Efficient Control of a SmartWheel via Internet with Compensation of Variable Delays ✩ In´ es Tejado a , S. Hassan HosseinNia a , Blas M. Vinagre a , YangQuan Chen b a Industrial Engineering School, University of Extremadura, 06006 Badajoz, Spain b Center for Self-Organizing and Intelligent Systems, Utah State University, 84322 Logan, UT, USA Abstract Control through networks requires effective strategies due to the presence of induced phenomena. This paper deals with the compensation of the effects of time-varying delays when controlling a delay-dominated system, called SmartWheel (SW), over the Internet in the framework of fractional order control (FOC). In particular, the gains of a nominal fractional order PI α controller, designed for a local purpose, are adapted with respect to the cur- rent delay condition to perform an efficient control over the network. The quadratic stability of the controlled system is proved by a frequency domain method on the basis of switching systems theory. Experimental results are given to show the effectiveness of the proposed control strategy, referred to the significantly better system performance in comparison with the applica- tion of the nominal PI α , especially for large Internet-induced delays. Keywords: Networked control system, Variable delay, Gain scheduling, Fractional order PI controller, Stability, SmartWheel NCS testbed. 1. Introduction Networked control systems (NCS) have been one of the main research interests in industrial applications for many decades, especially due to ad- ✩ This work was supported by the Spanish Ministry of Science and Innovation under the research project TRA2008-06602-C03-01. Email addresses: itejbal@unex.es (In´ es Tejado), hoseinia@unex.es (S. Hassan HosseinNia), bvinagre@unex.es (Blas M. Vinagre), yqchen@ieee.org (YangQuan Chen) Preprint submitted to Mechatronics February 8, 2013