Topological and motion measuring tool

• US 6,127,672 A
• Filed: 05/23/1997
• Issued: 10/03/2000
• Est. Priority Date: 05/23/1997
• Status: Expired due to Term

• Current Assignee: Canadian Space Agency (Government of Canada)
• Original Assignee: Canadian Space Agency (Government of Canada)
• Inventors: Danisch, Lee
• Primary Examiner(s): Le, Que T.
• Assistant Examiner(s): Luu, Thanh X.
• Application Number:
  US08/863,063
• Time in Patent Office: 1,229 Days
• Field of Search: 250/227.14, 250/227.11, 250/227.16, 250/227.24, 250/227.28, 250/221, 250/224, 73/655, 341/20, 341/31, 600/595, 128/782, 340/555, 340/556, 340/557
• US Class Current: 250/227.14
• CPC Class Codes: G01B 11/18 using photoelastic elements
• 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

A position, orientation, shape and motion measuring tool is provided in the form of a flexible substrate with bend and twist sensors distributed along its surface at known intervals. A ribbon-type substrate is preferred. The geometric configuration of the substrate is calculated from inter-referencing the locations and orientations of the sensors based upon the detected bend and twist values. Suitable applications include motion capture for humans for use in animation, six degree of freedom input to a computer, profile measurement and location tracking within a large, singularity-free working space.

Claims

1. A measuring tool for providing data corresponding to a geometric configuration in space comprising:

(1) a longitudinally extending, flexible substrate having a compliant reference surface and being capable of bending in at least two degrees of freedom so as to be configurable in three dimensional space;

(2) a plurality of spaced bend sensor means and a plurality of spaced twist sensor means each of said plurality of sensor means being respectively coupled to and positioned at specific discrete locations, on and at known respective bend sensor and twist sensor spacing intervals along the longitudinal extent of the substrate to provide flexure signals indicating the respective local state of bend and twist present in the substrate at the respective locations where the respective bend sensor means and twist sensor means are coupled to the substrate; and

(3) sensor data processing means coupled to the bend sensor means and twist sensor means for receiving flexure signals therefrom and for presenting data on the geometric configuration of the reference surface of the substrate in three dimensional space,

wherein the sensor data processing means operates by determining the geometric configuration of the substrate from bend and twist signals derived from the flexure signals provided by the bend sensor means and twist sensor means at their specific locations and from the spacings intervals for such sensors.

2. A measuring tool as in claim 1 wherein the bend sensor means and twist sensor means are positioned at common, shared bend and twist sensor spacing intervals along the length of the substrate.

3. A measuring tool as in claim 1 wherein the shape of the substrate is in the form of a ribbon having a longitudinal dimension, the substrate being substantially limited to bending along its length about axes which are transverse to the longitudinal dimension of the substrate but being free to twist about such longitudinal dimension.

4. A measuring tool as in claims 1 or 3 wherein the bend sensor means and twist sensor means are provided as pairs of bend sensors co-located at locations along the substrate and respectively positioned to measure bending occurring about respective, splayed intersecting bend axes, the bend and twist signals being respectively provided by additively combining the output of the two co-located bend sensors and by extracting a difference from the output of said two, co-located, bend sensors.

5. A measuring tool as in claims 1 or 3 wherein:

(1) the bend sensor means and twist sensor means comprise optical fibers that have been rendered sensitive to their state of curvature by having treated surface portions of their outer surfaces rendered absorbent to light passing through such fibers;

(2) the fibers have reversing loops and the treated surface portions are located in the region of the loops;

(3) the reversing loops define median lines;

(4) the loops are mounted in pairs along the substrate, to provide a combined bend and twist sensor means within each pair;

and wherein;

(5) the planes of the loops are parallel to the surface of the substrate; and

(6) the median lines of the loops are oriented at splayed angles from each other,

whereby the bend and twist signals are respectively obtained by additively combining the outputs of the loops in each pair and by extracting a difference value from the outputs of the loops in each pair.

6. A measuring tool as in claims 1 or 3 wherein the bend sensor means and twist sensor means comprise optical fibers that have been rendered sensitive to their state of curvature by having treated surface portions of their outer surfaces rendered absorbent to light passing through such fibers.

7. A measuring tool as in claim 6 wherein the optical fibers have reversing loops and the fibers have been rendered sensitive to their state of curvature in the region of the loops to provide said bend sensor means and twist sensor means.

