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A dynamic stability analysis model of a five-axle tractor semitrailer vehicle is developed using the MATLAB/SIMULINK application tool. The linearized vehicle model is utilized to investigate the impending instability limits under various design, and operating conditions. Computer simulations are performed for step steer and a typical highway maneuver as input conditions to generate the yaw response characteristics. The model development is accomplished in a modular form to accommodate interactive re-runs of the model with design variations. SIMULINK modeling provides greater flexibility in development and incorporation of active control system modules in the model in order to investigate possible enhancement of vehicle stability limits.

A directional dynamic model of a partially filled liquid tank vehicle is developed to investigate its dynamic characteristics during typical straight-line braking maneuvers. The computer simulation model is developed by integrating the fluid slosh model of a partially filled tank to the pitch plane vehicle model. The dynamic behavior of liquid within the tank is modeled using an equivalent mass-spring system. The analogous mechanical system model for the partially filled cleanbore cylindrical tank is developed by utilizing the potential flow theory for longitudinal oscillations. An approximate summation method is developed in order to obtain the mechanical system parameters and are validated against experimental results available in literature. Computer simulation of the tank vehicle for typical braking maneuvers is then performed by incorporating the slosh forces and moments computed using the mechanical analogy model into the vehicle model.

Dynamic analysis of vertical seat suspensions of off-road vehicles is performed via computer simulation models in order to establish their ride performance. The PC-based computer simulation program is capable of analyzing various commercially available seat suspensions under different input excitations. The software is developed using the Visual Basic interface on Microsoft Windows platform and is entirely menu driven. The software is organized in a systematic fashion with the pre-processor, analysis and post-processing modules and has the option to choose any module from the initial selection screen. A database of various seat-suspension characteristics, along with other off-road vehicle input parameters is available in the pre-processor module. Analysis of the dynamic system is performed using a generalized two-degree of freedom model characterizing the vertical seat and suspension motion.

The computation of dynamic slosh forces arising due to liquid motion within a partially filled tank is quite important in analyzing the directional behavior of tank trucks during various highway maneuvers. The most precise computation of liquid motion and the associated slosh forces involves solving complex non-linear fluid mechanics equations and is extremely cumbersome. The motion of liquid within a partially filled tank is herein investigated by representing the fluid slosh through an equivalent mechanical system using a pendulum analogy model. The model parameters are computed based on inviscid fluid flow conditions and the dynamic fluid slosh forces arising due to the dynamics of the vehicle during a given maneuver are computed using the equivalent mechanical system. The dynamic fluid slosh forces and moments are then integrated into the vehicle dynamics model to study the directional response characteristics of tank vehicles.

Dynamic fluid slosh and its influence on the dynamic roll stability of a partially filled tank truck has been investigated through a field test program undertaken jointly by the CONCAVE Research Centre and Transportation Technology and Energy Branch of Ontario Ministry of Transportation. The paper describes the test methodology, instrumentation, data acquisition, fluid slosh behaviour, and its influence on the directional response of the tank truck. The data acquired during different directional maneuvers is analyzed to highlight the fluid slosh and its impact on the dynamic load transfer and roll stability of the vehicle. The magnitude of dynamic load transfer, derived from the video records of the dynamic fluid movement, is presented and discussed for various tank fill levels and directional maneuvers. The test results revealed that the magnitude of dynamic fluid slosh is strongly related to the vehicle speed, lateral and longitudinal acceleration, and the fill level.

The directional dynamics of partially filled articulated tank vehicles is investigated via computer simulation assuming constant forward velocity. The directional response characteristics of an articulated tank vehicle is investigated for various steering manoeuvres and compared to that of an equivalent rigid cargo vehicle to demonstrate the destabilizing effects of liquid load shift. It is concluded that during a steady steer input, the distribution of cornering forces caused by the liquid load shift yields considerable deviation of the path followed by the tank vehicle. The lateral load shift encountered in a partially filled tank vehicle during lane change and evasive type of highway manoeuvres gives rise to roll and lateral instabilities.

General purpose tank vehicles often carry partial loads in view of variations in the weight density of the liquid cargo and are thus subject to slosh loads during highway manoeuvres. The magnitude of destabilizing forces and moments due to liquid slosh is strongly related to a number of vehicle and tank design factors, such as tires, suspension, articulation mechanism, weights and dimensions, tank geometry and fill level. The rollover threshold of the tank vehicle is compared to that of an equivalent rigid cargo vehicle to demonstrate the destabilizing effects of liquid slosh. The rollover threshold of the tank vehicle is evaluated for a number of tank design factors. Influence of tank size and cross-section on the rollover threshold of the tank vehicles is investigated. The study concludes that the lateral load shift and thus the rollover threshold is strongly related to the tank cross-section geometry.