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Running abilities of an off-road, all-wheel drive vehicle depend considerably not only on total traction effort but also on its distribution among the drive wheels. This distribution is largely determined by mechanisms and systems installed in power dividing transmission units. These are interwheel differentials, interaxle reduction gears, and transfer cases. To control the wheel driving forces for obtaining the optimum vehicle properties, a more creative and efficient way to design wheel drive systems and to control vehicle running abilities is being proposed. Optimization criteria for the tractive and velocity properties, fuel consumption, turnability, and ride stability of a vehicle have been used for the mathematical optimization of the wheel driving forces. The vehicle is modeled in motion with taking into account the kinematic requirements.

The field of Vehicle Dynamics as the theory of a vehicle in motion is to study the vehicle's properties (vehicle running abilities) in the interaction of the vehicle and it's surroundings. This interaction itself appears through forces acting on a vehicle. To control these forces leads to control the properties of a vehicle in motion such as tractive and velocity properties, fuel consumption, turnability, ride stability and others. This paper proposes a unique and novel theory of a vehicle in motion. This theory allows parallel control of the forces acting on a vehicle, which leads to considerable improvement of the vehicle's running abilities. This paper presents the interrelation between the criteria of vehicle running abilities and output characteristics of vehicle systems, which control the vehicle forces. To optimize a vehicle's running abilities require optimization of the combinations of forces acting on a vehicle.

Mass and geometric parameters of all-wheel drive off road vehicles, such as coordinates of the center of gravity and arrangement of the wheels, have been obtained to satisfy cross-country mobility profiles that reduce the dynamic normal loads on the running gear system. However, the influence of these parameters on tractive properties for basic cross-country mobility of vehicles receives less attention. The authors have developed a new method for determining mass and geometric parameters that provides optimal tractive properties for basic cross-country mobility of off-road vehicles. The methodology is realized using a mathematical model of a 6WD tractor on a deformable road surface. The mass and geometric parameters are achieved by optimizing the tractive efficiency function to provide the best transport efficiency on all running gears.