Networked Control Systems: A Model-Based Approach

A networked control system (NCS) is a control system in which a data network is used as a feedback medium. NCS is an important research area; see for example [16] and [15, 18, 19]. The use of networks as media to interconnect the different components in an industrial control system is rapidly increasing, although the use of an NCS poses some challenges. One of the main problems to be addressed when considering an NCS is the size of the bandwidth required by each subsystem. It is clear that the reduction of bandwidth necessitated by the communication network in an NCS is a major concern. This can perhaps be addressed by two methods: the first method is to minimize the transfer of information between the sensor and the controller/actuator; the second method is to compress or reduce the size of the data transferred at each transaction. Since shared characteristics among popular industrial networks are a small transport time and a big overhead, using less bits per packet has a small impact on the overall bit rate. So reducing the rate at which packets are transmitted brings better benefits than data compression in terms of the bit rate used. In this chapter, we consider the problem of reducing the packet rate of an NCS using a novel approach called model-based NCS (MB-NCS). The MB-NCS architecture makes explicit use of knowledge about the plant dynamics to enhance the performance of a system. The MB-NCS was introduced in [11].