In this study, a fault-tolerant control system is proposed for brake actuators in a vehicle. A degradation in deceleration performance and lateral stability caused by brake actuator failure can cause serious safety issues. The integration of braking system with either the drive or steering actuators has performance limitations, and previously studied fully integrated braking, driving, and steering systems have complex structures. Therefore, a coordinated control approach for fault-tolerant control of brake actuators was proposed herein to achieve a coordinated control of the drive, brake, and steering actuators. The drive and brake controller performed optimal torque allocation of the desired longitudinal force and yaw moment, and a constraint was set to ensure that the yaw moment error did not exceed the allowable limit. The unachieved yaw moment in the the drive and brake controllers was compensated by the front and rear wheel feedforward steering angles of the steering controller. This structure improved deceleration performance and lateral stability by allowing a certain amount of imbalance in braking force and compensating for it with the steering control. The fault-tolerant control system was verified via simulations and experiments, demonstrating that additional control of driving and steering improved the deceleration performance and lateral stability, respectively. Simulation results revealed that the proposed strategy considerably improved lateral stability compared to independent control strategy using the same actuators. The experiments further verified the applicability of the proposed strategy to vehicles and confirmed that yaw rate errors were reduced under both single and dual brake actuator failure conditions.

This study focuses on the tire–road friction estimation for the predictive control strategy of electronically limited slip differential (ELSD) to improve the handling and acceleration performance of front-wheel drive cars, which typically suffer from excessive understeer and inner drive wheel spin during acceleration while turning due to reduced vertical load on the wheel. To mitigate this, we propose a control logic for ELSD that enhances course followability and acceleration by pre-transferring the driving torque from the inside to the outside wheel, considering the estimated traction potential for rapid response. It is essential to improve the control accuracy of wheel spin prediction by predicting the friction coefficient of the road surface. Furthermore, this study extends to the analysis of vehicle dynamics during lane-change maneuvers on low-friction surfaces, emphasizing the role of accurate tire–road friction estimation in vehicle safety. A CarSim 2023-based simulation study was conducted to investigate the vehicle response on snowy roads with low friction coefficients (μ = 0.2) and low temperatures (−5 °C). The results demonstrated that even minimal steering input could result in significant side-slip angles, highlighting the nonlinear vehicle behavior and the critical need for robust traction estimation in such challenging conditions of general racing tracks. The proposed friction-estimation method was evaluated through vehicle testing and has been substantiated by patents for its originality in control and friction-estimation approaches. The outcomes of these combined methodologies underline the critical importance of tire–road friction coefficient estimation in both the effectiveness of the ELSD system and the broader context of active safety systems.

This study proposes a fault-tolerant control strategy to solve the performance degradation problem due to kingpin offset, especially the negative kingpin offset condition, when steering torque failure occurs in a Steer-by-Wire (SbW) system. Previous studies overlooked kingpin offset, particularly negative offset, and lacked methods for practical control under such conditions. To this end, differential-braking experiments were conducted using an experimental vehicle with a negative kingpin offset to verify the vehicle model. Using the validated model, offline optimization was conducted to identify the control inputs that maximize yaw rate across varying offset and speed conditions, revealing limitations of the conventional approach. Based on this analysis, differential-braking distribution guidelines for each kingpin offset were derived, and a torque distribution controller that reflects kingpin offset was proposed by utilizing the steady-state yaw rate gain of the front and rear wheel differential braking. The proposed strategy was evaluated through open- and closed-loop tests in the full vehicle model and IPG CarMaker simulation environment. The evaluation results showed that the conventional strategy had problems such as performance degradation and unintended vehicle turning under some kingpin offset conditions; however, the proposed strategy showed improved and consistent turning performance within the tested kingpin offset range (-30 to +30 mm). The control error and control effort were reduced over the entire tested kingpin offset conditions compared with that of the conventional strategy.