Date(s) - 24 Mar 2017
10:00 AM - 10:50 AM
3043 ECpE Building Addition
Title: Resilience of Transportation Networks: More Capacity is Not Always Better
Abstract: Infrastructure systems such as transportation, power, water, and communication networks face various disturbances and operate under the actions taken by numerous users with partial information about the overall system. Such a distributed operation often results in suboptimal global performance, and it may even lead to cascading failures with severe global consequences. Hence, resilience becomes a critical aspect in the design and operation of such systems. In this talk, I present provably-correct distributed control policies for resilient operation of transportation networks, which are modeled as dynamical flow networks under local routing decisions. In such networks, each link has some finite capacity, i.e., the maximum amount of flow that can be sustained by the link. Some external inflow is injected to the network, and the total inflow to each node is routed to its operational outgoing links based on their current densities of traffic, which are driven by the difference of the corresponding inflows and outflows. A link irreversibly fails if it reaches its jam density, and a systemic failure is observed if such failures propagate in the system and lead to throughput loss. In this setting, resilience is quantified through the minimum amount of capacity reduction (e.g., due to accidents, maintenance, or weather conditions) that would cause a systemic failure. I will first show that, contrary to what one might intuitively expect, link capacities do not have a monotonic influence on the resilience of such networks. In other words, larger link capacities do not always help in preventing systemic failures. Then, I will present how variable speed limits can be used as a flow control mechanism to operate the links below their actual capacities, when necessary, to mitigate the fragility stemming from the lack of global information and coordination in routing decisions in a provably-correct manner. The proposed approach is particularly useful in practice as it is much easier to adjust the speed limits than to build more physical capacity or to alter routing decisions that are determined by social behavior.
Bio: A. Yasin Yazicioglu is currently a postdoctoral research associate at the Laboratory for Information and Decision Systems (LIDS), MIT. He received his Ph. D. in Electrical and Computer Engineering from Georgia Tech in 2014. His recent research is primarily focused on decentralized control, multi-agent systems and networks. Prior to his studies at Georgia Tech, he received his B.S. (with a minor in mathematics) and M.S. degrees in Mechatronics Engineering from Sabancı University, Turkey, in 2007 and 2009, respectively.