Abstract
In this paper, yaw motion control of a tractor semi-trailer based on the integration of active front steering (AFS) and direct yaw-moment control (DYC) is presented. A three-layer hierarchical structure is adopted for the proposed control system. In the upper layer, an integrated controller based on direct Lyapunov method is designed by using a simplified three degree-of-freedom tractor semi-trailer model to determine a desired yaw moment. Taking into account the tire cornering characteristics in different tire’s operation regions, a fuzzy controller is designed to allocate the desired yaw moment for AFS and DYC in the middle layer. Implementation of additional front-wheel steering angle and braking torques for selected wheels is handled in the lower layer. Computer simulations of the tractor semi-trailer with the integrated control system during double lane change maneuvers are investigated in a TruckSim simulator using a high-fidelity vehicle dynamics. Simulation results show that the proposed control system can effectively enhance handling and stability of tractor semi-trailers and has considerable advantages over the AFS alone or DYC alone system.
KEYWORDS – Integrated control, Yaw stability, Tractor semi-trailer, Direct Lyapunov method, Fuzzy control