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The ride dynamics of typical North-American soil compactors were investigated via analytical and experimental methods. A 12-degrees-of-freedom in-plane ride dynamic model of a single-drum compactor was formulated through integrations of the models of various components such as driver seat, cabin, roller drum and drum isolators, chassis and the tires. The analytical model was formulated for the transit mode of operation at a constant forward speed on undeformable surfaces with the roller vibrator off. Field measurements were conducted to characterize the ride vibration environments during the transit mode of operation. The measured data revealed significant magnitudes of whole-body vibration of the operator-station along the vertical, lateral, pitch and roll-axes. The model results revealed reasonably good agreements with ranges of the measured vibration data.

The articulated frame steering (AFS) systems are widely implemented in construction, forestry and mining vehicles to achieve enhanced maneuverability and traction performances. The kinematic and dynamic performances of articulated steered vehicles are strongly influenced by properties of the frame steering system. In this paper, a flow volume regulated frame steering system is described and analytically modelled. The analytical model of the steering system is formulated in conjunction with yaw-plane model of a 35 tonnes mining vehicle to investigate steady as well as transient responses of the steering system and the vehicle. A field test program was undertaken to measure responses of the steering system and the vehicle under nearly constant speed turning as well as path-change maneuvers.

Baffles are known to help reduce the amplitude of fluid slosh in partly filled tanks, particularly during braking and acceleration. The transient fluid slosh approach is proposed to evaluate the effectiveness of baffles designs. A computational fluid dynamic (CFD) fluid slosh model is developed using the VOF (volume of fluid) technique coupled with a Navier-Stokes solver. The validity of the model is demonstrated using the experimental data acquired with a scale model tank. The validated CFD model is subsequently formulated for a full scale tank and simulations are performed under excitations idealizing the straight-line braking maneuvers to investigate the anti-slosh role of four different transverse baffles concepts. The fluid slosh responses are analyzed in terms of the fundamental slosh frequency, and the resulting forces and moments under different fill volumes of liquid cargos of constant load.

Dynamic behavior of a partly-filled liquid cargo vehicle subject to simultaneous application of cornering and braking maneuvers is investigated through computer simulation. A three-dimensional quasi-dynamic model of a partly-filled tank of circular cross-section is developed and integrated into a comprehensive three-dimensional model of an articulated vehicle to study its directional response under varying steering and braking inputs, fill volumes and road surface friction. The liquid load movement encountered under combined steering and braking is expressed in terms of variations in the instantaneous c.g. coordinates and mass moments of inertia of the liquid bulk, assuming negligible influence of fundamental slosh frequency and viscous effects.

A coupled human-seat-suspension model is developed upon integrating asymmetric and nonlinear models of the cushion, suspension and elastic end-stops with a three degrees-of-freedom biodynamic model of the occupant. The validity of the model is examined under harmonic and stochastic vibration excitations of different classes of vehicles, using the laboratory measured data. The suspension performance under continuous and shock excitations, assessed in terms of Seat Effective Amplitude Transmissibility (SEAT) and Vibration Dose Value (VDV) ratio, revealed that attenuation of continuous and shock-type excitations pose conflicting design requirements. It is thus proposed to develop suspension design for optimal attenuation of continuous vibration, while the severity of end-stop impacts caused by shock-type excitations be minimized through design of optimal buffers. Two different optimization problems are formulated to minimize the SEAT and VDV ratios.

Compared to the vehicles with conventional steering, the articulated frame steer vehicles (ASV) are known to exhibit lower directional and roll stability limits. Furthermore, the tire interactions with relatively rough terrains could adversely affect the directional and roll stability limits of an ASV due to terrain-induced variations in the vertical and lateral tire forces. It may thus be desirable to assess the dynamic safety of ASVs in terms of their directional control and stability limits while operating on different terrains. The effects of terrain roughness on the directional stability limits of an ASV are investigated through simulations of a comprehensive three-dimensional model of the vehicle with and without a rear axle suspension. The model incorporates a torsio-elastic rear axle suspension, a kineto-dynamic model of the frame steering struts and equivalent random profiles of different undeformable terrains together with coherence between the two tracks profiles.

The ride performance potentials of a prototype torsio-elastic axle suspension for an off-road vehicle were investigated analytically and experimentally. A forestry vehicle was fitted with the prototype suspension at its rear axle to assess its ride performance benefits. Field measurements of ride vibration along the vertical, lateral, fore-aft, roll and pitch axes were performed for the suspended and an unsuspended vehicle, while traversing a forestry terrain. The measured vibration responses of both vehicles were evaluated in terms of unweighted and frequency-weighted rms accelerations and the acceleration spectra, and compared to assess the potential performance benefits of the proposed suspension. The results revealed that the proposed suspension could yield significant reductions in the vibration magnitudes transmitted to the operator's station.

Automotive suspensions invariably exhibit asymmetric damping properties in compression and rebound, which is partly attributed to asymmetric damping and in-part to the suspension linkage kinematics together with tire lateral compliance. Although automotive suspensions have invariably employed asymmetric damping, the design guidelines and particular rationale for such asymmetry has not been explicitly defined. The influences of damper asymmetry together with the suspension kinematics and tire lateral compliance on the dynamic responses of a vehicle are investigated analytically under bump and pothole excitations, and the results are interpreted in view of potential design guidance. A quarter-car kineto-dynamic model of the road vehicle employing a double wishbone type suspension comprising a strut with linear spring and multiphase asymmetric damper is formulated for the analyses.

Transient fluid slosh within a partly-filled tank could impose high stresses on the tank structure and affect the directional performance in an adverse manner. A three-dimensional nonlinear model of a partly filled circular cylindrical tank with and without baffles is formulated and analyzed to derive the pressure distribution over the wetted tank surface. The baffles and end caps are modeled with curved shapes in accordance with the current standard. The analyses are performed for 40% and 60% fill volumes and different types of baffles, including single-nozzle and multiple-orifice baffles, using the FLUENT software under time varying acceleration fields representing simultaneous braking and turning maneuvers. The pressure data are further analyzed to evaluate steady-state and transient slosh forces, load shifts along the longitudinal and lateral axes, and the roll, pitch and yaw moments imposed on the tank structure.

Human-seat interactions are investigated through measurement and analysis of distribution of interface contact force and area under vertical vibration. The time histories of dynamic ischium pressure, effective contact area and contact force on a soft seat revealed significant asymmetry, under large magnitude vibration excitations occurring near the resonant frequency of the human-seat system. The asymmetric response characteristics of the cushion are mostly attributed to the nonlinear force-deflection properties of polyurethane foam materials, contour shape of human buttocks, body-hop motion and cushion bottoming tendencies. The results are utilized to propose a nonlinear and asymmetric seat cushion model incorporating body hop motion and cushion bottoming under vertical vibration. A combined human-seat model is derived upon integrating the proposed cushion model with a bio-dynamic model of the seated occupant.

In this paper, a gain-scheduling optimal control approach is proposed to enhance yaw stability of articulated commercial vehicles through active braking of the proper wheel(s). For this purpose, an optimal feedback control is used to design a family of yaw moment controllers considering a broad range of vehicle velocities. The yaw moment controller is designed such that the instantaneous tractor yaw rate and articulation angle responses are forced to track the target values at each specific vehicle velocity. A gain scheduling mechanism is subsequently constructed via interpolations among the controllers. Furthermore, yaw moments derived from the proposed controller are realized by braking torque distribution among the appropriate wheels. The effectiveness of the proposed yaw stability control scheme is evaluated through software-in-the-loop (SIL) co-simulations involving Matlab/Simulink and TruckSim under lane change maneuvers.