## Research interests
The overarching theme of our research is analysis, design, and control of high-performance and robust cyber-physical networks. In the Siami lab, we apply tools and techniques from control theory, optimization, graph theory, game theory, machine learning (ML), reinforcement learning (RL), and applied probability theory to control and solve decision-making problems in several application areas: cloud-based services, smart energy systems, networks of autonomous vehicles, and biological networks.
## Sparse Sensor and Actuator Selection in Cyber-physical networks:Given the increasingly large-scale nature of the problems presented by infrastructure networks (e.g., water and power networks), multi-robot systems, and the study of the human connectome, it is imperative to be able to estimate the overall state of the given system or to control the system using a small subset of available features (e.g., PMUs, camera sensors, EEG sensors, or data from 3-D mapping and radar technology). When the number of the state is large, finding the optimal yet low cardinality subset of features is like finding a needle in a haystack: the problem is computationally difficult and provably NP-hard. Previous studies have been mainly focused on solving the optimal feature selection problem using the greedy heuristic, as an approximation of the corresponding sparse-subset selection problem. While these results attempt to find approximation algorithms for finding the best sparse subset, our focus is to gain new fundamental insights into approximating various performance metrics compared to the case when all features are chosen. We adopt the machinery developed for the Kadison-Singer Conjecture to find a sparse subset of actuators/sensors to improve the controllability/ observability performance. We develop a framework for a sparse actuator/sensor schedule and show that by carefully designing a time-varying feature selection strategy, one can choose on average a constant number of relevant actuators/sensors at each time, to ensure proper control/monitoring of a linear dynamical system.
## Application in Epidemics: Regulation for “Vaccine Tourism” to Mitigate Waves of Pandemic
Centrality-Based Traffic Restriction in Delayed Epidemic Networks with A. Darabi
A. Darabi, and M. Siami, "Centrality in Epidemic Networks with Time-Delay: A Decision- Support Framework for Epidemic Containment," *American Control Conference*, New Orleans, Louisiana, USA, 2021.
Fighting the Virus is Like Fighting A War [news link]
## Application in Robotics and controlling Self-driving cars
Deterministic and Randomized Actuator Scheduling With Guaranteed Performance with A. Jadbabaie and A. Olshevsky Rapid Autonomous Complex-Environment Competing Ackermanndrive Robotics is featured in MIT’s Spectrum Magazine
During the Independent Activities Period (IAP-2018) at MIT, my group (shag!) and I implemented and tested our perception and planning algorithms for self-driving cars that can quickly navigate through complex environments video. Here is a fun video from an informal mini self-driving car competition; our perception and planning algorithms run on the leading mini self-driving robot. This is a powerful platform for robotics research and education based on the open-source MIT-RACECAR.
M. Siami, L. Carlone, and A. Jadbabaie, "Sparse Visual Attention Mechanism With Guaranteed Performance Bounds," *Working Paper*. Video link
## Application in Smart Power Networks
## Cloud-based Services and System Throttlers:
Structural Analysis and Optimal Design of Distributed System Throttlers IEEE Transactions on Automatic Control
https://ai.google/research/pubs/pub46233 is featured in Google AI
## Centrality Measures in Dynamical Networks
M. Siami, S. Bolouki, B. Bamieh and N. Motee, "Centrality measures in linear consensus networks with structured network uncertainties, " *IEEE Transactions on Control of Network Systems,*Volume 5, Issue 3, 2018, Pages: 924-934.Y. Ghaedsharaf, M. Siami, and N. Motee, ”Performance Improvement in Noisy Linear Consensus Networks with Time-Delay,” *IEEE Transactions on Automatic Control*, Vol. 64, Issue 6, 2019. To Appear.Y. Ghaedsharaf, M. Siami, C. Somarakis, and N. Motee, "Interplay Between Performance and Communication Delay in Noisy Linear Consensus Network," *In Proceedings of European Control Conference*, Aalborg, Denmark, 2016.
