is also a step for further research. 相似文献
822.
Two-dimensional numerical analyses were conducted and analyzed to simulate water splash produced by free falling object models
starting from the resting position. The equilateral prism-shaped object models were allowed to fall onto the free surface
of the water. The moving-particle semi-implicit (MPS) method was used to solve the unsteady Navier-Stokes equation for incompressible
fluid flows with and without the surface tension effect. Froude numbers of 0.75, 1.0, and 1.25 were used with different model
sizes for the entry velocity at the free surface. Splashes obtained by numerical computation closely agreed with the experimental
results. The surface tension force, the Froude number, and the Weber number were found in these calculations to play major
roles in determining various types of splash shapes. Model size was found to influence splash phenomena, even if the Froude
number remained the same. The dependencies on these two nondimensional numbers and the fundamental law of similarity on water
splash with and without the surface tension effect were thoroughly investigated in this research. Several two-dimensional
numerical simulations are presented in this article to describe the hydrodynamic behaviors of water splash with and without
the surface tension effect. 相似文献
823.
Miaomiao Zhang Wei Hong Fangxi Xie Yan Su Liwei Han Bin Wu 《International Journal of Automotive Technology》2018,19(3):393-404
A detailed investigation of the impact of injection timing and injection pressure on combustion and particles of a spray-guided GDI engine was conducted, under different engine operating conditions. The results indicated that, more proportion of large particles were emitted when increasing engine load, and the peak of accumulation mode particles moved toward smaller size when rising engine speed. With retarding the injection timing, the in-cylinder pressure and heat release rate rose first and then dropped at 2000 rpm, but they continuously rose at lower or higher speed conditions. The total particles concentration curves at all cases showed a trend of U-shape, and the corresponding timing of the lowest particles concentration advanced as the engine speed or load increased. The minimum value of emitted particles first rose and then fell when increasing load at 2000 rpm conditions, and it continuously rose when increasing speed at 40 Nm conditions. Generally, injection pressure did no sensitively affect combustion process except that it showed a relatively strong impact at low load conditions. However, particulate matter could be effectively inhibited by elevating fuel pressure from 5.5 to 11.5 MPa at all cases. In detail, the total particles concentration continuously fell at low speed and mid speed-high load cases, but it showed a rose trend when further increase fuel injection pressure at mid speed-low load and high-speed conditions. 相似文献
824.
Motivated by the development of high-precision digital maps for advanced driver assistance system (ADAS) in recent years, this study provides a new approach to solve the problems of the conventional automatic transmission vehicle travelling on sloping roads. Based on vehicle dynamics, shift problems on hilly roads are analyzed. A novel intelligent shift strategy is proposed, which consists of a dynamic shift schedule for the uphill, a safety shift schedule for the downhill, and a comprehensive economical shift schedule for the gentle slopes. A set of driver-in-loop co-simulation tests was conducted in a driving simulator that is equipped with a MATLAB/Simulink dynamics simulation platform. The test results verified the effectiveness of the new intelligent shift strategy. With the road information provided by a high-precision digital map, busy shifting can be eliminated, and improved dynamic performance can be achieved for a vehicle travelling on the uphill roads; undesired upshift can be prevented, and engine traction resistance can be used to relieve the load of braking system when a vehicle travelling on the downhill roads; also, fuel consumption can be reduced for a vehicle travelling on a gently sloped road. Consequently, this novel intelligent shift strategy offers a reliable and effective solution for improving a vehicle’s driving performance on a hilly road. 相似文献
825.
Nie Wu 《船舶与海洋工程学报》2002,1(2):1-5
The appropriate prediction of the hull deflection of a severely damaged warship is an important area in the research of the warship survivability. In this paper, the asymmetrical beam bending theory is applied to set up the damaged model, a comparison of the longitudinal strength, the deflections of damaged hull subjected to both hagging and sagging moments, and shear forces is carried out. The external loads are also calculated according to different damaged positions. Finally, some results and conclusions are obtained. 相似文献
826.
ZHANGJing-juan LIXue-lian HAOYan-ling 《船舶与海洋工程学报》2003,2(1):60-65
A new algorithm is proposed for underwater vehicles multi-path planning. This algorithm is based on fitness sharing genetic algorithm, clustering and evolution of multiple populations, which can keep the diversity of the solution path, and decrease the operating time because of the independent evolution of each subpopulation. The multi-path planning algorithm is demonstrated by a number of two-dimensional path planning problems. The results show that the multi-path planning algorithm has the following characteristics: high searching capability, rapid convergence and high reliability. 相似文献
827.
