System and method for motion detection using a PPG sensor

Patent metadata

Field	Value
Publication number	US-10466783-B2
Application number	US-201816103876-A
Country	US
Kind code	B2
Filing date	Aug 14, 2018
Priority date	Mar 15, 2018
Publication date	Nov 5, 2019
Grant date	Nov 5, 2019

Abstract

A photoplethysmography (PPG) circuit obtains PPG signals at one or more wavelengths. The PPG signal is processed to identify motion artifacts. The motion artifacts are correlated with predetermined PPG signal patterns associated with a movement of a body part. The PPG signals may thus be used to detect movement of the body part. A user device may be controlled in response to the detected movement of the body part.

First claim

The invention claimed is:

1. A biosensor, comprising:
a sensor configured for positioning over an area of tissue of a user and configured to obtain a photoplethysmography (PPG) signal, wherein the PPG signal includes a spectral response around a first wavelength of light detected from the area of the tissue of the user, and wherein a distance between the sensor and the area of the tissue remains relatively constant;
a processing device configured to:
process the PPG signal at the first wavelength detected over the area of the tissue of the user to identify a first motion artifact at a first time interval; and
process the PPG signal at the first wavelength detected over the same area of the tissue of the user to identify a second motion artifact at a second time interval, wherein the first and second motion artifacts reflect changes in blood flow through vessels in the area of the tissue;
correlate the first motion artifact in the PPG signal to a first predetermined PPG signal pattern, wherein the first PPG signal pattern reflects changes in blood flow through vessels in the area of the tissue at the first time interval;
correlate the second motion artifact in the PPG signal to a second predetermined PPG signal pattern, wherein the second PPG signal pattern reflects changes in blood flow through vessels in the same area of the tissue at the second time interval;
obtain first motion data for a first moving body part associated with the first predetermined PPG signal pattern, wherein the first motion data includes a direction of movement of the first moving body part and a speed of the movement of the first moving body part;
obtain second motion data for a second moving body part associated with the second predetermined PPG signal pattern, wherein the second motion data includes a direction of movement of the second moving body part and a speed of the movement of the second moving body part and wherein the first moving body part and the second moving body part are different than a body part of the area of tissue of the user; and
control operation of a device in response to the first motion data or the second motion data.

2. The biosensor of claim 1 , wherein the first predetermined PPG signal pattern is associated with the first motion data, wherein the first motion data includes an identification of the first moving body part; and
wherein the second predetermined PPG signal pattern is associated with the second motion data, wherein the second motion data includes an identification of the second moving body part.

3. The biosensor of claim 2 , wherein the first motion data further includes a force of the movement of the first moving body part; and
wherein the second motion data further includes a a force of the movement of the second moving body part.

4. The biosensor of claim 1 , wherein the sensor is included in a band configured for positioning over the area of the tissue of a wrist or arm of the user and comprises:
a photodetector configured to detect light from the area of the tissue of the wrist or arm of the user;
a plurality of light sources spatially distributed around the photodetector, wherein the plurality of light sources emits light at a plurality of wavelengths in multiple spectrums; and
wherein the first moving body part includes a first finger of the user and the second moving body part includes a second finger of the user.

5. The biosensor of claim 1 , wherein the processing device is configured to:
process a third PPG signal at a second wavelength to identify a third motion artifact in the third PPG signal;
correlate the third motion artifact in the third PPG signal to a third predetermined PPG signal pattern; and
obtain third motion data using the third predetermined PPG signal pattern.

6. The biosensor of claim 5 , wherein the processing device is configured to compare the first motion data and the third motion data for verification of the first motion data.

7. The biosensor of claim 1 , wherein the processing device is configured to:
obtain a direct current (DC) level or a maximum amplitude of the first motion artifact; and
determine a force of movement of the first moving body part using the DC level or the maximum amplitude of the first motion artifact.

8. The biosensor of claim 1 , wherein the processing device is configured to:
obtain a heart rate using the first or second PPG signal;
determine a quality factor of the heart rate signal; and
process the first and second PPG signals when the quality factor exceeds a predetermined threshold.

9. The biosensor of claim 1 , wherein the processing device is configured to:
process the PPG signal at the first wavelength to identify a level of vasodilation; and
determine the movement of the first moving body part using the level of vasodilation.

10. The biosensor of claim 1 , wherein the biosensor further includes a motion sensor including one or more of: a gyroscope or an accelerometer; and
wherein the processing device is further configured to obtain motion data relating to movement of the biosensor in three-dimensional space relative to a control plane.

11. The device of claim 1 , wherein the processing device is a neural network processing device and wherein an input vector is generated using the PPG signal and wherein the neural network processing device generates an output vector including: an identification of the movement of the first moving body part, the direction of the movement of the first moving body part, the speed of the movement of the first moving body part and a force of the movement of the first moving body part.

12. A wearable device for detecting movement, comprising:
a PPG sensor configured to obtain a PPG waveform from light detected from an area of skin adjacent to the wearable device of a user;
a processing circuit in communication with the PPG sensor and configured to:
determine a heart rate signal from the PPG waveform;
determine a quality factor of the heart rate signal;
when the quality factor exceeds a predetermined threshold, identify a first motion artifact at a first time interval and a second motion artifact at a second time interval in the PPG waveform detected from the same area of skin adjacent to the wearable device of the user;
compare the first and second motion artifacts to a plurality of predetermined PPG patterns in a database, wherein each of the plurality of predetermined PPG patterns is associated with one of a plurality of movements and one of a plurality of body parts;
correlate the first motion artifact in the PPG waveform to a first predetermined PPG pattern in the database and determine a speed, direction and an identification of a first body part of the user associated with the first predetermined PPG pattern in the database;
correlate the second motion artifact in the PPG waveform to a second predetermined PPG pattern in the database and determine a speed, direction and an identification of a second body part of the user associated with the second predetermined PPG pattern in the database; and
wherein the first body part and the second body part are different than a body part including the skin adjacent to the wearable device.

13. The wearable device of claim 12 , wherein the processing circuit is further configured to: control an input device in response to the direction and speed of the first or second body part, wherein the input device includes at least one of: a mouse, a keyboard, a touchscreen, a touchpad, a smart watch, a smart phone, a game controller, a vehicle, a joystick, or a graphical user interface (GUI) on a display.

14. The wearable device of claim 12 , where

Assignees

• Sanmina Corp

Inventors

• Newberry Robert

Classifications

• G06F1/169

  the I/O peripheral being an integrated pointing device, e.g. trackball in the palm rest area, mini-joystick integrated between keyboard keys, touch pads or touch stripes (G06F1/1643 takes precedence; constructional details of pointing devices G06F3/033) · CPC title

• G06F1/163

  Wearable computers, e.g. on a belt · CPC title

• G06F1/1694

  the I/O peripheral being a single or a set of motion sensors for pointer control or gesture input obtained by sensing movements of the portable computer · CPC title

• G06F3/014 Primary

  Hand-worn input/output arrangements, e.g. data gloves · CPC title

• G06F3/015

  Input arrangements based on nervous system activity detection, e.g. brain waves [EEG] detection, electromyograms [EMG] detection, electrodermal response detection · CPC title