A Formal Traffic Characterization of LTI Event-triggered Control Systems

TL;DR

This paper introduces a formal method to model and analyze event-triggered control systems for LTI systems, enabling better understanding of their sampling behavior and aiding in system design.

Contribution

It presents a novel abstraction approach that captures the sampling behavior of event-triggered strategies, using a finite state model equivalent to a timed automaton.

Findings

The abstraction accurately simulates the sampling behavior of the control system.

The quotient system is shown to be equivalent to a timed automaton.

LMI-based techniques effectively determine sampling intervals.

Abstract

Unnecessary communication and computation in the periodic execution of control tasks lead to over-provisioning in hardware design (or underexploitation in hardware utilization) in control applications, such as networked control systems. To address these issues, researchers have proposed a new class of strategies, named event-driven strategies. Despite of their beneficiary effects, matters like task scheduling and appropriate dimensioning of communication components have become more complicated with respect to traditional periodic strategies. In this paper, we present a formal approach to derive an abstracted system that captures the sampling behavior of a family of event-triggered strategies for the case of LTI systems. This structure approximately simulates the sampling behavior of the aperiodic control system. Furthermore, the resulting quotient system is equivalent to a timed automaton. In the construction of the abstraction, the state space is confined to a finite number of convex regions, each of which represents a mode in the quotient system. An LMI-based technique is deployed to derive a sampling time interval associated to each region. Finally, reachability analysis is leveraged to find the transitions of the quotient system.