Seongjin Yim

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.

Coordinated Control of Hybrid 4WD Vehicles for Enhanced Maneuverability and Lateral Stability

This paper presents a method for coordinated control of hybrid four-wheel drive (4WD) vehicles (H4Vs), which consists of a front internal combustion engine and independent motor-driven rear wheels. H4Vs are equipped with electronic stability control (ESC), active front steering (AFS), and 4WD. For maneuverability and lateral stability, a yaw moment controller is designed. After generating a control yaw moment with a direct yaw moment control, it is distributed with ESC, AFS, and 4WD. Several actuator configurations of ESC, AFS, and 4WD are presented in the framework of the weighted pseudo-inverse based control allocation. Simulation-based tuning is proposed to improve the performance of the yaw moment distribution. Simulations show that the proposed method is effective for the coordinated control of H4Vs for enhanced maneuverability and lateral stability.

Design of a Preview Controller for Vehicle Rollover Prevention

This paper presents a method for designing a preview controller for vehicle rollover prevention. It is assumed that a drivers steering input is previewable with a Global Positioning System (GPS) and an inertial measurement unit (IMU), or with an automatic steering system for collision avoidance. Based on a linear vehicle model, a linear optimal preview controller is designed. To avoid the full-state measurement of a linear quadratic regulator (LQR), linear quadratic static output feedback (LQ SOF) control is adopted. To compare with several types of controllers such as LQR or LQ SOF with respect to rollover prevention capabilities, Bode plot analysis based on a linear vehicle model is performed. To show the effectiveness of the proposed controller, simulations are performed on a vehicle simulation package CarSim.

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.

Design of rollover prevention controller with linear matrix inequality-based trajectory sensitivity minimisation

This paper presents a method to design a rollover prevention controller for vehicle systems. The vehicle rollover can be prevented by a controller that minimises the lateral acceleration and the roll angle. Rollover prevention capability can be enhanced if the controlled vehicle system is robust to the variation of the height of the centre of gravity and the speed of the vehicle. For this purpose, a robust controller is designed with linear matrix inequality-based trajectory sensitivity minimisation. Differential braking and active suspension are adopted as actuators that generate yaw and roll moments, respectively. The newly proposed method is shown to be effective in preventing rollover by the simulation on a non-linear multibody dynamic simulation software, CarSim®.

Design of active roll control system and integrated chassis control for hybrid 4WD vehicles

This paper presents a method for designing an active roll control system (ARCS) and an integrated chassis control (ICC) for hybrid 4-wheel drive vehicles (H4Vs). ARCS adopts an active anti-roll bar as an actuator. ARCS is designed by sliding mode control with an open-loop roll observer. To maintain the maneuverability of a vehicle with ARCS, ICC for H4Vs is designed. H4V consists of a front internal combustion engine and independent motor-driven rear wheels, and is equipped with electronic stability control (ESC), active front steering (AFS) and 4-wheel drive (4WD). Direct yaw moment control (DYC) is used to generate a control yaw moment. Weighted least square (WLS) and simulation-based optimization are proposed to distribute the control yaw moment. Simulations on vehicle simulation software, CarSim®, show that the proposed ARCS with ICC is effective for H4V.

Coordinated control with electronic stability control and active front steering using the optimum yaw moment distribution under a lateral force constraint on the active front steering

This paper presents an optimum yaw moment distribution scheme with electronic stability control and active front steering for vehicle stability control. Direct yaw moment control is used to derive the control yaw moment needed to stabilize the lateral motion of a vehicle. The yaw moment distribution is formulated as an optimization problem, whose objective is to coordinate the braking of electronic stability control and the corrective steering obtained by active front steering. To tune the relative magnitude of the braking of electronic stability control to the corrective steering obtained by active front steering, an adaptive tuning rule is proposed. To cope with the situation that the lateral tyre force of active front steering exceeds its physical limit, a new constraint is added to the original optimization problem. To solve the problem, weighted pseudo-inverse-based control allocation is adopted. By using the vehicle simulation software CarSim®, the proposed method is shown to be effective for coordination between electronic stability control and active front steering.

Design of an active roll control system for hybrid four-wheel-drive vehicles

This paper presents a method for designing an active roll control system, combined with integrated chassis control for hybrid four-wheel-drive vehicles. The active roll control system adopts an active anti-roll bar as an actuator and is designed by model matching control with a roll estimator. To maintain the manoeuvrability of hybrid four-wheel-drive vehicles with an active roll control system, integrated chassis control is adopted. The hybrid four-wheel-drive vehicle consists of a front internal-combustion engine and independent motor-driven rear wheels and is equipped with electronic stability control, active front steering and four-wheel drive. Direct yaw moment control is used to generate a control yaw moment. Weighted pseudo-inverse-based control allocation and simulation-based optimization are proposed to distribute the control yaw moment. Simulations on the vehicle simulation software CarSim® show that the proposed active roll control system with integrated chassis control is effective for controlling the roll motion and the yaw motion of a hybrid four-wheel-drive vehicle.

Control of the motorized active suspension damper for good ride quality

This paper presents a control algorithm for the motorized active suspension damper. The control algorithm consists of supervisory, upper-level and lower-level controllers. The supervisory controller determines the control modes, such as the passive mode, the roll mode and the body acceleration mode. The upper-level controller computes the damping force using linear quadratic control theory. The actuator input is determined by the lower-level controller. Three state estimators, namely the vehicle body’s velocity estimator, the suspension state estimator and the friction estimator, are proposed to estimate the sprung-mass and unsprung-mass velocities, the tyre deflection, the roll angle, the roll rate and the friction. The performance of the proposed control algorithm was evaluated via simulations and vehicle tests. It was shown from both simulations and vehicle tests that the proposed control algorithm can improve the ride quality using a motorized active suspension damper.

Integrated chassis control with adaptive algorithms

This paper presents the application of adaptive algorithms to integrated chassis control. Integrated chassis control uses electronic stability control and active front steering as actuators. In order to generate the control yaw moment using electronic stability control and active front steering, and to coordinate the relative magnitude of the tyre force generated by active front steering with that generated by electronic stability control, a fast and simple yaw moment distribution procedure is needed. For this purpose, adaptive methods, namely the least-mean-square algorithm, the sign–sign least-mean-squares algorithm and the leaky least-mean-square algorithm, are applied. To coordinate active front steering and electronic stability control in the leaky least-mean-square algorithm, a particular weight set is selected. To check the effectiveness of the adaptive algorithms in integrated chassis control, simulations using the vehicle simulation package CarSim® were carried out.