Are commercially implemented adaptive cruise control systems string stable?

TitleAre commercially implemented adaptive cruise control systems string stable?
Publication TypeJournal Article
Year of Publication2020
AuthorsGunter, G, Gloudemans, D, Stern, RE, McQuade, S, Bhadani, R, Bunting, M, Monache, MLaura Dell, Seibold, B, Sprinkle, J, Piccoli, B, Work, DB
JournalIEEE Transactions on Intelligent Transportation Systems
Pagination12 pages
Date Published06/2020
KeywordsAdaptive Cruise Control, String Stability

In this article, we assess the string stability of seven 2018 model year adaptive cruise control (ACC) equipped vehicles that are widely available in the US market. A total of seven distinct vehicle models from two different vehicle makes are analyzed using data collected from more than 1,200 miles of driving in designed car-following experiments with ACC engaged by the following vehicle. The data is used to identify the parameters of a linear second order delay differential equation model that approximates the behavior of the proprietary ACC systems. The string stability of the data fitted model associated with each vehicle is assessed, and the main finding is that all seven vehicle models have string unstable ACC systems. For one commonly available vehicle that offers ACC as a standard feature on all trim levels, we validate the string stability finding with a multi-vehicle platoon experiment in which all vehicles are the same year, make, and model. In the multi-vehicle platoon test, an initial disturbance of 6 mph is amplified by 19 mph to a 25 mph disturbance, at which point the last vehicle in the platoon is observed to disengage the ACC and return control to the human driver. The data collected the driving experiments is made available, representing the largest available driving dataset on ACC equipped vehicles.