MONITORING THE CHANGE IN HEIGHT OF A DEVICE USING AN AIR PRESSURE SENSOR

• US 20150025817A1
• Filed: 03/11/2013
• Published: 01/22/2015
• Est. Priority Date: 03/13/2012
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Ten Kate, Warner Rudolph Theophile
• Granted Patent: US 9,664,584 B2
• Time in Patent Office: Days
• US Class Current: 702/50
• CPC Class Codes: A61B 2560/0242 adapted to measure environmental factors, e.g. temperature, pollution
• CPC Class Codes: A61B 5/1117 Fall detection
• CPC Class Codes: A61B 5/1118 Determining activity level
• CPC Class Codes: G01C 5/06 by using barometric means
• CPC Class Codes: G01L 27/002 Calibrating, i.e. establishing true relation between transducer output value and value to be measured, zeroing, linearising or span error determination
• CPC Class Codes: G01L 7/00 Measuring the steady or quasi-steady pressure of a fluid or a fluent solid material by mechanical or fluid pressure-sensitive elements G01L11/004 takes precedence; transmitting or indicating the displacement of mechanical pressure-sensitive elements by electric , e.g., photoelectric or magnetic means G01L9/00; measuring differences of two or more pressure values G01L13/00; measuring two or more pressure values simultaneously G01L15/00
• CPC Class Codes: G08B 21/043 detecting an emergency event, e.g. a fall
• CPC Class Codes: G08B 21/0446 worn on the body to detect changes of posture, e.g. a fall, inclination, acceleration, gait

Abstract

There is provided a method of monitoring a change in height of a device, the device comprising a sensor for measuring the air pressure at the device, the method comprising determining a pressure change threshold from a pre-determined height change and an estimate or measurement of air pressure; obtaining a plurality of measurements of the air pressure at the device; determining a change in the air pressure from two or more of the measurements; and determining if the height of the device has changed by more than the pre-determined height change using the determined change in the air pressure and the determined pressure change threshold.

Claims

1. A method of monitoring a change in height of a device, the device comprising a sensor for measuring the air pressure at the device, the method comprising:

determining a pressure change threshold from a predetermined height change and an estimate of air pressure or a measurement of air pressure at the device;

obtaining a plurality of measurements of the air pressure at the device;

determining a change in the air pressure from two or more of the plurality of measurements; and

determining if the height of the device has changed by more than the predetermined height change using the determined change in the air pressure and the determined pressure change threshold.

2. A method as claimed in claim 1, wherein the step of determining the pressure change threshold comprises determining the pressure change threshold from the predetermined height change and an estimate of air pressure at a predetermined altitude.

3. A method as claimed in claim 1, wherein the step of determining the pressure change threshold comprises determining a pressure change threshold from the predetermined height change and at least one measurement of the air pressure at the device.

4. A method as claimed in claim 1, wherein the step of determining a pressure change threshold is repeated using at least one new measurement of the air pressure at the device.

5. A method as claimed in claim 1, wherein the step of determining a pressure change threshold comprises evaluating

Δ

P∝

−

γ

Δ

H

where Δ

P is the pressure change threshold, γ

is dependent on pressure and Δ

H is the predetermined height change.

6. A method as claimed in claim 1, wherein the step of determining if the height of the device has changed by more than the predetermined height change comprises comparing the determined change in the air pressure to the determined pressure change threshold.

7. A method as claimed in claim 1, wherein the step of determining if the height of the device has changed by more than the predetermined height change comprises normalizing the determined change in the air pressure and determining a likelihood that the height of the device has changed by more than the predetermined height change from the normalized change in air pressure.

8. A method as claimed in claim 1, further comprising the steps of:

determining the effective pressure that gravity and/or other accelerations superimpose on each of the measurements of air pressure by the sensor; and

correcting each of the measurements of air pressure for the determined effective pressure.

9. A method as claimed in claim 8, wherein determining the effective pressure that gravity and/or other accelerations superimpose on a measurement of air pressure comprises:

obtaining a measurement of the acceleration acting on the device at or around the time that the measurement of air pressure at the device was made by the sensor; and

determining the effective pressure using the measurement of the acceleration and a calibration factor.

10. A method as claimed in claim 1, the method further comprising the step of:

obtaining an estimate or a measurement of the temperature of the environment around the device;

and wherein the step of determining a pressure change threshold comprises determining the pressure change threshold from the threshold height change, at least one of the plurality of measurements of the air pressure at the device and the estimate or measurement of the temperature of the environment around the device.

11. A method as claimed in claim 10, wherein the step of determining a pressure change threshold comprises evaluating:

Δ

P=−

γ

Δ

H

where Δ

P is the pressure change threshold, γ

is dependent on air pressure and temperature of the environment around the device and Δ

H is the predetermined height change.

15. A computer program product, comprising a computer readable medium having computer program code embodied therein, the computer program code being configured such that, when executed by a suitable computer or processor, the computer or processor performs the method as claimed in claim 1.

12. An apparatus for monitoring a change in height of a device that comprises an air pressure sensor for measuring the air pressure at the device, the apparatus comprising:

a processing unit configured to;

determine a pressure change threshold from a predetermined height change and an estimate of air pressure or a measurement of air pressure at the device;

receive a plurality of measurements of the air pressure at the device;

determine a change in the air pressure from two or more of the plurality of measurements; and

determine if the height of the device has changed by more than the predetermined height change using the determined change in the air pressure to and the determined pressure change threshold.

13. A user device that is configured to be worn by a user, the device comprising:

an air pressure sensor that measures the air pressure at the device; and

an apparatus as claimed in claim 12.

14. A system, comprising:

a device that is configured to be worn by a user, the device comprising an air pressure sensor that measures the air pressure at the device; and

a base unit or other electronic device that is remote from the device and that is configured to communicate with the device to receive measurements of the air pressure at the device, the base unit or other electronic device comprising an apparatus as claimed in claim 12.