Satyajit Patwardhan

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.

A general framework for automatic steering control: system analysis

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 nontrivial. The limitations of pure output-feedback of lateral vehicle displacement from the road reference are examined under practical constraints and performance requirements such as robustness, maximum lateral error and passenger comfort. The in-depth system analysis directly leads to a new alternative design direction which allows to harness the benefits of look-ahead reference systems for look-down highway speed automatic driving.

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.

Theory and experiments of tire blow-out effects and hazard reduction control for automated vehicle lateral control system

This paper concentrates on the scenario of tire blow out and its effects on lateral control of automobiles in an IVHS environment. A computer model for the tire burst phenomenon was developed to simulate the behavior of a car with a tire blow out. Based on this modeling, a control algorithm to compensate for the tire blow out was designed. Finally the tire burst experiments were conducted on a car to validate the tire burst model.

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.

Coding of Road Information for Automated Highways

This paper discusses coding of road information in a lateral reference system using magnetic markers designed for Automated Highway Systems ( AHS). The coding is utilized to communicate road information such as up- coming road geometry or lane merges/diverges from the roadway infrastructure to AHS vehicles. The work presented here is based on experiences with the preparation of the I-15 test track near San Diego, CA, for the National AHS Consortium demonstration in 1997. Information about road features was encoded into the magnets used as a lateral reference system for automatic steering control by exploiting binary polarity coding.

Lane following during backward driving for front wheel steered vehicles

This paper addresses the problem of automatic backward driving of passenger vehicles following a specified path. Additional difficulties associated with backward driving, as compared to forward driving are pointed out, with special attention to the sensor location. A special controller structure, based on a concept of kinematic linkage is proposed to overcome the dynamic difficulties associated with backward driving. Simulations and experiments demonstrate its performance and functionality.

Changing Lanes on Automated Highways with Look-Down Reference Systems 1

Abstract Lane change is a vital component of the steering control system for automated vehicles. Look-down system faces the challenge of having to bridge the gap between the references in the center of the respective lanes. This paper discusses two methods that were employed in the platoon demonstration of the National Automated Highway Systems Consortium: infrastructure guided lane changes using cross-over references and free lane changes using dead-reckoning. Similar techniques were applied to steering control on entrance and exit ramps of automated highways.

Experimental Results of Tire Burst Controller for AHS

Abstract In this paper, we investigate 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 hurst. The feed-forward term is approximated by the output of a second order filter. The approximation also provided 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 the front tire blow out.

VALIDATION OF SOFTWARE TESTING RESULTS FOR REAL-TIME VEHICLE CONTROL SOFTWARE

In this paper, an approach, based on Monte Carlo black-box testing, is presented to test the California Partner for Advanced Transit and Highways (PATH) programs lateral control system software. The paper concludes with a report on the validation of the results obtained from the software testing experiment.