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441.
D.A. Crolla H. B. Spencer 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1984,13(1):1-17
Tractor behaviour on sloping ground following a control loss due to rear wheel locking is examined. A mathematical model to predict the tractor trajectory is presented and the results obtained from this model are compared with those obtained from experiments with a remotely controlled tractor.
Reasonable agreement is reached between measured and predicted results - the discrepancies arise from limited tyre data or local random variations in slope, ground roughness or tyre/ground frictional values.
Within these limitations, the model is used to examine possible driver strategies following a control loss. Applying and maintaining full lock for this particular type of accident appears to improve safety; it certainly tends to avoid the worst situation in which the tractor accelerates backwards down the slope and reaches dangerously high speeds although inevitably it increases the likelihood of a low speed overturn. 相似文献
Reasonable agreement is reached between measured and predicted results - the discrepancies arise from limited tyre data or local random variations in slope, ground roughness or tyre/ground frictional values.
Within these limitations, the model is used to examine possible driver strategies following a control loss. Applying and maintaining full lock for this particular type of accident appears to improve safety; it certainly tends to avoid the worst situation in which the tractor accelerates backwards down the slope and reaches dangerously high speeds although inevitably it increases the likelihood of a low speed overturn. 相似文献
442.
In contrast to the centralized port-planning framework that is utilized in some industrialized countries, the US relies on a complex and fragmented framework in which responsibility for the planning, development and operation of landside maritime infrastructure rests with State and local governments. It has been argued that the separation of the federal government from port policy was rooted in the port preference clause of the Constitution. This paper is an effort to determine whether the current decentralized port policy in fact stems from the Constitution and, to that end, reviews how over the years the US Supreme Court has construed the port preference clause in the Constitution. It was found that there is no evidence to support the assertion that the port preference clause has restricted the development of Federal port policy. Moreover, the decentralized and fragmented decision-making process that is evident today does not imply the absence of federal impact. Rather, it reflects federal involvement through multiple agencies and regulatory processes and is a conscious effort, consistent with other areas of transport infrastructure development, to retain local decision-making for infrastructure investments. It is concluded by raising the issue whether current federal involvement in ports (that is, existing federal port policy), through dredging, landside transportation improvements or subsidized capital, among other things, needs to be reappraised before a new round of capital intensive investment begins. 相似文献
443.
Christopher H. Lovelock 《Transportation》1975,4(3):253-265
Most models of modal choice are macroanalytic in nature — focusing on the behavior of large groups of travelers — and have limited explanatory power. Transportation managers need to know more about the decision processes of individual travelers in selecting a mode for a particular trip, if they are to be able to develop strategies for influencing these decisions. A microanalytic model of modal choice is therefore developed in flow-chart form, clarifying the stages in the modal choice decision process for any given trip. Individual consumers are seen as trying to satisfy a particular travel need by first specifying the characteristics of the trip itself and then specifying the “ideal” modal attributes required for this trip. Next, the perceived characteristics of a limited number of modes are evaluated against this “ideal” solution and the consumer is assumed to select that mode which provides the best match. The model explicitly recognizes the impact of psychological variables on modal choice as well as the consumer's need for information if he or she is to evaluate realistically all alternatives. 相似文献
444.
