In research on networked control systems (NCS), 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, two delay compensation methods are studied, adaptive Smith Predictor and robust control, in the framework of Networked Control Systems while considering the protocol specifications. 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 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.
Author 's accepted manuscript, published in Control Engineering Practice 16 (2008)
AbstractFault diagnosis methods based on process history data have been studied widely in recent years, and several successful industrial applications have been reported. Improved data validation has resulted in more stable processes and better quality of the products. In this paper, an on-line fault detection and isolation system consisting of a combination of principal component analysis (PCA) and two neural networks (NNs), radial basis function network (RBFN) and self-organizing map (SOM), is presented. The system detects and isolates faulty operation of the analyzers in an ethylene cracking furnace. The test results with real-time process data are presented and discussed.
Evaluating control performance has attracted considerable interest in recent years. A set of performance indices appropriate to monitoring and assessment in flotation cells is presented and discussed in this paper. A graphical, user-friendly and interpretable program for displaying performance indices for operators has been developed. Finally, the testing results from flotation cells in a zinc plant are presented and discussed.
Recent interest in networked control systems (NCS) has instigated research in various areas of both communication networks and control. The analysis of NCS has often been performed either from the network, or the control point of view and not many papers exist were the analysis of both is done in the same context. Here a simple overall analysis is presented. In the paper the procedure of obtaining the upper bound delay value in the switched Ethernet network is proposed and the obtained delay estimate is used in stability analysis of the feedback loop and in the control compensation. The upper bound delay algorithm is based on the network calculus theory, the stability analysis uses the small gain theorem, and control compensating strategy is based on Smith predictor, where however the upper bound delay is utilised in obtaining the delay estimate.
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