Method and apparatus for characterizing movement of a mass within a defined space

• US 6,051,981 A
• Filed: 11/30/1998
• Issued: 04/18/2000
• Est. Priority Date: 02/03/1994
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Gershenfeld, Neil, Smith, Joshua R.
• Primary Examiner(s): BROWN, GLENN WARNER
• Application Number:
  US09/201,336
• Time in Patent Office: 505 Days
• Field of Search: 324/663, 324/725, 324/690, 324/661, 324/662, 324/687, 324/688, 324/452, 324/457, 324/658, 324/671, 324/676, 324/678
• US Class Current: 324/663
• CPC Class Codes: B60N 2/002 Seats provided with an occupancy detection means mounted therein or thereon detection means responsive to presence or absence of children B60N2/266
• CPC Class Codes: B60N 2/28 Seats readily mountable on, and dismountable from, existing seats or other parts of the vehicle
• CPC Class Codes: B60N 2/286 forward facing B60N2/2866 takes precedence
• CPC Class Codes: B60N 2/2863 backward facing
• CPC Class Codes: B60R 21/01532 using electric or capacitive field sensors
• CPC Class Codes: B60R 21/01556 Child-seat detection systems
• CPC Class Codes: G01B 7/003 for measuring position, not involving coordinate determination coordinate measuring G01B7/004
• CPC Class Codes: G01B 7/004 for measuring coordinates of points
• CPC Class Codes: G01D 5/24 by varying capacitance
• CPC Class Codes: G01V 3/088 operating with electric fields G01V3/082 takes precedence
• CPC Class Codes: G06F 3/011 Arrangements for interaction with the human body, e.g. for user immersion in virtual reality blind teaching G09B21/00
• CPC Class Codes: G06F 3/017 Gesture based interaction, e.g. based on a set of recognized hand gestures interaction based on gestures traced on a digitiser G06F3/04883
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 2217/94052 with evaluation of actuation pattern or sequence, e.g. tapping
• CPC Class Codes: H03K 2217/960775 Emitter-receiver or "fringe" type detection, i.e. one or more field emitting electrodes and corresponding one or more receiving electrodes

Abstract

Apparatus and methods for resolving movement of a mass within a defined space utilizes at least one electrode proximate to the space to be observed. An AC signal is applied to the electrode, and the current measured from that electrode and also to any other electrodes included in the system and which are effectively connected to the ground return of the AC-coupled electrode. A person (or object) to be sensed intercepts a part of the electric field extending beween the AC-coupled "sending" electrode and the other "receiving" electrodes, the amount of the field intercepted depending on the size and orientation of the sensed person, whether or not the person provides a grounding path, and the geometry of the distributed electrodes. Given the nonlinear spatial dependence of the field, multiple electrodes can reliably distinguish among a set of expected cases. The invention detects motion by taking sequential measurements at different times and utilizing the time variation in signal magnitudes as well as the absolute magnitudes themselves.

Claims

1. Apparatus for characterizing movement of a mass within a defined space, the apparatus comprising:

a. at least one electrode proximate to the space;

b. an AC source;

c. means for sequentially connecting each of the at least one electrode to the AC source at fixed intervals so as to produce a plurality of electric fields;

d. means for measuring current flowing from the electrode that is connected to the AC source; and

e. means for characterizing movement of the mass within the space based on the measurements.

2. The apparatus of claim 1 further comprising:

a. a computer memory for storing (i) the measurements and (ii) a pattern of measurement clusters each associated with a movement; and

b. a processor for comparing the measurements against the pattern to thereby characterize movement of the mass.

3. Apparatus for characterizing movement of a mass within a defined space, the apparatus comprising:

a. at least two electrodes proximate to the space, the electrodes having fixed positions relative to each other;

b. an AC source;

c. means for momentarily connecting at least a first electrode to the AC source a plurality of times so as to produce a plurality of electric fields;

d. means for measuring current flowing into at least one unconnected electrode each time the first electrode is connected to the AC source, thereby producing a plurality of measurements; and

e. means for characterizing movement of the mass within the space based on the plurality of measurements.

4. The apparatus of claim 3 comprising at least three electrodes, the connecting means being configured to sequentially connect each of the electrodes to the AC source, and the measuring means being configured to make at least two measurements of current flowing into one of the unconnected electrodes and at least one measurement of current into another of the unconnected electrodes.

5. The apparatus of claim 3 comprising at least three electrodes, the connecting means being configured to connect a first of the electrodes to the AC source, and the measuring means being configured to make at least two measurements of current into a second of the electrodes and at least one measurement of current into a third of the electrodes.

6. The apparatus of claim 3 further comprising:

a. a computer memory for storing (i) the measurements and (ii) a pattern of measurement clusters each associated with a movement; and

b. a processor for comparing the measurements against the pattern to thereby characterize movement of the mass.

7. A method of characterizing movement of a mass within a defined space, the method comprising the steps of:

a. providing at least one electrode proximate to the space;

b. sequentially transmitting an AC signal through the at least one electrode at fixed intervals so as to produce a plurality of discrete electric fields separated in time;

c. measuring current flowing out of the electrode each time the AC signal is sent; and

d. characterizing movement of the mass within the space based on the measurements.

8. The method of claim 7 wherein the mass is a person.

9. The method of claim 7 wherein the characterization step comprises the substeps of:

a. providing a pattern of measurement clusters each associated with a movement; and

b. comparing the measurements against the pattern to thereby characterize movement.

10. A method of characterizing movement of a mass within a defined space, the method comprising the steps of:

a. providing at least two electrodes proximate to the space, the electrodes having fixed positions relative to each other;

b. momentarily transmitting an AC signal through a first electrode a plurality of times so as to produce a plurality of discrete electric fields separated in time;

c. measuring current flowing into at least one unconnected electrode each time the signal is transmitted by the first electrode, thereby producing a plurality of measurements; and

d. characterizing movement of the mass within the space based on the plurality of measurements.

11. The method of claim 10 wherein the characterization step comprises the substeps of:

a. providing a pattern of measurement clusters each associated with a movement; and

b. comparing the measurements against the pattern to thereby characterize movement.

12. The method of claim 10 wherein the mass is a person.

13. A method of characterizing movement of a mass within a defined space, the method comprising the steps of:

a. providing at least one electrode proximate to the space;

b. sequentially transmitting an AC signal through the at least one electrode at fixed intervals so as to produce a plurality of electric fields;

c. measuring current flowing from the electrode as the AC signal is sent; and

d. characterizing movement of the mass within the space based on the measurements by (i) providing a pattern of measurement clusters each associated with a movement, (ii) comparing the measurements against the pattern, and (iii) based on the comparison, characterizing the movement.