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361.
Underwater acoustic channels are recognized for being one of the most difficult propagation media due to considerable difficulties such as: multipath, ambient noise, time-frequency selective fading. The exploitation of sparsity contained in underwater acoustic channels provides a potential solution to improve the performance of underwater acoustic channel estimation. Compared with the classic l 0 and l 1 norm constraint LMS algorithms, the p-norm-like (l p ) constraint LMS algorithm proposed in our previous investigation exhibits better sparsity exploitation performance at the presence of channel variations, as it enables the adaptability to the sparseness by tuning of p parameter. However, the decimal exponential calculation associated with the p-norm-like constraint LMS algorithm poses considerable limitations in practical application. In this paper, a simplified variant of the p-norm-like constraint LMS was proposed with the employment of Newton iteration method to approximate the decimal exponential calculation. Numerical simulations and the experimental results obtained in physical shallow water channels demonstrate the effectiveness of the proposed method compared to traditional norm constraint LMS algorithms. 相似文献
362.
This paper presents an accurate engine fuel injection quantity control technique for high pressure common rail (HPCR) injection
systems by an iterative learning control (ILC)-based, on-line calibration method. Accurate fuel injection quantity control
is of importance in improving engine combustion efficiency and reducing engine-out emissions. Current Diesel engine fuel injection
quantity control algorithms are either based on pre-calibrated tables or injector models, which may not adequately handle
the effects of disturbances from fuel pressure oscillation in HPCR, rail pressure sensor reading inaccuracy, and the injector
aging on injection quantity control. In this paper, by using an exhaust oxygen fraction dynamic model, an on-line parameter
calibration method for accurate fuel injection quantity control was developed based on an enhanced iterative learning control
(EILC) technique in conjunction with HPCR injection system. A high-fidelity, GT-Power engine model, with parametric uncertainties
and measurement disturbances, was utilized to validate such a methodology. Through simulations at different engine operating
conditions, the effectiveness of the proposed method in rejecting the effects of uncertainties and disturbance on fuel injection
quantity control was demonstrated. 相似文献
363.
In this paper, with the parameters acquired from measured and tested data, a three-phase mathematical model is applied to
the motor component of the developed electromagnetic suspension actuator. A main/inner-loop structure is used for its active
control, and the constraints of the control current and energy flow states of actuator are analyzed by simplifying the inner-loop
control system. Two different control modes, i.e., Consumptive Full Active (CFA) and Regenerative Semi Active (RSA) modes,
which emphasize vibration control of sprung mass and vibration energy regeneration caused by road roughness, respectively,
are proposed. Simulations are carried out using different road conditions, and the results demonstrate that the CFA mode can
improve vehicle ride comfort by more than 30 percent, despite battery energy consumption; in RSA mode, the ride comfort can
be improved by up to 10 percent with the battery charged by regenerated energy. 相似文献
364.
B. Assadsangabi F. Daneshmand N. Vahdati M. Eghtesad Y. Bazargan-Lari 《International Journal of Automotive Technology》2011,12(6):921-932
In this paper, first a new design for a disk-type magneto-rheological (MR) brake for automotive applications is proposed and
then, a finite element analysis is performed to analyze the resulting magnetic field intensity distribution within the MR
brake configuration. This finite element model of the brake is then utilized in a optimization process which incorporates
Genetic Algorithm (GA) to obtain optimal design parameters. The optimization process goal is to increase the braking torque
capacity of the brake while keeping the weight of the brake as low as possible. Although, the braking torque of the present
design is larger compared to the previous designs, the braking toque capacity of the present design is still smaller than
the required braking torque for automobiles. 相似文献
365.
