DETECTING ACTIVITY BY A WHEELCHAIR USER

• US 20170347885A1
• Filed: 06/07/2017
• Published: 12/07/2017
• Est. Priority Date: 06/07/2016
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Tan, Xing, Raghuram, Karthik Jayaraman, Ullal, Adeeti, Srinivas, Umamahesh, Agarwal, Mrinal, Trietsch, Daniel, Alvarado, Alexander Singh, Pham, Hung A., Huang, Ronald K., Howell, Adam
• Granted Patent: US 10,687,707 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 5/0022 Monitoring a patient using a global network, e.g. telephone networks, internet
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/1112 Global tracking of patients, e.g. by using GPS
• CPC Class Codes: A61B 5/1118 Determining activity level
• CPC Class Codes: A61B 5/1123 Discriminating type of movement, e.g. walking or running A61B5/1116, A61B5/112 take precedence
• CPC Class Codes: A61B 5/22 Ergometry; Measuring muscular strength or the force of a muscular blow exercising apparatus A63B21/00 ; measuring of work or force in general G01L
• CPC Class Codes: A61B 5/222 combined with detection or measurement of physiological parameters, e.g. heart rate
• CPC Class Codes: A61B 5/4866 Evaluating metabolism A61B5/083 takes precedence
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61G 2203/36 for motion
• CPC Class Codes: A61G 5/02 propelled by the patient or disabled person
• CPC Class Codes: A61G 5/10 Parts, details or accessories
• CPC Class Codes: A61G 5/1035 manipulated by wheelchair user

Abstract

The present disclosure relates to a system and method of detecting activity by a wheelchair user. In one aspect, a method comprises collecting motion data of a user device located on an appendage of the user; detecting, by a processor circuit, that one or more activities by the wheelchair user occurred based on the motion data; calculating, by a processor circuit, an energy expenditure by the user based the one or more activities by the wheelchair user occurred; and outputting, by a processor circuit, the energy expenditure estimation.

Claims

1. A method for tracking activity by a wheelchair user, the method comprising:

collecting motion data of a user device located on an appendage of the user;

detecting, by a processor circuit, that one or more activities by the wheelchair user occurred based on the motion data;

estimating, by a processor circuit, an energy expenditure by the user based on the one or more activities; and

outputting, by a processor circuit, the estimated energy expenditure.

2. The method of claim 1, wherein the motion sensor comprises an accelerometer, a gyroscope, a magnetometer, or a combination thereof.

3. The method of claim 1 wherein detecting that one or more activities by the wheelchair user occurred comprises tracking pushes by the wheelchair user.

4. The method of claim 3, wherein tracking pushes by the wheelchair user comprises:

determining a pose angle and a calculated energy based on the motion data; and

detecting, by a processor circuit, that a push occurred based on a determined pose angle and a calculated energy.

5. The method of claim 4, wherein tracking pushes by the wheelchair user comprises:

comparing, by a processor circuit, the determined pose angle with a pose angle threshold;

comparing, by a processor circuit, the calculated energy with an energy threshold; and

determining, by a processor circuit, that a push occurred if the determined pose angle is below the pose angle threshold and the calculated energy is above the energy threshold.

6. The method of claim 5, wherein tracking pushes by the wheelchair user comprises:

storing pose angles and calculated energies for the wheelchair user;

updating, by a processor circuit, the pose angle threshold using the stored pose angles; and

updating, by a processor circuit, the energy threshold using the stored calculated energies.

7. The method of claim 6, wherein storing pose angles and calculated energies for the wheelchair user comprises:

calculating, by a processor circuit, a current push rate for the user;

determining, by a processor circuit, if the current push rate is consistent with previous push rates; and

storing the determined pose angle and calculated energy if the current push rate is consistent with previous push rates.

8. The method of claim 6, wherein storing pose angles and calculated energies for the wheelchair user comprises:

determining, by a processor circuit, a current speed for the user using a Global Positioning System (GPS) sensor; and

storing the determined pose angle and calculated energy if the user'"'"'s current speed is greater than or equal to a minimum speed threshold.

