Ride dynamics of high mobility wheeled/tracked off-road vehicles: Computer simulation with field validation

This thesis deals with the ride dynamic aspects of high mobility wheeled/tracked off-road vehicles through comprehensive computer modeling of the vehicle-terrain dynamical system and field validation of the computer model predictions. A multi-purpose ride dynamic simulation model (RIDSIM) is developed and proposed as an effective and precise tool to study and improve the ride comfort and safety, and thus the performance of wheeled/tracked off-road vehicles.;The development of RIDSIM is primarily based on the modeling strategies adopted for the ride model formulation of a typical high-speed multi-wheeled tracked vehicle (an armoured personnel carrier: M113 APC), which was selected as a candidate vehicle for this study. Consequently, this study has largely focused on the analytical and experimental ride investigations of the candidate vehicle. An extensive field testing of the candidate vehicle was carried out. Field test data were recorded for a variety of test conditions (i.e. vehicle configurations, field courses, vehicle speeds), and conditioned/reduced for ride quality assessment and computer model validation.;The candidate vehicle ride model is conceived based on three formalisms of varying complexities: MODEL I, MODEL II, and MODEL III. These are time-domain simulation models developed assuming an in-plane representation of the vehicle negotiating an arbitrary rigid terrain profile at constant forward speed. These models incorporate nonlinear suspension characteristics, a continuous radial spring and an equivalent damper model of the wheel/track-terrain interaction, and dynamic track loads computed considering kinematic constraining effects of the track belt loop. Effective computational algorithms are developed to establish wheel-terrain and track-terrain contact patches, and wheel-track connectivity. The equations of motion are written with respect to the vehicle's zero-force reference in order to simulate the vehicle-terrain contact loss. Computational procedures are devised to establish the zero-force and static equilibrium configurations of the vehicle.;The ride response predictions of the candidate vehicle are evaluated using all three models, and directly compared against field measurements in order to assess the relative performance of these models. The ride predictions obtained using MODEL I show generally good agreement with field measurements. However, the agreement between measured and predicted ride response is considerably improved through refinements of the ride dynamic model (MODEL II and MODEL III). The wheel and track sub-models proposed in this study are also compared with those reported in the literature, and shown to yield relatively accurate ride predictions while requiring less computational time.;A parametric sensitivity analysis is carried out using MODEL III to study the influence of suspension design parameters on the ride dynamics of the candidate vehicle. In addition, the ride performance potentials of an alternate hydrogas suspension system exclusively developed for application with the candidate vehicle are investigated. The hydrogas suspension system is found to reduce the ride acceleration levels, however, at the expense of relatively high displacement magnitude especially due to the vehicle pitch.