## Network Synthesis for Performance Enhancement
M. Siami and N. Motee, "Network Abstraction with Guaranteed Performance Bounds," *IEEE Transactions on Automatic Control*, Vol. 63, Issue 10, 2018, Pages: 3301-3316. [arXiv]M. Siami and N. Motee, "Growing Linear Dynamical Networks Endowed by Spectral Systemic Performance Measures," *IEEE Transactions on Automatic Control*, Volume 63, Issue 7, 2018, Pages: 2091-2106. [arXiv]"Architecting better connectivity" is featured in Lehigh's News [Paper Award]
## On the Signed Edge Domination Number of Graphs
* S. Akbari, S. Bolouki, P. Hatami and M. Siami, "The Signed Edge Domination Number of Graphs," *Discrete Mathematics*, Volume 309, Issue 3, 2009, Pages: 587-594. [* Authors appear in alphabetical order.]My Erdos number is 3 (Hatami-Behzad-Erdos, or Akbari-Kostochka-Erdos)
## Performance Analysis and Tradeoffs in Complex Dynamical NetworksThe recent interest in understanding fundamental limitations of feedback in complex interconnected dynamical networks from biological systems and physics to engineering and economics has created a paradigm shift in the way systems are analyzed, designed, and built. Typical examples of such complex networks include metabolic pathways, vehicular platoons, arrays of micro-mirrors, micro-cantilevers, and smart power grids. These systems are diverse in their detailed physical behavior. However, they share an important common feature that all of them consist of an interconnection of a large number of systems.
M. Siami and N. Motee, "Network Abstraction with Guaranteed Performance Bounds," *IEEE Transactions on Automatic Control*, Vol. 63, Issue 10, 2018, Pages: 3301-3316. [arXiv]M. Siami and N. Motee, "Growing Linear Dynamical Networks Endowed by Spectral Systemic Performance Measures," *IEEE Transactions on Automatic Control*, Volume 63, Issue 7, 2018, Pages: 2091-2106. [arXiv]M. Siami, J. Skaf, "Structural Analysis and Optimal Design of Distributed System Throttlers," *IEEE Transactions on Automatic Control*, Volume 63, Issue 2, 2018, Pages: 540-547. [arXiv]M. Siami, and N. Motee, "Fundamental Limits and Tradeoffs on Disturbance Propagation in Linear Dynamical Networks," *IEEE Transactions on Automatic Control*, Volume 61, Issue 12, 2016, Pages: 4055-4062. [arXiv]M. Siami and N. Motee, "New Bounds on H_2-Norm of Noisy Linear Dynamical Networks," *Automatica*, Volume 53, Issue 5, 2017, Pages: 305-312. [arXiv]M. Siami, S. Bolouki, B. Bamieh and N. Motee, "Centrality measures in linear consensus networks with structured network uncertainties, " *IEEE Transactions on Control of Network Systems,*Volume 5, Issue 3, 2018, Pages: 924-934.
## Application in Biological Networks
M. Siami, N. Motee, G. Buzi, B. Bamieh, M. Khammash, and J.C. Doyle, "Fundamental Limits and Tradeoffs in Autocatalytic Pathways," *IEEE Transactions on Automatic Control*, 2018, Accepted. [arXiv]M. Siami and N. Motee, "Robustness and Performance Analysis of Cyclic Interconnected Dynamical Networks," In Proceedings of the SIAM Conference on Control and Its Application, San Diego, CA, USA, 2013.
## Adaptive Networked Control with Noisy CommunicationsIn this project, we consider a stabilization problem for uncertain plants over networks subject to packet loss and quantization via a direct adaptive control approach. Specifically, for a discrete-time linear time-invariant plant whose parameters are uncertain, we propose a design method for an adaptive controller and an input quantizer. The proposed framework is Lyapunov-based and guarantees Lyapunov stability in probability of the closed-loop system states and almost sure convergence of the plant states. Two results have been obtained corresponding to the situations where the controller is informed of packet losses or not by means of acknowledgement messages.
