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Several new mathematical models of a rider ATV system are developed. These new models allow the ATV to have either three or four wheels, the rider to be placed at any orientation relative to the vehicle, and the ATVs wheels to rotate. These models are used to investigate the simulated motion of an ATV system over a bump profile. For each model, overturning stability plots are generated as a function of the rider's side lean angle and the vehicle's initial velocity. These results show that the four-wheeled ATV system is more stable than the three-wheeled ATV system over the bump profile. In addition, the inclusion of wheel rotation only slightly improves the overturning stability of the ATV system and this improvement occurs only at high vehicle speeds.

The nonlinear dynamical equations governing a thirteen degrees-of-freedom mathematical model of a three-wheeled all-terrain vehicle/rigid-rider system are formulated in this paper. The system is composed of seven rigid bodies. The vehicle has front mechanical suspensions as well as independent rear swing-arm mechanical suspensions. At the time of this writing, no three-wheeled all-terrain vehicle of this configuration is known to exist. Hence, parameter values for this vehicle were obtained through educated engineering estimations based on information available for other three-wheeled vehicles and other engineering data.

This paper is the second in a series on three-wheeled all-terrain vehicle with full suspension. It investigates and compares the roll, pitch and vertical motions of a thirteen degrees-of-freedom mathematical model of a vehicle/rider system with full mechanical suspensions and a six degrees-of-freedom system with no mechanical suspensions. The three different bump profiles - rectangular, parabolic and sinusoidal - employed in the excitation of the system in Ref. (1)* were used for this system. The results show that the current system has substantially reduced roll, pitch and vertical displacements. As a result, it is better in ride and handling as compared to the previously simulated system (1).

This paper presents the dynamical equations of motion governing a six degrees-of-freedom mathematical model of a three-wheeled all-terrain vehicle/rigid-rider system. The parameter values associated with two commercially available three-wheeled all-terrain vehicles, a 1980 Honda ATC 110D and a 1980 Kawasaki KLT 200, are presented. In addition, tire properties such as non-rolling vertical stiffness, cornering stiffness and damping ratio for a 22×11-8 Ohtsu tire and a 22×11-8 Goodyear tire are given. These parameter values are used to simulate the motions of the vehicle/ rider system with the results presented in Part II (1)*

This paper is the second in a series on three-wheeled all-terrain vehicles and investigates the handling and ride characteristics of the six degrees-of-freedom mathematical model of a vehicle/rigid-rider system with no suspension. This vehicle/rider system was simulated over three different bump profiles of rectangular, parabolic and sinusoidal shapes. The results show that a light vehicle/rider system equipped with a set of stiff tires has the poorest handling and ride characteristics whereas a heavy vehicle/rider system equipped with a set of soft tires has the best handling and ride characteristics. It was also shown that, for the particular profiles selected, a longer ramp-like bump profile disturbed the vehicle/rider sytems significantly more than a shorter length bump profile.