Benedicte Bougler

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.

Evaluation of cooperative roadside and vehicle-based data collection for assessing intersection conflicts

Intersection collisions represent a significant portion of highway accidents. Recent research and development activities have suggested potential solutions to address this critical safety issue by supplying timely alerts to drivers of imminent collisions. These intersection decision support systems utilized sensor, communication and computer technologies to help drivers recognize risky conditions, thus actions can be taken to avoid collisions. A cooperative vehicle-infrastructure concept, built upon such premises, seek to combine the information available from vehicles and roadside in a synergistic framework so that a flexible yet sensible system can be deployed in the near future. The work presented in this paper represents an experimental effort conducted at a real-world intersection, by the use of an instrumented vehicle and roadside traffic monitoring, to explore technical challenges encountered in a vehicle-infrastructure integration approach.

Lane changing with look-down reference systems on automated highways

Abstract Automated lane changing is a vital component of the steering control system for automated vehicles. The most important requirements of such maneuvers are smoothness and robustness. Look-down sensing systems face the challenge of having to bridge the gap whenever reference lines of the respective lanes are not measurable. This paper discusses two methods that were successfully employed in the platoon scenario of the 1997 National Automated Highway Systems Consortium Feasibility Demonstration in San Diego, USA: infrastructure-guided lane changes using an additional cross-over marker reference, and free lane changes using a yaw rate sensor for dead reckoning. Both systems achieved good passenger comfort and exhibited high reliability. Similar techniques were applied to the entrance and exit ramps of the automated highways.

Dependence of Cooperative Vehicle System Performance on Market Penetration

Cooperative vehicle systems (CVS) can provide intelligent transportation systems services such as probe vehicle information and hazard warnings by exchanging data among suitably equipped vehicles as they travel. The sensitivity of the performance of CVS to the market penetration of suitably equipped vehicles is explained by using Monte Carlo analyses and simulations of wireless message propagation. The CVS functions are implemented by using wireless vehicle-vehicle data communications, which can be successful only when other equipped vehicles exist within wireless range to receive the messages and relay them to further vehicles. These relays may be accomplished by direct wireless transmission to nearby vehicles, but they may also be facilitated by transport relay, by which vehicles traveling in the opposite direction carry the messages and rebroadcast them to the vehicles that they pass. The effectiveness of both direct and transport relay mechanisms as a function of wireless communication range, market penetration, and traffic density and their influence on the speed of message propagation is shown. The direct relay is most effective with a high density of equipped vehicles, but when the density of equipped vehicles is low, the relays become much more dependent on the slower transport relay. When the market penetration is low early in the development of CVS, the most promising use cases are likely to be those that do not require rapid message propagation.

A Real-World Application of Lane-Guidance Technologies—Automated Snowblower

This paper describes the development process and the initial field test results of an automated snowblower, focusing on one of the more difficult snow removal operations: blowing snow off the freeway alongside a guardrail without the snowblower touching the guardrail. The development process includes transforming this highway winter maintenance operation into a control problem, modeling a snowblower, designing control algorithms, devising a human-machine interface, and equipping a 20-ton snowblower with sensors and an actuator. Specific challenges include modeling the low-speed tire-induced oscillation, designing high-gain automatic control on front wheels while keeping rear steering under driver control, and implementing such a system under practical limitations. A new dynamic deflection tire model is incorporated into a bicycle model to account for the additional lateral dynamics. A low-order controller was first generated based on the understanding of the specific control problem and, then, refined and tuned iteratively using linear-matrix-inequality optimization. The initial winter field tests were successfully conducted with embedded magnetic markers along the guardrails installed on the shoulders of Interstate-80 in the Sierra Mountain region close to Donner Summit, CA, during the winter of 2005.

SNOWPLOW STEERING GUIDANCE WITH GAIN STABILIZATION

Acquisition and utilization of lateral guidance information is crucial for steering a vehicle. With practice, drivers can successfully perform the steering function using visual perception and hand-eye coordination. However, this seemingly simple task becomes difficult when the visual information loses its clarity. Driving a snowplow during whiteout conditions is one such example. In order to improve the safety and efficiency of snow removal operations, a supplemental guidance display was proposed and successfully implemented in a California Department of Transportation (Caltrans) snowplow. The guidance information was calculated based on the magnetic markers embedded in the roadway. The crucial step to this success is a transformation of the guidance display problem into a robust driver-in-the-loop control problem. This transformation considers the ‘display’ law as part of the overall driver-steering-control algorithm. Two key ‘assumptions’ for this design are (1) the ‘display’ law should be designed in such a way that drivers can use ‘proportional’ control gain alone to satisfy the performance and stability requirements of the steering tasks, and (2) the driver steering model can be described as a combination of gain and dynamic delay under the display law in (1). This paper describes the validation process for the ‘gain’ stabilization design concept as well as the associated driver steering model using the initial snowplow test data.

Characterization of magnetic tape and magnetic markers as a position sensing system for vehicle guidance and control

In the studies of advanced vehicle control and safety systems, position measurement is an important link that provides essential information for the identification of vehicle locations. One type of critical information used by vehicle control systems is the measurement of lateral position relative to a lane or a desired trajectory. Among the technologies that have been developed for such purposes are electrically powered wire, computer vision, magnetic sensing, optical sensing, inertia navigation and global positioning systems. The paper focuses on two types of magnetic systems that have been experimentally demonstrated in earlier years. The objective is to identify the characteristics of these two sensing systems and to offer a comparison of their distinct features. Experimental data from the measurement of the magnetic fields around tape and marker systems are shown to illustrate their characteristics and functioning principles. The magnetic markers are implemented by a series of magnetic pieces installed under the road surface at a specified spacing along the subject trajectory. The magnetic tape embeds magnetic materials in a thin and narrow strip, which is laid on or under the surface of a roadway. The two systems exhibit distinct features in their field patterns, yet they possess similar properties that can be identified with sensing algorithms. Also presented in the paper is a preliminary assessment of the two systems for the use of vehicle control and safety systems. The criteria to be considered in evaluation include accuracy, range, reliability, durability, applicability, and economic costs.

Naturalistic Findings for Assisted Snowplow Operation

Performance data on the benefit of a driver assistance system for snowplows was collected during normal snow removal operations. Collection occurred during a series of ride-alongs by research staff over two winters. The test area was a major interstate freeway over a western mountain pass that historically has had numerous low visibility conditions and heavy snowfall. Variables examined were lateral displacement from the lane center, speed, steering wheel angle standard deviation, and nearest forward target when following. The driver assistance system appeared to be quantifiably similar to unaided driving in good weather conditions. The findings suggest that the system was particularly beneficial during low visibility and obscured road marking conditions - the scenarios for which the system was designed.

A steering guidance system for snowplow - an interesting control problem

Acquisition and utilization of the lateral guidance information is crucial for steering a vehicle. However, this task becomes difficult when the visual information loses its clarity. Driving a snowplow during whiteout condition is one such example. In order to improve the safety and efficiency of the snow removal operation, a supplemental steering guidance display was proposed and instrumented in a Caltrans snowplow. The guidance information was calculated based on the magnetic markers embedded under the roadway. Operations were successfully conducted on a 6.25 km freeway over Donner Summit on Interstate 80 in California during the 1998-1999 winter season. The key to this success was a clever transformation of the display problem into a control problem. This paper describes the problem formulation and the solution concept for this steering guidance system.