Magnetic motion tracker with transmitter placed on tracked object

• US 5,744,953 A
• Filed: 08/29/1996
• Issued: 04/28/1998
• Est. Priority Date: 08/29/1996
• Status: Expired due to Term

• Current Assignee: Ascension Technology Corporation (Roper Technologies, Inc.)
• Original Assignee: Ascension Technology Corporation (Roper Technologies, Inc.)
• Inventors: Hansen, Per Krogh
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US08/705,305
• Time in Patent Office: 607 Days
• Field of Search: 324/207.17, 324/207.26, 324/226, 342/450, 342/451, 342/463, 342/464, 342/465, 128/782
• US Class Current: 324/207.17
• CPC Class Codes: A61B 5/1036 Measuring load distribution, e.g. podologic studies
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/1114 Tracking parts of the body
• CPC Class Codes: A61B 5/1127 using markers
• CPC Class Codes: A61B 5/6801 specially adapted to be attached to or worn on the body surface
• CPC Class Codes: G01B 7/004 for measuring coordinates of points
• 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

Abstract

The motion of a person is measured in real time using magnetic fields. A magnetic transmitter and a number of magnetic receivers are placed at different points on the person. The transmitter transmits magnetic fields sequentially from three orthogonal coils. The magnetic field is received at each receiver, which consists of three orthogonal coils. The computer resolves the sequential position and orientation coordinates from each receiver into the person'"'"'s movement, relative to the transmitter, from knowledge of where each receiver is placed on the person. Other embodiments measure the transmitter'"'"'s position and orientation relative to a fixed location outside of the person. The computer then resolves the position and orientation data into the person'"'"'s motion relative to the fixed location outside of the person. A second embodiment uses pressure sensitive switches and accelerometers placed on the person'"'"'s feet and a computer program to find the transmitter'"'"'s position and orientation relative to a fixed starting location. A third embodiment uses an optical subsystem to find the transmitter'"'"'s position and orientation relative to a fixed location. A fourth embodiment uses at least one further receiver placed in a fixed location outside of the person to find the transmitter'"'"'s position and orientation relative to a fixed location. A fifth embodiment utilizes a special magnetic transmitter consisting of a one-axis long range transmitter and a two-axis short range transmitter and two further receivers placed at two fixed locations outside of the person to find the transmitter'"'"'s position and orientation relative to a fixed location.

Claims

1. A motion tracking system for tracking motions of an object, comprising:

a) a transmitter mounted on an object, said transmitter including three orthogonal magnetic coils including a one-axis long range transmitter and a two-axis short range transmitter;

b) at least one sensor mounted on said object spaced from said transmitter;

c) a computer including control means for controlling operation of said transmitter; and

d) said computer receiving signals from said sensor and, therefrom, calculating position and orientation of said sensor with respect to said transmitter.

8. The system of claim 1, further including a further sensor located in a fixed location spaced from said object, said computer receiving further signals from said further sensor responsive to activation of said one-axis long range transmitter and, therefrom, determining position and orientation of said object with respect to a fixed coordinate system defined about said further sensor.

9. The system of claim 8, said further sensor comprising two further sensors.

2. A motion tracking system for tracking motions of an object, comprising:

a) a transmitter mounted on an object, said object comprising a person having a head, arms, legs, feet and lower back;

b) at least one sensor mounted on said object spaced from said transmitter, said sensor comprising a plurality of discrete sensors mounted on a person;

c) a computer including control means for controlling operation of said transmitter;

d) said computer receiving signals from said sensor and, therefrom, calculating position and orientation of said sensor with respect to said transmitter; and

e) said system further including an on-off switch mounted under one foot of the person, said switch being closed when said one foot is engaging a ground surface, said switch being incorporated into a sub-circuit connected to said computer whereby status of said switch is sensed by the computer.

3. The system of claim 2, including one on-off switch mounted under each foot of a person and interconnected in parallel sub-circuits with said computer.

