Networked Control System Co-Simulation for Co-Design: Theory and Experiments

Justin Hartman
May 27, 2004
Submitted in partial fullfillment of the requirements for the degree of Master of Science

Abstract:

The study of networked control systems (NCSs) brings together the historically separate disciplines of computer networks and control theory. Current research in NCSs focuses on co-simulation for co-design, which postulates that the analysis and design of the network portion and control system portion of an NCS are inseparable. In this thesis, we compare two methods of simulating system dynamics inside the ns-2 network simulator: ODE solution through a linked package, and Euler approximations. We introduce a hybrid system to verify the accuracy of these methods. We examine the fundamental phenomena of NCSs, including pole locations, stability regions, network-induced delay, effective sampling period, and scheduling policies. We introduce the traffic locus, which describes the network performance of an NCS as a function of network load. We also examine average-based and Markov-based models of packet loss, and propose means of designing controllers to compensate for varying network-induced delay and packet loss patterns.

Vincenzo Liberatore / vincenzo.liberatore@case.edu