A. H. Wickens 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1975,5(1):15-46
For railway vehicles having coned wheels mounted on solid axles there is a conflict between dynamic stability and steering ability
It is shown that the stiffness and kinematic properties of all possible interwheelset connections are characterised by two properties describing the distortional characteristics of the vehicle in plan. Within this framework, the various possibilities for steered wheelsets are considered, and several past and current proposals are reviewed. Using the linear approach to dynamic stabibty and curve negotation the performance of existing and newly proposed configurations is discussed
For any symmetric, two-axle vehicle it is shown that for perfect steering on a curve there should be zero bending stiffness between the wheelsets. It is further shown that if the bending stiffness is zero, the vehicle lacks dynamic stability as the critical speed of instability, is zero. In this case, the vehicle undergoes a steering oscillation which occurs at the kinematic frequency of a single wheelset and which is a motion in which pure rolling occurs
Similar results are obtained with vehicles with three or more axles if adjacent axles are connected by shear structures. However, it is shown that it is possible to satisfy both the requirements of perfect steering and a non-zero critical speed if the vehicle has zero bending stiffness and if, in addition to adjacent wheelsets being connected in shear, at least one pair of non-adjacent axles are connected by a shear structure. 相似文献
It is shown that the stiffness and kinematic properties of all possible interwheelset connections are characterised by two properties describing the distortional characteristics of the vehicle in plan. Within this framework, the various possibilities for steered wheelsets are considered, and several past and current proposals are reviewed. Using the linear approach to dynamic stabibty and curve negotation the performance of existing and newly proposed configurations is discussed
For any symmetric, two-axle vehicle it is shown that for perfect steering on a curve there should be zero bending stiffness between the wheelsets. It is further shown that if the bending stiffness is zero, the vehicle lacks dynamic stability as the critical speed of instability, is zero. In this case, the vehicle undergoes a steering oscillation which occurs at the kinematic frequency of a single wheelset and which is a motion in which pure rolling occurs
Similar results are obtained with vehicles with three or more axles if adjacent axles are connected by shear structures. However, it is shown that it is possible to satisfy both the requirements of perfect steering and a non-zero critical speed if the vehicle has zero bending stiffness and if, in addition to adjacent wheelsets being connected in shear, at least one pair of non-adjacent axles are connected by a shear structure. 相似文献
445.
J. Yang G. L. Wang Z. J. Wan C. Liang H. C. Zhou 《International Journal of Automotive Technology》2016,17(4):639-649
Two types of radial tire 11.00R20 and 385/65R22.5 are chosen as the research objects, and their carcass contours are redesigned by using Sakai Hideo’s, Frank’s and the new non-natural equilibrium contour design theories, which were based on analyzing the current non-equilibrium contour design theories of radial tire. Then the tire wear, rolling resistance and grip performance of the two radial tires designed by different non-natural equilibrium contour design theories are comprehensively analyzed with the finite element software ABAQUS. The results show that Frank’s contour design theory can reduce tire wear; the new non-natural equilibrium contour design theory can enhance tire wear, rolling resistance performance, etc. It is also found that the tire carcass contour has great influence on tire performance, especially on the tire rolling resistance. The new non-natural equilibrium contour theory provides a guidance to reduce the tire rolling resistance, and it can break through the target conflicts in tire performance. The tire with the new non-natural equilibrium carcass contour can enhance its comprehensive performance. 相似文献
446.
Motor vehicle passenger airbags have been proven to be effective for reducing the possibility of passenger injury during a crash. However, the inflation of the airbag sometimes causes serious injury when a passenger is positioned close to the airbag. The United States Federal Motor Vehicle Safety Standard (FMVSS) 208 requires the use of a low-riskdeployment (LRD) passenger airbag system. This paper proposes a newly developed airbag system comprising two slim airbags mounted on the instrument panel. A series of tests were conducted using the FMVSS 208 test procedures to demonstrate the effectiveness of the proposed system. It was found that the system not only satisfied the injury criteria of FMVSS 208, but was also effective for protecting passengers of all sizes. 相似文献
447.
J. S. Kim S. M. Kim J. H. Jeong S. C. Jeong J. W. Lee 《International Journal of Automotive Technology》2016,17(5):865-872
In recent years, a hybrid electric vehicle (HEV) has been considered a successful technology. Especially, in case of a full HEV, the motor can drive the vehicle by itself at low velocity or assist the engine at high load. To improve the hybrid electric vehicle’s efficiency, a regenerative braking system is also applied to recover from kinetic energy. In this study, an experimental control apparatus was set up with a parallel hybrid electric vehicle mounted on a chassis dynamometer to measure ECU (engine control unit) and MCU (motor control unit) signals, including the current and state of charge in the battery. In order to analyze regenerative braking characteristics, user define braking driving cycle was introduced and carried out using different initial velocities and braking times. The FTP 75 driving cycle was then adapted under different initial SOC (state of charge) levels. The experiment data was analyzed in accordance with the vehicle velocity, battery current, instant SOC level, motor RPM, engine RPM, and then vehicle driving mode was decided. In case of braking driving cycle, it was observed that SOC were increased up to 1.5 % when the braking time and the velocidy were 6 second and 60 km/h, respectively. In addition, using the FTP 75 driving cycle, mode 1 was most frequently operated at SOC 65 conditions in phase 1. In phase 2, due to frequent stop-go hills, percentage of mode 1 was increase by 22 %. Eventually, despite of identity, it was shown that the characteristics of phase 3 differed from phase 1 due to the evanishment of the effects of initial SOCs. 相似文献
448.
