A Simplified Framework for String Stability

One of the most important issues in longitudinal control of vehicles in automated highway systems (AHS) is string stability, that is, the attenuation of spacing errors as they propagate upstream the platoon. In this paper we use a mass-spring-damper system as a simpliied framework for string stability analysis and study the properties of several longitudinal control schemes which have been proposed in the literature. 1. INTRODUCTION A widely proposed strategy for eeectively increasing traf-c throughput on existing highways is to group auto-These are formations which require small inter-vehicle spacing and many vehicles in each platoon in order to provide signiicantly higher traac throughput. Therefore, the control design for platoons of automated vehicles has to guarantee not only the desired performance of any individual vehicle but also of the whole formation. A key property is string stability, which ensures attenuation of errors as they propagate upstream the platoon. Since string stability is one of the most important issues related to AHS safety and performance, it would be desirable to develop an eecient method for establishing the stability properties of diierent control approaches. As a rst step in this search, we consider a simpliied framework in which we view vehicles as