Adaptive filtering for presence detection

• US 9,826,082 B2
• Filed: 02/12/2015
• Issued: 11/21/2017
• Est. Priority Date: 02/12/2015
• Status: Active Grant

• Current Assignee: Motorola Mobility LLC (Lenovo Group Ltd.)
• Original Assignee: Motorola Mobility LLC (Lenovo Group Ltd.)
• Inventors: Alameh, Rachid M, Bousley, Adam J, Merrell, Thomas Y
• Primary Examiner(s): Ajibade Akonai, Olumide T
• Application Number:
  US14/620,257
• Publication Number:
  US 20160241704A1
• Time in Patent Office: 1,013 Days
• CPC Class Codes: H04M 1/67 by electronic means
• CPC Class Codes: H04M 1/72454 according to context-related or environment-related conditions
• CPC Class Codes: H04W 52/0251 using monitoring of local events, e.g. events related to user activity
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A system and method for sensing a user presence via thermal signature sensing employs adaptive filtering of a motion spectrum to discern a user presence signature over background thermal noise. In an embodiment, adaptive sub-band filters are applied within the motion spectrum, and a user presence is indicated by the presence of a thermal signature having at least a predetermined magnitude or profile within any searched sub-band. In an embodiment, a low pass filter is applied to search for a stationary presence if the sub-band search procedure does not yield a user thermal signature.

Claims

1. An electronic device with thermal user-sensing, the electronic device comprising:

a device housing;

a thermal sensor at least partially within the device housing; and

a device controller configured to sense a user presence via the thermal sensor by searching for a thermal signature of at least a predetermined magnitude or profile within a predetermined frequency band, wherein searching within the predetermined frequency band comprises searching within each of a plurality of sub-bands within the predetermined frequency band, and determining that a user is present if a thermal signature of at least the predetermined magnitude or profile is detected within any searched sub-band, and to stop searching within the predetermined frequency band when a user presence is detected, and to switch to a single filter over the entire predetermined frequency band when an overall thermal signal strength exceeds a predetermined switch limit.

2. The electronic device in accordance with claim 1, wherein the predetermined frequency band primarily extends from about 0.1 Hz to about 6 Hz, and wherein the device controller is further configured to determine a user speed of motion based on which searched sub-band yielded the thermal signature of at least the predetermined magnitude or profile.

3. The electronic device in accordance with claim 2, wherein the predetermined frequency band further comprises a separate sub-band that includes 0 Hz representing a motionless state.

4. The electronic device in accordance with claim 1, wherein the controller is further configured to search within the predetermined frequency band by switching among a plurality of sub-band filters corresponding to the plurality of sub-bands.

5. The electronic device in accordance with claim 4, wherein the width and number of the plurality of sub-band filters is selected based on overall thermal signal strength, wherein sub-band filter width increases continuously or discretely with increasing overall thermal signal strength, whereas the number of sub-band filters decreases continuously or discretely with increasing overall thermal signal strength.

6. The electronic device in accordance with claim 1, wherein the controller is further configured to search within the predetermined frequency band by sweeping a sub-band frequency filter through the entire spectrum of the predetermined frequency band.

7. The electronic device in accordance with claim 1, wherein the controller is further configured to search within the predetermined frequency band by starting the search at a first frequency and proceeding to a second frequency, the first frequency being higher than the second frequency.

8. The electronic device in accordance with claim 7, wherein the widths of the plurality of sub-band filters vary based on overall thermal signal strength, wherein higher overall thermal signal strengths correspond continuously or discretely to broader widths for each of the plurality sub-band filters.

9. A method of thermal user-sensing within an electronic device having a thermal sensor, the method comprising:

searching for a thermal signature of a predetermined amplitude range or profile within a predetermined frequency band by searching within each of a plurality of sub-bands within the predetermined frequency band;

determining that a user is present if a thermal signature of at least the predetermined amplitude range or profile is detected within any searched sub-band;

stopping searching within the predetermined frequency band when a user presence is detected; and

switching to searching with a single filter over the entire predetermined frequency band when an overall thermal signal strength exceeds a predetermined switch limit.

10. The method in accordance with claim 9, wherein the predetermined frequency band primarily extends from about 0.1 Hz to about 6 Hz, the method further comprising determining a user speed of motion based on which searched sub-band yielded the thermal signature of at least the predetermined amplitude range or profile.

11. The method in accordance with claim 10, wherein the predetermined frequency band further comprises a separate sub-band that includes 0 Hz.

12. The method in accordance with claim 9, wherein searching within each of the plurality of sub-bands within the predetermined frequency band comprises switching among a plurality of sub-band filters corresponding to the plurality of sub-bands.

13. The method in accordance with claim 9, wherein searching within each of the plurality of sub-bands within the predetermined frequency band comprises sweeping a sub-band narrow band pass frequency filter through the entire spectrum of the predetermined frequency band.

14. The method in accordance with claim 9, wherein the width and number of sub-bands is selected based on overall thermal signal strength such that a higher overall thermal signal strength is associated with a lower number of sub-bands and a broader width for each sub-band.

15. A method of determining user presence from a portable electronic device comprising:

detecting an overall thermal signal magnitude;

searching for a thermal signature of a user within a predetermined spectrum by searching for a user thermal signature within each of a predetermined number of sub-bands which together span the predetermined spectrum, wherein the bandwidth and number of the predetermined number of sub-bands are selected in a continuous or discrete manner based on the overall thermal signal magnitude; and

stopping searching and indicating a user presence when a user thermal signature is detected prior to all sub-bands being searched, and stopping searching and indicating a lack of user presence when a user thermal signature has not been detected when all sub-bands have been searched.