Researchers: Anton Cervin, Toivo Henningsson, Erik Johannesson, Karl Johan Åström
Duration: January 2006 – December 2009
Funding: Swedish Research Council (VR)
In this project, we investigate the timing aspects of networked control and focus on the interplay between network scheduling and control performance. We study the fundamental trade-offs that exist between sampling rates, delays, and jitter in networked control. We want to be able to answer questions such as "What level of control performance can be achieved using time-triggered vs priority-based communication protocols?", "How can impact of network-induced jitter be handled in control design?", and "How can primitives suitable for control be included in existing and new communication protocols?"
A very promising approach to more efficient usage of the network bandwidth is event-based control. The idea is to communicate measurement and control signals only when something unexpected and significant has happened in the system. We are investigating how this approach compares to ordinary, periodic control, and how event-based sampling and control can be incorporated in network scheduling algorithms.
During 2009 we have investigated event-based PID control, exploring various discretization methods, limit cycle detection, and gain adaptation. In another line of research, we have been developing sub-optimal event-based reset controllers for higher-order systems. The results of the project so far were presented in a PhD course at the Universidad Politécnica de Valencia. During the year, a major revision of the TrueTime toolbox for simulation of networked control loops has also been undertaken.
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