Abstract
Keywords - T-SBW System, Torque Map, Ackerman Constraint, Stability, Bond Graph Modeling
This paper presents control algorithm for a Steer-by-Wire(SBW) system. In a SBW system of a passenger car, there is no mechanical coupling between the steering wheel and the steering mechanism. SBW system consists of two parts. One is steering wheel system and the other is front wheel system. Even though the mechanical linkage, between the steering wheel and the road wheels has been eliminated, a SBW steering system is expected not only to implement the same functions as a conventional mechanically linked steering system, but it is also expected to provide the advanced steering functions.
This research considers the tie rod actuating type of the front wheel system, in which two independently actuating motors control the front wheels. To improve steering feel and to transfer road information to the driver, the steering wheel system control algorithm used a torque map to generate reactive torque and damping. Torque map can be easily adjusted by changing control parameters and define input and output relationship between the outer front wheel angle and the inner front wheel angle to apply for the tie rod actuating SBW system.
On-center handling characteristic treats steering-torque gradient and steering-wheel returnability as important control factors. The control factors that affect on-center handling performance are analyzed. To improve vehicle stability variable gear ratio and active steering control algorithm as stability factor are proposed. Moreover understeer and oversteer effect using stability control factor apply to the inner front wheel and the outer front wheel. In the development of the tie-rod actuating type SBW system described herein, the Ackerman constraint was used for control of the two motors to improve stability at high speed and maneuverability at low speed.
In this study, an experiment for steering wheel system is performed through Hardware-In-the- Loop-Simulation (HILS) and a simulation is performed through CarSim. And some vehicle test results are included.