Optimal Tracking Performance Of Networked Control Systems With Multiple Communication Constraints

Networked control systems(NCSs)have emerged as a result of the rapid development and deep integration of network communication technology,control technology and computer technology.For at least the last two decades,The problem of optimal control of NCSs has been a very active research area in the field of control.A distinctive feature of NCSs compared to traditional control systems is the use of non-transparent communication links for information transfer,which has the advantages of low installation costs,flexibility and easy installation and maintenance.However,as networks are unreliable,there are inevitable communication constraints such as bandwidth,network induced delays and packet loss,which can have a significant negative impact on the stability and optimal performance of NCSs.It is with this in mind that this dissertation fully investigates the optimal tracking performance of NCSs under multiple communication constraints,using matrix analysis and some special decomposition techniques.The research results of this dissertation are summarized as follows.(1)A new model for networked control systems under fading channels is constructed,for the steady-state of the feedback control systems,an equivalent average channel model was developed by retaining the effects of the first and second moments of the multiplicative channel output,and on the basis of the coprime decomposition,all-pass factorization,and Youla parameterization,exact expressions for the optimal tracking performance were derived by designing two compensators.The expressions quantitatively show the relationship between the optimal tracking performance and inherent features of the plant.Specifically,the directions and locations of unstable poles and nonminimum phase zeros adversely affect the tracking performance.Furthermore,the bandwidth limitation and the presence of colored noise also degrade the tracking performance.(2)A new model of multi-input multi-output discrete-time networked control system with multiple communication constraints is constructed,a single-degree-of-freedom(SDOF)controller and a two-degree-of-freedom controller(TDOF)are designed and obtained,respectively,and the optimal tracking performance of multi-input multi-output NCSs with encoder-decoder,bandwidth,and quantization in the control path and with packet loss,delay,and additive Gaussian white noise in the feedback path is obtained.The results show that the intrinsic characteristics of the controlled plant and the communication constraints in the channel can limit the tracking performance of NCSs.(3)A new model of networked control system under the influence of colored noise is constructed,based on the frequency domain analysis method,the tracking performance limits of NCSs with limited bandwidth and colored noise in feedback channels are studied.From the explicit expression of optimal tracking performance,it is not difficult to find that the essential characteristics of the controlled plant can have a negative impact on the tracking performance of NCSs.In addition,bandwidth constraints and colored noise in communication channels can worsen the tracking performance of NCSs.