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Featured Application: Path Tracking Control for Autonomous Driving. This paper presents a method to design a path tracking controller with a constraint on tire slip angles under low-friction road conditions. On a low-friction road surface, a lateral tire force is easily saturated and decreases as a tire slip angle increases by a large steering angle. Under this situation, a path tracking controller cannot achieve its maximum performance. To cope with this problem, it is necessary to limit tire slip angles to a value where the maximum lateral tire force is achieved. The most commonly used controllers for path tracking, linear quadratic regulator (LQR) and model predictive control (MPC), are adopted as a controller design methodology. The control inputs of LQR and MPC are front and rear steering angles and control yaw moment, which have been widely used for path tracking. The constraint derived from tire slip angles is imposed on the steering angles of LQR and MPC. To fully verify the performance of the path tracking controller with the constraint on tire slip angles, a simulation is conducted on vehicle simulation software. From the simulation results, it is shown that the path tracking controller with the constraint on tire slip angles presented in this paper is quite effective for path tracking on low-friction road surface. [ABSTRACT FROM AUTHOR]

This study proposes a haptic control of steer-by-wire systems for tracking a target steering feedback torque to achieve the conventional steering feedback torque. The haptic feedback control with a steer-by-wire steering-wheel system model was used to provide drivers with a conventional steering feedback torque. The steer-by-wire steering-wheel system model was developed, and a haptic control algorithm was designed for a desired steering feedback torque with a three-dimensional target steering torque map. In order to track the target steering torque to let the drivers feel the conventional steering efforts, an adaptive sliding-mode control was used to ensure robustness against parameter uncertainty. The angular velocity and angular acceleration used in the control algorithm were estimated using an infinite impulse response filter. The performance of the proposed controller was evaluated by computer simulation and hardware-in-the-loop simulation tests under various steering conditions. The proposed haptic controller successfully tracked the steering feedback torque for steer-by-wire systems. [ABSTRACT FROM AUTHOR]