GB2222455A

GB2222455A - Locating a position in space

Info

Publication number: GB2222455A
Application number: GB8919768A
Authority: GB
Inventors: Michael Robin Paine
Original assignee: Westland Helicopters Ltd
Current assignee: AgustaWestland Ltd
Priority date: 1988-09-01
Filing date: 1989-09-01
Publication date: 1990-03-07
Also published as: GB8820642D0; GB8919768D0

Abstract

A method and apparatus for locating a position 22 in space using a support table and a remote measuring system having at least two theodolites 19, 20, 21. The support table is placed at the desired position 22 and is rotatable and includes at least two location means for locating optical targets of the remote measuring system in a known positional relationship. The method and apparatus is particularly useful in the manufacture of jigs and fixtures as used for example in the aircraft industry. <IMAGE>

Description

Description of Invention Title: Method and Apparatus for locating a position in space This invention relates to a method and apparatus for locating a position in space.

Remote measuring systems have been developed using two or more electronic theodolites linked to a computer. Using basic triangulation principles the theodolites are set up in a known relationship by being pointed at each other and at a reference scale such as a calibration bar. Coordinates derived from these measurements are input to the computer which calculates the spatial relationship of the theodolites.

This provides a precisely determined base upon which very accurate measurements of an object can be taken.

Pointing the theodolites at positions on an object provides a series of measurements from the base which are transmitted to the computer for comparison with stored parameters to provide accurate measurements of the object. Also the computer can be used to calculate desired positions in space relative the base and provide the co-ordinates for appropriate alignment of the theodolite on to the position.

Specially designed optical targets have been developed to aid calibration of the theodolites and for attachment to an object to improve accuracy of measurement and the applicant has introduced the use of a low power laser attached to each theodolite to monitor misalignment between the theodolite and an optical target.

Whilst such remote measuring systems are presently used for accurately measuring dimensions of large or small objects, and for alignment and calibration operations, difficulties arise in their use for accurately locating a position in space.

It is an objective of this invention to provide a method for locating a position in space and apparatus for use in such method.

The invention utilises a remote measuring system as hereinbefore defined and references in the specification to remote measuring systems are to be construed accordingly.

Accordingly in one aspect this invention provides a method for locating a required position in space using a remote measuring system and comprising the steps of: computing the location of said position, aligning at least two theodolites so that their lines of sight intersect at said position, locating a support table having a rotatable planar surface in the vicinity of said position with its planar surface located in either a horizontal plane or a vertical plane, locating a first optical target on the planar surface of the support table and concentrically of an axis of rotation of the support table, adjusting said support table until said first target is located at the intersecting lines of sight from the theodolites, locating a second optical target on the planar surface of said support table and at a known linear distance from said first target, computing the required position of the second target, pointing one of the theodolites at the required position for the second target, and rotating the support table about said axis until the second target is aligned with the line of sight from said one theodolite.

The method may include the further steps of locating a third optical target on the planar surface of said support table in a known linear and angular relationship to said first and second targets, computing the required position of the third target, and pointing a theodolite at a desired position for said third target so as to check that said position in space is correctly located and that the planar surface of the support table is correctly aligned in either the horizontal or vertical plane.

When three optical targets are in position on the support table the method may further include the step of locating a second support table having a planar upper surface on said targets and adjusting the angle of the planar surface of the second table with respect to the planar surface of the first table.

Angular adjustment of the second support table may be achieved by locating spacers between one or more of the targets and the second support table.

Preferably, a laser means is associated with each theodolite so as to provide visible lines of sight to aid positioning of said targets.

A further refinement of the method of the invention may include inputting the coordinates of the position of each theodolite to a computer having signal connection to each theodolite whereby the computer calculates the coordinates of the desired location position of the optical targets to permit alignment of the theodolites with said positions.

In another aspect the invention provides apparatus for use in locating a position in space comprising a support table having a planar upper surface rotatable about an axis, adjustment means for translating said support table about two mutually normal axes in its plane, first location means for locating a first optical target of a remote measuring system on the planar surface at the axis of rotation thereof, and second location means for locating a second optical target of said remote measuring system on the planar surface in known linear relationship with said first location means.

Preferably, said support table includes a third location means on the planar surface for locating a third optical target of said remote measuring system in known linear and angular relationship with said first and second location means.