M. Siami, T. Hayakawa, H. Ishii and K. Tsumura, "Adaptive quantized control for linear uncertain discrete-time systems over channels subject to packet loss," In Proceedings of the 49th IEEE Conference on Decision and Control, Atlanta, GA, USA, 2010.
## Stability and Harmonic Analysis of Time-varying Dynamical Systems
M. Siami and M. S. Tavazoei, "Oscillations in Fractional Order LTI Systems: Harmonic Analysis and Further Results," *Signal Processing*, Volume 93, Issue 5, 2013, Pages 1243-1250.M. Siami, M. S. Tavazoei and M. Haeri, "Stability Preservation Analysis in Direct Discretization of Fractional Order Transfer Functions," *Signal Processing*, Volume 91, Issue 3, 2011, Pages 508-512.M. S. Tavazoei, M. Haeri M. Siami and S. Bolouki, "Maximum Number of Frequencies in Oscillations Generated by Fractional Order LTI Systems," *IEEE Transactions on Signal Processing*, Volume 58, Issue 8, 2010, Pages: 4003-4012.M. S. Tavazoei, M. Haeri, M. Attari, S. Bolouki and M. Siami, "More Details on Analysis of Fractional-Order Van Der Pol Oscillator," *Journal of Vibration and Control*, Volume 15, 2009, Pages: 803-819.M. S. Tavazoei, M. Haeri, S. Jafari, S. Bolouki and M. Siami, "Some Applications of Fractional Calculus in Suppression of Chaotic Oscillations," *IEEE Transactions on Industrial Electronics*, Volume 55, 2008, Pages 4094-4101.M. S. Tavazoei, M. Haeri, S. Bolouki and M. Siami, "Stability Preservation Analysis for Frequency Based Methods in Numerical Simulation of Fractional Order Systems," *SIAM Journal on Numerical Analysis*, Volume 47, 2008, Pages 321-338.M. S. Tavazoei, M. Haeri, S. Bolouki and M. Siami, "Using Fractional-Order Integrator to Control Chaos in Single-Input Chaotic Systems,” *Nonlinear Dynamics*, Volume 55, Number 1-2, 2009, Pages 179-190.M.Sc. Thesis, "Analysis of Oscillations in Linear Fractional-Order Systems," Sharif University of Technology, 2012. Advisor: Prof. M. S. Tavazoei B.Sc. Thesis, "Analysis in Methods of Finding Approximation of Fractional-Order Systems," Sharif University of Technology, 2009. Advisor: Prof. M. Haeri
## Competitive Contagion with Sparse SeedingThis project studies a strategic model of marketing and product diffusion in social networks. We consider two firms offering substitutable products which can improve their market share by seeding the key individuals in the market. Consumers update their consumption level for each of the two products as the best response to the consumption of their neighbors in the previous period. This results in linear update dynamics for the product consumption. Each consumer receives externality from the consumption of each neighbor where the strength of the externality is higher for consumption of the products of the same firm. We represent the above setting as a duopoly game between the firms and introduce a novel framework that allows for sparse seeding to emerge as an equilibrium strategy. We then study the effect of the network structure on the optimal seeding strategies and the extent to which the strategies can be sparsified. In particular, we derive conditions under which near Nash equilibrium strategies can asymptotically lead to sparse seeding in large populations. The results are illustrated using a core-periphery network.
S. Bolouki, R.P. Malhame, M. Siami and N. Motee. "Eminence Grise Coalitions: On the Shaping of Public Opinion," *IEEE Transactions on Control of Network Systems*, June 2017, Pages 133-145. [arXiv]M. Siami, A. Ajorlou, and A. Jadbabaie, "Competitive Contagion with Spare Seeding,” The 8th IFACWorkshop on Distributed Estimation and Control in Networked Systems (NecSys19), Chicago, IL, 2019 [arXiv].
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