Vehicular Ad-hoc Networks (VANETs) facilitate the broadcasting of status information among vehicles. In the IEEE 802.11p/WAVE vehicle network environment, the strict periodic beacon broadcasting of safety messages requires status advertisement to assist drivers in maintaining safety. The beacon broadcasting is required for real-time communication, and for avoiding the degradation of communication channels in high vehicular density situations. However, a periodic safety beacon in the IEEE 802.11p/WAVE standard can only transmit packets on a single channel using the MAC protocol. In high vehicular density situations, the channel becomes overloaded, thereby increasing the probability of beacon collision, and hence reducing the influx of successfully received beacons, which increases the delay. Many studies have indicated that appropriate congestion control algorithms are essential to provide efficient operation of a network. In this paper, to avoid beacon congestion, we have considered game theoretic models of wireless medium access control (MAC) where each transmitter makes individual decisions regarding their power level or transmission probability. We have evaluated the equilibrium transmission strategies of both the selfish and the cooperative user. In such a game-theoretic study, the central question is whether Bayesian Nash equilibrium (BNE) exists, and if so, whether the network operates efficiently at the equilibrium point. We proved that there exists only one BNE point in our game and validated our result using simulation. The performance of the proposed scheme is illustrated with the help of simulation results. 相似文献
449.
J. M. Pi Y. S. Bak Y. K. You D. H. Park H. S. Kim 《International Journal of Automotive Technology》2016,17(6):1101-1111
A route information based driving control algorithm was developed for an RE-EV which consists of two motorgenerators, MG1 and MG2. A threshold power which controls the engine on/off to charge the battery was obtained by an optimization process using route information, such as the vehicle velocity and altitude. The threshold power allows the vehicle to travel to the final destination while making the final battery SOC close to SOC low. Using the threshold power, route based control (RBC) was proposed by considering the driver’s characteristics and traffic conditions using the driving data base. In addition, a relationship between the threshold power and various initial battery SOC was obtained by off-line optimization. The performance of the RBC was evaluated by simulation and human-in-the-loop simulation (HILS) for city driving. It was found from the simulation and HILS results that the RBC achieved approximately 4 % to 12 % reduction in fuel consumption compared to the existing charge depleting/charge sustaining (CD/CS) driving control. 相似文献
450.
Y. H. Kwon 《International Journal of Automotive Technology》2016,17(6):1113-1120
The advent of vehicle-to-everything (V2X) communication has opened the opportunity to design advanced driver assistance systems (ADAS) that collect information from sensors in neighboring vehicles and roadside infrastructure. IEEE and ETSI have designed network protocol standards for V2X communications. Despite the differences between the vehicular wireless communication architecture defined by ETSI and the IEEE protocol stack, the two standards have multichannel operations as a main commonality, with some channels dedicated to safety-critical applications and others to nonsafety services. Some recent studies have demonstrated that these standards might not provide sufficient channel utilization for reliable exchange of information in mid- and heavily congested scenarios. In this paper, we propose and evaluate the performance of a driver-assistance system to reduce the connectivity gaps between vehicles and roadside units (RSUs). This cooperative system of multi-service channel allocation will improve radio channel utilization. We also show that the required latency for this inter-vehicle communication can be obtained using the IEEE-WAVE standards and dedicated short-range communication (DSRC) proposed for vehicular environments. Simulation results show that the proposed scheme can improve the average throughput by up to 15 % in various traffic density conditions compared with the dynamic channel allocation method. 相似文献