基于Multi-Agent的城市停车需求预测系统研究

近年来,停车问题随着现代化进程的发展而日益受到人们的关注,因此,急需解决停车问题。鉴于一般的停车需求预测模型得不到很好的结果,所以,尝试结合土地与交通影响分析的停车需求预测模型以及Agent技术,建立基于Multi-Agent的城市停车需求预测系统。     

Experimental investigation of TARMAX model for modeling of hydrodynamic forces on cylinder-like structures

A new approach that models lift and drag hydrodynamic force signals operating over cylindrical structures was developed and validated. This approach is based on stochastic auto regressive moving average with exogenous (ARMAX) input and its time-varying form, TARMAX. Model structure selection and parameter estimation were discussed while considering the validation stage. In this paper, the cylindrical structure was considered as a dynamic system with an incoming water wave and resulting forces as the input and outputs, respectively. The experimental data, used in this study, were collected from a full-scale rough vertical cylinder at the Delft Hydraulics Laboratory. The practicality of the proposed method and also its efficiency in structural modeling were demonstrated through applying two hydrodynamic force components. For this purpose, an ARMAX model is first used to capture the dynamics of the process, relating in-line forces provided by water waves;secondly, the TARMAX model was applied to modeling and analysis of the lift forces on the cylinder. The evaluation of the lift force by the TARMAX model shows the model is successful in modeling the force from the surface elevation.     

节温器总成密封失效故障分析及优化设计

针对某小型汽油机在试验中出现的节温器总成泄露故障,全面分析可能导致失效的影响因素,逐一排查,并建立有限元模型加以分析,结合实验数据,提出优化方案加以改进,最终通过对比试验,确认优化措施得当,改进效果显著,有效解决了泄露问题.     

Experimental and numerical investigation of fuel mixing effects on soot structures in counterflow diffusion flames

Experimental and numerical analyses of laminar diffusion flames were performed to identify the effect of fuel mixing on soot formation in a counterflow burner. In this experiment, the volume fraction, number density, and particle size of soot were investigated using light extinction/scattering systems. The experimental results showed that the synergistic effect of an ethylene-propane flame is appreciable. Numerical simulations showed that the benzene (C₆H₆) concentration in mixture flames was higher than in ethylene-base flames because of the increase in the concentration of propargyl radicals. Methyl radicals were found to play an important role in the formation of propargyl, and the recombination of propargyl with benzene was found to lead to an increase in the number density for cases exhibiting synergistic effects. These results imply that methyl radicals play an important role in soot formation, particularly with regard to the number density.     

Advanced hybrid energy storage system for mild hybrid electric vehicles

Hybrid electric vehicles (HEV) utilize electric power and a mechanical engine for propulsion; therefore, the performance of HEVs is directly influenced by the characteristics of the energy storage system (ESS). The ESS for an HEV generally requires high power performance, long cycle life, reliability and cost effectiveness; thus, a hybrid energy storage system (HESS) that combines different types of storage devices has been considered to fulfill both performance and cost requirements. To improve the operating efficiency and cycle life of a HESS, an advanced dynamic control regime in which pertinent storage devices in the HESS can be selectively operated based on their status is presented. Verification tests were performed to confirm the degree of improvement in energy efficiency. In this paper, an advanced HESS with a battery management system (BMS) that includes an optimal switching control function based on the estimated state of charge (SOC) is presented and verified.     

On-road assessment of in-vehicle driving workload for older drivers: Design guidelines for intelligent vehicles

There has been recent interest in intelligent vehicle technologies, such as advanced driver assistance systems (ADASs) or in-vehicle information systems (IVISs), that offer a significant enhancement of safety and convenience to drivers and passengers. However, the use of ADAS- and IVIS-based information devices may increase driver distraction and workload, which in turn can increase the chance of traffic accidents. The number of traffic accidents involving older drivers that are due to distraction, misjudgment, and delayed detection of danger, all of which are related to the drivers’ declining physical and cognitive capabilities, has increased. Because the death rate in traffic accidents is higher when older drivers are involved, finding ways to reduce the distraction and workload of older drivers is important. This paper generalizes driver information device operations and assesses the workload while driving by means of experiments involving 40 drivers in real cars under actual road conditions. Five driving tasks (manual only, manual primarily, visual only, visual primarily, and visual-manual) and three age groups (younger (20–29 years of age), middle-aged (40–49 years of age), and older (60–69 years of age)) were considered in investigating the effect of age-related workload difference. Data were collected from 40 drivers who drove in a real car under actual road conditions. The experimental results showed that age influences driver workload while performing in-vehicle tasks.     

