Robert D. Ervin

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.

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.

An electrorheologically controlled semi-active landing gear

This study is to explore the application of electrorheology (ER) to the real-time control of damping forces that are transmitted through the nose landing gear for an F-106B aircraft. The main part of the landing gear is a strut that consists of a pneumatic spring and an ER controlled damper that is situatted on the strut centerline and applies a force directly opposing the vertical displacement of the nose wheel. The damping element rotates in response to strut displacement, employing a co-axial arrangement of stator and rotor plates connected to the opposing electrodes in the control circuit. The vertical displacement is conveted into rotation of the damper through a screw-nut mechanism. The ER fluid between the electrodes is thus engaged in shear along circumferential lines of action. This design results in a fast time response and a high ratio of strut forces achieved under Er-vs. zero-field control. Compact size and simplicity in fabrication are also attained. The analysis shows that when using an ER fluid of a yield stress of 7kPa, the energy absorption efficiency of the landing gear can reach almost 100% at various sink rates.

EVALUATING THE INFLUENCES OF ADAPTIVE CRUISE CONTROL SYSTEMS ON THE LONGITUDINAL DYNAMICS OF STRINGS OF HIGHWAY VEHICLES

SUMMARY This paper presents experimental results, analytical findings, and simulation evaluations pertaining to the longitudinal dynamics and headway performance of strings of vehicles with and without adaptive cruise control (ACC) systems. It focuses on the amplification of speed disturbances along a string of vehicles, i.e., the stability of string behavior. The work describes measurement, analysis, and simulation tools that are suitable for use in evaluating the impact of ACC system characteristics on traffic flow.

Tests Characterizing Performance of an Adaptive Cruise Control System

This paper describes methods for characterizing the headway control performance of adaptive cruise control (ACC) systems. The inputs to the test are the speed of the preceding vehicle. Results of the tests are based upon measurements of range, range rate, velocity transmission shift commands,, and velocity commands. Numerical performance measures are derived from these data and are used to characterize system performance quantitatively.

Test Procedures for Studying Vehicle Dynamics in Lane-Change Maneuvers

The use of both closed- and open-loop test procedures for evaluating the performance of motor vehicles in lane-change maneuvers is reviewed. It is found that (a) variations in driver skill, (b) differences in the amount of information imparted to the driver by the layout of the test course, (c) the asymmetry in response between right and left lane-changes, and (d) the lack of understanding of the connection between open- and closed-loop performance present difficulties in evaluating lane-change performance. Further study is recommended using a particular form of evasive performance test to seek identifiable ergonomic and vehicle dynamics bounds on driver-vehicle system performance.

Intelligent Systems for Aiding the Truck Driver in Vehicle Control

This paper describes two prototype systems designed to aid truck drivers in controlling an articulated heavy-duty vehicle. The systems involve a roll stability advisor (RSA) and a rearward amplification suppression system (RAMS). Both systems are described in terms of their concept, design, and application.

The influence of viscometer dynamics on the characterization of an electrorheological fluid under sinusoidal electric excitation

The dynamic response of a controlled‐strain, Couette viscometer employed for the characterization of the frequency response of an electrorheological (ER) fluid is studied both numerically and experimentally. In the numerical model, the ER fluid flow between the cup and bob elements of the viscometer is coupled with the mechanical response of the cup–torque sensor system. The Bingham model is used for describing the ER fluid, with various functional forms for relating the electric field strength to the Bingham stress. Variation in the shear‐rate dependency of the Bingham stress response is also represented. Dynamic resonance tends to dominate the cup rotation response and the shear rate of the fluid. The Bingham stress response contains higher harmonic components whenever it does not follow a second power‐law relationship exactly with the electric field strength. Higher harmonics induce their own resonances at relatively lower values of excitation frequency. Experimental results obtained with zeolite‐based...

A FIELD OPERATIONAL TEST OF ADAPTIVE CRUISE CONTROL : SYSTEM OPERABILITY IN NATURALISTIC USE

This paper describes the results from a field operational test which tested for differences in the longitudinal control of headway between manual driving and driving with an adaptive cruise control (ACC) system. It was found that the ACC mode of driver assistance contributed to longer following distances and improved driver comfort and convenience. Recommendations for improving the ACC function are also presented.