Modeling and Analysis of a Self-Steering Axle for Heavy Vehicles

Self-steering axles installed on commercial (heavy) vehicles offer important benefits, including improvements to vehicle performance such as off-tracking reduction and improved maneuverability, as well as reduction in pavement wear and damage that otherwise can result from the operation of heavy vehicles on the roadway. Traditional design methods for self-steering axles include empirical and trial-and-error methods to set steering mechanism design parameters based on known design baselines and prior experience. While the design of self-steering axles has not changed very much since their introduction, increasingly regulations and competitive market pressures have promoted the need for new designs to improve the performance of self-steering axles and differentiate new product offerings such as a new integrated steering knuckle concept which provides steering return stiffness and damping using a non-traditional design. This paper introduces models useful in the analysis of the steering return stiffness and damping performance of self-steering axle systems and shows how to identify the steering stiffness and damping characteristics that provide acceptable performance for these systems. The paper offers reduced order models that capture the self-steering axle’s shimmy behavior and discusses how to arrive at acceptable steering and damping characteristics. It presents results of the evaluations of the steering system performance including with comparisons between physical testing and simulations with a self-steering axle installed on a commercial vehicle.