Robert E. Fenton

Automated highway studies at the Ohio State University-an overview

A long-range program on various aspects of automated highway operations conducted at The Ohio State University (OSU) from 1964 to 1980 is described. This program included studies on headway safety policy, longitudinal control, lateral control, and highway system operations. The principal emphasis was on the design and development of reference system/controllers for both longitudinal and lateral vehicle control. Relate activities ranged from the theoretical development of control concepts to their realization and field testing. The policy and system operation studies guided the vehicle control activities and provided overall program direction. These resulted in a requirement for a 6.4-km, automated vehicle control facility that was almost completed when this work was terminated in 1980. >

On the steering of automated vehicles: Theory and experiment

Several facets of the automatic lateral control of individual ground vehicles are considered in detail. First, a path-dependent coordinate system for describing vehicle motion is defined, and the availability of motion quantities for control purposes is specified. Second, the lateral dynamics of a typical U.S. passenger sedan are empirically obtained and validated with data from full-scale studies. Third, various designs, in which different types of compensation are employed, are evaluated in terms of specified requirements and attractive candidates are specified. Finally, several controller designs were tested under full-scale conditions wherein a wire-reference configuration and a dual-mode test vehicle were employed. The latter was automatically steered on both straight and curving roads at speeds up to 35.8 m/s (80 mph). In one typical case, the maximum tracking error observed was 0.0635 m and occurred both when a sidewind was present and when the vehicle entered a curving section of roadway. Excellent lateral control-close tracking, good insensitivity to disturbance forces, and a comfortable ride-can be obtained using a relatively simple controller.

On the steering of automated vehicles—A velocity-adaptive controller

A velocity-adaptive lateral controller is designed to meet requirements pertaining to lateral-position tracking accuracy, ride comfort, and an insensitivity to both changes in critical vehicle parameters and disturbance forces. This controller was tested under full-scale conditions wherein a wire-follower configuration and a dual-mode test vehicle were employed. The latter was automatically steered on straight sections of roadway at speeds up to 35.8 m/s, lane-changing maneuvers were performed up to this speed, and small-radius (100 m) curves were traversed at speeds up to 17.9 m/s. Excellent lateral control, close tracking, good insensitivity to disturbance forces, and a comfortable ride resulted; thus, a relatively simple controller can be effectively employed for nonemergency situations.

On the optimal design of an automotive lateral controller

An optimization approach is used to design a velocity-adaptive, lateral controller to meet requirements pertaining to lateral-position, tracking accuracy, robustness, and ride comfort. The resulting controller, which is nonlinear with velocity, requires full-state feedback and thus an observer is included. The observer/controller compensator was implemented using a 16-bit microcomputer and evaluated in a laboratory study wherein vehicle lateral dynamics were simulated on an analog computer. Excellent lateral control, i.e. close tracking (with absolute value of lateral-position error below 0.024 m in curve tracking), good sensitivity to disturbance forces, and probable ride comfort resulted. The selected control algorithm was realized using some 5% of the available computation time, thus allowing the microcomputer to be used for other control functions and vital-function monitoring. >

On the design of a vehicle longitudinal controller

A methodology for designing an automated vehicle longitudinal controller is presented and applied to an automobile characterized by velocity-dependent dynamics. The design consists of a cascade compensator, which is selected to achieve small tracking errors, and an observer/controller compensator. The controller portion was designed to achieve a velocity-invariant response, and the observer to derive the state-feedback signals. Both compensators were realized on an eight-bit microcomputer, and the vehicle dynamics were simulated on an analog computer. The performance of the resulting system was evaluated using a large-signal, entry merging command and small-signal mainline commands. Excellent results were obtained with typical values being a maximum position error of 0.63 m during an entry maneuver and 0.15 m during a mainline maneuver; however, the designed system was sensitive to large changes in critical vehicle parameters. Thus, there is a need to modify the controller so that it can adaptively compensate for such changes. Then, the designed digital controller, with its flexibility to perform other functions and its ease of reliability enhancement, is an attractive candidate for implementation, and at the very least, indicates the type of longitudinal performance one can expect from a realistically designed controller over the speed range 0-30 m/s.

