Stability and convergence of adaptive controllers-continuous systems

The first self-adaptive control systems were proposed some 25 years ago. The paper traces the historical development of model-reference adaptive control systems and especially their theoretical basis. The use of Lyapunov functions and hyperstability theory in analysis and synthesis is considered, the r¿¿le played by positive real transfer functions being particularly emphasised. Some practical applications and current and possible future theoretical developments are briefly described.