Steer Laws for Steerable Trailer Axles to Reduce Tire Wear

Majority of the tractor/semi-trailers are equipped with non-steerable solid trailer axles. In low speed cornering maneuvers, the trailer tires scrub in opposite directions, generating unnecessary tire wear. Steerable-axle trailers are beginning to appear in the commercial vehicle market to improve maneuverability and treadwear. In this paper, tire slip characteristics of traditional three-axle trailers in turning maneuvers are investigated analytically. Trailer-axle steer laws, defined as a relation between tractor/trailer articulation angle and trailer axle steer angle, are derived for each trailer configuration. The objective is to minimize tire scrub in low speed turning maneuvers and to generate even treadwear for different wheel positions. Effect of the vehicle forward speed on steer laws is discussed. The steer laws are further evaluated using multi-body vehicle dynamic simulation models. The proposed steer laws are also evaluated for their potential in increasing maneuverability of the articulated vehicles.