Tidal Current Fundamental Frequency Determination Algorithm for Integer Arithmetic Units

In this paper, fundamental frequencies of tidal currents are determined from accelerations measurements using an algorithm in integer arithmetic for ultra-low power consumption applications. Experimental measurements of accelerations were obtained from an inertial instruments attached to mooring lines of offshore aquaculture cages. The sampling rate and resolution for acquiring the 3-axis accelerations was 12.5 Hz and 16 bits, respectively. By filtering the input signal with a band-pass digital filter of moving average for 8 and 4 points and internal width of 32 bits, the bandwidth at −3 dB was established in 4 Hz. The resulting filtered signal was post-processed by a novel peak and valley detector for obtaining the fundamental frequency components. On an ARM Cortex M0+ core, the energy required for processing 25 samples was 54 nAh, and the CPU time 427.34 ms.