R.J. Mayhan

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. >

Synchronous longitudinal reference signal generation—An experimental study of its use in automatic vehicle control

A method of obtaining a continuous reference signal for use in the synchronous longitudinal control of automated ground transport systems is presented and evaluated in preliminary full-scale tests. The results of the latter, which were obtained using a reference signal in conjunction with an instrumented vehicle at speeds from 0 to 46 ft/s over 1600 ft of roadway, are presented. Successful operation was achieved with both steady-state and time-varying velocity command signals. A significant finding, with respect to implementation of the method, was that the roadway environment introduces signal attenuation (2 dB/100 ft) that must be circumvented before practical long-distance operation can be achieved. However, with system refinement, the technique holds great promise for future implementation.

Longitudinal reference signal generation for automatic-vehicle control

A method of reference signal generation for synchronous longitudinal control of automatic vehicles is presented. The principles of operation are given along with some preliminary experimental results which indicate that the technique should be usable on existing roadways.

A two-frequency radar for vehicle automatic lateral control

The use of a side-looking radar in conjunction with a sidewall reflector is one means of obtaining lateral position information for use in vehicle automatic lateral control. The principle of operation of a two-frequency radar for such use is presented along with a discussion of the reflector design and construction difficulties. Some results of the full-scale testing of this radar using two different types of reflecting surfaces are included. The performance of this radar system is compared with that of the highly accurate wire follower. In general, tracking errors on the order of twice those obtained with the wire follower were achieved. It appears that with some redesign of the radar, performance equal to or better than that of the wire follower should eventually result.

A continuous longitudinal control signal for automated transportation systems via the low-frequency excitation of helical transmission lines

A method of generating continuous position information for use in the longitudinal control of automated ground transport systems is presented. The technique utilizes two specially excited four-wire helically wound transmission lines. The method of excitation, the signal detection, and processing schemes necessary to obtain the control signal, and the results of laboratory tests are presented. The technique should provide accurate, easily implementable, and environmentally impervious means of generating information for longitudinal control.

The experimental evaluation of flat periodic transmission lines for use as an information source in automated transportation systems

A brief summary of some past studies of the use of transmission lines as an information source for automated ground transportation systems is presented. One method, which involves the use of helically wound transmission lines, was found to be promising [6] but such lines are difficult to implement. Here the geometry-dependent properties of the magnetic-field distribution of flat periodic transmission lines is developed. It is found that such lines should be usable as a replacement for helically wound lines. The results of an experimental evaluation of several flat lines are presented with emphasis on triangular-shaped lines. It is found that the performance characteristics are even better than those of the helically wound line.

The use of enhancement plates for improved Doppler radar performance for ground transport systems

A method of improving the performance of X-band Doppler radars for ground transport vehicles is presented. The technique utilizes small metallic reflectors placed directly below the guideway surface. From the results of preliminary laboratory and on-road tests it is concluded that improved accuracy of on-board position and velocity measurements result.

A continuous longitudinal control signal via the low frequency excitation of helical transmission lines

A method of generating a continuous position reference signal for use in the longitudinal control of automated ground transport systems is presented. The technique utilizes two specially excited four-wire helically wound transmission lines. The method of excitation, the signal detection and processing schemes necessary to obtain the control signal, and the results of preliminary laboratory tests are presented. The technique should provide a highly accurate, easily implementable and environmentally impervious means of generating a longitudinal reference signal.

On Future Automated Ground Transport--Individual Vehicle Longitudinal Control

EXTRAIT La realisation d’un controle longitudinal sur et efficace est probablement le probleme technique le plus significatif en relation avec un vehicule automatique individuel, des systemes de transport tels que PRT, a double fonction, et avec la voierie publique automatique. Une structure de controle generale implequerait un controller central pour surveiller le fonctionnement du reseau, cela comprenant la coordination d’ordinateurs de secteur dont l’un superviserait et controlerait les vehicules fonctionnant dans le secteur qui lui est affecte. A ce niveau les trois facettes essentielles des operations sont: a) La determination de l’etat de chaque vehicule et quel rapport cet etat a avec l’etat desire; b) b) Les communications entre chaque vehicule controle et le controle de secteur; c) Le controle de chaque vehicule individuel. De recents progres concernant la conception, le developpement et l’experimentation de ces facettes seront decrits dans le contexte de la realisation d’un fonctionnement sur et efficace dans un court intervalle de temps (1-2 sec). Precisement, deux techniques ont ete mises au point en fournissant a un vehicule en marche des renseiqnements sur la position (ne permettant une marge d’erreur que de 20 cm ou moins), et sur la velocite (ou la marge d’erreur ne depasse pas 1.7%). D’autre part, un controller longitudinal de vehicule dont la marge d’erreur ne depasse pas 30 cm a l’arrivee de signaux de moindre et de grande intensite, reste insensible aux forces de perturbation et permet aussi aux passagers de jouir d’un trajet confortable, a ete concu, mis a l’epreuve et juge dans des conditions reelles de fonctionnaient.

Automated ground transport systems: Some observed materials problems

One promising partial approach to many of our anticipated future transportation problems is the automation of various facets of ground transportation. This could include automated captive-vehicle systems for central-business-district circulation, dual-mode vehicle systems for urban area use, and intercity automated highways. Certain control functions are critical in such systems and the development of new technology will be required for their successful implementation. The functions include network control and both the automatic longitudinal and lateral control of individual vehicles. Current component developments, which are directed toward such functions will be described, together with the results of roadway testing. Several problem areas, which are related to the electrical properties of conventional construction materials, are defined together with preferred operating environments for electrical components and materials.