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The power train system for Utility Vehicles (UVs) or All-Terrain Vehicles (ATVs) mainly consists of a rubber V-belt CVT. The adjustment of the CVT specification requires many steps to realize the shifting operations of the CVT so as to satisfy the acceleration feeling of the driver. In this paper, we report on the simulation technology that predicts the transient behavior during an acceleration of the vehicle equipped with a belt tension clutching CVT, which has both functions of the shift operation and the clutch action. By using the developed simulation technique, it has become possible to adjust the CVT specifications efficiently.

Motorcycle configurations, such as CG (center of gravity) location, have come to be fixed to the current ones by trial and error since motorcycle was born. Generally motorcycles' ratio of CG height to wheelbase is relatively higher than four-wheel cars'. We have analyzed the optimal motorcycle CG location with relatively simple formulas, which we have derived to calculate the maximum acceleration with three performance limitations and calculate the maximum speed and the shortest time to run through a course. The results show that the calculated speed is significantly close to actual sport motorcycle's and that the optimal CG locations for various courses are bounded in a certain limited area which is near actual sport motorcycle's.

Multibody dynamic simulations have become a powerful tool to analyze motorcycles. One of the purposes of motorcycle simulations is to complement experimental data and obtain immeasurable physical values. The other purpose is for parameter studies. With computer simulations, one can easily change motorcycle parameters without changing other parameters. In this paper, turning simulations at the circuit corner are conducted to demonstrate the effectiveness of simulations for these two purposes. By estimating the tire forces at the turning, the remaining friction margin is revealed. The parameter study shows the effects of influential parameters on maneuverability and stability.

In case of all-terrain vehicles (ATVs), which have characteristics of both motorcycles and cars, the effect of the rider movement can not be ignored when analyzing ATVs' behavior. We have developed a simulation system of an ATV with rider operations, which are throttle control and rider movement, by using multibody dynamic simulation software. To quantify the rider operations and verify the validity of the simulation system, we have conducted experiments and simulations on a sport-ATV in two jumping patterns. In this paper the results of comparison between simulation and experiment are reviewed. Then, we report the analysis results of the effects of the rider operations and the ground profile to ATV jumping behavior with using the simulation system.

Full vehicle simulations with commercially available software are becoming powerful tools for evaluating motorcycles. Among various motorcycles, motocrossers are most affected by rider operations. We have developed a simulation system that consists of a motocrosser and rider operations. The simulations of three accelerating patterns and two typical jumping patterns have been conducted by using the rider operations that are measured by experiment. With the experimental results, soil-tire traction parameters are identified. The comparison of the simulations and experiments indicates this simulation system effectively analyzes motocrosser-rider systems.

It is necessary to predict motorcycle performance at an early stage of development to minimize the period for designing, experimenting, and tuning. In order to do that, we have developed a motorcycle model with a mechanical dynamic simulation program. This model includes the bodies of a motorcycle, aerodynamic forces, tire forces, engine characteristics, simplified gear trains and driving chains, and rider operations. With this program, we have conducted motion simulation on steady state turn and disturbance response tests with two kinds of tire stiffness. We have also conducted experiment on the steady state turn and disturbance response tests to validate the program. In this paper, we analyze the results of the simulation and experiment. As a result, it is confirmed that the simulation results accord with the experimental results, and we have found that the steer angle and bank angle at the steady state turn depend on tire stiffness.