Robust Team-Triggered Coordination for Real-Time Control of Networked Cyber-Physical Systems

Abstract:

The aim of this project is to lay down the foundations of a novel approach to real-time control of networked cyber-physical systems (CPS) that leverages their cooperative  nature. Most networked controllers  are not implementable over embedded digital computer systems because they rely on continuous time or synchronous executions that are costly to enforce. These assumptions are unrealistic when faced with the cyber-physical world, where the interaction be- tween computational and physical components is multiplex, information acquisition is subject to error and delay, and agent schedules are asynchronous. Even without implementation obstacles, the periodic availability of information leads to a wasteful use of resources. Tuning controller execution to the task at hand offers the potential for great savings in communication, sensing, and actuation. The goal of this project is to bring this opportunity to fruition by employing state-triggered control ideas. The key conceptual novelty is for agents to make promises to one another about their future states and warn each other if they later decide to break them. The information provided by promises allows agents to autonomously determine when fresh information is needed, resulting in an efficient network performance. The current scientific directions of the project are: (i) the development of methods for designing distributed event-triggered communication and control for multi-agent average consensus, and (ii) the development of methods for de- signing state-triggered controllers that operate under bounded bit rates. The direction (i) is motivated by the widespread applications of average consensus in distributed control and estimation (e.g., fusion, filtering, tracking, motion coordination, and beyond). We have synthesized efficient event-triggered com- munication and control strategies that do not rely on individual agents having continuous or periodic access to information about the state of its neighbors to achieve average consensus. The direction (ii) is motivated by the observation that existing state-triggered control strategies generally  abstract  communica- tion as an instantaneous, infinitely precise, and delay-free process, while in real networked cyber physical systems, information is communicated over communication channels with possibly low, time varying and unreliable channel capacity. Information-theoretic approaches do take into account communication constraints, but do not incorporate the idea of being opportunistic and strategic about when to communicate, and are therefore usually not amenable to guar- anteeing specific performance criteria. Our current research builds on these two fields to synthesize opportunistic state-triggered stabilization strategies under bounded bit rates for linear time-invariant systems.