The apparatus may include a second support table having a planar upper surface and three location means at an under surface thereof corresponding in linear and angular relationship with the three location means on the first support table so as to facilitate location of said second table on optical targets located by the location means on the first table, and means may be provided for adjusting the angular relationship of the second support table with respect to the first support table.

Means may be provided on the apparatus for vertical adjustment of the rotatable support table.

The location means may comprise conical indents for locating the optical targets.

Preferably, the apparatus includes at least three theodolites each having signal connection with a computer.

In one embodiment a camera may be associated with each theodolite for displaying on a monitor screen having quadrant markings an image of the optical target being sighted by each theodolite. In an alternative embodiment a laser may be associated with each theodolite to provide visible lines of sight to aid positioning of the targets and indicating means such as a photo-electric cell device may be associated with each target to facilitate accurate alignment of the theodolites.

The invention will now be described by way of example only and with reference to the accompanying drawings in which, Figure 1 is a side elevation of apparatus for use in the method of this invention, Figure 2 is a plan view of the apparatus of Figure 1, Figures 3 to 6 are schematic drawings showing a method for locating a position in space according to this invention, and Figures 7 and 8 are schematic drawings illustrating further steps in the method of Figures 3 to 6.

Referring now to Figures 1 and 2, a position in space tool 11 includes a support table 12 having a planar upper surface and attached to a base member 13 for rotation about an axis 14. Threaded adjustment screws 15 are associated with adjustment slides (not shown) to adjust the position of table 12 along mutually normal axes x and y (Figure 2) in its plane.

The planar surface of table 12 is provided with location means 16 comprising a conical or spherical indent coincident with rotation axis 14 for locating a theodolite optical target (not shown) that is contained in a housing having a part spherical external surface. Two further similar location means 17 and 18 are located on the planar surface of table 12 in known linear and angular relationship to the central location means 16 and each other.

A method of using the apparatus for accurately locating a position in space will now be described with reference to Figures 3 to 8 inclusive.

Three theodolites 19, 20 and 21 of a remote measuring system are located around the object (not shown) with which it is desired to locate a specific position in space.

The theodolites are connected to a computer and are calibrated in known manner relative each other, a reference scale and the object with which a desired position in space is to be located. Appropriate x, y and z co-ordinates are fed into the computer which is instructed to align the three theodolites 19, 20 and 21 to point at the precise position in space that it is desired to locate.

The desired position, illustrated in Figure 3, is the intersection 22 of the lines of sight 19c, 20c, 21c from the respective theodolites.

The position in space tool 11 (Figures 1 and 2) is located in the vicinity of position 22 and the table 12 is adjusted so that its planar upper surface is in either a horizontal plane or a vertical plane as dictated by the particular installation. Conveniently the tool 11 is mounted on a stand provided with means for height adjustment.

A first optical target 23 is located in the location means 16 that is coincident with an axis of rotation 14 of support table 12, and the adjustment screws 15 and the stand height adjuster are adjusted until the intersection 22 of the lines of sight of the three theodolites is centred on the graticule of target 23 (Figure 4).

A second optical target 24 is located in location means 17 and, using the known linear dimension from location means 16, the required position of target 24 is computed. The computer is instructed to point theodolite 20 at the defined position for the second target 24, and table 12 is rotated about axis 14 and the first target 23 in the direction of arrow 30 (Figure 5) until the line of sight 20a from theodolite 20 is centred on the graticule of target 24.

The method so far described is sufficient to accurately locate desired position 22 (Figure 3) however, as a check procedure and to extend the method as hereinafter defined it is necessary to repeat the procedure at location means 18 (Figure 2). Thus, a third optical target 25 is positioned in location means 18 and, using the known linear and angular relationship with location means 16 and 17, the computer calculates the correct position for target 25 and is instructed to point theodolite 19 at the centre of the graticule on target 25.It will be understood that, provided that targets 23 and 24 are set correctly, the theodolite 19 should centre on target 25 without further rotation of table 12, and this provides an accurate check that the position is correctly located and that the planar surface of support table 12 is truly level in a horizontal plane or truly vertical with respect to a horizontal plane if it is so positioned.

