Scheduling and Controller Design in Networked Control Systems

Title of dissertation: Access Scheduling and Controller Design in Networked Control Systems Lei Zhang, Doctor of Philosophy, 2005 Dissertation directed by: Assistant Professor Dimitrios Hristu-Varsakelis Department of Mechanical Engineering A Networked Control System (NCS) is a control system in which the sensors and actuators are connected to a feedback controller via a shared communication medium. In an NCS, the shared medium can only provide a limited number of simultaneous connections for the sensors and actuators to communicate with the controller. As a consequence, the design of an NCS involves not only the specification of a feedback controller but also that of a communication policy that schedules access to the shared communication medium. Up to now, this task has posed a significant challenge, due in large part to the modeling complexity of existing NCS architectures, under which the control and communication design problems are tightly intertwined. This thesis proposes an alternative NCS architecture, whereby the plant and controller choose to “ignore” the actuators and sensors that are not actively communicating. This new architecture leads to simpler NCS models in which the design of feedback controller and communication polices can be effectively decoupled. In that setting, we propose a set of medium access scheduling strategies and accompanying controller design methods that address a broad range of stabilization, estimation, and optimization problems for a general class of NCSs. The performance of the proposed methods is illustrated through a set of simulations and hardware experiments. ACCESS SCHEDULING AND CONTROLLER DESIGN IN NETWORKED CONTROL SYSTEMS by Lei Zhang Dissertation submitted to the Faculty of the Graduate School of the University of Maryland, College Park in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2005 Advisory Committee: Assistant Professor Dimitrios Hristu-Varsakelis, Chair/Advisor Professor William S. Levine, Dean’s Representative Professor Amr Baz Professor Balakumar Balachandran Associate Professor Jeffrey Herrmann c © Copyright by Lei Zhang 2005 To my mother, Shulan An, and my father, Chongxi Zhang.