Real-time implementation of a burst error compensator for wireless control systems

The use of wireless communications systems in automation and real-time control applications is increasing at a steady rate. The use of wireless technologies in these applications poses several severe problems, which include out-of-order packet transmission, high levels of packet jitter and high probabilities of packet losses; these problems are especially problematic in systems with strict timing constraints. This paper is concerned with ameliorating the effects of packet loss in time-triggered sampled-data control systems, in which the feedback connection is implemented via one or more wireless links. In particular, the paper develops a simple predictive compensator that reconstructs the best estimates of a sequence of one or more missing data samples using an ARMA model of the process under control. An embedded implementation of the compensator is applied to a case study, in which ARM7 microcontrollers and ISA band wireless transceivers are employed in a real-time servomotor control system experiencing artificially induced packet losses. Experimental results are presented which indicate that the technique has the potential to maintain system tracking performance and stability in the presence of sever interference and burst errors affecting the feedback channel.