Delay Evaluation and Compensation in Ethernet-Networked Control Systems

Research in networked control systems (NCS), deals with both communication networks and control. Usually, these two points of view are treated separately and rarely together in the same context. In this paper, an overall study of a networked control system is presented. First, a formal method to evaluate the response time of Ethernet-based automation architectures using a client server protocol is presented. It is based on a modeling by the use of timed event graphs and Max-plus algebra. An algorithm and analytical formulas to evaluate the response time are obtained. This approach is validated using measurements taken on a real platform. Thereafter, the results are used in the synthesis of a Smith predictor-based delay compensation strategy to improve the performance of the whole NCS.