Research On The Analysis, Modeling And Control Of Networked Control System

Networked Control System (NCS) is an outcome of development and integration of control science, computer technology, network communication and other technologies. NCS reduces complexity in wiring connection, provides ease in maintenance and enables information shared among users. When network is introduced in the system, delay or packet dropout is induced by waiting, collision and congestion because of bandwidth constraint, time sharing multiplexing, uncertainty in transmission path, etc. The delay, which is affected by network load, communication protocol and some other factors, whether constant, time-varying, bounded or unbounded, can influence control performance, it can even cause system instability, which brings difficulties to analysis and design of NCS. Therefore, how to use existing control theory approaches or create new theory and means to solve the problems in NCS is a hot issue for researchers, pointing at NCS characteristics.Analysis of real-time characteristic, sampling period choice and time delay in NCS is made, factors that influence real-time characteristics and methods to reduce delay are discussed. Impact of sampling period and delay on system performance is also studied. A general continuous model of multiple inputs and multiple outputs (MIMO) linear networked control system is built, considering system disturbance. Graphs of time sequence of information transmission and discrete models of NCS with any bounded delay are constructed at four different driven modes. Discrete models of MIMO networked control system with any bounded delay are also established, which extends the range of model application.For NCS with deterministic delay, design of controller and state observer based on output feedback is presented, which guarantees stability of close-loop system and good performance. Sliding mode variable structure control scheme with delay compensation is given,then a sliding manifold that compensates control delay is introduced, the designed sliding controller guarantees the stability of closed loop system, and upper bound of allowed delay is given, simulation shows the effectiveness of the approach. Stability analysis criteria of delay-dependent and delay-independent for non-deterministic closed-loop NCS is derived, the maximum allowable network-induced delay for delay-dependent NCS with uncertainty is obtained.For NCS with time-varying delay, it is considered as a discrete time jump system,...