ABSTRACT: With his sigma-modification (1983), Petros Ioannou secured the survival of adaptive control in the face of non-parametric uncertainties, and then, with his students at USC, took robustification of adaptive control to numerous extensions in the 1980s-1990s. Yet, sigma-modification’s regulation bias is unknown and irreducible. Decades of brightest minds in adaptive control trying to improve robustness, without success, created a never-proven BELIEF that improvement must be impossible. Even the goal for the improvement remained unclear, with all attempts, at various objectives, simply having not succeeded. The code for improving robust adaptive control was finally cracked after 40 years, by another Greek, an NTU-Athens mathematician Iasson Karafyllis, as I hindered him with skepticism and finally lent a smidgen of assistance. The goal attained is asymptotic regulation arbitrarily close to zero, under unlimited disturbances and parametric uncertainty. What exactly is new in the design? A deadzone is applied to adaptation, while the control is strengthened with a previously untried form of nonlinear damping with dynamic gain. Details in the talk but a bit of intuition here. The closed-loop robust adaptive dynamics resemble a (stabilized) predator-prey system. The plant state error is the prey population, starting potentially vast. The gain being adapted, starting as a potentially scant population, predates upon that prey and drives it to near-extinction, regardless how diminished the gain’s predating fitness gets as a result of disturbance.

BIOSKETCH: Miroslav Krstic is Distinguished Professor of Mechanical and Aerospace Engineering and Senior Associate Vice Chancellor for Research at UC San Diego. Krstic is Fellow of IEEE, IFAC, ASME, SIAM, AAAS, IET (UK), AIAA (Assoc. Fellow), and member of the Serbian Academy of Sciences and Arts. He has received the Richard E. Bellman Control Heritage Award, Bode Lecture Prize, SIAM Reid Prize, ASME Oldenburger Medal, Nyquist Lecture Prize, Paynter Outstanding Investigator Award, Ragazzini Education Award, IFAC Nonlinear Control Systems Award, IFAC Ruth Curtain Distributed Parameter Systems Award, IFAC Adaptive and Learning Systems Award, Chestnut textbook prize, several your investigator and best paper awards, and is the inaugural winner of the AV Balakrishnan Award for the Mathematics of Systems. He serves as Editor-in-Chief of Systems & Control Letters and starts in 2026 as Editor-in-Chief of IEEE Transactions on Automatic Control. Krstic has coauthored nineteen books on adaptive, nonlinear, and stochastic control, extremum seeking, control of PDE systems including turbulent flows, and control of delay systems.