Yuen-Kwok Chin

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.

A Pattern-Recognition Approach for Driving Skill Characterization

Information about a drivers driving skill can be used to adapt vehicle control parameters to facilitate the specific drivers needs in terms of vehicle performance and safety. This paper presents an approach to driving skill characterization from a pattern-recognition perspective. The basic idea is to extract patterns that reflect the drivers driving skill level from the measurements of the drivers behavior and the vehicle response. The experimental results demonstrate the feasibility of using a pattern-recognition approach to characterize a drivers handling skill. This paper concludes with the discussions of the challenges and future works to bring the proposed technique to practical use.

Vehicle antilock braking and traction control : a theoretical study

Abstract A longitudinal one-wheel vehicle model is described for both antilock braking and traction control acceleration. Based on this vehicle model, a time-optimal solution is obtained for the vehicle straight-line antilock braking and traction control acceleration. The optimal solution suggests ‘bang-bang’ control and leads to the development of sliding-mode control for antilock braking and traction control. Sufficient conditions for applying sliding-mode control to regulate vehicle traction are derived via Lyapunov stability theory. With the understanding of these sufficient conditions, variable-structure control laws are designed to control vehicle traction. Both the sufficient conditions and the control laws for antilock braking are verified using computer simulations.

Driving skill characterization: A feasibility study

Information about drivers driving skill can be used to adapt vehicle control parameters to facilitate the specific drivers needs in terms of vehicle performance and driving pleasure. This paper presents an approach to driving skill characterization from a pattern-recognition perspective. The basic idea is to extract patterns that reflect the drivers driving skill level from the measurements of the drivers behavior and the vehicle response. The preliminary experimental results demonstrate the feasibility of using pattern recognition approach to characterize drivers handling skill. This paper concludes with the discussions of the challenges and future works to bring the proposed technique to practical use.

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.

Fast software prototype development for chassis/ driveline controls and integration

This paper describes an integrated environment for building quick software prototype for chassis/driveline controls and integration. Under this environment, engineers are able to focus on chassis/driveline controls and integration algorithm development quickly and effectively through user-friendly modelling and simulation interfaces. The system architecture for providing the flexibility in control algorithm development is discussed. The environment under which chassis/driveline dynamics controls are seamlessly integrated is described and the features of control algorithm library sharing and reusability are briefly discussed.

Feasibility Study for a Vehicle-Trailer Backing Up Control

A rear-wheel steer-by-wire mechanism has been applied to assist driver on backing up a vehicle with trailer. To address the issues related to the mechanical limitation on the rear-wheel steering angle, a comprehensive feasibility study has been conducted using analysis and simulation. Four modes of steering (front-wheel only steering, rear-wheel only steering, rear-wheel angle which is slave to front-wheel angle, and four wheel steering for backing control) are compared in terms of various parameters, such as achievable path curvature and hitch angle. Four wheel steering achieves the largest curvature range. Sensitivity to the variation in trailer tongue length also has been investigated. It is concluded that a proper driver interaction mechanism is needed to further assist the driver, since the ±12 degree limitation on rear-wheel only steering may not provide full counter-steer capability.

CHARACTERIZING DRIVING SKILL BASED ON ENTROPY ANALYSIS OF STEERING FREQUENCY RESPONSE

As a first step towards a dynamic control-oriented driver model that can describe various levels of driving skill in the driver’s primary vehicle control functions, this paper attempts to recognize the driving skill manifested in the low-level control characteristics. Vehicle tests on a DLC course were conducted with twenty subjects of different skill levels. A variance-based analysis was applied to the steering angle to generate both the frequency responses and the time sequences for frequency-domain and time-domain analysis. Two entropy measures are developed to evaluate the effectiveness of drivers’ steering control, and preview errors are used to provide an absolute measure for drivers’ preview performance. Simple rules using these three measures are developed, and data analysis verifies that the above three measures can effectively distinguish the driving skill levels of the twenty subjects participated in the DLC vehicle test.Copyright

Vehicle Handling and Stability Enhancement With Active Steering Control Systems

This paper presents an analysis and comparison of a vehicle with active front steering and rear-wheel steering. Based on linear analysis of base vehicle characteristics under varying speed and road surfaces, desirable vehicle response characteristics are presented and a set of performance matrices for active steering systems is formulated. Using pole-placement approach, controllability issues under active front wheel steering and rear- wheel steering controls are discussed. A frequency response optimization approach is then used to design the closed-loop controllers.Copyright

Fast software prototype development for chassis/driveline controls and integration

This paper describes an integrated environment for building quick software prototype for chassis/driveline controls and integration. Under this environment, engineers are able to focus on chassis/driveline controls and integration algorithm development quickly and effectively through user-friendly modelling and simulation interfaces. The system architecture for providing the flexibility in control algorithm development is discussed. The environment under which chassis/driveline dynamics controls are seamlessly integrated is described and the features of control algorithm library sharing and reusability are briefly discussed.