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951.
Vincenzo Alfieri Giuseppe Conte Carmen Pedicini 《International Journal of Automotive Technology》2018,19(3):405-412
The objective of this study is to investigate a nonlinear model-based multivariable (MIMO, Multi Input Multi Output) technique to decouple actuators interaction and to reduce the calibration effort, while increasing control performances, above all in transient conditions, and robustness with respect to model uncertainties and system parameter variations. The presented control technique is based on the development of a nonlinear dynamical physical model of the diesel air and charging system. Feedback Linearization control is then applied to decouple actuators’ interactions and compensate for nonlinearities. A new set of virtual inputs are defined inverting the system differential equations. Relation among the new virtual inputs and the outputs is purely linear and decoupled, meaning that each virtual input affects linearly only one output. Moreover, a linear control block is added to guarantee transient and steady state performances and closed loop robustness. The proposed control approach has been validated through small diesel engine dyno and vehicle activities. Transient test bench maneuvers show that the control is able to coordinate the actuators in order to fulfill the targets and to guarantee similar performances in different operating points. In addition the robustness to environmental changes has been demonstrated by vehicle tests at different ambient conditions. 相似文献
952.
WANGDong LIZhuang-yun ZHUYu-quan 《船舶与海洋工程学报》2003,2(1):35-40
Water hydraulic systems have provoked major interest because of the human friendly and environmental safety aspects. Piston pump is one of the most frequently used hydraulic units in recent engineering technique. In water hydraulic piston pump, poor lubrication is more likely to happen than in oil hydraulic one because of difference in properties between water and oil. So there are some key problems such as corrosive wear and erosion, which are investigated briefly. Many new materials have been developed, which give longer life expectancies with water without corrosion and erosion. A new type of seawater hydraulic piston pumps with better suction characteristics had been developed at HUST. Much of this research has concentrated on new materials, structure and experiments, which are also specially introduced. 相似文献
953.
The energy distribution model of motion blurred star point is analyzed. The distribution of the star point approximates to a two-dimensional (2D) Gaussian distribution under degeneration. Two multi-parameter nonlinear Gaussian fitting methods (GFMs) are proposed, and the relationship between fitting parameters and motion blur parameters is analyzed. Estimation of the parameters of motion blur by fitting parameters is calculated to realize the error compensation of the motion blur. The simulation results show the effectiveness and accuracy. 相似文献
954.
The dissolution of a relationship is a life event that often coincides with many other changes in life, such as a decline in income level or household size or a change in place of residence. This study aims to provide more insight into the ways in which circumstances shortly following the disruption of a relationship affect travel behaviour. Register data that combines information on the Dutch population, income and vehicle registration are used to understand how personal situations that are closely related to relationship disruption affect car ownership. The study shows that several characteristics of singles and single partners shortly after a breakup negatively affect car ownership. For instance, a relatively low income level, unemployment, living in a city or a residential move all affect car ownership negatively. This study focuses on the role of circumstances shortly after relationship disruption, demonstrating the importance of such an event. 相似文献
955.
Most efficient indeces and query techniques over XML (extensible markup language) data are based on a certain labeling scheme, which can quickly determine ancestor-descendant and parent-child relationship between two nodes. The current basic labeling schemes such as containment scheme and prefix scheme cannot avoid relabeling when XML documents are updated. After analyzing the essence of existing dynamic XML labels such as compact dynamic binary string (CDBS) and vector encoding, this paper gives a common unifying framework for the numeric-based generalized dynamic label, which can be implemented into a variety of dynamic labels according to the different user-defined value comparison methods. This paper also proposes a novel dynamic labeling scheme called radical sign label. Extensive experiments show that the radical sign label performs well for the initialization, insertion and query operations, and especially for skewed insertion where the storage cost of the radical sign label is better than that of former methods. 相似文献
956.
