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Stability of Networked Control Systems

The defining characteristic of a networked control system (NCS) is having a control loop that passes through a local area network. In NCS classical point-to-point connections between the controller and plant are replaced by a serial communication channel to which all sensors, actuators and controllers are connected as nodes. For example, this technology is used in fly-by-wire aircraft and drive-by-wire cars. This typically reduces cost, weight and volume of the system and simplifies its installation and maintenance but the analysis and controller design become much harder. We consider a two-step design framework for NCS that was proposed by G. C. Walsh and his co-workers. First, the designer uses standard continuous-time control methodologies to design a controller ignoring the network. In the second step, the designer chooses the network protocol and bandwidth in order to ensure stability, performance and/or robustness of the system when implemented via the network. To deal with this problem, we first propose a novel (hybrid) model for the NCS that generalizes pre-existing models and allows for explicit modelling of the scheduling protocol. Then, we show for a large class of protocols that sufficiently high bandwidth preserves stability of the system. More importantly, our explicit bounds on the required bandwidth are analytically shown to be much better than any such bounds previously obtained in the literature. This is further confirmed by an example of a batch reactor taken from the literature. Our results are presented for general nonlinear systems and they provide performance and robustness guarantees via the input-output Lp stability formalism.
Type of Seminar:
Public Seminar
Prof. Dragan Nesic
University of Melbourne, Australia
Dec 20, 2005   08:30

ETH-Zentrum, Main Building HG F 33.1, Rämistrasse 101, Zurich
Contact Person:

Prof. L. Guzzella
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