Modifications and design of a frequency estimation algorithm for disturbance rejection

Modifications and design of an algorithm for identifying the frequency of periodic signal or disturbance are studied in this paper. The approach utilizes a feedback control system and can achieve true frequency estimation without error in the steady state. High frequency ripple has been observed in the frequency estimate of the original algorithm. This problem is analyzed on a theoretical basis in the paper. An alternative solution is presented to eliminate this ripple other than the previous adaptive notch filter approach. The design issue of the algorithm is also discussed in this paper, especially when multiple frequency components are present in the input signal. LQR optimal control technique is employed in determining the feedback gains in the estimation system. Simulations are conducted and results are presented.