Stability Of Network-Based Feedback Interconnection

The networked control system (NCS) is an outcome of the development and integration of control science, computer technology, network communication and other technologies. The introduction of the data network in the feedback loop has many advantages over the traditional point-to-point design such as low cost, high reliability, less wiring and easy maintenance, etc. However, the network-induced delay and the packet lose are inevitable due to the insertion of the communication network, which might cause the collision or even congestion because of bandwidth constraint, time sharing multiplexing uncertainty in transmission path. The network-induced delay, whatever it is constant or time-varying, and whatever it is bounded or unbounded, would definitely influence the control performances, it can even cause system unstable. This could surely bring difficulties for the analysis and design of NCS. Therefore, how to use the existing control theories or create new principles to solve the problems in NCSs is a hot issue for researchers.The network-based feedback interconnection (NBFI) is a feedback interconnecti_ on inserted networks with limited bandwidth as data transmission media. In fact, the NBFI is a natural extention of the NCS. An NCS may be a NBFI if the remote controller takes the form of dynamical feedback.The analysis and model of the NBFI are studied under the condition that the network-induced delay is less than one sampling period. The input of the plants are supposed to hold at the previous value when delay occurs in the network. We analyze and present the relationship between the network states and the system variables, and the NBFI can be modeled as a closed-loop system. By using Lyapunov theories, some sufficinet conditions for stability of the NBFI are derived.Taking into consideration of network-induced delay and data packet dropout, this thesis studies the stability of the NBFI. For the case of fixed data packet dropout rates and constant time delays, the NBFI is modeled as an asynchronous dynamical system subject to configuration event rates. By using Lyapunov theories and linear matrix inequality techniques, the sufficient conditions of exponential stability of the NBFI constrained by data packet dropout rates are derived.Finally, the simulation shows that the the analysis methods are valid and the stability criterial are feasible.