4. A motion tracking system for tracking motions of an object, comprising:

a) a transmitter mounted on an object, said object comprising a person having a head, arms, legs, feet and lower back;

b) at least one sensor mounted on said object spaced from said transmitter, said sensor comprising a plurality of discrete sensors mounted on a person;

c) a computer including control means for controlling operation of said transmitter;

d) said computer receiving signals from said sensor and, therefrom, calculating position and orientation of said sensor with respect to said transmitter; and

e) at least one accelerometer mounted on each foot of a person and interconnected to said computer.

5. A motion tracking system for tracking motions of an object, comprising:

a) a first transmitter mounted on an object;

b) a first sensor mounted on said object spaced from said first transmitter;

c) a computer including control means for controlling operation of said first transmitter;

d) said computer receiving first signals from said first sensor and, therefrom, calculating position and orientation of said first sensor with respect to said transmitter; and

e) a second sensor located in a fixed location, and a second transmitter mounted on the object, said computer including further control means for controlling operation of said second transmitter, said computer receiving second signals from said second transmitter and, therefrom, calculating position and orientation of said second transmitter with respect to said second sensor;

f) wherein said second transmitter comprises a light source and said second sensor comprises a light sensitive receiver.

6. The system of claim 5, said light source comprising an infrared light source and said second sensor comprising an infrared light sensitive position sensing detector.

7. A motion tracking system for tracking motions of an object, comprising:

a) a transmitter mounted on an object;

b) a first sensor mounted on said object spaced from said transmitter;

c) a computer including control means for controlling operation of said transmitter;

d) said computer receiving signals from said first sensor and, therefrom, calculating position and orientation of said first sensor with respect to said transmitter; and

e) a second sensor located in a fixed location spaced from said object, said computer receiving further signals from said second sensor responsive to activation of said transmitter and, therefrom, determining position and orientation of said object with respect to a fixed coordinate system defined by said second sensor.

10. A method of tracking motions of a person having a head, arms, legs, feet and a lower back, including the steps of:

a) mounting a transmitter on a person'"'"'s lower back;

b) mounting a sensor on any one of the head, arm or leg of the person;

c) providing a computer connected to control operation of said transmitter and to receive signals from said sensor;

d) activating said transmitter to transmit magnetic fields;

e) receiving signals from said sensor;

f) calculating position and orientation of said sensor with respect to said transmitter;

g) providing two on-off switches;

h) mounting one of said switches on each foot of the person;

i) electrically connecting said switches to said computer; and

j) monitoring said switches to determine when one foot or both feet are engaging a floor surface.

11. A method of tracking motions of a person having a head, arms, legs, feet and a lower back, including the steps of:

a) mounting a transmitter that transmits magnetic fields on a person'"'"'s lower back;

b) mounting a sensor on any one of the head, arm or leg of the person;

c) providing a computer connected to control operation of said transmitter and to receive signals from said sensor;

d) activating said transmitter to transmit magnetic fields;

e) receiving signals from said sensor;

f) calculating position and orientation of said sensor with respect to said transmitter;

g) providing a further sensor;

h) locating said further sensor in a fixed location spaced from said person;

i) providing a further source and mounting said further source on the person;

j) connecting said further source and further sensor to said computer;

k) activating said further source;

l) said further sensor receiving waves from said further transmitter;

m) sending further signals from said further sensor to said computer; and

n) calculating position and orientation of said person with respect to a fixed coordinate system defined by location of said further sensor.

12. The method of claim 11, wherein said further source comprises an infrared light source.

13. The method of claim 11, wherein said further sensor comprises at least one position sensing device.

14. A method of tracking motions of a person having a head, arms, legs, feet and a lower back, including the steps of:

a) mounting a transmitter on a person'"'"'s lower back;

b) mounting a sensor on any one of the head, arm or leg of the person;

c) providing a computer connected to control operation of said transmitter and to receive signals from said sensor;

d) activating said transmitter to transmit magnetic fields;

e) receiving signals from said sensor;

f) calculating position and orientation of said sensor with respect to said transmitter; and

g) providing a further sensor located in a fixed location with respect to said person.

