Han-Shue Tan

Robust automatic steering control for look-down reference systems with front and rear sensors

This paper describes a robust control design for automatic steering of passenger cars. Previous studies showed that reliable automatic driving at highway speed may not be achieved under practical conditions with look-down reference systems which use only one sensor at the front bumper to measure the lateral displacement of the vehicle from the lane reference. An additional lateral displacement sensor is added here at the tail bumper to solve the automatic steering control problem. The control design is performed stepwise: an initial controller is determined using the parameter space approach in an invariance plane; and this controller is then refined to accommodate practical constraints and finally optimized using the multiobjective optimization program. The performance and robustness of the final controller was verified experimentally at California PATH in a series of test runs.

Analysis of Automatic Steering Control for Highway Vehicles with Look-down Lateral Reference Systems

SUMMARY In this paper, steering control for passenger cars on automated highways is analyzed, concentrating on look-down reference systems. Extension of earlier experimental results for low speed to highway speed is shown to be non-trivial. The limitations of pure output-feedback of lateral vehicle displacement from the road reference are examined under practical constraints and performance requirements like robustness, maximum lateral error and comfort. The in-depth system analysis directly leads to a new alternative design direction which allows to preserve look-ahead reference systems for highway speed automatic driving.

Vehicle traction control : variable-structure control approach

A longitudinal one-wheel vehicle model is described for both anti-lock braking and anti-span acceleration. Based on this vehicle model sufficient conditions for applying sliding-mode control to a vehicle traction are derived via Lyapunov Stability Theory. With the understanding of these sufficient conditions, control laws are designed to control vehicle traction. Both the sufficient conditions and the control laws are verified using computer simulations.

Demonstration of an automated highway platoon system

The National Automated Highway System Consortium (NAHSC), in partnership with the Department of Transportation, demonstrated several potential AHS technologies on I-15 in San Diego in August 1997. One of the key elements in this demonstration event was a platoon system that contained a group of fully automated automobiles traveling at close spacing. The platoon system demonstrated a number of AHS features such as lane keeping, lane changing, longitudinal space and speed regulation using proved enabling technologies. The paper describes the platoon concept, the configuration of the demonstration system, the demonstration scenarios and reports the development of the platoon demonstration system and the data collected during the demonstration.

Linear parameter varying controller for automated lane guidance: experimental study on tractor-trailers

Proposes a linear parameter-varying (LPV) controller design for automated lane keeping for vehicles. The lane keeping objective is to keep the vehicle centered with respect to the lane boundaries by applying appropriate steering action. Most current implementation of lane keeping controllers were based on linear synthesis techniques because linear techniques offer a direct tradeoff between steering action, passenger comfort, robustness, and tracking performance. However, linear methods assume constant longitudinal velocity of the vehicle for controller synthesis. It is known that the position response of the vehicle to the steering input varies significantly with the longitudinal velocity of the vehicle. The LPV design technique deals with this issue by synthesizing a velocity dependent controller. The controller minimizes the induced /spl Lscr//sub 2/ norm of the closed loop from the road curvature to the tracking error. The design has been successfully implemented on a tractor-trailer vehicle and experiments conducted up to longitudinal velocity of 60 mi/h are presented.

Discrete-time controller design for robust vehicle traction

A discrete-time control algorithm for robust vehicle traction, which includes antiskid braking and antispin acceleration, is presented. The algorithm is a nonlinear feedback scheme that can be designed via classical digital control theory. The algorithm is easy to tune and modify to incorporate higher-order dynamics, which may be necessary for a practical hardware setup. The robust controller provides stable and reliable performance under a variety of uncertainties involved in the vehicle/brake system that are difficult to measure. The effectiveness of this new scheme is demonstrated by experiments on antiskid braking.<<ETX>>

Design and field testing of a Cooperative Adaptive Cruise Control system

This paper describes the development of an Cooperative Adaptive Cruise Control (CACC) experimental system with vehicle-to-vehicle communication based on a car with factory installed ACC system. The controller design will be introduced in detail on how to incorporate the information shared through wireless communication link. The structure of the proposed CACC controller and an indirect adaptive Model Predictive Control (MPC) based gap regulation controller are presented. Experimental results from field testing at both vehicle proving ground and public highway are shown to verify the effectiveness of the proposed controller design.

Error Analysis and Performance Evaluation of a Future-Trajectory-Based Cooperative Collision Warning System

This paper focuses on the robustness and reliability of a future-trajectory-based cooperative collision warning system (CCWS), which estimates and communicates vehicle positions and predicts and processes future trajectories for collision decision making. The feasibility of the system design has been demonstrated in previous work, and this paper analyzes the error propagation and its impact on detection performance. The reliability of the CCWS heavily depends on the reliability of the differential Global Positioning System (DGPS)-based positioning system and the reliability of intervehicle communication. This paper uses the Kalman filter technique to statistically characterize the errors in position estimation and trajectory prediction, incorporates communication errors as part of the prediction error, and accordingly determines the probability of conflicts and the quality of the detection performance. Results with experimental data are presented to illustrate the error propagation and to demonstrate the reliability of the system.

Automatic Steering Based on Roadway Markers: From Highway Driving to Precision Docking

Bus Rapid Transit (BRT) is an effective alternative for providing rail-like corridor transit service. An advanced BRT concept involves the use of automated buses to provide functions of a rail transit system. A vehicle under automatic steering control following a prescribed trajectory is operated like a train on a rail. A lateral position sensing that uses roadway markers, such as magnetic markers embedded under the roadway, as lateral reference is one of the promising approaches for a reliable sensing system. The BRT concept requires the steering control system to consistently perform all necessary steering functions from high speed driving to low speed precision docking. This paper describes a single steering controller that achieves all performance objectives. Various data collected during several public demonstrations are presented in this paper to illustrate the effectiveness of the approach. These data include the following automatic steering control scenarios: over 100 mph high-speed driving, high-g maneuvers, sharp curve following, and low speed precision docking.

Experimental results of a tire-burst controller for AHS

Abstract This paper investigates the problem of tire burst, and how to mitigate its adverse effects in an AHS environment. The problem is approached by first modeling the tire burst. A feed-forward controller is designed, based on inverting the nonlinear tire-burst dynamics for controlling the car after the tire burst. The feed-forward term is approximated by the output of a second-order filter. The approximation also provides a way to characterize the feed-forward term for different road curvature and different tires (front/rear, left/right). Two different tire blow-out detection algorithms are discussed. This is followed by the experimental phase. Open-loop experiments were conducted to verify the tire-burst model. Closed-loop tests were then carried out to validate the automatic lane-following performance after a tire burst. The results have shown that the burst controller enables the car to follow the lane, even after a front tire blow-out.