Kinematic Analysis of Tractor-Semitrailer with Split Fifth Wheel Coupling During Low Speed Turning Maneuvers

Over the years, commercial vehicles, especially tractor-semitrailer combinations have become larger and longer. With the increasing demand for their accessibility in remote locations, these vehicles face the problem of off-tracking, which is the ensuing difference in path radii between the front and rear axles of a vehicle as it maneuvers a turn. Apart from steering the rear axle of the semitrailer, one of the feasible ways of mitigating off-tracking is to shift the fifth wheel coupling rearwards. However, this is limited by the distribution of the semitrailer’s load between the two axles of the tractor; any rearward shift of the fifth wheel coupling results in the reduction of the total static load on the tractor’s front axle and hence available traction. This may in turn lead to directional instability of the vehicle. In the present work, a new model of the fifth wheel coupling is proposed which the authors call Split fifth wheel coupling (SFWC). Here, unlike the Conventional fifth wheel coupling (CFWC), the point of load transfer from the semitrailer to the tractor and the point of articulation are separated by a certain distance. A comparative study of the kinematic analysis for the vehicle combination with CFWC and SFWC is discussed in this paper. It is observed that the latter noticeably reduces off-tracking when compared to the vehicle with CFWC for a tractor-semitrailer combination of similar dimensions.