This paper describes adaptive sliding mode control of a steer-by-wire (SBW) system to guarantee rack position tracking performance in various driving situations. The proposed control algorithm was developed using only motor position sensors (MPS) without information on tire/road friction. A stiffness parameter adaptation law was designed to compensate for disturbances in the SBW rack system. It is demonstrated that the proposed adaptation algorithm provides good tracking performance without using an additional gain tuning approach under various road conditions. Moreover, in the proposed algorithm, a dynamic stiffness model has been developed to improve rack position tracking performance under a zero vehicle speed scenario. In a dynamic stiffness model, the stiffness center is not fixed but changes depending on the actual rack position. In the event than an SBW vehicle is parking, it is important to ensure rack position tracking performance at low and zero vehicle speeds. Computer simulations and vehicle tests were performed under various driving situations to test the performance of the proposed control algorithm. The results demonstrate that the proposed control algorithm ensures tracking performance on dry asphalt and wet road conditions, as well as at zero vehicle speed. INDEX TERMS steer-by-wire (SBW) system, adaptive sliding mode control, rack position tracking,

This paper describes a haptic control of steer-by-wire systems for rendering the conventional steering system under various road conditions using parameter estimation of rack system lateral load model. To design the conventional steering system model, the dynamic model of a rack system has been developed as a mass-spring-damper system with a friction model. An online parameter estimation of the rack system was designed to consider the various road conditions in the haptic rendering. In a steering wheel system, which is a haptic device, a limit cycle, and instable behavior can occur due to the sampling rate and quantization. To prevent the limit cycle and instable behavior, a passivity analysis was conducted and constraint conditions of the rendering coefficient was derived. The haptic control algorithm is designed to render the conventional steering system without limit cycles using passivity conditions. The performance of the proposed controller was evaluated via both computer simulations and vehicle tests under various steering conditions. The results demonstrate that the proposed algorithm ensures haptic rendering performance on dry and wet asphalt conditions.

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.

This paper presents a comparison among path tracking controllers on low-friction roads for autonomous vehicles. There are two goals in this paper. The first is to check the performance of path tracking controllers on low-friction roads, and the second is to check the effectiveness of four-wheel steering (4WS) for path tracking. To fully investigate the performance of path-tracking controllers on low-friction roads in this paper, the pure pursuit method, Stanley method, PID control, linear quadratic regulator, sliding mode control and model predictive control are designed and compared in terms of some measures. Front and four-wheel steering are adopted as actuators for path tracking. To utilize 4WS in the pure pursuit method, Stanley method and PID control, a yaw rate tracking control is adopted. With the designed path tracking controllers, a simulation is conducted on vehicle simulation software. From the simulation results, it is shown that most path tracking controllers are effective for path tracking on low-friction roads if finely tuned, and that 4WS is not recommended for path tracking on low-friction roads.

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