Analyzing the Interdependence between a 4x4 Automobile’s Slip and the Self-Generated Torque within its Transmission

Abstract

This paper presents an analysis that aims at identifying the interdependence between the wheels slip and the self-generated torque that occurs at the inter-axle level of a 4x4 automobiles driveline. We consider that this paper has a high degree of novelty since it succeeds in establishing causality relationships between different automotive typical parameters. Moreover, the paper provides the specific mathematical, theoretical equations as well as an example of a generalized mathematical model derived from time or frequency analysis.The theoretical mathematical elements consist of terms referring to the rigid wheels kinematics and specific working conditions of the vehicle when it runs with tire radii differences at the inter-axle level. To achieve the goal of our work we developed a large experimental research work that involved an extended instrumentation of an all-wheel driven military vehicle in such a manner that allowed getting information concerning different shafts torque and angular speed. The vehicle has transfer case, involving a longitudinal differential. The tests were developed with the locking device of the differential working in the engaged mode. Aiming at revealing the connection between the tire radii and the self-generated torque, we have subjected the vehicle to different tire radii running modes. The rolling radius of the wheels that were on the same axle was the same. The bigger the tire radii difference the bigger the self-generated torque; hence the interdependence started to reveal itself as far as the tire slip also followed the behavior of the self-generated torque. In order to determine the wheels slip we also measured the vehicles speed with a GPS. The results are graphically presented.Following the results of the data processing stage, we concluded that the interdependence between wheels slip and the self-generated torque exists and a relationship between these two phenomena can be mathematically expressed, using a generalized model. We consider that a kind of model like this proves its utility in simulating similar conjectures; thus, the experimental research effort can be significantly reduced either by lacking either in torque measuring or wheels slip measuring. Such a determination could have a positive impact by optimizing the vehicle exploitation or even its modernization.