Wanki Cho

An investigation into unified chassis control scheme for optimised vehicle stability and manoeuvrability

This paper describes a unified chassis control (UCC) strategy to improve the lateral stability andmanoeuvrability of vehicles by integrating individual chassis control modules such as electronic stability control (ESC), active front steering (AFS) and continuous damping control (CDC). In order to achieve a target lateral vehicle response, an integrated AFS and four individual wheel braking controls have been used for an optimum distribution of longitudinal and lateral tyre forces the desired yaw moment for lateral stability has been designed by the sliding control method using a planar bicycle model and taking into consideration cornering stiffness uncertainties. The desired yaw moment is generated by the coordinated control of AFS and ESC. Optimal coordination of the control authority for the AFS and the ESC has been determined to minimise longitudinal deceleration. Estimated vertical tyre forces have been used for the optimum distribution of the longitudinal and lateral tyre forces. For the improved performance of the lateral stability control system, the damping forces at the four corners have been controlled to minimise roll angle by the CDC system. The response of the vehicle to the UCC system has been evaluated via computer simulations using vehicle dynamic software CarSim and a UCC controller coded with Matlab/Simulink. Computer simulations of a closed-loop driver–vehicle–controller system subjected to double lane change have been carried out to prove the improved performance of the proposed UCC strategy over a conventional ESC.

Estimation of Tire Forces for Application to Vehicle Stability Control

Estimated tire forces can be used to implement unified-chassis-control (UCC) systems. This paper presents a scheme for longitudinal/lateral tire-force estimation. The longitudinal and lateral tire-force-estimation scheme has been designed, and this consists of the following five steps: vertical tire-force estimation, shaft torque estimation, longitudinal tire-force estimation based on a simplified wheel-dynamics model, lateral tire-force estimation based on a planar model, and the combined tire-force estimation. The combined tire-force-estimation scheme has been designed to compensate for the longitudinal/lateral tire-force estimator, which uses a random-walk Kalman filter. The proposed estimation scheme has been integrated into a UCC system. The performance of the UCC system, including the estimator, has been evaluated via computer simulations conducted using the vehicle dynamic software CARSIM, the ASM vehicle model, and the UCC system coded with Matlab/Simulink.

Unified Chassis Control for Rollover Prevention and Lateral Stability

This paper describes a unified chassis control (UCC) strategy to prevent vehicle rollover and improve vehicle lateral stability. A rollover index (RI), which indicates impending rollover, and a model-based roll state estimator are introduced to detect potential rollover. An RI/lateral stability-based rollover mitigation (ROM) controller is designed to reduce the danger of rollover without loss of vehicle lateral stability by integrating electronic stability control (ESC) and continuous damping control (CDC). Simulation results indicate that significant improvement in vehicle rollover prevention and lateral stability can be expected from the proposed UCC system.

Unified Chassis Control for the Improvement of Agility, Maneuverability, and Lateral Stability

This paper describes a unified chassis control (UCC) strategy for improving agility, maneuverability, and vehicle lateral stability by the integration of active front steering (AFS) and electronic stability control (ESC). The proposed UCC system consists of a supervisor, a control algorithm, and a coordinator. The supervisor determines the target yaw rate and velocity based on control modes that consist of no-control, agility-control, maneuverability-control, and lateral-stability-control modes. These control modes can be determined using indices that are dimensionless numbers to monitor a current driving situation. To achieve the target yaw rate and velocity, the control algorithm determines the desired yaw moment and longitudinal force, respectively. The desired yaw moment and longitudinal force can be generated by the coordination of the AFS and ESC systems. To consider a performance limit of the ESC system and tires, the coordination is designed using the Karush-Kuhn-Tucker (KKT) condition in an optimal manner. Closed-loop simulations with a driver-vehicle-controller system were conducted to investigate the performance of the proposed control strategy using the CarSim vehicle dynamics software and the UCC controller, which was coded using MATLAB/Simulink. Based on our simulation results, we show that the proposed UCC control algorithm improves vehicle motion with respect to agility, maneuverability, and lateral stability, compared with conventional ESC.

Design of an unified chassis controller for rollover prevention, manoeuvrability and lateral stability

This paper describes a unified chassis control (UCC) strategy to prevent vehicle rollover and improve both manoeuvrability and lateral stability. Since previous researches on rollover prevention are only focused on the reduction of lateral acceleration, the manoeuvrability and lateral stability cannot be guaranteed. For this reason, it is necessary to design a UCC controller to prevent rollover and improve lateral stability by integrating electronic stability control, active front steering and continuous damping control. This integration is performed through switching among several control modes and a simulation is performed to validate the proposed method. Simulation results indicate that a significant improvement in rollover prevention, manoeuvrability and lateral stability can be expected from the proposed UCC system.

