The self–steering behaviour of a tractor–semi–trailer at high–speed and its control to improve lateral stability

Abstract

The loss of stability by heavy highway tractor–semi–trailers can lead to serious traffic accidents. Among the contributing factors are variations in the operating conditions (e.g. different loading conditions, gusting side winds, and slippery patches on the road surface) which cannot entirely be controlled by the driver. In this paper, the behaviour of a 3–axle tractor–semi–trailer is examined from the point of view of steerability and a suitable measure of its handling characteristic is defined. On the basis of the results of this examination, some possible control methods are developed to improve the lateral stability of the tractor–semi–trailer using controlled steering of the tractor's rear wheels and of the trailer's wheels. The controller is designed using the virtual model following control law, and in the feedback loop both linear quadratic regulator (LQR) and H∞ controllers are applied.