Embedded systems for time–critical applications over Wi-Fi: design and experimental assessment

Networked embedded systems for industrial control based on wireless support provide several advantages over wired counterparts, but often reveal unsuitable for the most demanding industrial control applications, such as advanced manufacturing and cooperative robotics. Data exchange over IEEE 802.11 networks may theoretically represent an appropriate solution for time–critical applications, provided that unreliability and non– determinism issues are properly handled. In this respect, this paper hence proposes an original solution, based on a cross– layer approach, to allow the realization of high–speed industrial control–over–Wi-Fi networked embedded systems. The proposal implements a novel robust frame–delay state estimator, a time efficient communication policy, and a specific tuning of critical protocol parameters. Suitable hardware–in–the–loop experiments have been carried out implemented exploiting two different embedded systems. Preliminary results show that the proposed architecture enables industrial control applications requiring a sampling rate of up to 1 kHz, even in presence of non negligible communication errors.