Title :
Persistency of excitation and overparameterization in model reference adaptive control
Author :
Tao, G. ; Ioannou, P.A.
Author_Institution :
Dept. of Electr. Eng.-Syst., Univ. of Southern California, Los Angeles, CA, USA
Abstract :
It is shown that if a model-reference adaptive controller is designed for an overparameterized plant, the persistence of excitation of the measured vector signal in the adaptive loop will be lost independently of the number of frequencies in the reference input. The model-plant transfer-function-matching parameters lie in a linear variety in the parameter space. The estimated parameters will converge to this variety if the reference input has enough frequencies. Parameter perturbations and unmodeled dynamics in the plan may cause near-overparameterization which can result in a low level of persistent excitation (PE). The loss of PE or the low level of PE can lead to loss of stability and robustness in the presence of modeling errors
Keywords :
adaptive control; model reference adaptive control systems; parameter estimation; transfer functions; MRAC; adaptive control; model reference adaptive control; model-plant transfer-function-matching parameters; overparameterization; parameter estimation; parameter perturbation; persistent excitation; stability; unmodeled dynamics; Adaptive control; Convergence; Frequency estimation; Frequency measurement; Integrated circuit modeling; Parameter estimation; Polynomials; Programmable control; Transfer functions; Upper bound;
Conference_Titel :
Decision and Control, 1988., Proceedings of the 27th IEEE Conference on
Conference_Location :
Austin, TX
DOI :
10.1109/CDC.1988.194410