Adaptive Output Feedback for Nonsquare Systems with Arbitrary Relative Degree

Hanmin Lee, Venanzio Cichella, Naira Hovakimyan

Research output: Contribution to journalArticlepeer-review


This article considers adaptive output-feedback control problem for nonsquare multi-input-multi-output systems (MIMO) with arbitrary relative degree. The proposed controller, based on the \mathcal {L}_1 adaptive control architecture, is designed using the right interactor matrix and a suitably defined projection matrix. A state-output predictor, a low-pass filter, and adaptive laws are introduced that achieve output tracking of a desired reference signal. It is shown that the proposed control strategy guarantees closed-loop stability with arbitrarily small steady-state errors. The transient performance in the presence of nonzero initialization errors is quantified in terms of decreasing functions. Rigorous mathematical analysis and illustrative examples are provided to validate the theoretical claims.

Original languageEnglish (US)
Article number9075447
Pages (from-to)895-901
Number of pages7
JournalIEEE Transactions on Automatic Control
Issue number2
StatePublished - Feb 2021


  • Adaptive control
  • adaptive systems
  • nonlinear systems
  • nonsquare systems

ASJC Scopus subject areas

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


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