Sehyun Chang

Sensitivity Analysis of Steering Wheel Return-ability at Low Speed

The steering wheel of a vehicle has a typical characteristic of automatically returning to its neutral state when the driver releases it. Steering returnability originated from the tire forces and kingpin moments. It is proportional to the reaction torque that is generated through the rack and column, which are dependent on suspension and steering geometry. It is also important to accurately predict and design it because steering returnability is related to steering performance. In this study, a detailed multibody dynamics model of a vehicle was designed by using ADAMS/Car and simulated for steering returnability. In addition, a tolerance analysis of the chassis system in terms of part dimension and properties has been performed in order to minimize the design parameters. The sensitivity of the selected design parameters was then analyzed via Design of Experiments(DOE). As a result, we were able to obtain the main parameters through a contribution analysis. It can be used to predict steering returnability and improve its performance, which is represented by the angle of restoration and laterality.

Effects of Vehicle Electric Components on the Steering Input Torque

Abstract : For the robust design of Motor Driven Power Steering (MDPS) systems, it is important to consider energy efficiency from every aspect such as system configuration and current flow, etc. If design optimization is not considered, it has many problems on a vehicle. For example, when evaluating steering test, particularly the Catch-up test which turning the steering wheel left or right quickly, steering effort should be increased rapidly. Also a vehicle might have poor fuel efficiency. In this study, it is calculated energy consumption for each component of the steering system and analyzed factors of energy consumption. As a result, this paper redefines a method to estimate steering input torque using characteristics of vehicle electric components and then conducts an analysis of contribution for the Catch-up. Key words : Catch-up(캐치업), Rack force(랙추력), Energy consumption(소비에너지), Motor driven power steering (전동식 파워 스티어링), Robust design(강건설계) Nomenclature 1) P : power consumption [W]V : voltage [V]I : current [A]R : resistance [Ω]F : rack force [N]ω : angular velocity [rad/s]T : torque [Nm]C : gear ratio [m/rev]L : ball screw lead [m/rev]l : wire length [m]K : motor torque constantη : efficiencyr : reduction ratio