Section: New Results

Towards tight impossibility and possibility results for string stability

Participants: Alain Sarlette

This is the last step of the PhD thesis of Arash Farnam under the direction of A. Sarlette at Ghent University. The aim was to study which elements are really essential in so-called “string instability” results, which exist in several variants and with several assumptions. In [15], we have significantly extended the often frequency-based linear approach, by showing how the assumptions lead to string instability also in any nonlinear systems with reasonable bandwidth. This should allow to clarify that how the problem setting must be adapted in order to obtain more positive results. In [14], we show how other elements do not help, and we clarify how the knowledge of individual vehicles’ absolute velocity is key to enable strong versions of string stability, in conjunction with PID control. Previous studies had only considered weaker versions, with PD type control. A more detailed study of string stability with absolute velocity control has also been published in [25].