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An Active Independent Front Steering (AIFS) offers attractive potential for realizing improved directional control performance compared to the conventional Active Front Steering (AFS) system, particularly under more severe steering maneuvers. The AIFS control strategy adjusts the wheel steer angles in an independent manner so as to utilize the maximum available adhesion at each wheel/road contact and thereby compensate for cornering loss caused by the lateral load transfer. In this study, the performance potentials of AIFS are explored for vehicles experiencing greater lateral load transfers during steering maneuvers such as partly-filled tank trucks. A nonlinear yaw plane model of a two-axle truck with limited roll degree-of-freedom is developed to study the performance potentials of AIFS under different cargo fill conditions.

In this study the dynamic analysis of the vehicle system modeled as a hybrid discrete and continuous system has been investigated. The discrete system modeling has formed the traditional ride dynamic analysis model for vehicle systems. In such a model the chassis is assumed as a discrete block attached to different degrees of freedom that can account for the unsprung masses, engine and driver among many others. However, this model cannot accommodate all the aspects of a chassis which is strictly a continuous system. In the present study the chassis is assumed as a flexible beam on which a pair of single degree of freedom systems is added to account for the engine and driver. Moreover, the beam is mounted on a couple of spring-damper elements that simulate the suspension of the vehicle which results in a combination of continuous and discrete systems. In order to solve this problem, the assumed mode method has been employed using the mode shapes of a free-free beam.

Electro-Rheological (ER) and Magneto-Rheological (MR) fluid based advanced suspension dampers are emerging to be the next generation of suspension dampers for their attractive features and promising performance potential to overcome the limitations of existing dampers in market. This study compares the vibration and shock isolation performances of ER damper and MR damper with linear passive damper and two-stage asymmetric non-linear damper using a four degrees-of-freedom pitch plane ride model. The study reveals superior vibration and shock isolation performance of ER and MR dampers for sprung mass compared to linear passive and asymmetric non-linear dampers. At higher frequencies (above 10 Hz), these dampers transmit higher load to pavement compared to other two. The study suggests that asymmetricity should be included in the design of these dampers to achieve improved performance over the entire frequency range.

This paper summarizes the methodology and findings of an investigation to determine friction coefficients between typical loads and trailer deck materials in static, sinusoidal, and field measured random vibration environments. To conduct the tests in a controlled laboratory environment, a special sled-deck fixture was designed. Provisions were made to allow a change in sled-deck contact materials and to vary the load on the sled. For dynamic testing, the deck was subjected to sinusoidal and field based random signals obtained from tractor-trailer traversing paved and gravel roads. The results reveal that under vertical vibration, these friction coefficients can be as low as 25% of their corresponding static values. The random vibration tests revealed that friction coefficients can fall below 75% of the mean value for up to 35% of the total test duration. Thus, loads that rely on static friction for security may be highly prone to load shifts in a dynamic environment.

Relative rollover conditions of a heavy vehicle are analyzed to establish an array of potential dynamic rollover indicators towards development of an early warning device. A relative roll instability indicator defined as Roll Safety Factor (RSF) is proposed and shown to be a highly reliable indicator regardless of vehicle configurations and operating conditions. The correlation of various potential rollover indicators with the roll safety factor are then investigated for a 5-axle tractor semi-trailer combination using a comprehensive directional dynamic analysis model to determine the reliability of the proposed indicators over a range of operating conditions. The indicators are further examined in terms of measurability, lead time, and potential for application in an early warning system. The study shows that the trailer lateral acceleration and axle roll angles are closely correlated with the RSF.

In our earlier papers on thermocontrolled tank storage system, we presented the basic concept of storing natural gas and the results from optimization of the vessel design. In this paper we are presenting optimization results of the entire storage system, assuming that the vehicle is running in a certain pre-scheduled pattern. Two kinds of vehicles have been considered for investigation, a city bus with a continuous running schedule and a car with a short run-park schedule. The initial waiting time, parking time, safe pressure ratio and range of the two vehicles have been investigated and then optimized to define the performance requirements.

To increase the operational range of the vehicle equipped with direct injection gas supply and to eliminate the problems associated with the cryogenic pumps, a composite high pressure vessel is proposed for use as a thermocontrolled tank in vehicles. The test results showed that the liquefied natural gas can be brought from atmospheric pressure to the high pressure required for direct injection in a reasonable time period. Based on these results a mathematical model for the heat transfer to the natural gas was developed and simulated. Three different aspects of gas storage, namely, the initial operational temperature, the gas to vessel mass ratio and the gas weight to vessel volume ratio have been investigated and formulated as objectives for optimization. Due to the presence of different conflicting objectives, the problem was formulated as a nonlinear multi objective optimization problem and then solved.