Engine clutch torque estimation for parallel-type hybrid electric vehicles

This paper mainly focuses on the accurate estimation of the torque transferred through the engine clutch installed between the engine and the drive motor in parallel-type hybrid electric vehicles. The estimation of the engine clutch torque primarily relies on the forward-direction observer which uses the nominal engine net torque information. To overcome the limitation of using the nominal engine torque information that it may not be accurate during the transient states or due to the influence of external disturbance such as the road condition and wind, the forward-direction observer is supplemented by the use of reverse-direction observer which uses the driveline model and wheel speed measurements. In addition, the drive motor torque information is used to calibrate the nominal engine torque during the idle charging state, so that the driveline characteristic unique to parallel-type hybrid electric vehicle can be utilized to increase the estimation accuracy. Finally, the estimation performance of the designed observer is tested via simulation and experiments based on a real vehicle.     

Coordinated control of ESC and AFS with adaptive algorithms

This paper presents a coordinated control of electronic stability control (ESC) and active front steering (AFS) with adaptive algorithms for yaw moment distribution in integrated chassis control (ICC). In order to distribute a control yaw moment into control tire forcres of ESC and AFS, and to coordinate the relative usage of ESC to AFS, a LMS/Newton algorithm (LMSN) is adopted. To make the control tire forces zero in applying LMS and LMSN, the zero-attracting mechanism is adopted. Simulations on vehicle simulation software, CarSim®, show that the proposed algorithm is effective for yaw moment distribution in integrated chassis control.     

Subjective absolute discomfort threshold due to idle vibration in passenger vehicles according to sitting posture

Idle vibration, occurring when a vehicle comes to a stop while the engine is on, is known to be a main cause of discomfort for passengers, and the customer effect has been recently growing. The frequency of idle vibration is determined by the engine type. To lower the vibration, various technologies have been applied to optimize the engine mount and vehicle body structure. In addition to the technological developments, research on human response with a consideration of idle vibration is needed to effectively reduce the level of discomfort experienced by passengers. Seats aimed at enhancing static comfort influence the sitting posture of passengers; sitting posture is a factor affecting human body characteristics that response to idle vibration. This study examined the absolute discomfort threshold of idle vibration according to the sitting postures of 13 taxi drivers. The four sitting postures of subjects on a rigid-body seat without a backrest were variables in the determination of absolute discomfort threshold of idle vibration. The absolute discomfort threshold curves obtained in this experiment were less sensitive to frequency changes than the frequency weighting function of ISO 2631-1.     

In-depth understanding of lane changing interactions for in-vehicle driving assistance systems

Lane-changing events are often related with safety concern and traffic operational efficiency due to complex interactions with neighboring vehicles. In particular, lane changes in stop-and-go traffic conditions are of keen interest because these events lead to higher risk of crash occurrence caused by more frequent and abrupt vehicle acceleration and deceleration. From these perspectives, in-depth understanding of lane changes would be of keen interest in developing in-vehicle driving assistance systems. The purpose of this study is to analyze vehicle interactions using vehicle trajectories and to identify factors affecting lane changes with stop-and-go traffic conditions. This study used vehicle trajectory data obtained from a segment of the US-101 freeway in Southern California, as a part of the Next Generation Simulation (NGSIM) project. Vehicle trajectories were divided into two groups; with stop-and-go and without stop-and-go traffic conditions. Binary logistic regression (BLR), a well-known technique for dealing with the binary choice condition, was adopted to establish lane-changing decision models. Regarding lane changes without stop-and-go traffic conditions, it was identified based on the odd ratio investigation that he subject vehicle driver is more likely to pay attention to the movement of vehicles ahead, regardless of vehicle positions such as current and target lanes. On the other hand, the subject vehicle driver in stop-and-go traffic conditions is more likely to be affected by vehicles traveling on the target lane when deciding lane changes. The two BLR models are adequate for lane-changing decisions in normal and stop-and-go traffic conditions with about 80 % accuracy. A possible reason for this finding is that the subject vehicle driver has a tendency to pay greater attention to avoiding sideswipe or rear-end collision with vehicles on the target lane. These findings are expected to be used for better understanding of driver’s lane changing behavior associated with congested stop-and-go traffic conditions, and give valuable insights in developing algorithms to process sensor data in designing safer lateral maneuvering assistance systems, which include, for example, blind spot detection systems (BSDS) and lane keeping assistance systems (LKAS).     

