Low-complexity sensor displacement tolerant pulse oximetry based heart rate measurement

A method performed by a photoplethysmograph (PPG) heart rate monitor device, the method comprising:

• receiving an accelerometer signal from a motion sensor of the heart rate monitor device;
• capturing a PPG light signal, in which the PPG light signal is:
• filtered when the accelerometer signal is below a threshold;
• or
• motion compensated when the accelerometer signal is above the threshold;
• detecting a pulse in a portion of the filtered or motion compensated PPG light signal, including detecting a start point of the pulse;
• determining a summit point and an end point of the pulse based on the start point of the pulse, in which determining the summit point includes:
• determining a first maximum point within a first portion of the pulse;
• determining a second maximum point after the first maximum point;
• determining a direct linear path difference between the first maximum point and the second maximum point;
• determining an indirect path difference between the first maximum point and the second maximum point;
• and
• selecting the summit point as either the first maximum point or the second maximum point based on a comparison of the direct linear path difference and the indirect path difference;
• estimating a pulse rate based on the start point, the summit point, and the end point;
• and
• outputting the estimated pulse rate to another device.