Skin detection has been considered as the principal step in many machine vision systems, such as face detection and adult
image filtering. Among all these techniques, skin color is the most welcome cue because of its robustness. However, traditional
color-based approaches poorly perform on the classification of skin-like pixels. In this paper, we propose a new skin detection
method based on the cascaded adaptive boosting (AdaBoost) classifier, which consists of minimum-risk based Bayesian classifier
and models in different color spaces such as HSV (hue-saturation-value), YCgCb (brightness-green-blue) and YCgCr (brightness-green-red).
In addition, we have constructed our own database that is larger and more suitable for training and testing on filtering adult
images than the Compaq data set. Experimental results show that our method behaves better than the state-of-the-art pixel-based
skin detection techniques on processing images with skin-like background. 相似文献
957.
Indoor air pollutants impact human health, comfort and productivity. The method of photocatalysis has been applied mainly
in flow reactors and little information is available on indoor air pollutant removal in airtight reactors. In the paper, experiments
were carried out to remove formaldehyde (HCHO), ammonia (NH3) and volatile organic compounds (VOCs) in the airtight and ventilated chambers. Results demonstrated that 90.4% of HCHO,
92.3% of NH3 and 57.9% of VOCs were removed in the amine adsorption process, while 67.5% (hereinbefore, these are the mass fraction) of
HCHO, 60.0% of NH3, and 61.2% of VOCs were removed in the photocatalytic process. However, ozone-assisted photocatalytic process showed great
potential to degrade indoor air pollutants in the ventilated chamber. Factors and mechanisms of the photocatalytic degradation
of HCHO, NH3 and VOCs were also discussed. 相似文献
958.
A method of underwater simultaneous localization and mapping (SLAM) based on on-board looking forward sonar is proposed. The
real-time data flow is obtained to form the underwater acoustic images and these images are pre-processed and positions of
objects are extracted for SLAM. Extended Kalman filter (EKF) is selected as the kernel approach to enable the underwater vehicle
to construct a feature map, and the EKF can locate the underwater vehicle through the map. In order to improve the association
efficiency, a novel association method based on ant colony algorithm is introduced. Results obtained on simulation data and
real acoustic vision data in tank are displayed and discussed. The proposed method maintains better association efficiency
and reduces navigation error, and is effective and feasible. 相似文献
959.
The asymmetric deformation and eccentricity problems of near hemispherical diaphragm under the uniform surface load are quantitatively
characterized in the paper. The analysis is based on a 3D finite element analysis (FEA) model established according to elastic-plasticity
and large displacement nonlinear finite element method. Besides, the deformation experiments are taken to validate the reliability
of FEA model which shows that the simulation results are in good agreement with the experimental results. Then, three angle
parameters, deflection angle β, circumvolving angle θ and distributing angle γ, are introduced and expressed to characterize the asymmetric deformation and eccentricity quantitatively. According to the
angle parameters, the inversion processes of uniform thickness diaphragm and varying thickness diaphragm are calculated respectively.
The inversion process of varying thickness diaphragm is much steadier than that of uniform thickness diaphragm. The present
results show that the asymmetric deformation process can be characterized by curve of three angle parameters (β, θ, γ) exactly, the degrees of eccentricity can be indicated by the final value of deflection angle and the eccentricity position
can be characterized by the final values of the three angle parameters. 相似文献
960.
Underwater gliders are highly efficient, buoyancy-driven, and winged autonomous underwater vehicles. Their dynamics are multivariable
nonlinear systems with unstable internal dynamics and thus their motion control is a significant challenge. To improve the
inherent efficiency and enhance the behavior of the underwater glider over a wide operating regime, a nonlinear feedforward
and feedback controller was developed. The nonlinear feedforward control design is based on a new stable inversion technique
which determines a causal and bounded solution for the unstable internal dynamics. The feedback control law was designed by
a quadratic optimal control method. Simulation results show that the derived control system is able to deal with nonminimum
phase system and successfully achieves the tracking of planned output trajectories from initial to final conditions. Furthermore,
the control effort is very low, which means the glider with limited power storage has longer range and higher endurance. 相似文献