Sensor

• US 6,946,650 B2
• Filed: 02/27/2003
• Issued: 09/20/2005
• Est. Priority Date: 03/04/2002
• Status: Expired due to Fees

• Current Assignee: Independence Technology LLC (Johnson & Johnson)
• Original Assignee: Independence Technology LLC (Johnson & Johnson)
• Inventors: Nergaard, David K., Bradley, Albert M., Yoerger, Dana R.
• Primary Examiner(s): Porta, David
• Assistant Examiner(s): MONBLEAU, DAVIENNE N
• Application Number:
  US10/375,449
• Publication Number:
  US 20040016875A1
• Time in Patent Office: 936 Days
• Field of Search: 250/231.13, 250/226, 250/578.1, 250/231.18, 250/231.14, 356/402, 356/414, 356416-420, 341/21, 297/132, 359233-236, 435/455, 435/469
• US Class Current: 250/231.18
• CPC Class Codes: A61G 2203/38 for torque
• CPC Class Codes: A61G 2205/20 Color codes
• CPC Class Codes: A61G 5/10 Parts, details or accessories
• CPC Class Codes: G01D 5/26 characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
• CPC Class Codes: G01D 5/34715 Scale reading or illumination devices
• CPC Class Codes: G01D 5/3473 Circular or rotary encoders
• CPC Class Codes: G01L 3/12 involving photoelectric means

Abstract

The relative position of two members is determined based upon a detected relative intensities of first and second colors of light. The intensity balance associated with relative occlusion of first and second color filter portions on one member by a mask on the other member. An exemplary use is in rotational position sensing within a limited rotation range. With a given compliance between the two members, the position sensing can be used as a proxy for torque sensing.

Claims

1. A device for sensing relative position or orientation of first and second members comprising

a source of light having first and second color components;

a filter having first and second portions respectively preferentially passing said first and second color components, and substantially fixed relative to the first member;

a mask, having first and second portions respectively relatively transparent to and opaque to both said first and second color components, and substantially fixed relative to the second member; and

a sensor for detecting the first and second color components, wherein;

the mask and the filter are mounted along one or more light paths between the source and sensor; and

a change in said position or orientation causes a varying relative occlusion of said first and second filter portions by said second mask portions so as to vary a relative proportion of said first and second color components detected by the sensor.

2. The device of claim 1 used to measure a force or torque between the first and second members in view of a compliance resisting said change in said position or orientation.

3. The device of claim 1 wherein:

the combination of first and second members is carried by a third member;

the source and sensor are mounted to the third member so that the combination may move relative to the source and sensor; and

the device further includes a reflector carried by one of the first and second members and positioned so that the light path extends from the source to the sensor via the reflector and making at least one pass through the mask and filter.

4. The device of claim 3 wherein the light path makes two passes through the mask and filter.

5. The device of claim 1 wherein the first and second members are constrained so that the change in said position or orientation is substantially limited to relative rotation about an axis fixed relative to the first and second members.

6. The device of claim 5 wherein the first and second portions of the mask and filter are each alternating sectors of an annulus or disk.

7. The device of claim 1 wherein the source comprises one or more substantially discrete first sources of the first component and one or more substantially discrete second sources of the second component.

8. The device of claim 7 wherein the first and second sources are first and second light emitting diodes.

9. The device of claim 8 wherein first and second light emitting diodes are red and green, respectively.

10. The device of claim 1 wherein said sensor is sensitive to said first and second color components and said source is operated to alternatingly generate said first and second color components.

11. The device of claim 10 wherein there is a single photodiode synchronously sensing the first and second color components.

12. The device of claim 1 wherein said change in said position or orientation is substantially constrained by stops to be within a one-dimensional two-ended range.

13. The device of claim 12 wherein said one-dimensional two-ended range is a rotational range of between 0.5°

and 10.0°

.

14. The device of claim 12 wherein said one-dimensional two-ended range is a rotational range of between 1.0°

and 3.0° and

wherein a compliance tends to center the relative rotation within such range.

15. A wheelchair comprising:

a seat;

a frame;

left and right motors;

left and right drive wheels drivingly coupled to the left and right motors, respectively;

left and right hand rims concentric with and coupled to the left and right drive wheels, respectively;

left and right devices of claim 1 respectively associated with the left and right drive wheels wherein the first and second members are respective hub portions of the associated drive wheel and hand rim; and

a control system coupling the left device and motor and right device and motor so as to drive the left motor responsive to at least a torque sensed by the left device and drive the right motor responsive to at least a torque sensed by the right device.

16. A method for sensing a drive torque applied by a user to the handrim of a wheel chair comprising:

detecting a balance between first and second colors of light passed from a source through a mask and a filter, one of which is substantially fixed relative to the hand rim and the other of which is substantially fixed relative to a drive wheel associated with the hand rim, the relative orientation of the drive wheel and hand rim being indicative of said torque in view of a given compliance and the balance being indicative of the relative orientation of the filter and mask.

17. The method of claim 16 wherein:

the first and second colors are red and green;

the balance is relative to a neutral condition in which substantially equal amounts of red and green light are so passed; and

the detection has a range of no more than +/−

2°

from the neutral condition.