Patent ID: 9693726
Date: 2017-07-04
CPC Classifications: A61B,B60W,G16H

Claim:
1. An alertness device comprising: a heart rate sensor configured to obtain an electrocardiographic signal of a person; a calculation unit configured to calculate the electrocardiographic signal obtained from the heart rate sensor; a waveform generation unit configured to generate, from an electrocardiographic waveform of the electrocardiographic signal, an RRI waveform showing transitions for a predetermined time period with RRIs, each RRI of the predetermined time period being an R-R interval between R-waves of the electrocardiographic waveform; and a determination unit configured to determine an alertness state of the person based on the electrocardiographic signal; wherein the calculation unit replicates a same number of RRI waveforms as that of anchors, each anchor being a point where a certain RRI is shorter than an adjacent preceding RRI in the RRI waveform generated by the waveform generation unit, moves time axes of the replicated RRI waveforms such that the anchors of the replicated RRI waveforms are in phase with each other, and calculates a phase-rectified signal averaging (PRSA) signal, which is an RRI average for each time axis of the replicated RRI waveforms; and wherein the determination unit determines, based on the RRIs and the PRSA signals, whether the person is in an alert state or an unalert state.