Performance improvement of an NCS closed over the internet with an adaptive Smith Predictor

In this paper, the potential improvement in performance of an NCS (Networked Control System) subject to variable delays controlled by means of an adaptive system is analyzed. An adaptive Smith Predictor has been used to compensate the effects of varying delays measured on the network. The NCS, closed over the Internet, has been implemented using a platform called NCS-CMUF, composed of local and remote stations. The plant used to carry out the experimental tests is consisted of an optical oven in which the luminosity loop is the main controlled variable whose time constant lies in the range of milliseconds. This paper highlights the importance of synchronization between the clocks of the local and remote stations to perform consistent measurements of network delays, in order to provide an active compensation of the effects of delays. The results show the effectiveness of adaptive Smith Predictor in coping with different delays and the performance improvements achieved with the proposed scheme.