Heart rate path optimizer

Patent metadata

Field	Value
Publication number	US-9867575-B2
Application number	US-201414466890-A
Country	US
Kind code	B2
Filing date	Aug 22, 2014
Priority date	Aug 22, 2014
Publication date	Jan 16, 2018
Grant date	Jan 16, 2018

Abstract

A device for determining a heart rate of a user has a PPG sensor and an accelerometer to compensate for acceleration artifacts within the PPG signal. The device transforms time domain PPG and accelerometer signals into the frequency domain using a Fourier transformation and utilizes the Fourier coefficient magnitudes as indicative of the probability of candidate heart rate values. Candidate heart rate values are determined at sampling times over a time interval and a most probable heart rate path during the time interval is determined using a reward/penalty algorithm.

First claim

What is claimed is:

1. A device for determining a heart rate (HR) of a user comprising:
a (HR) sensor comprising a photoplethysmogram (PPG) sensor configured for providing HR signals;
an accelerometer coupled to the user; and
processing circuitry capable of:
providing HR values that have been compensated for artifacts from acceleration on the HR signals as measured by the accelerometer; the HR values provided for each of a plurality of times over a time interval, and
selecting a path of optimum HR values across the time interval, the selected path implementing a reward for candidate paths based on a sum of probabilities of a most probable path between consecutive points of candidate paths, and implementing a penalty based on differences between HR values of the consecutive points along the candidate paths.

2. The device of claim 1 , wherein providing the HR values includes transforming the HR signals into frequency domain HR signals (FDHR signals) and adding together at least a fundamental and first harmonic of Fourier component magnitudes of the FDHR signals corresponding to the HR signals to provide a harmonic boost.

3. The device of claim 2 , wherein the Fourier component magnitudes are absolute values of Fourier coefficients of the FDHR signals.

4. The device of claim 1 , wherein providing the HR values includes transforming the HR signals into frequency domain HR signals (FDHR signals) and low pass filtering Fourier component magnitudes of the FDHR signals.

5. The device of claim 4 , wherein the low pass filtering is provided by utilizing a Gaussian convolution.

6. The device of claim 1 , wherein providing the HR values includes transforming the HR signals into frequency domain HR signals (FDHR signals) and providing a peak boost to Fourier component magnitudes of the FDHR signals.

7. The device of claim 6 , wherein the peak boost multiplies each local maxima of the Fourier component magnitudes by a number larger than 1.

8. The device of claim 7 , wherein the Fourier component magnitudes are absolute values of Fourier coefficients of the FDHR signals.

9. The device of claim 1 , wherein providing the HR values includes transforming the HR signals into frequency domain HR signals (FDHR signals), and transforming signals from the accelerometer into the frequency domain to provide frequency domain artifact signals (FDART signals) and wherein the HR values are computed based on complex conjugates of Fourier transform coefficients of the FDHR signals and the complex conjugates of Fourier transform coefficients of the FDART signals.

10. The device of claim 1 , further comprising an analog to digital converter configured for converting the HR signals and signals from the accelerometer to digital signals.

11. The device of claim 10 , wherein providing the HR values includes applying a Fourier transform to the HR signals and the signals from the accelerometer after applying the analog to digital conversions to obtain Fourier coefficients.

12. The device of claim 11 , wherein providing the HR values includes taking an absolute value of the Fourier coefficients after applying the Fourier transform and the analog to digital conversion to obtain Fourier coefficient magnitudes.

13. The device of claim 12 , wherein providing the HR values includes identifying peak values in the Fourier coefficient magnitudes and replacing the identified peak values by interpolated values based on values on opposite sides of the identified peak values and utilizing the interpolated values for compensating for artifacts from acceleration.

14. The device of claim 1 ,
wherein providing the HR values includes transforming the HR signals into frequency domain HR signals (FDHR signals), and transforming signals from the accelerometer into the frequency domain to provide frequency domain artifact signals (FDART signals);
wherein the HR values are computed based on complex conjugates of Fourier transform coefficients of the FDHR signals to provide HR Fourier coefficient magnitudes and the complex conjugates of Fourier transform coefficients of the FDART signals to provide acceleration Fourier coefficient magnitudes, and
wherein providing the HR values includes identifying peak values in the HR Fourier coefficient magnitudes that correspond to acceleration Fourier coefficient magnitudes and replacing the identified peak values with interpolated values based on values on opposite sides of the identified peak values.

15. The device of claim 14 , the processing circuitry further capable of adding together at least a fundamental and first harmonic of Fourier component magnitudes of the FDHR signals corresponding to the HR signals to provide a harmonic boost and further providing a peak boost to Fourier component magnitudes of the FDHR signals by multiplying local maxima of the Fourier component magnitudes by a number larger than 1.

16. The device of claim 1 , wherein providing the HR values includes transforming the HR signals into frequency domain HR signals (FDHR signals) and adding together at least a fundamental and first harmonic of Fourier component magnitudes of the FDHR signals corresponding to the HR signals to provide a harmonic boost and further providing a peak boost to Fourier component magnitudes of the FDHR signals by multiplying local maxima of the Fourier component magnitudes by a number larger than 1.

17. A device for determining a heart rate (HR) of a user comprising:
a HR sensor comprising a photoplethysmogram (PPG) sensor configured for providing time domain HR signals, the time domain HR signals having time domain HR components indicative of the user's HR and time domain artifact components indicative of the user's acceleration movements;
an accelerometer providing time domain accelerometer output signals;
processing circuitry capable of:
converting the time domain HR signals into frequency domain HR (FDHR) signal magnitudes and converting the time domain accelerometer output signal into frequency domain accelerometer (FDA) signal magnitudes, the FDHR signal magnitudes having frequency domain HR (FDHR) component magnitudes corresponding to the user's heart rate and frequency domain artifact (FDART) component magnitudes corresponding to the FDA signals;
compensating for the FDART component magnitudes in the FDHR signal magnitudes to provide compensated FDHR component magnitudes for each of a plurality of times over a time interval; and
selecting a path of optimum HR values across the time interval based on the compensated FDHR component magnitudes for each of a plurality of times, the path selecting performed by implementing a reward for candidate paths based on a sum of the compensated FDHR component magnitudes of all points the candidate paths pass through, and a penalty based on a sum of distances between consecutive compensated FDHR component magnitudes along the candidate paths, the distances measured by differences between the HR values associated with consecutive path points.

18. The device of claim 17 , wherein the processing circuitry is further capable of providing a harmonic boost to the compensated FDHR component magnitudes by adding together at least a fundamental and a first harmonic of the compensated FDHR component magnitudes.

19. The device of claim 18 , wherein the processing circuitry is further capable of providing low pass filtering of the compensated FDHR component magnitudes.

20. The device of claim 19 , wherein the low pass filtering is provided by utilizing a Gaussian convolution.

21. The d

Assignees

• Apple Inc

Inventors

• Maani Ehsan
• Culbert Daniel J
• Shapiro Ian R

Classifications

• A61B2560/0493

  controlled by voice · CPC title

• A61B5/02416

  using photoplethysmograph signals, e.g. generated by infrared radiation (A61B5/14552 takes precedence) · CPC title

• A61B5/721 Primary

  using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured · CPC title

• A61B5/725

  using specific filters therefor, e.g. Kalman or adaptive filters (specific diagnostics methods using using bioelectric or biomagnetic signals A61B5/316) · CPC title

• A61B5/0205

  Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition · CPC title