Vehicle Dynamic Factor Characterized by Actual Velocity and Combined Influence of the Transmission and Driveline System

Abstract

A vehicle’s dynamic factor characterizes the potential that can be created by the powertrain that may be utilized to overcome the rolling resistance, grade resistance, and accelerate the vehicle. The dynamic factor is commonly given as a function of the vehicle's theoretical velocity and computed using the powertrain characteristics without taking into account the effect of the driveline configuration which can impact the tire slippages and vehicle’s actual velocity. The velocity reduction due to tire slip can considerably impact the vehicle speed for off-road vehicles operating with large traction requirements. In this paper, a new approach to interpretation of the dynamic factor is presented which is based on the vehicle's actual velocity and driveline characteristics. The computation of the actual velocity accounts for the individual tire slippages of vehicles with multiple driving axles, which is influenced by the ground condition and power splitting characteristics of the driveline. A comparison of the conventional and proposed approach is given for a 4x4 off-road vehicle. A set of factors for vehicle design are proposed based on integral qualities of the ideal and actual dynamic factor to characterize the combined influence of the transmission and driveline system to utilize the engine power for vehicle acceleration performance.