Output-feedback global tracking for unknown control direction plants with application to extremum-seeking control

  • Authors:
  • Tiago Roux Oliveira;Liu Hsu;Alessandro Jacoud Peixoto

  • Affiliations:
  • Department of Electronics and Telecom. Engineering, State University of Rio de Janeiro, 20550-900, Brazil;Department of Electrical Engineering, COPPE/Federal University of Rio de Janeiro, 21945-970, Brazil;Department of Electrical Engineering, COPPE/Federal University of Rio de Janeiro, 21945-970, Brazil

  • Venue:
  • Automatica (Journal of IFAC)
  • Year:
  • 2011

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Abstract

This paper addresses the design of a sliding mode tracking controller for single-input-single-output (SISO) uncertain plants with relative degree one and unknown control direction, i.e., with unknown sign of the high frequency gain (HFG). We demonstrate that, for a class of linear plants with nonlinear output function, it is possible to achieve global exact tracking using only output-feedback by combining a recently introduced periodic switching function with a well-known control parameterization of Model Reference Control (MRC). Simulation results are presented to illustrate the good tracking performance. One significant advantage of the new scheme is its robustness to time-varying control direction which is here theoretically justified for jump variations of the HFG and successfully tested by simulation in more general conditions. This property makes it adequate for solving extremum-seeking problems. Theoretical justification is presented for a class of systems with nonlinear output function using only output-feedback. An application to the wheel slip control in Antilock Braking Systems (ABSs) illustrates the practical viability of the proposed control scheme.