Cadence Detection Based on Inertial Harmonics

• US 20150366509A1
• Filed: 01/06/2014
• Published: 12/24/2015
• Est. Priority Date: 01/09/2013
• Status: Active Grant

• Current Assignee: Yukka Magic LLC
• Original Assignee: Valencell, Inc.
• Inventors: Romesburg, Eric Douglas
• Granted Patent: US 9,993,204 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2562/0214 Capacitive electrodes
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 2562/0233 Special features of optical sensors or probes classified in A61B5/00
• CPC Class Codes: A61B 2562/028 Microscale sensors, e.g. electromechanical sensors [MEMS]
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/112 Gait analysis
• CPC Class Codes: A61B 5/6817 Ear canal
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61B 5/7235 Details of waveform analysis A61B5/349 takes precedence
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: G01C 22/006 Pedometers

Abstract

The method and apparatus disclosed herein determine a user cadence from the output of an inertial sensor mounted to or proximate the user'"'"'s body. In general, the disclosed cadence measurement system determines the user cadence based on frequency measurements acquired from an inertial signal output by the inertial sensor. More particularly, a cadence measurement system determines a user cadence from an inertial signal generated by an inertial sensor, where the inertial signal comprises one or more frequency components. The cadence measurement system determines a peak frequency of the inertial signal, where the peak frequency corresponds to the frequency component of the inertial signal having the largest amplitude. After applying the peak frequency to one or more frequency threshold comparisons, the cadence measurement system determines the user cadence based on the peak frequency and the frequency threshold comparison(s).

Claims

1-50. -50. (canceled)

51. A method of determining a user cadence from an inertial signal generated by an inertial sensor and comprising one or more frequency components, the method comprising:

determining a peak frequency of the inertial signal, said peak frequency corresponding to the frequency component having the largest amplitude;

applying the peak frequency to one or more frequency threshold comparisons; and

determining the user cadence based on the peak frequency and the one or more frequency threshold comparisons.

52. The method of claim 51 further comprising determining a spectral signal based on a frequency transform of the inertial signal, wherein determining the peak frequency comprises determining a frequency of a peak of the spectral signal.

53. The method of claim 51 wherein determining the user cadence comprises calculating the user cadence based on the peak frequency and a previous user cadence when the peak frequency exceeds a frequency threshold.

54. The method of claim 53 wherein calculating the user cadence based on the peak frequency and the previous user cadence comprises:

determining two or more test user cadences based on the peak frequency; and

setting the user cadence to the test user cadence closest to the previous user cadence.

55. The method of claim 51 wherein determining the user cadence comprises setting the user cadence equal to the peak frequency divided by a harmonic factor when the peak frequency is less than a frequency threshold.

56. The method of claim 55 wherein the harmonic factor comprises one of ½

, 1, 3/2, and 2.

57. The method of claim 51 further comprising:

determining a power of the inertial signal; and

comparing the power to a power threshold;

wherein determining the user cadence further comprises determining the user cadence based on a comparison between the power and the power threshold.

58. The method of claim 51 further comprising determining whether the peak frequency is ramping up from a first low frequency value, wherein determining the user cadence further comprises determining the user cadence based on whether the peak frequency is ramping up from the first low frequency value.

59. The method of claim 51 further comprising:

determining a power of the inertial signal;

comparing the power to a power threshold; and

comparing the peak frequency to a frequency threshold;

wherein determining the user cadence comprises determining the user cadence based on the peak frequency and a previous user cadence when the power is less than the power threshold and the peak frequency exceeds the frequency threshold.

60. The method of claim 51 further comprising:

determining a power of the inertial signal; and

comparing the power to a power threshold; and

comparing the peak frequency to a frequency threshold;

determining whether sprinting is possible based on user input;

if sprinting is possible, determining the user cadence based on the one or more frequency threshold comparisons under sprinting conditions when the power exceeds the power threshold or the peak frequency is less than the frequency threshold; and

if sprinting is not possible, determining the user cadence based on one or more frequency threshold comparisons under non-sprinting conditions when the power exceeds the power threshold or the peak frequency is less than the frequency threshold.

61. The method of claim 51 further comprising determining at least one frequency threshold based on a previous user cadence.

62. The method of claim 51 further comprising determining at least one frequency threshold based on an inertial power of the inertial signal.

63. The method of claim 51 further comprising determining at least one frequency threshold based on an empirical value.

64. The method of claim 51 further comprising determining a user activity parameter based on user input, wherein determining the user cadence comprises determining the user cadence based on the user activity parameter and the one or more frequency threshold comparisons.

65. The method of claim 51 wherein the inertial sensor comprises at least one of an accelerometer, a Micro-Electro-Mechanical System (MEMS) device, an optical sensor, a gyroscope, an opto-mechanical sensor, a blocked channel sensor, a capacitive sensor, and a piezoelectric sensor.

66. The method of claim 51 further comprising using the determined user cadence as a noise reference to attenuate motion artifacts from a physiological signal.

67. A cadence measurement system configured to determine a user cadence comprising:

an inertial sensor configured to output an inertial signal comprising one or more frequency components; and

a cadence circuit operatively connected to the inertial sensor, said cadence circuit comprising;

a peak frequency circuit configured to determine a peak frequency of the inertial signal, said peak frequency corresponding to the frequency component having the largest amplitude;

a comparison circuit configured to apply the peak frequency to one or more frequency threshold comparisons; and

a cadence processor configured to determine the user cadence based on the peak frequency and the one or more frequency threshold comparisons.

68. The cadence measurement system of claim 67 wherein the peak frequency circuit comprises a spectral circuit configured to:

determine a spectral signal based on a frequency transform of the inertial signal; and

determine the peak frequency by determining a frequency of a peak of the spectral signal.

69. The cadence measurement system of claim 67 wherein the cadence circuit further comprises a memory operative to store a previous user cadence, wherein the cadence processor determines the user cadence by calculating the user cadence based on the peak frequency and the previous user cadence when the peak frequency exceeds a frequency threshold.

70. The cadence measurement system of claim 69 wherein the cadence processor is further configured to determine two or more test user cadences based on the peak frequency, and wherein the cadence processor determines the user cadence by setting the cycle user cadence equal to the test user cadence closest to the previous user cadence.