Abstract
In this paper, we suggest new control algorithms of electric power steering (EPS) system to improve steering maneuverability. Conventional EPS system supports a driver to steer easily through an electric motor. Therefore, it is possible to stabilize vehicle movement by applying additional control algorithms to conventional EPS system without any other equipment. Proposed control algorithms allow EPS system to distinguish vehicle state independently without other systems, such as electronic stability control (ESC) system and stabilize vehicle movement through additional torque. Proposed algorithms consist of two algorithms - road surface detection algorithm and yaw compensation algorithm. First, road surface detection algorithm is to distinguish road surface using estimated alignment torque and to calculate surface index (SI) as a new vehicle state. Yaw compensation algorithm generates additional steering torque, which makes vehicle movement more stable, using SI. Yaw compensation algorithm improves steering maneuverability. It guides a driver to return a steering wheel more rapidly to center in dangerous situations and improves yaw stability. We have implemented this algorithm in ECU of EPS system and conducted an actual vehicle test to verify performances of proposed control algorithms. Test results were compared with test results of conventional EPS system and it proves vehicle stability improvement of proposed control algorithms.
Keywords: EPS (Electric Power Steering), Vehicle Stability Control, Steering Maneuverability, Alignment Torque Estimation, Vehicle Dynamics