Robust stability of a two-degree-of-freedom servosystem incorporating an observer with multiplicative uncertainty

관측기를 갖는 2자유도 서보계의 승법적인 불확실성에 대한 강인한 안정성

  • 김영복 (부경대학교 제어기계공학과) ;
  • 양주호 (부경대학교 제어기계공학과)
  • Published : 1997.02.01


In order to reject the steady-state tracking error, it is common to introduce integral compensators in servosystems for constant reference signals. However, if the mathematical model of the plant is exact and no disturbance input exists, the integral compensation is not necessary. From this point of view, a two-degree-of-freedom(2DOF) servosystem has been proposed, in which the integral compensation is effective only when there is a modeling error or a disturbance input. The present paper considers robust stability of this 2DOF servosystem incorporating an observer to the structured and unstructured uncertainties of the controlled plant. A robust stability condition is obtained using Riccati inequality, which is written in a linear matrix inequality (LMI) and independent of the gain of the integral compensator. This result impies that if the plant uncertainty is in the allowable set defined by the LMI condition, a high-gain integral compensation can be carried preserving robust stability to accelerate the tracking response.


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