Sample-induced delays in synchronous multirate systems

In many industrial applications the communication in a distributed control system is done over layered synchronous or asynchronous control buses. In this paper we consider the type of delays and control deterioration that can be obtained due to the communication delays. The main source of the delays considered in this paper is the sample-induced delays caused by the multirate sampling in the communication between the different parts of the control system and the process. The paper analyzes some bus structures with respect to delays and possibilities for control. The result is that it sometimes can be surprisingly long delays that have to be compensated for in the design of the controller. Some possible ways for compensation are discussed and illustrated in the paper.