An Intervehicular Spacing Display for Improved Car-Following Performance

A drivers inability to detect small headway changes and small relative velocities is a primary reason for his poor car-following performance. This can be greatly improved if he is given information?headway and relative velocity?concerning the state of a lead car. This may be provided visually, tactually, or audibly. In the study reported, a control stick with a built-in kinesthetictactile display was tested in a car-following situation. Performances with this display were compared to those obtained when no aiding was used in a similar situation. Sizable reductions in velocity variance and headway variance were obtained for the aided case relative to the unaided case. These were obtained for headways of 23 feet at 30 mi/h and 33 feet at 40 mi/h. Thus, this display can be effectively used at short headways.

An Improved Man-Machine Interface for the Driver-Vehicle System

A control stick with a built-in tactile aiding device was tested in a simulated car-following situation. The tactile device gave the driver of a following car information—headway and relative velocity—concerning the state of a lead car. Experimental results (relative velocity and headway variance) with the simulator were compared with those obtained using conventional automobile controls in a similar situation. Sizeable reductions in these quantities, 55 and 85 percent, respectively, were obtained when the tactile display was partially quickened. Some evidence indicated that the driver behaved as an amplifier when using such a display.

Automatic vehicle guidance and control—A state of the art survey

Highway automation is an attractive possible solution to some of the problems posed by an ever-increasing number of motor vehicles, as it would probably result in substantial increases in traffic-flow rates and a dramatic reduction in the numbers of highway accidents and fatalities. One practical system involves a roadway complex of the future, consisting of both automated and nonautomated roads, which will have evolved in an orderly and progressive manner from the roadway system of today. Only the main highways would be automated, and dual-mode vehicles would be used. The two major related technical areas in this framework are the physical characteristics of the various required subsystems for vehicle guidance and control and the optimum operation of the overall highway system. The elements of the former are divided into eleven categories: automatic longitudinal control, vehicle-spacing detection, communication systems, automatic lateral control, automatic merging control, controlled lane changing, vehicle propulsion, system decision-making capability, compatible manual mode, automatic vehicle checkout, and evolutionary developments. The role and state of the art of each category are discussed in detail, together with the complex interrelationships which exist among categories. Although some research has been accomplished, substantial future research and development progress will be necessary before an automated highway system is a practical reality.

State observers and state-feedback controllers for a class of non-linear systems

A design methodology for observers and controllers for a class of single-input, single-output non-linear systems is developed. A non-linear observer form is defined, and a corresponding observer using non-linear observer gains is specified. The resulting error dynamics, which are non-linear, are asymptotically stable for a proper choice of those gains and bounded inputs and outputs. A non-linear controller form is defined and a corresponding controller, which results in linear closed-loop dynamics with arbitrary eigenvalue placement, is devised. Transformations from the class of interest to the defined forms are derived. In the observer case, the transformation to the observer form and the non-linear entries in the state matrix of that form can be determined separately, leading to a system of linear partial-differential equations—a major simplification. In the controller case, a simple, well-known system of linear partial-differential equations is obtained. The efficacy of the developed methodology is sho...

A describing-function approach to antiskid design

A describing-function approach is employed in the design of an antiskid braking system. This includes the specification of the dynamics of a braking vehicle, a proposed system employing a feedback compensator to provide antiskid behavior, and the determination of the design parameters by a describing-function analysis. A wide range of tire-roadway conditions was considered in the latter. The resulting design was implemented and evaluated in field tests. The observed antiskid braking performance was approximately that predicted from the design. Thus the describing-function approach, especially in view of its ease of application and the insights it provides, appears to be a useful one for the control aspect of antiskid design.