Design of a Robust Load-dependent Steering Controller for Improved High Capacity Vehicle Safety

This paper proposes a robust load-dependent controller synthesis to improve the lateral stability and performance of an A-double vehicle (tractor-semitrailer-dolly-semitrailer) at high speeds and consequently road safety by active steering of the dolly unit. The mass of the semitrailers resides in an interval between empty and fully-loaded scenarios and can be measured online. The yaw moments of inertia of the semitrailers can significantly change depending on loading conditions. In order to design a gain-scheduled controller with the mass of the semitrailers as scheduling parameters and to guarantee the system performance against the yaw moment of inertia variations in the semitrailers, a linear matrix inequality (LMI)-based design framework has been utilized. In this formulation, a descriptor-form representation of the vehicle model is used in order to avoid dealing with rational parameter dependency. The controller synthesis is formulated as an H∞-type static output feedback (SOFB), which uses information from one articulation angle which is easily measurable in practice. The simulations results indicate significant improvements in the high-speed lateral performance of the A-double in various loading conditions by suppressing undesired oscillations in the yaw rate of the last semitrailer during sudden lane change manoeuvres.