Networked control with delay measurement and estimation

In research on networked control systems (NCSs), the performance of the control system is assumed to be affected by network-induced parameters such as delays, jitters, packet losses and link failures. In this paper, compensation methods are studied, in the framework of NCS while considering the protocol specifications. The aim is to propose two different methods for the control over a network, adaptive Smith predictor approach and robust control based approach, which are imposed by the accessible information about the network. First, a clock synchronization protocol is implemented in each device of the network, thereby providing the possibility of end-to-end delay measurement, and a compensation strategy based on this measurement and the adaptive Smith predictor approach is applied. Secondly, the end-to-end upper bound delay estimate is calculated on the basis of the network architecture and the traffic estimation, and then subsequently used in a robust control based compensation strategy. The switched Ethernet network is used as an example of the communication network of the NCS. The efficiency of proposed approaches is evaluated with Matlab simulation as well as in the experimental prototype.