Optimal Tracking of Networked Control Systems Over the Fading Channel With Packet Loss

For networked systems, the communication processes between sensors, actuators, and controllers pose many challenges such as instability and performance degradation that may result from bandwidth limitations, signal-to-noise ratio constraints, and frequent occurrences of packet loss. The constraints of these elements can negatively affect the performance of control systems. In this study, we used a fading channel model to analyze the fundamental tracking performance of a networked control system (NCS). We considered the additive channel noise, external disturbances, and packet losses under the premise that an equivalent average channel can replace the fading channel to model the steady-state output. Frequency-domain analysis techniques, including all-pass factorization, Bezout identity, and Youla parameterization, were used to compute optimal values for the tracking performance. Based on the results, we were able to quantify the relation between the NCS performance and intrinsic features of the controlled object, including nonminimum phase zeros and unstable poles. Explicit expressions were obtained for the negative effects of noise, disturbance, and packet losses on the tracking performance. Furthermore, an illustrative example is presented to verify our conclusions.