Sensor assembly and method for measuring forces and torques

Patent metadata

Field	Value
Publication number	US-10048145-B2
Application number	US-201614993318-A
Country	US
Kind code	B2
Filing date	Jan 12, 2016
Priority date	Mar 12, 2013
Publication date	Aug 14, 2018
Grant date	Aug 14, 2018

Abstract

A sensor assembly comprises a base plate and a sensor member displaceable relative to the base plate. A spring arrangement operates in first and second stages in response to displacement of the sensor member relative to the base plate. Different resolutions of force and torque measurements are associated with the first and second stages. A light sensitive transducer senses displacement of the sensor member relative to the base plate and generates corresponding output signals. A collimator directs a plurality of light beams onto the light sensitive transducer so that the light beams strike different pixels of the light sensitive transducer to sense displacement of the sensor member relative to the base plate.

First claim

What is claimed is:

1. A sensor assembly comprising:
a base plate;
a sensor member displaceable relative to said base plate;
a spring arrangement responsive to displacement of said sensor member relative to said base plate;
a light sensitive transducer fixed to said base plate and having a plurality of pixels;
a light source configured to provide light directed in a plurality of light beams onto said light sensitive transducer so that the light beams strike different pixels of said light sensitive transducer to sense the displacement of said sensor member relative to said base plate; and
a collimator having a plurality of openings for directing the plurality of light beams onto said light sensitive transducer wherein said collimator is movable relative to said light sensitive transducer.

2. The sensor assembly of claim 1 wherein said plurality of openings are further defined as a plurality of throughbores arranged so that the light beams extend through said throughbores to strike different clusters of said pixels on said light sensitive transducer.

3. The sensor assembly of claim 2 wherein said plurality of pixels are arranged in rows and columns with each of said pixels being configured to generate an output signal proportional to a quantity of light that strikes each of said pixels.

4. The sensor assembly of claim 2 including a controller in communication with said light sensitive transducer and configured to determine forces and torques based on movement of the light beams relative to said light sensitive transducer.

5. The sensor assembly of claim 4 wherein said plurality of throughbores includes two angled bores formed at an acute angle to a surface of said collimator such that two of the light beams extend through said angled bores to detect displacement of said sensor member along a z-axis normal to said light sensitive transducer based on a change in distance between locations of the light beams extending through said angled bores on said light sensitive transducer.

6. The sensor assembly of claim 4 wherein said plurality of throughbores includes a normal bore formed normal to a surface of said collimator so that one of the light beams extends through said normal bore.

7. The sensor assembly of claim 6 wherein said plurality of throughbores further includes two angled bores formed at an acute angle to said surface of said collimator so that two of the light beams extend through said angled bores.

8. The sensor assembly of claim 4 wherein said plurality of throughbores includes four normal bores formed normal to a surface of said collimator and two angled bores formed at an acute angle to said surface of said collimator so that six of the light beams extend through said normal bores and said angled bores.

9. The sensor assembly of claim 1 wherein said collimator is disc shaped.

10. A method of assessing forces and torques using a sensor assembly including a base plate, a sensor member displaceable relative to the base plate, a spring arrangement responsive to displacement of the sensor member relative to the base plate, and a light sensitive transducer having a plurality of pixels, said method comprising the steps of:
directing a plurality of light beams through a collimator onto the light sensitive transducer, wherein the collimator is movable relative to the light sensitive transducer and the spring arrangement is responsive to displacement of the sensor member relative to the light sensitive transducer so that each of the plurality of light beams move on the light sensitive transducer in response to application of a load on the sensor member; and
determining forces and torques based on differences in locations of pixels lighted by the light beams as the light beams move in response to the applied load.

11. The method of claim 10 wherein directing the plurality of light beams through the collimator onto the light sensitive transducer includes directing the plurality of light beams onto the light sensitive transducer so that a first light beam strikes an initial first cluster of pixels, a second light beam strikes an initial second cluster of pixels, a third light beam strikes an initial third cluster of pixels, and a fourth light beam strikes an initial fourth cluster of pixels, the light beams striking the initial clusters of pixels at a start of a time frame.

12. The method of claim 11 including determining an initial location of each of the first, second, third, and fourth light beams on the light sensitive transducer at the start of the time frame by generating an initial output signal from each of the pixels proportional to a quantity of light that strikes each of the pixels at the start of the time frame and analyzing the initial output signals to determine an initial centroid of each of the light beams.

13. The method of claim 12 wherein the load is applied on the sensor member so that the first light beam moves from the initial first cluster of pixels to a final first cluster of pixels, the second light beam moves from the initial second cluster of pixels to a final second cluster of pixels, the third light beam moves from the initial third cluster of pixels to a final third cluster of pixels, and the fourth light beam moves from the initial fourth cluster of pixels to a final fourth cluster of pixels, the light beams striking the final clusters of pixels at an end of the time frame.

14. The method of claim 13 including determining a final location of each of the first, second, third, and fourth light beams on the light sensitive transducer at the end of the time frame by generating a final output signal from each of the pixels proportional to a quantity of light that strikes each of the pixels at the end of the time frame and analyzing the final output signals to determine a final centroid of each of the light beams.

15. The method of claim 14 wherein directing the plurality of light beams through the collimator onto the light sensitive transducer includes directing light from a light source through a plurality of throughbores spaced from one another.

16. The method of claim 15 wherein directing the light from the light source through the plurality of throughbores is further defined as directing the light from the light source through at least two normal bores formed normal to a surface of the collimator and through two angled bores formed at an acute angle to the surface of the collimator wherein the first and second light beams pass through the at least two normal bores and the third and fourth light beams pass through the two angled bores.

17. The method of claim 16 wherein determining the forces and torques includes calculating a difference in the initial and final locations of the first light beam on the light sensitive transducer.

18. The method of claim 17 wherein determining the forces and torques includes calculating an initial slope of a line between the initial locations of the first and second light beams on the light sensitive transducer and calculating a final slope of the line between the final locations of the first and second light beams on the light sensitive transducer.

19. The method of claim 18 wherein determining the forces and torques includes calculating a difference in the initial and final locations of the third light beam on the light sensitive transducer.

20. The method of claim 19 wherein determining the forces and torques includes calculating an initial distance between the initial locations of the third and fourth light beams on the light sensitive transducer a

Assignees

• Stryker Corp

Inventors

• Janik John J
• Brindley Robert A
• Tang Edward
• Spangler Leland J

Classifications

• G01L3/08

  involving optical means for indicating · CPC title

• G01L3/1421

  using optical transducers · CPC title

• G01L5/226

  to manipulators, e.g. the force due to gripping · CPC title

• G01L5/166 Primary

  using photoelectric means · CPC title

• G01L5/16

  for measuring several components of force · CPC title