PEDOMETER DEVICE AND STEP DETECTION METHOD USING AN ALGORITHM FOR SELF-ADAPTIVE COMPUTATION OF ACCELERATION THRESHOLDS

• US 20070143068A1
• Filed: 10/02/2006
• Published: 06/21/2007
• Est. Priority Date: 10/03/2005
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Binda, Ivo, Pasolini, Fabio
• Granted Patent: US 7,463,997 B2
• Time in Patent Office: Days
• US Class Current: 702/160
• CPC Class Codes: G01C 22/006 Pedometers

Abstract

In a pedometer device for detecting and counting steps of a user on foot, an accelerometer sensor detects a vertical acceleration generated during the step. A processing unit, connected to the accelerometer sensor, processes an acceleration signal relating to the acceleration in order to detect the occurrence of a step, and in particular compares the acceleration signal with a first reference threshold. The processing unit automatically adapts the first reference threshold as a function of the acceleration signal. In particular, the processing unit modifies the first reference threshold as a function of an envelope of the amplitude of the acceleration signal.

Claims

1. A pedometer device for detecting and counting the steps of a user, comprising:

an accelerometer sensor configured to detect an acceleration generated during a step; and

a processing unit connected to said accelerometer sensor, and configured to process an acceleration signal relating to said acceleration to detect the occurrence of a step, said processing unit including;

first comparator means for comparing said acceleration signal with a first reference threshold, and

threshold-adaptation means for modifying said first reference threshold as a function of said acceleration signal.

2. The device according to claim 1, wherein said processing unit further comprises envelope-calculation means for calculating an envelope of an amplitude of said acceleration signal, and wherein said threshold-adaptation means are configured to modify automatically said first reference threshold as a function of said envelope.

3. The device according to claim 2, wherein said threshold-adaptation means are configured to assign to said first reference threshold a value equal to a fraction of the value of said envelope, in particular, said fraction being smaller than 1.

4. The device according to claim 3, wherein said fraction is approximately 0.65.

5. The device according to claim 3, wherein said processing unit further comprises:

length-estimation means for determining an estimated step length at each detection of a step, as a function of a maximum value of said first reference threshold; and

distance-calculation means for calculating a distance traveled by said user as a function of said estimated step length.

6. The device according to claim 1, wherein said first reference threshold has positive values, and wherein said processing unit further comprises second comparator means for comparing said acceleration signal with a second reference threshold having negative values;

and wherein said threshold-adaptation means are further configured to modify automatically said second reference threshold as a function of said acceleration signal, in particular as a function of an envelope of an amplitude of said acceleration signal.

7. The device according to claim 6, wherein said first and second reference thresholds have, in absolute value, a respective lower-limit value, and wherein said processing unit further comprises setting means for setting said lower-limit value.

8. The device according to claim 6, wherein said processing unit is configured to detect the occurrence of a step, when said acceleration signal has a given relation with said first reference threshold, and subsequently with said second reference threshold within a given time interval.

9. The device according to claim 1, wherein said processing unit further comprises:

mean-value calculation means for calculating a d.c. component of the acceleration detected by said accelerometer sensor;

eliminating said d.c. component from said acceleration; and

producing said acceleration signal.

10. The device according to claim 1, wherein said accelerometer sensor is a MEMS sensor, and said acceleration is directed along a vertical axis.

11. The device according to claim 10, wherein said processing unit further comprises axis-determination means for determining a vertical axis of detection of said accelerometer sensor, along which said acceleration is to be detected.

12. An electronic mobile phone, comprising:

a pedometer device for detecting and counting the steps of a user, the pedometer device including;

an accelerometer sensor configured to detect an acceleration generated during a step; and

a processing unit connected to said accelerometer sensor, and configured to process an acceleration signal relating to said acceleration to detect the occurrence of a step, said processing unit including;

first comparator means for comparing said acceleration signal with a first reference threshold, and

threshold-adaptation means for modifying said first reference threshold as a function of said acceleration signal.

13. The mobile phone according to claim 12, wherein said processing unit further comprises envelope-calculation means for calculating an envelope of an amplitude of said acceleration signal, and wherein said threshold-adaptation means are configured to modify automatically said first reference threshold as a function of said envelope.

14. The mobile phone according to claim 12, wherein said first reference threshold has positive values, and wherein said processing unit further comprises second comparator means for comparing said acceleration signal with a second reference threshold having negative values;

and wherein said threshold-adaptation means are further configured to modify automatically said second reference threshold as a function of said acceleration signal, in particular as a function of an envelope of an amplitude of said acceleration signal.

15. The mobile phone according to claim 14, wherein said first and second reference thresholds have, in absolute value, a respective lower-limit value, and wherein said processing unit further comprises setting means for setting said lower-limit value.

16. The mobile phone according to claim 12, wherein said processing unit further comprises:

mean-value calculation means for calculating a d.c. component of the acceleration detected by said accelerometer sensor;

eliminating said d.c. component from said acceleration; and

producing said acceleration signal.

17. A step detection method for detecting steps in the gait of a user, comprising:

producing an acceleration signal relating to an acceleration generated during a step; and

processing said acceleration signal to detect the occurrence of the step, the processing step including;

comparing said acceleration signal with a first reference threshold, and

modifying said first reference threshold as a function of said acceleration signal.

18. The method according to claim 17, wherein the processing step further comprises calculating an envelope of an amplitude of said acceleration signal, and wherein the modifying step comprises modifying automatically said first reference threshold as a function of said envelope.

19. The method according to claim 18, wherein the modifying step comprises assigning to said first reference threshold a value equal to a fraction of the value of said first envelope;

in particular said fraction being smaller than 1.

20. The method according to claim 19, wherein the fraction is approximately 0.65

21. The method according to claim 19, wherein the processing step further comprises:

determining an estimated step length at each step detection, as a function of a maximum value of said first reference threshold; and

calculating a distance traveled by said user as a function of said estimated step length.

22. The method according to claim 17, wherein said first reference threshold has positive values;

and wherein the processing step further comprises comparing said acceleration signal with a second reference threshold having negative values; and

the modifying step further comprises modifying automatically said second reference threshold as a function of said acceleration signal, in particular as a function of an envelope of said acceleration signal.

23. The method according to claim 22, wherein said first and second reference thresholds have, in absolute value, a respective lower-limit value, and wherein the processing step comprises setting said positive and negative lower-limit values.

24. The method according to claim 22, wherein the processing step comprises detecting the occurrence of a step, when said acceleration signal has a given relation with said first reference threshold, and subsequently with said second reference threshold within a given time interval.

25. The method according to claim 17, wherein producing an acceleration signal further comprises:

calculating a d.c. component of said acceleration; and

eliminating said d.c. component from said acceleration to produce said acceleration signal.

26. The method according to claim 17, wherein producing an acceleration signal further comprises determining a vertical axis of detection along which said acceleration is to be detected.