15. A method of tracking motions of a person having a head, arms, legs, feet and a lower back, including the steps of:

a) mounting a transmitter on a person'"'"'s lower back;

b) mounting a sensor on any one of the head, arm or leg of the person;

c) providing a computer connected to control operation of said transmitter and to receive signals from said sensor;

d) activating said transmitter to transmit magnetic fields;

e) receiving signals from said sensor;

f) calculating position and orientation of said sensor with respect to said transmitter; and

g) providing two further sensors located in fixed locations with respect to said person.

16. The method of claim 15, further including the step of providing said transmitter with three mutually orthogonal coils which comprise a one-axis long range transmitter and a two-axis short range transmitter.

17. A method of tracking motions of a person having a head, arms, legs, feet and a lower back, including the steps of:

a) mounting a transmitter on a person'"'"'s lower back;

b) mounting a sensor on any one of the head, arm or leg of the person;

c) providing a computer connected to control operation of said transmitter and to receive signals from said sensor;

d) activating said transmitter to transmit magnetic fields;

e) receiving signals from said sensor;

f) calculating position and orientation of said sensor with respect to said transmitter; and

g) calculating motions of the person from calculations of sequential positions and orientations of said sensor with respect to said transmitter.

18. The method of claim 17, further including the step of mounting a sensor on each of said arm, said leg and said head.

19. The method of claim 17, further including the step of providing said transmitter with three mutually orthogonal magnetic coils.

20. The method of claim 19, further including the step of providing a plurality of sensors, each of which comprises three mutually orthogonal coils.

21. A motion tracking system for tracking motions of an object, comprising:

a) a transmitter mounted on an object;

b) at least one sensor mounted on said object spaced from said transmitter;

c) a computer including control means for controlling operation of said transmitter;

d) said computer receiving signals from said sensor and, therefrom, calculating position and orientation of said sensor with respect to said transmitter;

e) said computer receiving sequential signals from said sensor related to sequential positions and orientations of said sensor with respect to said transmitter and, therefrom, calculating motions of said object.

22. The system of claim 21, wherein said sensor is mounted on said object at a first location thereon movable with respect to a second location thereon where said transmitter is located, said computer further translating said position and orientation of said sensor into motion of said object.

23. The system of claim 21, wherein said sensor comprises a plurality of discrete sensors mounted at spaced locations on said object.

24. The system of claim 21, wherein said transmitter includes three mutually orthogonal magnetic coils.

25. The system of claim 24, wherein said sensor comprises three mutually orthogonal coils.

26. The system of claim 25, wherein said sensor comprises a plurality of discrete sensors mounted at spaced locations on said object.

27. The system of claim 21, wherein said object comprises a person having a head, arms, legs, feet and lower back, said sensor comprising a plurality of discrete sensors mounted on a person.

28. The system of claim 27, wherein said plurality of discrete sensors includes a first sensor mounted on a person'"'"'s head, a second sensor mounted on one of the person'"'"'s arms, and a third sensor mounted on one of the person'"'"'s legs.

29. The system of claim 28, wherein said transmitter is mounted on a person'"'"'s lower back.

30. A motion tracking system for tracking motions of an object, comprising:

a) a transmitter mounted on an object;

b) at least one sensor mounted on said object spaced from said transmitter;

c) a computer including control means for controlling operation of said transmitter;

d) said computer receiving signals from said sensor and, therefrom, calculating position and orientation of said sensor with respect to said transmitter;

e) a further sensor located in a fixed location separate from said object;

f) a further source mounted on said transmitter on said object;

g) said computer receiving further signals from said further sensor and, therefrom, calculating position and orientation of said further source with respect to said further sensor;

h) said computer further being programmed to determine position and orientation of said object with respect to a fixed coordinate system defined about said further sensor.