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This article discusses a vehicle stability improvement control method that utilizes an electric power steering system (EPS) with blushless motor. The purpose is to improve the vehicle stability by increasing the steering return torque in a region where the alignment torque is saturated due to the driver's excessive steering maneuver on a slippery road. In this study, a factor analysis was performed for the alignment torque on a slippery road and the basic control to improve the vehicle dynamics stability is studied by using a linear m1odel. Next, a new control algorithm was developed based on these studies. Finally, the new control algorithm was verified to be effective through an on-vehicle test. The proposed strategy can be realized only by adding a steering wheel angle sensor signal to a conventional EPS. That can be easily obtained from electronic stability control system.

Accuracy of positioning with GNSS (Global Navigation Satellite System) has been improved in recent years. Especially in Japan, high accuracy GNSS service, QZSS (Quasi Zenith Satellite System), will start in 2018 and the first QZS, “MICHIBIKI” has been already launched. They will broadcast correction data which enhances GNSS performance and realize cm-order positioning. In this paper, we, Mitsubishi Electric develop the estimation algorithm of vehicle position and attitude and also adapt the algorithm to a test vehicle which can trace automatically the calculated path with EPS (Electric Power Steering) and high accuracy GNSS. Although the GNSS receiver calculates the longitude and latitude of the vehicle every second, it is not enough to control vehicle dynamics smoothly. So we estimate vehicle position and attitude of the vehicle with GNSS and vehicle sensors in high frequency.

Mitsubishi Electric has been developing a lane keeping assist system (LKAS). This system consists of our products such as an electric power steering (EPS), a camera, and an electronic control unit (ECU) for ADAS. In this system, the camera detects a lane marker, the ECU estimates reference path and vehicle position, and calculates reference steering wheel angle, and the EPS controls a steering wheel angle based on reference steering wheel angle. In this paper, we explain the calculation method of reference steering wheel angle for path tracking control. We derive a formula of reference steering wheel angle calculation that converges lateral position deviation in desired time by using lateral position deviation change rate control on forward gaze point as path tracking control algorithm. Since the formula is obtained from the vehicle model, we can easily design a controller depending on the vehicle type, by using known vehicle specifications.