Design and Optimization of a Bus Steering Linkage by Using Response Surface Methodology

Computer-aided design phases of the steering linkage of a passenger bus are presented. In the first part of the study, proper joint positions of the mechanism which satisfy the kinematic requirements such as, acceptable toe deviation and steering error ranges, were determined. For this purpose, a rigid multibody model of the mechanism was built by taking the physical design restrictions of the front axle into account. Subsequently, a response surface methodology (RSM)-based kinematic optimization study was carried out by using Adams®/Insight software. In order to determine the service forces acting on the structural elements of the linkage, a full multibody dynamics (MBD) model of the bus was also composed. By using this model, standard lane change maneuver was performed. Furthermore, the theoretical steering torque at the tire contact patch, necessary to steer the front wheels of the bus at zero speed, was calculated. Force analysis of the linkage was also performed for this condition. In the second part, mechanical design of the full steering mechanism was carried out for critical design load. Finite element analysis (FEA) was implemented to predict the stress concentration regions of the primary design model for the selected load cases such as zero speed steering, lane change and braking. Design optimization of the linkage components were also carried out by using ANSYS® Workbench™ software. Hence, optimal shapes of the structural elements, which satisfy the design targets such as minimum equivalent stress and maximum stiffness, were determined. According to the results obtained from this study, the steering linkage satisfies the safety condition for critical load cases.