Distributed control of systems over communication networks

In distributed control systems that operate with multimedia data over communication networks, meeting the application requirements for the control system and the multimedia communication is a challenging task. We are interested in direct control of remote systems where control and monitoring information are transmitted continuously between the end-systems. The control loop in such distributed systems contains time-varying delays that occur because of shared network medium, shared computing resources and unsynchronized components at the end-systems. From a control theory perspective, the time-varying delays in a feedback control loop affect the stability and performance of the control system. The difficulty in analysis and synthesis of time-delayed control systems arises due to modeling of these delays. We propose a robust control approach which guarantees robust performance with the assumption that the delay bounds are known. Our proposed DisCoNet architecture is based on multidimensional QoS specification and end-to-end resource allocation. The QoS specification includes a guaranteed robust control performance level and a given frame rate for the video transfer. Experimental results are given for a mobile robot tracking control application over ATM networks. We show that with efficient QoS mapping and end-to-end resource allocation, direct continuous control of remote systems is possible over reservation-based communication networks even when other multimedia data (video, audio) are incorporated into the control environment.