Double eccentric positioning apparatus

Patent metadata

Field	Value
Publication number	US-9573198-B1
Application number	US-201314016709-A
Country	US
Kind code	B1
Filing date	Sep 3, 2013
Priority date	Jun 6, 2013
Publication date	Feb 21, 2017
Grant date	Feb 21, 2017

Abstract

A double eccentric positioning apparatus uses two equal offset eccentric bushings to accurately position a tool in two dimensions. Miniature servo motors and precise gearing control the rotation of each eccentric bushing, which controls the direction of the offset vectors. The offset vectors are used to determine the final position of the drill bushing. The desired rotation angles can be mathematically calculated based on desired position. The inner eccentric bushing is located concentric to the offset of the outer eccentric bushing. This allows any position, within a radius of two times the eccentric offset, to be achieved. The use of worm gearing on the eccentric bushings prevents back-driving of the servo motors, due to the lead angle of the worm gears, and the friction between the worm wheel and worm gear.

First claim

The invention claimed is:

1. A system comprising:
a double eccentric positioning apparatus having a hole with an axis, said double eccentric positioning apparatus comprising a first motor which operates in accordance with received first motor encoder counts and a second motor which operates in accordance with received second motor encoder counts;
a vector target comprising a body supported by said double eccentric positioning apparatus, and first and second optical targets supported by said body, an axis of said first and second optical targets being coaxial with said axis of said double eccentric positioning apparatus;
an optical coordinate measuring machine operable to measure coordinates of a measured hole vector based in part on light received from said first and second optical targets, said measured hole vector representing a location of said axis of said double eccentric positioning apparatus in a global coordinate system; and
a computer system programmed to perform the following operations:
convert the location of said axis of said double eccentric positioning apparatus in said global coordinate system into a location of said axis of said double eccentric positioning apparatus in a bushing coordinate system;
computing a distance to move said axis of said double eccentric positioning apparatus in said bushing coordinate system; and
converting said distance into said first and second motor counts.

2. The system as recited in claim 1 , wherein said computer system is programmed to compute a distance separating a nominal wing intersect point and an actual vector and plane intersect point, wherein said nominal wing intersect point represents an intersection of a nominal hole vector and a nominal wing surface, and said actual vector and plane intersect point represents an intersection of said measured hole vector and a plane normal to said nominal hole vector that intersects said nominal wing intersect point.

3. The system as recited in claim 1 , wherein said computer system is programmed to compute a distance separating a nominal wing intersect point and an actual vector and plane intersect point, wherein said nominal wing intersect point represents an intersection of said nominal hole vector and a nominal wing surface, and said actual vector and plane intersect point represents an intersection of said measured hole vector and a plane normal to said measured hole vector that intersects said nominal wing intersect point.

4. The system as recited in claim 1 , further comprising:
a base plate that supports said double eccentric positioning apparatus; and
a clamping device for clamping said base plate to a workpiece.

5. The system as recited in claim 1 , wherein said double eccentric positioning apparatus comprises:
an outer eccentric bushing having an outer circular cylindrical surface and an inner circular cylindrical surface off-center from said outer circular cylindrical surface of said outer eccentric bushing;
means for coupling said outer eccentric bushing to said first motor;
an inner eccentric bushing having an outer circular cylindrical surface in contact with said inner circular cylindrical surface of said outer eccentric bushing and an inner circular cylindrical surface off-center from said outer circular cylindrical surface of said inner eccentric bushing; and
means for coupling said inner eccentric bushing to said second motor.

6. The system as recited in claim 5 , wherein offsets of said inner and outer eccentric bushings are equal.

7. A method of positioning a drill bushing in overlying relationship with a nominal drillhole location on a workpiece, comprising:
installing a drill bushing in a double eccentric positioning apparatus so that an axis of the drill bushing is coaxial with an axis of the double eccentric positioning apparatus;
positioning the double eccentric positioning apparatus on a workpiece at a location where a nominal drill hole location lies within a range of movement of the axis of the double eccentric positioning apparatus; and
controlling the double eccentric positioning apparatus so that the axis of the double eccentric positioning apparatus moves closer to the nominal drillhole location.

8. The method as recited in claim 7 , wherein said controlling step is performed by a computer system programmed to output first and second motor encoder counts that cause the axis of the double eccentric positioning apparatus to move closer to the nominal drillhole location.

9. The method as recited in claim 8 , wherein an outer eccentric bushing of the double eccentric positioning apparatus is rotated a first angle proportional to said first motor encoder count, and an inner eccentric bushing of the double eccentric positioning apparatus is rotated a second angle proportional to said second motor encoder count.

10. The method as recited in claim 8 , further comprising:
(a) installing a vector target in the drill bushing, the vector target comprising first and second optical targets, an axis of the first and second optical targets being coaxial with the axis of the double eccentric positioning apparatus;
(b) measuring coordinates of a measured hole vector based in part on light transmitted toward and reflected from the first and second optical targets, said measured hole vector representing a location of the axis of the double eccentric positioning apparatus in a global coordinate system;
(c) converting the location of the axis of the double eccentric positioning apparatus in said global coordinate system into a location of the axis of the double eccentric positioning apparatus in a bushing coordinate system;
(d) computing a distance to move the axis of the double eccentric positioning apparatus in the bushing coordinate system; and
(e) converting said distance into said first and second motor encoder counts,
wherein steps (c) through (e) are performed by the computer system.

11. A method of positioning a drill bushing, comprising:
(a) applying a drill jig to a wing surface;
(b) using a metrological tool to measure a home location of an adjustable bushing attached to the drill jig;
(c) using metrology data to determine a desired location of the adjustable bushing; and
(d) moving the adjustable bushing from the home location to the desired location while the drill jig remains stationary,
wherein step (b) comprises:
moving the adjustable bushing to the home position;
installing optical targets in the adjustable bushing;
placing scale bars and supporting optical targets on the wing surface;
acquiring metrology data using a camera which is directed at the drill jig;
processing the metrology data; and
computationally extracting a measured hole vector from the metrology data, said measured hole vector intersecting the optical targets installed in the adjustable bushing.

12. The method as recited in claim 11 , wherein step (c) comprises:
virtually intersecting the measured hole vector with an engineering nominal wing surface; and
computing a distance from the virtual intersection of the measured hole vector with the engineering nominal wing surface to a nominal intersection point, and
wherein step (d) comprises:
moving the adjustable bushing a distance equal to the computed distance from the virtual intersection of the measured hole vector with the engineering nominal wing surface to the nominal intersection point.

Assignees

• Boeing Co

Inventors

• Favilla Stephan J
• Merkley Alan Ray
• Lagally Christie Dusty
• Collins Ronald J

Classifications

• B23B2260/062

  Electric motors · CPC title

• B23B2260/146

  Wedges · CPC title

• B23B2270/48

  Measuring or detecting · CPC title

• F16H2057/02034

  Gearboxes combined or connected with electric machines · CPC title

• F16H2001/327

  with the orbital gear having internal gear teeth · CPC title