8. A measuring tool as in claim 7 wherein the substrate is a ribbon with a longitudinal dimension, the reversing loops of said twist sensor means define bisecting median lines, the median lines of the loops being aligned with the longitudinal dimension of the ribbon, the loops having surfaces that are disposed parallel to the plane of the substrate and are outwardly directed from the loops, and wherein the treated surface portions on each loop are located on the outwardly directed surfaces of the fiber on only opposite halves and opposite, outwardly-directed surfaces of each such loop.

9. A measuring tool as in claim 7 wherein the loops of the bend sensor means are mounted in nested pairs, the treated surface portions of the fibers in the two loops of each pair being located at complimentary, opposite, outwardly directed face surface portions in each loop, whereby, when the nested loops undergo a common change in bend curvature, the intensity of light passing through the respective loops in each pair changes value in opposite directions.

10. A measuring tool as in claim 9 wherein the difference in outputs of the loops in the nested pair is provided to the sensor data processing means as a measure of bend curvature.

11. A geometric configuration monitoring tool with a configuration monitoring reference surface for measuring the relative location and orientation in three dimensional space of a surface to be measured with respect to a reference location comprising:

(1) a flexible, longitudinally extending substrate capable of flexure in three dimensional space and compliance with the shape of a surface to be measured, said substrate carrying said configuration monitoring reference surface and reference location; and

(2) a plurality of bend sensor means and a plurality of twist sensor means serving as angular displacement sensors and respectively spaced at known intervals along the longitudinal extent of said substrate

whereby the position and orientation in three dimensional space of said configuration monitoring reference surface with respect to the said reference location is determinable geometrically from the values for angular displacement provided by said angular displacement sensors at their respective locations along said substrate, combined with the values for the intervals separating such sensors, and the spacing of at least one bend sensor means or twist sensor means from the reference location.

12. A tool as in claim 11 wherein said bend sensor means and twist sensor means are interspersed alternately between each other along the longitudinal extent of the substrate.

13. A tool as in claim 11 wherein said bend sensor means and twist sensor means are co-located with each other.

14. A tool as in claim 13 wherein said bend sensor means and twist sensor means comprise two bend sensors positioned to measure bending in splayed directions to provide bend and twist signals derived from the sum and difference in the outputs of said bend sensors.

15. A tool as in claims 11, 12, 13 or 14 wherein said substrate is in the form of a structure of ribbon-like configuration with a longitudinal extent, said ribbon-like structure being free along its length to flex about axes that are transverse to its longitudinal extent but resistant to flexure about axes that are parallel to the longitudinal extent of the ribbon.

16. A tool as in claims 11, 12, 13 or 14 for measuring the relative location and orientation in space of first and second surfaces to be measured with respect to each other, said tool having:

(1) a first portion of the shape monitoring reference surface lying adjacent to a first surface to be measured; and

(2) a second portion of the shape monitoring reference surface lying adjacent to a second surface to be measured,

wherein the first and second portions of the shape monitoring reference surface bound an intermediate portion of the monitoring tool which is unconstrained in space except at its juncture with said first and second portions of the shape monitoring reference surface.

17. A tool as in claims 11, 12, 13 or 14 wherein said substrate is in the form of a sheet carrying the reference surface and having said bend sensor means and twist sensor means attached thereto.

18. A method of providing data defining the spatial configuration of a path extending in three dimensional space, comprising conforming a substrate in the form of a flexible sheet into a spatial configuration along the path to be defined, providing multiple bend sensor means and multiple twist sensor means attached to said substrate at predetermined intervals along and proximate to the path to be defined, collecting bend signals and twist signals from said respective sensor means, and processing said signals to produce data on the spatial configuration of the path along its extent in three dimensional space, said processing of said signals operating by combining bend signals and twist signals from said bend sensor means and twist sensor means together with the spacing intervals therebetween to produce such data.

19. A method as claimed in claim 18, the substrate being in the form of a ribbon having a longitudinal dimension and substantially limited to bending along its length about axes transverse to the longitudinal dimension, and twisting about its longitudinal dimension.

20. A method as claimed in claims 18 or 19, said sensors comprising optical fibres rendered sensitive to their state of curvature by having treated surface portions of their outer surfaces rendered absorbent for light passing through the fibers.