A new result on the stability and convergence of self-tuning adaptive control

Among various types of self-tuning control schemes, only one-step-ahead self-tuning control of deterministic plant and minimum variance self-tuning control of stochastic plant can guarantee the stability and convergence of closed-loop system without requiring the convergence of parameter estimation. This paper presents a new result that the convergence of parameter estimates is not necessary for the stability and convergence of a general self-tuning control system comprising of any admissible control strategy and any admissible parameter estimation algorithm. This breakthrough result is owing to the adoption of a new type of virtual equivalent system: slow switching control system, whose stability and tracking performance are guaranteed under mild conditions.