9. The method of claim 6, wherein:

updating the pose angle threshold comprises calculating a candidate pose angle threshold as a percentile of stored pose angles; and

updating the energy threshold comprises calculating a candidate energy threshold as a percentile of stored calculated energies.

10. The method of claim 9, wherein:

updating the pose angle threshold comprises calculating a new pose angle threshold using the candidate pose angle threshold and a first low-pass filter; and

updating the energy threshold comprises calculating a new energy threshold using the candidate energy threshold and a second low-pass filter.

11. The method of claim 3, wherein tracking pushes by the wheelchair user comprises:

selecting by a processor circuit a dominant motion sensor axis based on a calculated motion energy per motion sensor axis.

12. The method of claim 11, wherein tracking pushes by the wheelchair user comprises:

calculating, by a processor circuit, a motion energy for each motion sensor axis; and

selecting, by a processor circuit, a motion sensor axis with a most energy as a dominant motion sensor axis.

13. The method of claim 11, wherein tracking pushes by the wheelchair user comprises:

performing, by a processor circuit, a frequency domain transformation of the collected motion data for the dominant motion sensor axis; and

determining, by a processor circuit, a fundamental push frequency based on the frequency domain transformed data;

14. The method of claim 13, wherein the frequency domain transformation comprises a fast Fourier transform (FFT) operation, wherein detecting that a push occurred comprises:

determining, by a processor circuit, a FFT peak of a lowest frequency that rises above a pre-determined threshold level of energy; and

selecting, by a processor circuit, the lowest frequency as a fundamental frequency of pushing.

15. The method of claim 13, wherein tracking pushes by the wheelchair user comprises:

filtering the collected data including adjusting an intelligent filter to pass motion sensor signals within a frequency band corresponding to the fundamental push frequency and to reduce motion sensor signals within a frequency band corresponding to harmonics of the fundamental push frequency.

16. The method of claim 15, wherein the intelligent filter comprises a low-pass filter with adjustable passband width.

17. The method of claim 16, wherein the intelligent filter comprises a bank of low-pass filters with increasing passband widths.

18. The method of claim 16, wherein the intelligent filter comprises an adjustable bandpass filter with adjustable passband cutoff frequencies and widths.

19. The method of claim 3, wherein tracking pushes by the wheelchair user comprises:

filtering, by a processor circuit, the collected motion data to produced filtered motion data; and

determining, by a processor circuit, a push count based on zero-crossings of the filtered motion data.

20. The method of claim 3, wherein determining a push count comprises:

detecting, by a processor circuit, one or more zero-crossings of the filtered motion data in one direction; and

determining, by a processor circuit, a push count equal to the number of zero-crossings.

21. The method of claim 3, further comprising:

cross-checking, by a processor circuit, the determined push count with motion data from a different motion sensor axis.

22. The method of claim 1, wherein detecting that one or more activities by the wheelchair user occurred comprises detecting when a wheelchair user is traveling on a ramp.

23. The method of claim 22, wherein detecting when the wheelchair user is traveling on a ramp comprises:

determining, by a processor circuit, a ramp classification based on the collected motion data; and

filtering, by a processor circuit, the determined ramp classification using a filter.

24. The method of claim 23, wherein determining a ramp classification comprises determining a ramp classification based on a push rate, a first push rate threshold, an energy component of the collected motion data, and at least one of a first energy threshold, a second energy threshold, a pose angle, a pose angle threshold, and a second push rate threshold.

25. The method of claim 24, wherein detecting when the wheelchair user is traveling on a ramp comprises comparing, by a processor circuit, the push rate with the first push rate threshold, and at least one of:

comparing, by a processor circuit, the energy component of the collected motion data with the first energy threshold;

comparing, by a processor circuit, the pose angle with the pose angle threshold;

comparing, by a processor circuit, the energy component of the collected motion data with the second energy threshold; and

comparing, by a processor circuit, the push rate with the second push rate threshold.

