Tracking performance limitations of networked control systems with packet dropouts and logarithmic quantization

In this paper, we focus on the tracking performance (TP) limitations of networked control systems (NCSs). The control system considered is a multi-input and multi-output (MIMO) discrete-time network control system with time delay, channel noise, packet dropouts, and logarithmic quantization communication constraints. When modeling the channel, we assumed the channel noise to be additive white Gaussian noise (AWGN) and used a binary random process to model packet dropouts and a logarithmic quantizer to model the quantization process. The explicit expression of the TP limitations of NCSs utilizing the two-degree-of-freedom (TDOF) controller is then derived using the frequency-domain approach, coprime decomposition, and Youla parameterization method. The results show that the essential characteristics of the plant (locations and directions of non-minimum phase zeros and unstable poles) and network constraints (time delay, packet dropouts, quantization, and noise power spectral density) are closely related to the TP limitations.