Characterization and evolution of spatial density patterns in urban areas

This paper examines the spatial patterns of population density, household automobile ownership and other socio-demographic variables that affect urban travel, as a function of distance from the central city core. Spatial density functions provide a useful characterization of urban structure, and of its evolution when taken at different time intervals. Analysis of the data from four case cities (Austin, Atlanta, Dallas, Phoenix) for 1960, 1970 and 1980 reveals continuing overall dispersion away from the traditional central core, accompanied by the densification of formerly low-density suburbs. This presents implications for high congestion levels in the densifying suburban communities, comparable to those typically associated with the CBD. In addition, the analysis has captured the continuing growth of average household automobile ownership and revealed a distinct spatial pattern that seems to be robust across the case areas considered, as well as within radial corridors in the one case that was so analyzed (Austin).List of symbols Y gross population density in census tractt - X _t distance in miles from the center of tract to the CBD - parameter representing the central business district density - y density gradient parameter - X₀, X₁, X2, and X3 locations of the knots in a three segment division of the x-axis - D_i dummy variable defined for thei-th segment - ₁ normally distributed disturbance term,a _i,b _i,c _i,d _i,i = 1, 2, 3 — parameters to be estimated - A _t area of census tractt     

Research on the Influencing Factors on Quality of Railway Construction EPC Project from the Owner's PerspectiveEI北大核心

Research purposes: With the advancement of system reform of China railway, the railway construction project is promoting the application of general contracting (EPC) model, and in this mode, how the owners effectively control the construction quality has become the focus of the current research. To explore of the key factors influencing quality of railway construction project, based on the owner's perspective, from the three stages of design, procurement and construction selecting 10 factors, the DEMATEL method is adopted to analyze the logical relationship between various factors and mutual influence, screening factors which have higher centrality and causality as the key factors affecting the quality of the owner engineering. Research conclusions:(1) The design port and interface management, the comprehensive strength of the construction companies have high centrality and causality, which are the key factors influencing quality of the EPC railway construction project. (2) The situation of carrying out periodic inspection work belongs to the factor with low centrality and high causality. In the process of improving quality of the EPC railway construction project, this factor can be the secondary consideration. (3) The research result can provide scientific and effective references for improving quality of the EPC railway construction project from the owner's perspective. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

Static Load Test of Low Vibration Track under Heavy Haul TrainEI北大核心

Research purposes: Low vibration track is a suitable track structure in the heavy haul railway long tunnel. Taking the low vibration track in the middle-south channel tunnel as the research object, through the full-scale model static load test, this paper studies the mechanical properties of a single bearing block under the vertical load at the end of the track bed slab (working condition 1), the horizontal and vertical load at the end of the track bed slab (working condition 2), the vertical load at the middle of the track bed slab (working condition 3) and track's crack development trend. Research conclusions:(1) Taking the static load of 30 t axle load train as a reference, the track slab and bearing block concrete of working condition 1 reach the axial tensile strength at 3.3 and 3.1 times static wheel load, the track slab and bearing block concrete of working condition 2 reach the axial tensile strength at 3.0 and 3.1 times static wheel load, the track slab and bearing block concrete of working condition 3 reach the axial tensile strength at 4.9 and 2.9 times static wheel load. (2) Track slab's crack of working condition 1 appears at the corner of the bearing block and the midline of the long side of the bearing block and extends to the short side of the track slab. The crack extension at the corner point is in the shape of "eight". There is no obvious crack of working condition 3 in the track slab. (3) The horizontal load of the train leads to the increase of the force of the concrete in the corner of the bearing block. (4)The research results have guiding significance for the design, construction and maintenance of low vibration track. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

Training Needs of Coastal Resources Decision Makers in Ohio's Lake Erie Basin

This article describes results from a study focused on informational and knowledge needs of local coastal resources decision makers in the Ohio Lake Erie basin. New information was obtained through a series of focus groups of local decision makers and key training providers in the basin. The results suggest that training providers and local coastal resources decision makers have differing perceptions of knowledge and information needs and training venues. The results suggest a role for state and federal agency training providers as coordinators and facilitators of an enhanced learning network among decision makers, including support of an information clearinghouse, adoption of appropriate e-based learning modalities, and regionally based learning and practice networks to improve the function of the training market to meet local decision maker needs.     

Economic value of natural Coastal wetlands: A critique

Recent estimates by J. Gosselink, E. Odum, and R. Pope of the economic value of natural wetlands have had considerable impact on analyses and discussions of public policies concerning natural wetlands management. However, these economic value estimates are neither conceptually nor empirically correct. First, these workers failed to recognize the nature of the process by which economic values are determined and made an illegitimate marriage of the principles of systems ecology and economic theory. Second, where Gosselink et al. attempted to apply proper economic principles, their calculations resulted in economic value estimates that are most likely in error.     

A velocity and payload dependent emission model for heavy-duty road freight transportation

The paper develops a forecasting model of emissions from traffic flows embracing the dynamics of driving behavior due to variations in payload. To measure of emissions at the level of individual vehicles under varying payloads a portable emission measurement system is used. This paper reports on a model based on data at the level of individual vehicles for a representative road trajectory. The model aggregates the data to the level of a homogeneous flow dependent of velocity and specific power, which is dependent on payload weight. We find a lean specification for the model that provides emission factors for CO₂, NO_x, HC, CO, and NO₂. The results indicate that, in comparison with earlier models, NO_x emissions in particular tend to be underestimated.