26. The method of claim 24, wherein detecting when the wheelchair user is traveling on a ramp comprises:

obtaining per-user thresholds; and

adjusting, by a processor circuit, at least one of the first and second push rate thresholds, the first and second energy thresholds, and the pose angle threshold using the per-user thresholds.

27. The method of claim 23, wherein the filter comprises a windowing filter.

28. The method of claim 27, wherein the windowing filter comprises an odd number of points in the window.

29. The method of claim 28, wherein the windowing filter comprises a three-point window.

30. The method of claim 22, wherein detecting when the wheelchair user is traveling on a ramp comprises:

collecting elevation information by an elevation detection module of the user device; and

determining, by a processor circuit, the ramp classification based on the collected elevation information.

31. The method of claim 22, wherein detecting when the wheelchair user is traveling on a ramp comprises:

measuring the user'"'"'s heart rate by a heart rate monitor of the user device; and

determining, by the processor circuit, the ramp classification based on the measured heart rate.

32. The method of claim 1 wherein detecting that one or more activities by the wheelchair user occurred comprises detecting wheelchair user stroke type, wherein detecting the wheelchair user stroke type comprises:

measuring X axis and Y axis accelerometer data from an accelerometer located on an arm of the user;

detecting a Y axis accelerometer peak corresponding to a push phase;

determining adjacent zero crossings to the Y axis accelerometer peak to determine the start and end of the push phase and a return phase;

determining a length of the push phase;

detecting X peaks in X axis accelerometer data during the return phase;

detecting Y peaks in Y axis accelerometer data during the return phase;

determining signs for the X peaks and the Y peaks;

determining an ordered sequence of the determined X signs;

determining an ordered sequence of the determined Y signs;

determining stroke type based on the sequence of X signs and the sequence of Y signs; and

applying one of the determined stroke type and the determined push phase length in a calorie expenditure tracking system.

33. The method of claim 1 wherein estimating the energy expenditure by the user comprises:

measuring at least one of X accelerometer data, Y accelerometer data, Z accelerometer data, X rotational data, Y rotational data, Z rotational data, barometer data, altimeter data, GPS position data, GPS speed data, GPS altitude data, and heart rate data;

receiving user input regarding at least one of fitness level, age, weight, injury type, and mobility level;

determining an estimated speed based on the measured data;

determining an estimated MET value based on the estimated speed;

determining a ramp state based on the measured data;

refining the estimated MET value based on the determined ramp state;

determining an energy expenditure estimate based on the estimated MET value;

determining a physiological efficiency estimate based on the user input;

refining the physiological efficiency estimate based on the measured data;

refining the energy expenditure estimate using the physiological efficiency estimate; and

applying the refined energy expenditure estimate in a calorie expenditure tracking system.

34. The method of claim 1, wherein detecting that one or more activities by the wheelchair user occurred comprises detecting when the wheelchair user is engaging in a transfer from or shift in the wheelchair, the method comprising:

collecting motion data of a user device located on an appendage of the user;

extracting, by a processor circuit, one or more features of interest from the collected motion data;

detecting, by a processor circuit, that the user engaged in a wheelchair shift or transfer based on the one or more features and one or more corresponding thresholds for the one or more features;

in response to detecting the wheelchair shift or transfer, updating a current state of a state machine; and

triggering a reminder to the user based on the current state of the state machine.

35. A system for tracking activity by a wheelchair user comprising:

a motion sensor located on an appendage of the user and configured to collect motion data;

a processor circuit coupled to the motion sensor and configured to execute instructions causing the processor circuit to;

collect motion data of a user device located on an appendage of the user;

detect, by a processor circuit, that one or more activities by the wheelchair user occurred based on the motion data;

calculate, by a processor circuit, an energy expenditure by the user based detecting that the one or more activities by the wheelchair user occurred; and

output, by a processor circuit, the energy expenditure estimation.