  In this paper, the tracking performance limitation of networked control
systems (NCSs) is studied. The NCSs is considered as continuous-time linear
multi-input multi-output (MIMO) systems with random reference noises. The
controlled plants include unstable poles and non-minimum phase (NMP) zeros. The
output feedback path is affected by multiple communication constraints. We
focus on some basic communication constraints, including additive white noise
(AWN), quantization noise, bandwidth, as well as encoder-decoder. The system
performance is evaluated with the tracking error energy, and used a two-degree
of freedom (2DOF) controller. The explicit representation of the tracking
performance is given in this paper. The results indicate the tracking
performance limitations rely to internal characteristics of the plant (unstable
poles and NMP zeros), reference noises (the reference noise power distribution
(RNPD) and its directions) and the characteristics of communication
constraints. Moreover, the tracking performance limitations are also affected
by the angles between the each transform NMP zero direction and RNPD direction,
and these angles between each transform unstable poles direction and the
direction of communication constraint distribution/allocation. In addition, for
MIMO NCSs, bandwidth (there are not identical two channels) always can affects
the direction of unstable poles, and the channel allocation of bandwidth and
encode-decode may be used for a feasible method for the performance allocation
of each channels. Lastly, a instance is given for verifying the effectiveness
of the theoretical outcomes.
