Control for canceling periodic disturbances with uncertain frequency

Presents an algorithm to cancel periodic disturbances with uncertain frequency. The disturbances are canceled using a controller with an internal model structure in parallel with a traditional PI controller. It is shown that under ideal circumstances the time varying states of the internal model can be mapped to two time invariant variables, the magnitude or energy of the internal model and the difference between the nominal error frequency and the true error frequency. An additional integral controller then can be used to reduce this error to zero. The stability of the feedback control system including this algorithm is justified by singular perturbation theory. Simulations demonstrate the validity of the analytical results, the ability of this algorithm to identify the frequency of periodic disturbances and the capability of this feedback control system to reject periodic disturbances with uncertainty in frequency