Intelligent vehicle safety control strategy in various driving situations

This paper describes a safety control strategy for intelligent vehicles with the objective of optimally coordinating the throttle, brake, and active front steering actuator inputs to obtain both lateral stability and longitudinal safety. The control system consists of a supervisor, control algorithms, and a coordinator. From the measurement and estimation signals, the supervisor determines the active control modes among normal driving, longitudinal safety, lateral stability, and integrated safety control mode. The control algorithms consist of longitudinal and lateral stability controllers. The longitudinal controller is designed to improve the drivers comfort during normal, safe-driving situations, and to avoid rear-end collision in vehicle-following situations. The lateral stability controller is designed to obtain the required manoeuvrability and to limit the vehicle bodys side-slip angle. To obtain both longitudinal safety and lateral stability control in various driving situations, the coordinator optimally determines the throttle, brake, and active front steering inputs based on the current status of the subject vehicle. Closed-loop simulations with the driver–vehicle-controller system are conducted to investigate the performance of the proposed control strategy. From these simulation results, it is shown that the proposed control algorithm assists the driver in combined severe braking/large steering manoeuvring so that the driver can maintain good manoeuvrability and prevent the vehicle from crashing in vehicle-following situations.

An investigation into unified chassis control for agility, maneuverability and lateral stability

This paper propose a unified chassis control (UCC) strategy to improve agility, maneuverability and, vehicle lateral stability by the integration of active front steering (AFS) and electronic stability control (ESC). The proposed UCC system consists of a supervisor, a control algorithm, and a coordinator. The supervisor determines a target yaw rate and a target velocity. To achieve a target yaw rate and velocity, the control algorithm determines a desired yaw moment and a desired longitudinal force, respectively. The desired yaw moment and the desired longitudinal force can be generated by the coordination of the AFS and ESC systems. To consider a performance limit of the ESC system and tires, the coordination is designed using the optimal method. Closed loop simulations with a driver-vehicle-controller system were conducted to investigate the performance of the proposed control strategy using CarSim vehicle dynamics software and the UCC controller coded using Maltab/Simulink.

Unified Chassis Control for Vehicle Rollover Prevention

This paper describes an unified chassis control (UCC) strategy to prevent vehicle rollover and improve maneuverability. In order to detect a danger of rollover, rollover index (RI) which indicates an impending rollover is determined. The rollover index is calculated using estimated roll angle, roll rate and measured lateral acceleration. Lateral and vertical model-based roll state estimators are designed and combined to obtain the vehicle roll state induced by maneuvering and road disturbances. The vehicle mass is adapted to improve the robustness of the roll state estimator. The RI-based rollover mitigation controller (RMC) is designed by integrating the electronic stability control (ESC), active front steering (AFS) and continuous damping control (CDC). The RI/lateral stability-based RMC is also designed to ensure maneuverability. Computer simulation is conducted to evaluate the proposed UCC scheme by using validated vehicle simulation software. From the simulation results, it is shown that the proposed UCC can prevent vehicle rollover and load to improvements in vehicle stability.

Vehicle stability control using individual brake force based on tire force information

Development of an Electronic Stability Control using individual brake force distribution based on tire force information was presented in this paper. The objective of the proposed ESC algorithm is to determine the individual brake forces to improve the performance of the controller. This ESC algorithm consists of an upper level controller and a lower level controller. The upper level controller calculates the desired yaw moment for satisfying the drivers intention. The lateral dynamic model can be more accurate by getting rid of the uncertainties caused by complex tire model. In the lower level controller, the individual braking forces are determined by the optimal strategy. The closed loop computer simulation results with driver-vehicle-controller system confirm the effectiveness of the proposed control system and the improvements in vehicle stability.

Integrated Chassis Control for the Driving Safety

This paper describes an integrated chassis control for a maneuverability, a lateral stability and a rollover prevention of a vehicle by the using of the ESC and AFS. The integrated chassis control system consists of a supervisor, control algorithms and a coordinator. From the measured and estimation signals, the supervisor determines the vehicle driving situation about the lateral stability and rollover prevention. The control algorithms determine a desired yaw moment for lateral stability and a desired longitudinal force for the rollover prevention. In order to apply the control inputs, the coordinator determines a brake and active front steering inputs optimally based on the current status of the subject vehicle. To improve the reliability and to reduce the operating load of the proposed control algorithms, a multi-core ECU platform is used in this system. For the evaluation of this system, a closed loop simulations with driver-vehicle-controller system were conducted to investigate the performance of the proposed control strategy.