Distributed Controller Design for Dynamic Speed Limit Control Against Shock Waves on Freeways

Abstract

Shock waves are special types of relatively short traffic jams that propagate opposite to the driving direction. These jams increase travel time, air pollution, and negatively impact safety. One way of dealing with shock waves is to impose dynamic speed limits to eliminate them. Control strategies proposed so far are based either on expert knowledge, or are centralized controllers with high computational demand, such as model predictive control. In this paper, we design decentralized feedback controllers with a fixed structure. For the purpose of design, we use a direct optimization technique capable of dealing with the design objectives and the non-linear character of the system. The advantages of using such simple controllers are that they do not require extensive on-line computations, use only local information and are therefore more attractive from the implementation point of view. We show that a simple, static control law achieves performance similar to previous results with centralized control for the considered scenario. The controller successfully resolves the shock wave and reduces the total time spent by 20%, compared to the uncontrolled case.