HMM based estimation of NCS network load and its application in switching control

The analysis and design of the Networked Control System (NCS) are more challenging due to the random time delays brought by the network. And modeling the uncertain time delays has been becoming a significant focus of research. This paper modeled the network delays with Hidden Markov Model (HMM), and then on the basis of Viterbi algorithm, proposed a method to estimate the network's current load state using random time delay sequence. In further simulation we first designed PID controllers corresponding to the network's different load states respectively, and applied the proposed method to guide switching control of the networked closed-loop system. The results showed the effectiveness of HMM in network state estimation and switching control.