Multirate control implementation for an integrated communication and control system

When controlling a large manufacturing plant, there are a great number of devices (sensors and actuators) to connect with the main controller. The long distance in this kind of control systems suggests a shared communication link. Certain additional control problems appear when the communication between controller and plant is not always available. A multirate solution for the problem of the random access delays, involved on the resource sharing policy, is proposed in this paper. In addition, as there is not an exclusive link, it is difficult to guarantee the synchronisation of sensor, controller and actuator. The time skew between the sample, control and application instants, in combination with the random access delay, causes a loss of information that can make the system unstable. Multirate control techniques can be used to adjust the system behaviour to the desired reference model in the presence of time skew. (C) 2002 Elsevier Ltd. All rights reserved.