Paul S. Fancher

Human-Centered Design of an Acc-With-Braking and Forward-Crash-Warning System

This paper addresses the development of driver assistance systems whose functional purposes are to provide both adaptive cruise control (ACC) and forward collision warning (FCW). The purpose of the paper is to combine concepts from human factors psychology, vehicle-dynamics, and control theory, thereby contributing to the body of knowledge and understanding concerning human-centered approaches for designing and evaluating driver assistance systems. Conceptual and experimental results pertaining to driving manually and with the assistance of ACC and FCW are presented. The following human-centered aspects of driver-assistance systems are analyzed and presented: the looming effect; including rule-based and skill-based behavior in the design of ACC systems; using desired dynamics in controlling the driving process; braking rules that trade headway range for deceleration level; and collision-warning rules based on two different stress indicators. Field-test data are examined to justify and verify the parametric values selected for use in human-centered ACC systems. Measured data from on-road driving are used to evaluate the performance of proposed FCW systems in braking situations. The paper concludes with observations concerning the difficulty of developing a clear understanding of when and why drivers brake.

Measurement and Representation of the Mechanical Properties of Truck Leaf Springs

The force-vs.-deflection characteristics of truck leaf springs were investigated with respect to the influences of stroking frequency and amplitude and nominal static load on hysteretic damping and effective spring rate. Measurements were made on five currently employed leaf springs at five stroking frequencies (0.5 to 15.0 Hz) for three stroking amplitudes at two static loads. Test results indicate that the stroking frequency over the studied range has no influence on the spring rate and energy dissipation properties of truck leaf springs. Truck leaf springs are highly nonlinear devices for which the average damping force in a stroking cycle increases directly with either the stroking amplitude or nominal static load, and the effective spring rate decreases inversely with the stroking amplitude or directly with the static load. A mathematical method is presented which represents the force-vs.-deflection characteristics of truck leaf springs in a form suitable for use in the simulation (digital calculations) of vehicle dynamics.

Directional performance issues in evaluation and design of articulated heavy vehicles

This review of the dynamics of heavy road–vehicle systems emphasizes directional performance. The review presents information on the following topics: why are articulated vehicles used; units, hitches, and combination vehicles; multiple axle suspensions and steering systems; important performance issues; models and simulation tools; and controlling directional performance. The concluding section summarizes the material presented and provides ideas regarding the application of vehicle system dynamics concepts in developing controllers for road trains.

Evaluating Headway Control Using Range Versus Range-Rate Relationships

SUMMARY This paper uses range versus range-rate diagrams to illustrate concepts concerning the objectives of headway control, linear trajectories in the range versus range-rate space, and the influences of acceleration/deceleration limits on headway control systems. Relationships illustrated in range versus range-rate diagrams are used in evaluating first, second, and higher order systems for automatically controlling headway. Ideas for comparing driver control of headway with automatic control of headway are presented.

Methodology for assessing adaptive cruise control behavior

This paper reports on nonintrusive methods for characterizing the longitudinal performance of vehicles equipped with adaptive cruise control (ACC) systems. It reports the experimental set-up and procedures for measuring ACC system performance, followed by the modeling and simulation of the measured ACC performance. To further assess the interaction of ACC vehicles with human-controlled traffic, microscopic simulation involving both a human-driver model and an ACC model is discussed.

USING BRAKING TO CONTROL THE LATERAL MOTIONS OF FULL TRAILERS

Abstract This paper provides analytical and simulation results showing the performance benefits available from using an electronic braking system to apply yawing torques (through differential side-to-side braking) so as to aid in controlling the lateral snaking motions of multiply articulated heavy vehicles employing full trailers.

The Static Stability of Articulated Commercial Vehicles

SUMMARY This review of the state of the art emphasizes recent results that have been obtained in extending conventionalanalysis techniques to the treatment of “Highway Trains”, that is, to heavy trucks that have multiple articulation points and employ suspensions with multiple axles. Equations of motion applicable to the equilibrium turning performances of articulated vehicles are examined with respect to using analysis techniques involving steering gains, understeer gradients, effective wheel-bases, handling diagrams, and critical speeds. These examinations provide the basis for in sights into simplified approaches for understanding the steady turning mechanics of articulated, multi-axle vehicles riding on pneumatic tires.

USING NEURAL NETWORKS TO IDENTIFY DRIVING STYLE AND HEADWAY CONTROL BEHAVIOR OF DRIVERS

SUMMARY This paper illustrates the use of neural network techniques for analyzing headway data collected from a group of 36 driving subjects during normal on-highway driving. Pattern recognition methods are used to identify different types of headway-keeping behavior exhibited by these drivers and their relative distributions. Possibilities for using neural networks to represent longitudinal control behavior of drivers are also considered and discussed.

Evolving model for studying driver-vehicle system performance in longitudinal control of headway

A model for studying and evaluating the performance of drivers in controlling headway situations is currently being used to better understand how a driver’s perception of headway range and its rate of change in time (range rate) influence the performance of the driver-vehicle system in freeway driving situations. The model is based upon ideas derived from vehicle dynamics, control theory, and human factors research. It is an interpretive model in the sense that results obtained during real driving are processed to evaluate the parameter values and functional relationships used in the model. In this way, the model evolves as new data and information become available and as calculated results are interpreted and understood.

REPRESENTING TRUCK TIRE CHARACTERISTICS IN SIMULATIONS OF BRAKING AND BRAKING-IN-A-TURN MANEUVERS

ABSTRACT The tire characteristics and modeling concepts presented here are intended for use in studying the performance of trucks (including articulated vehicles) in braking and braking-in-a-turn maneuvers such as those included in recent versions of U.S. Federal Motor Vehicle Safety Standard (FMVSS) 121. A semi-empirical tire model is used to provide example truck-tire characteristics. The semi-empirical model is based upon the theoretical concepts employed in brush type tire models. Tire dynamics are included using a relaxation length approach. These postulated tire concepts are employed in conjunction with measured or specified tire stiffnesses and tire-road frictional properties to predict longitudinal and lateral forces.