Method and apparatus for position and motion sensing

• US 7,054,687 B1
• Filed: 08/29/2002
• Issued: 05/30/2006
• Est. Priority Date: 02/24/2000
• Status: Expired due to Term

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Andersen, Dean, Ryat, Marc
• Primary Examiner(s): Jastrzab, Jeffrey R.
• Assistant Examiner(s): ALTER, ALYSSA MARGO
• Application Number:
  US10/232,044
• Time in Patent Office: 1,370 Days
• Field of Search: 607/6, 607/9, 607/17, 607/18, 607/19, 600/509, 600/516, 600/517, 600/521
• US Class Current: 607/19
• CPC Class Codes: A61B 5/1112 Global tracking of patients, e.g. by using GPS
• CPC Class Codes: A61B 5/1116 Determining posture transitions
• CPC Class Codes: A61B 5/1118 Determining activity level
• CPC Class Codes: A61N 1/36542 controlled by body motion, e.g. acceleration

Abstract

An apparatus for extracting activity information and position information from a composite signal generated by a motion sensor includes an analog to digital converter for converting the composite signal from analog to digital format. A wide-band low pass filter having a frequency response of about zero hertz to about ten hertz and a narrow low pass filter having a frequency response of about zero hertz to about 0.5 hertz filter the digitized composite signal. An adder subtracts the output of the narrow-band low pass filter from the output of the wide-band low pass filter. The resulting difference represents information regarding the activity level of the motion sensor, and the output of the narrow-band low pass filter represents information regarding the position of the sensor.

Claims

1. A method for separating information representing position of a patient from information representing the patient'"'"'s level of activity in a composite signal, said method comprising:

sigma-delta converting said composite signal into a digitized composite signal;

filtering said digitized composite signal to produce a filtered signal, wherein said filtered signal includes information from said composite signal representing the patient'"'"'s position; and

subtracting said filtered signal from said digitized composite signal to produce a difference signal, wherein said difference signal includes information from said composite signal representing the patient'"'"'s level of activity.

2. The method of claim 1, further comprising:

rectifying said difference signal to produce a rectified difference signal; and

integrating said rectified difference signal.

3. The method of claim 1, wherein said filtering passes frequencies in a range of about zero hertz to about 0.5 hertz.

4. The method of claim 1, wherein said filtering passes frequencies in a range of about zero hertz to about one hertz.

5. An apparatus for separating information representing position of a patient from information representing the patient'"'"'s level of activity in a composite signal, said apparatus comprising:

converting means for converting said composite signal to digital format to produce a digitized composite signal;

filtering means for filtering said digitized composite signal to produce a filtered digitized composite signal, wherein said filtered digitized composite signal includes information from said composite signal representing the patient'"'"'s position; and

subtracting means for subtracting said filtered digitized composite signal from said digitized composite signal to produce a difference signal, wherein said difference signal includes information representing the patient'"'"'s level of activity.

6. The apparatus of claim 5, wherein said converting means comprises a sigma-delta converter.

7. The apparatus of claim 6, wherein said sigma-delta converter has a frequency response of about zero hertz to about ten hertz, and said filtering means has a frequency response of about zero hertz to about 0.5 hertz.

8. The apparatus of claim 6, wherein said sigma-delta converter has a frequency response of about zero hertz to about twenty hertz, and said filtering means has a frequency response of about zero hertz to about one hertz.

9. The apparatus of claim 5, wherein said converting means comprises an analog to digital converter and a low pass filter.

10. The apparatus of claim 9, wherein said low pass filter has a frequency response of about zero hertz to about ten hertz, and said filtering means has a frequency response of about zero hertz to about 0.5 hertz.

11. The apparatus of claim 9, wherein said low pass filter has a frequency response of about zero hertz to about twenty hertz, and said filtering means has a frequency response of about zero hertz to about one hertz.

12. The apparatus of claim 5, further comprising means for generating said composite signal.

13. An apparatus for separating information representing position of a patient from information representing the patient'"'"'s level of activity in a composite signal, said apparatus comprising:

a sigma-delta converter configured to receive as an input said composite signal;

a filter configured to receive as an input an output of said sigma-delta converter, wherein an output of said filter includes information from said composite signal representing the patient'"'"'s position; and

an adder configured to subtract said output of said filter from said output of said sigma-delta converter, wherein an output of said adder includes information from said composite signal representing the patient'"'"'s level of activity.

14. The apparatus of claim 13, further comprising a motion sensor for generating said composite signal.

15. The apparatus of claim 14, wherein said motion sensor comprises a microelectomechanical system.

16. The apparatus of claim 14, wherein said motion sensor comprises an accelerometer.

17. The apparatus of claim 13, wherein a data capacity of said adder is sufficiently limited that subtraction of a positive number from a smaller positive number produces a positive number.

18. The apparatus of claim 17, further comprising:

a rectifier configured to receive as an input said output of said adder; and

an integrator configured to receive as an input an output of said rectifier.

19. The apparatus of claim 18, wherein said rectifier includes a comparator.

20. The apparatus of claim 13, wherein said frequency response of said filter is about zero hertz to about 0.5 hertz.

21. The apparatus of claim 13, wherein said frequency response of said filter is about zero hertz to about one hertz.

22. The apparatus of claim 13, wherein said sigma-delta converter has a frequency response of about zero hertz to about ten hertz.

23. The apparatus of claim 13, wherein said sigma-delta converter has a frequency response of about zero hertz to about twenty hertz.