A New Indirect Adaptive Control Scheme for Time-Varying Plants

Konstantinos Tsakalis, Petros A. Ioannou

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


An indirect robust adaptive controller designed for linear time-invariant plants may also meet its control objective approximately for slowly time-varying plants. The plant parameter variations act as a disturbance in the estimation and control parts of the indirect scheme, and therefore, for stability, they are required to be slow. In this paper, we develop new structures for the control and estimation parts of the indirect adaptive scheme which are more appropriate for time-varying plants. In contrast to the usual pointwise schemes, the new controller structure can meet the control objective exactly for a wide class of plants with smooth, but otherwise unrestricted, parameter variations. On the other hand, the possibly available knowledge of the form or frequency of variation of the “fast” parameters is included in the new estimator structure so that for successful estimation, the overall plant is not restricted to vary slowly with time. The new estimator and control law are combined using the certainty equivalence principle to develop an indirect adaptive control scheme meeting the control objective for plants with time-varying parameters whose fast varying parts are of known form and the unknown parts are slow in the mean.

Original languageEnglish (US)
Pages (from-to)697-705
Number of pages9
JournalIEEE Transactions on Automatic Control
Issue number6
StatePublished - Jun 1990

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Computer Science Applications
  • Electrical and Electronic Engineering


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