The application of understeer gradient in stability analysis of articulated vehicles

Abstract

This paper introduces the generalised algebraic formula for understeer gradient (Ku) of articulated vehicles. This formula plays a similar role as that for a single vehicle system. The articulated vehicle is understeer if Ku is positive, neutral steer if it is equal to zero, and oversteer if it is negative. It is not stable in the yaw plane if it is oversteer and driven above the critical speed. The algebraic solutions are validated numerically and compared to experimental data measured from an 18-wheel tractor semi-trailer system. The impedance concept is introduced to facilitate the process of the algebraic analysis of articulated vehicles. This allows Ku and critical speed equations to be expressed in a compact systematic form.