Improving roll stability of articulated heavy vehicles using active semi-trailer steering

This paper discusses an optimal linear quadratic control algorithm to improve the roll stability of a tractor semi-trailer using active semi-trailer steering. The controller minimises a combination of the path-tracking deviation of the trailer rear end relative to the path of the hitch point (5th wheel) and the lateral acceleration of trailer centre of gravity (CoG). First a linear vehicle model of tractor semi-trailer is constructed. Then a ‘virtual driver’ model for trailer steering control is introduced to minimise the path-tracking deviation of trailer rear end. The lateral acceleration of trailer CoG is included as a second objective of the optimal controller so as to improve roll stability. A Kalman filter with linear vehicle model is used to estimate unknown vehicle states, needed by the controller. Simulation results show that optimal control of semi-trailer steering could improve the roll stability significantly during transient manoeuvres while keeping the path-tracking deviation of trailer rear end within an acceptable range.