Naoya Umeda Hirotada Hashimoto Akihiko Matsuda 《Journal of Marine Science and Technology》2003,7(3):145-155
We have attempted to develop a more consistent mathematical model for capsizing associated with surf-riding in following
and quartering waves by taking most of the second-order terms of the waves into account. The wave effects on the hull maneuvring
coefficients were estimated, together with the hydrodynamic lift due to wave fluid velocity, and the change in added mass
due to relative wave elevations. The wave effects on the hydrodynamic derivatives with respect to rudder angles were estimated
by using the Mathematical Modelling Group (MMG) model. Then captive ship model experiments were conducted, and these showed
reasonably good agreements between the experiments and the calculations for the wave effects on the hull and the rudder maneuvring
forces. It was also found that the wave effects on restoring moments are much smaller than the Froude–Krylov prediction, and
the minimum restoring arm appears on a wave downslope but not on a wave crest amidship. Thus, an experimental formula of the
lift force due to the heel angle of the ship is provided for numerical modelling. Numerical simulations were then carried
out with these second-order terms of waves, and the results were compared with the results of free-running model experiments.
An improved prediction accuracy for ship motions in following and quartering seas was demonstrated. Although the boundaries
of the ship motion modes were also obtained with both the original model and the present one, the second-order terms for waves
are not so crucial for predicting the capsizing boundaries themselves.
Received: June 20, 2002 / Accepted: October 10, 2002
Acknowledgments. This research was supported by a Grant-in-Aid for Scientific Research of the Ministry of Education, Culture, Sports, Science
and Technology of Japan (No. 13555270). The authors thank Prof. N. Rakhmanin of the Krylov Ship Research Institute for providing
the Russian literature, as well as Mr. H. Murata of NHK (Japan Broadcasting Corporation) for translating it into Japanese.
Address correspondence to: N. Umeda (e-mail: umeda@naoe.eng.osaka-u.ac.jp) 相似文献
828.
Sadegh Arefnezhad Ali Ghaffari Alireza Khodayari Sina Nosoudi 《International Journal of Automotive Technology》2018,19(2):271-279
Lane change maneuver is one of most riskiest driving tasks. In order to increase the safety level of the vehicles during this maneuver, design of lane change assist systems which are based on dynamics behavior of driver-vehicle unit is necessary. Therefore, modeling of the maneuver is the first step to design the driver assistance system. In this paper, a novel method for modeling of lateral motion of vehicles in the standard double-lane-change (DLC) maneuver is proposed. A neuro-fuzzy model is suggested consisting of both the vehicle orientation and its lateral position. The inputs of the model are the current orientation, lateral position and steering wheel angle, while the predicted lateral position and orientation of the vehicle are the outputs. The efficiency of the proposed method is verified using both simulation results and experimental tests. The simulation and experimental maneuvers are performed in different velocities. It is shown that the proposed method can effectively reduce the undesirable effects of environmental disturbances and is significantly more accurate in comparisons with the results in the recent available papers. This method can be used to personalize the advanced driver assistance systems. 相似文献
829.
Pinyung Chen Shinhung Chang Rongshun Chen 《International Journal of Automotive Technology》2017,18(4):663-670
This paper is aimed to propose a decoupled self-tuning proportional plus integral (PI) controller with simple law for an idling stop system applied to scooters. An integrated starter generator (ISG) of the idling stop system is designed with a high efficiency permanent magnet synchronous motor (PMSM). The PMSM used as an ISG must have a high torque characteristic to ensure that the engine can be accelerated up to firing speed. A conventional and useful control algorithm named PI control is unable to handle motor current very well for dynamic load, parametric variation, and external disturbance, especially in a vehicle application. Therefore, a robust algorithm for current control in an ISG is proposed. The decoupled selftuning PI controller based on the Lyapunov stability theorem is utilized to guarantee the control performance. Numerical simulations demonstrate the effectiveness of the proposed control algorithm. Experimental results show that the engine of a 150 cm3 scooter can be cranked to reach firing speed by a ISG within 0.1?0.2 second. The proposed method is simple, robust, as well as stable for idling stop system, and can be effectively implemented. 相似文献
830.
Efficient estimation of extreme non-linear roll motions using the first-order reliability method (FORM) 总被引:1,自引:0,他引:1
Jørgen Juncher Jensen 《Journal of Marine Science and Technology》2007,12(4):191-202
In on-board decision support systems, efficient procedures are needed for real-time estimation of the maximum ship responses
to be expected within the next few hours, given online information on the sea state and user-defined ranges of possible headings
and speeds. For linear responses, standard frequency domain methods can be applied. For non-linear responses, as exhibited
by the roll motion, standard methods such as direct time domain simulations are not feasible due to the required computational
time. However, the statistical distribution of non-linear ship responses can be estimated very accurately using the first-order
reliability method (FORM), which is well known from structural reliability problems. To illustrate the proposed procedure,
the roll motion was modelled by a simplified non-linear procedure taking into account non-linear hydrodynamic damping, time-varying
restoring and wave excitation moments, and the heave acceleration. Resonance excitation, parametric roll, and forced roll
were all included in the model, albeit with some simplifications. The result is the mean out-crossing rate of the roll angle
together with the most probable wave scenarios (critical wave episodes), leading to user-specified specific maximum roll angles.
The procedure is computationally very effective and can thus be applied to real-time determination of ship-specific combinations
of heading and speed to be avoided in the actual sea state. 相似文献