Development of a fiber-reinforced plastic armrest frame for weight-reduced automobiles

This paper presents the design optimization process of a short fiber-reinforced plastic armrest frame to minimize its weight by replacing the steel frame with a plastic frame. The analysis was carried out with the equivalent mechanical model and design of experiment (DOE) method. Instead of considering the whole structure, it is divided into three simpler regions to reduce the complexity of the problem through examining its structural characteristics and load conditions. The maximum stress and deflection of the regions that carry the normal load are calculated by the analytical mathematical form derived from an equivalent model. The other regions loaded by contact stress are handled by FEM (finite element method), the DOE method, and the RSM (response surface model). To optimize the design variables in both cases, the object functions derived from these calculations are solved with a CAE (computer aided engineering) tool. This method clearly shows the mechanical and mathematical representation of structural optimization and reduces the computing costs. After design optimization, the weight of the optimum plastic-based armrest frame is reduced by about 18% compared to the initial design of a plastic frame and is decreased by 50% in comparison with the steel frame. Some prototypical armrest frames were also made by injection molding and tested. The research results fulfilled all of the design requirements.     

Automobile defrosting system analysis through a full-scale model

Adequate visibility through the automobile windshield is of paramount practical significance, most often at very low temperatures when ice tends to form on the windshield screen. But the numerical simulation of the defrost process is a challenging task because phase change is involved. In this study numerical solution was computed by a finite volume computational fluid dynamics (CFD) program and experimental investigations were performed to validate the numerical results. It was found that the airflow produced by the defrost nozzle is highly nonuniform in nature and does not cover the whole windshield area. The nonuniformity also severely affected the heating temperature pattern on the windshield. The windshield temperature reached a maximum in the vicinity of the defroster nozzle in the lower part of the windshield and ranged from 9∼31°C over a period of 30 min, which caused the frost to melt on the windshield. The melting time was under 10 minutes, which satisfied the NHTSA standard. The numerical predictions were in close agreement with the experimental results. Thus, CFD can be a very useful design tool for an automobile HVAC system.     

Effect of punch angle on energy absorbing characteristics of tube-type crash elements

As a crash energy absorber, a tube-type crash element (expansion tube) dissipates kinetic energy through the internal deformation energy of the tube and through frictional energy. In this paper, the effects of the variation of punch angles on the energy-absorbing characteristics of expansion tubes were studied by quasi-static tests using three punch angles (15°, 30°, and 45°). A finite element analysis of the tube expanding process (m = τ _max /K) was performed using a shear friction model to confirm the variation of the shear friction factor with respect to punch angles using the inverse method. Additional analyses were performed using angles of 20°, 25°, 35°, and 40° to study the effect of the punch angles on the internal deformation energy, frictional energy, and expansion ratio of the tubes. The results of the experiment and finite element analysis showed that the shear friction factor was inversely proportional to the punch angles, and a specific punch angle existed at which the absorbed energy and expansion ratio remained constant.     

Sideslip angle estimation considering short-duration longitudinal velocity variation

The accurate estimation of sideslip angle is necessary for many vehicle control systems. The detection of sliding and skidding is especially critical in emergency situations. In this paper, a sideslip angle estimation method is proposed that considers severe longitudinal velocity variation over the short period of time during which a vehicle may lose stability due to sliding or spinning. An extended Kalman filter (EKF) based on a kinematic model of a vehicle is used without initialization of the inertial measurement unit to estimate vehicle longitudinal velocity. A dynamic compensation method that compensates for the difference in the locations of the vehicle velocity sensor and the IMU in on-road vehicle tests is proposed. Evaluations with a CarSim™ 27-degree-of-freedom (DOF) model for various vehicle test scenarios and with on-road tests using a real vehicle show that the proposed sideslip angle estimation method can accurately predict sideslip angle, even when vehicle longitudinal velocity changes significantly.