Output harmonic disturbance compensation for nonlinear plant

The paper deals with the problem of compensation of unmeasured output biased harmonic disturbance for nonlinear plant. We propose a frequency identifier for unmeasured disturbance ̅y(t)=̅σ₀ + ̅σsin(̅ωt + ̅φ). Using this identifier the disturbance compensation algorithm was designed. This algorithm is based on observing the extended plant model and designing a control signal for the disturbance compensation by measured states of the designed observer. It is demonstrated that the proposed algorithm is applicable under variable disturbance frequency.