Youssef A. Ghoneim

INTEGRATED CHASSIS CONTROL SYSTEM TO ENHANCE VEHICLE STABILITY.

Vehicle stability enhancement system, by controlling vehicle dynamics, is the latest active safety technology introduced since Antilock Brake System (ABS) and Traction Control System (TCS). This system provides the driver with enhanced vehicle stability and handling. It is the intent of this paper to provide an understanding of the fundamentals of control of vehicle stability. The paper describes a complete stability control algorithm. Starting with a model for the vehicle yaw-plane dynamics, we derive a desired vehicle response, using both time-domain and frequency-domain approaches. Control structures include both yaw rate feedback design, and full-state feedback design. The latter approach requires the estimation of vehicle side-slip velocity. Estimations based on integration of lateral acceleration, the use of algebraic equation using vehicle kinematics, and the use of a Luenberger observer are presented. Computation of the required wheel differential velocity to achieve control objectives is described. Finally, computer simulation is used to investigate and confirm the concepts being discussed.

Integrated model-based and data-driven fault detection and diagnosis approach for an automotive electric power steering system

Integrity of electric power steering system is vital to vehicle handling and driving performance. Advances in electric power steering (EPS) system have increased complexity in detecting and isolating faults. In this paper, we propose a hybrid model-based and data-driven approach to fault detection and diagnosis (FDD) in an EPS system. We develop a physics-based model of an EPS system, conduct fault injection experiments to derive fault-sensor measurement dependencies, and investigate various FDD schemes to detect and isolate the faults. Finally, we use an SVM regression technique to estimate the severity of faults.

Enhanced traction stability control system

This paper is directed to an Enhanced Traction Stability Control System (ETSC) that is based on the estimate of vehicle yaw rate and does not require yaw rate or lateral accelerometer sensors information. The validity of the yaw rate estimate is determined and used to select the appropriate control methodology. We estimate the vehicle yaw rate based on the measured speeds of the un-driven wheels of the vehicle, and we utilize various other conditions to determine if the estimated yaw rate is valid for control purposes. When it is determined that the yaw rate is valid, a combined closed-loop yaw rate feedback, and an open-loop feed-forward derivative control based on the driver input is employed. Whereas in conditions under which it is determined that the estimated yaw rate is not valid, an open-loop feed-forward control with a proportional, derivative and a diminishing integrator terms, is employed. In addition, we develop a bank angle compensation algorithm using the steering angle, vehicle speed, and the estimated yaw rate to compensate for the effect of banked road. Test results indicate marked enhancement of vehicle stability with ETSC when compared with ABS and TCS. Finally, we present test results to compare the performance of ETSC system to yaw rate feedback control only Electronic Stability Control System (ESC) using yaw rate and lateral accelerometer sensors information.

Tire-Force Based Holistic Corner Control

This paper describes an analytical methodology and the related algorithms for controlling the vehicle tire forces. The purpose of the control is to provide the driver with a normal driving feel and keep the vehicle on a target path even under demanding road conditions. All the control variables are calculated in real time by minimizing a weighted cost function of the errors between actual and target CG forces and moments. Such real time optimization is possible due to the availability of analytical solutions for the tire force adjustments. A key ingredient of the approach is the idea of making the weights in the cost function dependent on tire states after the optimal linear solution is obtained. When the tire reserve approaches its upper limit, the corresponding weighted element increases exponentially. As a result, the stability element in the cost function dominates the gradient of the target function regardless of CG force error magnitudes. Once the tire state becomes normal then the CG force error correction becomes the dominant component in the control solutions.Copyright

Control strategy for integrating the active front steering and the electronic stability control system: analysis and simulation

This paper describes the research into the integrated control of vehicles fitted with Electronic Stability Control (ESC) and Active Front Steering (AFS). The AFS is integrated with ESC and the performance of the vehicle with these systems is investigated using the CarSim™ simulation environment. First, we develop corrective yaw moment commands for ESC and AFS using the method of control hierarchy. This design approach uses variable-structure control and converts the design problem into two single input design problems. Second, we present the control activation algorithm to coordinate the ESC and the AFS controls. Finally, we present simulations to demonstrate the performance of the integrated system.

Active roll control and integration with electronic stability control system: simulation study

This paper describes research into the control of vehicles fitted with Electronic Stability Control System (ESC) and Active Roll Control (ARC). Both single-channel and dual-channel ARC are combined with ESC and the handling performance of the vehicle with these systems is investigated using CarSimTM simulation environment. The capability of a single-channel ARC provided by a supplier as a black box for roll compensation, and a dual-channel ARC, developed in this paper that combines a feed-forward and feedback control are investigated. The feed-forward control controls the vehicle roll motion, and the feedback control modifies the front and rear roll stiffness from the feed-forward setting to influence the vehicle understeer behaviour. First, we study the effect of the single channel ARC on the steady state and transient characteristics of the vehicle by modifying the roll characteristics of the car. Second, we investigate the possibility of influencing the vehicle handling using dual channel ARC to vary the roll moment distribution to reduce vehicle oversteer and improving yaw velocity tracking by actively controlling the front-to-rear roll stiffness distribution. Finally, we present simulations to demonstrate the handling performance of the integrated ESC and both single-channel and dual-channel ARC.

Model-based fault diagnosis and prognosis for Electric Power Steering systems

Electric Power Steering (EPS) is an advanced steering system that consists of two subsystems: electrical and mechanical subsystems. EPS systems not only provide steering assist to drivers but they are also actuators for recently developed active safety features, such as lane keeping and lane changing assist. Failure of some component of the EPS system can lead to walk-home situations and increased warranty costs. Hence, for the improvement of reliability, safety, and efficiency of EPS systems, fault detection, diagnosis, and prognosis become increasingly important. This paper provides fault detection for EPS systems through model-based techniques using parameter estimation to determine the current electric parameters of the EPS motor. In addition, by monitoring the deviation of the self-aligning torque (SAT) estimated from two different methods, changes in EPS mechanical parameters can be detected. The progression of this deviation can be fed into a health state estimator which can give an indication of state of health and remaining useful life. Computer simulations as well as hardware-in-the-loop (HIL) experiments are provided to illustrate this method. Finally, for integrated system diagnosis and fault isolation, a fault signature table is constructed based on estimations of motor parameters, calculations of road SAT, and residuals of parity equations. This table can be used to detect and isolate considered electrical, mechanical, and sensor faults in the EPS system and simulation results are shown to verify the developed ideas.

Application of variable-structure output feedback control to active front steering for understeer and oversteer conditions

This paper describes an approach to the design of Active Front Steering (AFS) based on Variable-Structure Output Feedback Control (VSOFC) with integral action to enhance vehicle stability during understeer and oversteer conditions. We determine the understeer and oversteer behaviour of the vehicle and we change the AFS control strategy based on the understeer and oversteer behaviour of the vehicle so that the road wheel steering angle is in the ideal position to provide the intended steering angle. The control law ensures not only that the vehicle trajectory follows a desired reference trajectory but also that its convergence rate can be specified. Finally we present simulation results to demonstrate the potential benefits of the control strategy under different driving scenarios.