F. Uffelmann Direktor: Prof. Dr.-Ing. M. Mitschke 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1978,7(4):183-201
Simulation of Steering and Braking Behaviour of Tractor-Semitrailer Vehicles in Extreme Situations
This paper deals with the simulation of the behaviour of tractor-semitrailer vehicles at braking on wet, slippery road surface. The nonlinear model used for the computation enables to simulate extreme situations at wheel locking and swerving
The instabilities during braking such as jackknifing and trailer swing as well as non steerability are investigated. Straightline braking shows the influence of cornering on the behaviour during braking in a turn. 相似文献
This paper deals with the simulation of the behaviour of tractor-semitrailer vehicles at braking on wet, slippery road surface. The nonlinear model used for the computation enables to simulate extreme situations at wheel locking and swerving
The instabilities during braking such as jackknifing and trailer swing as well as non steerability are investigated. Straightline braking shows the influence of cornering on the behaviour during braking in a turn. 相似文献
366.
367.
Sergio?Jara-DíazEmail author Beatriz?Tovar De La Fé Lourdes?Trujillo 《Transportation》2005,32(3):275-291
Cargo handling in ports is a multioutput activity, as freight can arrive in many forms such as containers, bulk, rolling stock, or non-containerised general cargo. In this paper, the operation of cargo handling firms in a Spanish port is analysed through the estimation of a multioutput cost model that uses monthly data on three representative firms located at the Las Palmas port. This permits the calculation of product specific marginal costs, economies of scale (general and by firm) and economies of scope, which help identifying optimal pricing policies and the potential cost advantages of increasing production. 相似文献
368.
Ronald F. Kirby 《Transportation》1981,10(1):61-86
This paper reviews a number of recent innovations in the regulation and operation of taxicabs in U. S. cities. The paper discusses the growing involvement of various levels of government in public transportation programs which affect the taxicab industry, and identifies the opportunities and problems created for the industry by this increased government activity. Innovations in the types of public transportation services which can be provided by taxicabs are discussed first, followed by a review of the administrative procedures which can be employed to involve taxicab companies in publicly funded programs. Proposals for changes in the regulations governing taxicab services and prices are discussed next, with particular attention to significant regulatory changes which have been implemented in U.S. cities in recent years. Finally, innovations in the technology of taxicab operations are reviewed, including improvements to vehicles, computerized dispatching techniques, and procedures and equipment for computing fares for taxicab services. 相似文献
369.
Helmut F. Bauer 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1972,1(3):227-260
The unrestrained free surface of a liquid has an alarming propensity to undergo large excursions for even very small motions of the container. This fact may endanger the stability, as well as the riding and maneuvering quality of the vehicle considerably. It is particularly true for fuel- or cargo tanks of automotive vehicles, railroad tank cars, for fuel tanks of large ships and tankers, for which violent sea conditions at times result in fairly large amplitudes of pitching, heaving and rolling, as well as for airplanes and spacevehicles flying through atmospheric disturbances. The response of liquids contained in cargo- or fuel tanks is therefore of quite some concern, especially in those cases where the sloshing liquid masses occupy a large amount of the total mass of the vehicle.
For this reason the theory of liquid motion with a free surface is presented for containers of various geometries. Forces and moments of the liquid exerted upon the vehicle are presented and a simple mechanical model for the representation of the liquid motion is derived. Methods for the reduction of the destabilizing effect of the liquid motion, such as baffles, cross walls and surface coverings are presented and shall exhibit their effectiveness. In addition the interaction of the liquid motion with the elastic structure of the container, as well as the interaction with a controlling system of the vehicle shall be demonstrated. Stability boundaries, design criteria and dynamic responses to disturbances shall be presented for a particular case. 相似文献
For this reason the theory of liquid motion with a free surface is presented for containers of various geometries. Forces and moments of the liquid exerted upon the vehicle are presented and a simple mechanical model for the representation of the liquid motion is derived. Methods for the reduction of the destabilizing effect of the liquid motion, such as baffles, cross walls and surface coverings are presented and shall exhibit their effectiveness. In addition the interaction of the liquid motion with the elastic structure of the container, as well as the interaction with a controlling system of the vehicle shall be demonstrated. Stability boundaries, design criteria and dynamic responses to disturbances shall be presented for a particular case. 相似文献
370.