A New Frequency Estimator with Dynamics That Are Independent of Input Amplitude and Its Application to Notch Filters

This paper proposes a new frequency estimator (FE) and its application to a notch filter (NF). There are many well-known methods for estimating the frequency of a signal in both frequency and time domains. A previously reported time-domain FE was designed by rescaling the forcing signal term and achieved accurate estimation performance. However, the estimation speed was slow when the input signal is in a low-frequency range or when the input amplitude is small. An improved version was developed which decreased the dependency on the frequency. This paper presents a new FE to make the estimation speed less dependent on both the signal frequency and amplitude. The stability properties of the proposed FE are shown, using the averaging theorem under the assumption of slow adaptation. The performance of the proposed FE is also evaluated by both simulations and experiments, which show excellent performance in accuracy and speed in all conditions.