Hindawi Publishing Corporation Journal of Control Science and Engineering V olume 2012, Article ID 827353, 2pages doi:10.1155/2012/827353 Editorial Adaptive Control Theory and Applications Chengyu Cao,1Lili Ma,2and Y unjun Xu3 1Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269-4077, USA 2Electronics and Mechanical Department, Wentworth Institute of Technology, Boston, MA 02115, USA 3Department of Mechanical, Materials, and Aerospace Engineering, University of Central Florida, Orlando, FL 32816, USA Correspondence should be addressed to Chengyu Cao, ccao@engr.uconn.edu Received 15 August 2012; Accepted 15 August 2012 Copyright © 2012 Chengyu Cao et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproductio n in any medium, provided the original work is properly cited. Adaptive control is an active field in the design of control sys- tems to deal with uncertainties. The key di fference between adaptive controllers and linear controllers is the adaptivecontroller’s ability to adjust itself to handle unknown model uncertainties. Adaptive control is roughly divided into two categories: direct and indirect. Indirect methods estimate theparameters in the plant and further use the estimated modelinformation to adjust the controller. Direct methods are oneswherein the estimated parameters are those directly used inthe adaptive controller. Recently, much e ffort has been placed in adaptive control in both theory and applications. Theory-wise, new controllerdesign techniques are introduced to handle nonlinear andtime-varying uncertainties. Broader systems with larger non-linear uncertainties can be covered by these developments.As a result, adaptive control finds use in various real worldapplications. This special session generalizes some of thelatest results of adaptive control in both theory and appli-cations. After a thorough review process, 8 papers wereselected. The papers in this special section include the fol-lowing. The paper entitled “Adaptive control for nonlinear systems with time-varying control gain” byA. Rincon and F. Angulo ,a scheme for nonlinear plants with time-varying control gainsand time-varying plant coe fficients is proposed and applied on a plant model consisting of a Brunovsky type modelwith polynomials as approximators. The methodology hasbeen applied to the speed control of a permanent magnet synchronous motor (PMSM) and proper tracking results have been achieved. The paper entitled “Adaptive impedance control to enhance human skill on a haptic interface system ”b y S. Suzuki andK. Furuta , adaptive assistive control for a haptic interface system is proposed. An adaptive mechanism derived from aLyapunov candidate function is used to tune an impedanceof the virtual model for the haptic device according to the identified operator’s characteristics for enhanced perfor- mance. It was verified that the operator’s characteristics canbe estimated and further enhanced. The paper entitled “Pilot-induced oscillation suppression by using L1 adaptive control” byC. Wang and C. Cao ,w h e r e pilot-induced oscillation (PIO) is a phenomenon that occursin both flight tests and operational aircrafts. In this paper, theL1 adaptive controller has been introduced to suppress PIO, which is caused by rate limiting and pure time delay. Dueto its architecture, the L1 adaptive controller will achieve a desired response with fast adaptation. The simulation resultsindicate that the L1 adaptive control is e fficient in solving this kind of problem. In the paper entitled “Adaptive control for a class of nonlinear system with redistributed models ”b y H. Ke ,a n d J. Li, a novel multiple model adaptive controller for a classof nonlinear system in parameter-strict-feedback form isproposed. It not only improves the transient performancesignificantly, but also guarantees the stability of all the statesof the closed-loop system