Considering for the moment an exemplary practical use of the method and apparatus of the invention as so far described. In the building of large jigs and fixtures as are used for example in the aircraft industry, the accurate positioning of location brackets has been a difficult operation. Conventionally, this has been achieved using stick micrometers, spherical ball suspended by cotton or wire, straight edges clamped to jig structure, spirit levels etc. Such methods are very time consuming, the desired level of accuracy is extremely difficult to achieve, and often production time is extended because construction work has to be suspended while measurements are taken.

In the method and apparatus of this invention it is envisaged that a bracket 26 to be attached to the jig would be located on the planar surface of table 12 in known relationship with intersection point 22 centred on target 23. The accurate positioning of point 22 as hereinbefore described ensures that the bracket 26 is positioned accurately relative the jig and can be attached to the jig by any suitable means such as by plastic metal or dowelling or both directly from its location on table 12.

Figures 7 and 8 illustrate schematically an extension of the method and apparatus hereinbefore described.

A second support table 27 has three conical or spherical location indents in its lower surface corresponding geometrically with the location means 16, 17 and 18 of support table 12, and is located on the three spherically enclosed targets 23, 24 and 25 as shown in Figure 7.

Slip gauges 29 of a desired thickness are located between target 23 and the lower surface of table 27 to set its upper surface at a pre-determined angle to axis 14 (Figure 8). This facilitates the accurate location of a bracket 26 supported by support table 27 at a second angle against the vertical axis, and enables compound angle settings to be achieved.

In preferred embodiments of the invention a camera or low power laser light source is associated with each theodolite so as to enable the intersecting lines of sight to be viewed on a remote monitor to facilitate accurate alignment. In the former case an image of the optical target being sighted by each theodolite can be displayed on a monitor screen having quadrant markings and in the latter case an indicating means such as a photo-electric cell can be associated with each target. This is particularly useful in alignment of the targets when the table 12 is located a long way from the theodolites and/or in a location not easily accessible.

Whilst several embodiments have been described and illustrated it will be understood that many modifications may be made without departing from the scope of the invention. For example, two theodolites is the minimum number required to set up support table 12, and more than the three theodolites of the described embodiment can be used if desired. Height adjustment means can be incorporated in the base 13 of tool 11 so that the tool 11 can be used independently of a support stand and could, for example, be attached directly to a jig in the vicinity of the position that it is desired to locate. As an aid in some applications the surface of support table 12 may be located vertically and suitable retention means used to retain the theodolite targets in position. Other suitable forms of optical targets than those enclosed in part-spherical housings may be used in which case the location means in the support tables may be redesigned accordingly. As an alternative to location of a bracket on the support table 12, the bracket may comprise a drill jig with bushed holes through which attachment holes can be drilled/reamed in the jig itself to facilitate attachment of pre-drilled brackets. As a further alternative the table 12 itself may be provided with one or more sets of bushed holes in known relationship to the position 22 so that dowel holes can be drilled and reamed in a jig directly from the support table 12 for attachment of the bracket. In such an embodiment it may be desirable for the table 12 itself to be rotationally mounted on a support surface on the jig itself and in the required horizontal or vertical orientation.

Claims

1. A method for locating a required position in space using a remote measuring system and comprising the steps of, computing the location of said position, aligning at least two theodolites so that their lines of sight intersect at said position, locating a support table having a rotatable planar surface in the vicinity of said position with its planar surface located in either a horizontal plane or a vertical plane, locating a first optical target on the planar surface of the support table and coincident with an axis of rotation of the support table, adjusting the support table until the first target is located at the intersecting lines of sight from the theodolites, locating a second optical target on the planar surface of the support table and at a known linear distance from the first target, computing the required position of the second target, pointing one of the theodolites at the required position for the second target, and rotating the support table about said axis until the second target is aligned with the line of sight from said one theodolite.

2. The method of Claim 1 including the further steps of, locating a third optical target on the planar surface of the support table in known linear and angular relationship to said first and second targets, computing the required position of the third target, and pointing a theodolite at the required position for the third target whereby the line of sight is automatically aligned with the third target so as to provide a check that the position in space is correctly located and that the planar surface of the support table is correctly aligned in either the horizontal or vertical plane.

3. The method of Claim 2 including the further steps of, locating a second support table having a planar upper surface on said targets and adjusting the angle of the planar surface of the second table with respect to the planar surface of the first table.

4. The method of Claim 3, wherein said angular adjustment is achieved by locating spacers between one or more of the targets and the second support table.

5. A method according to any preceding Claim, wherein a laser means is associated with each theodolite so as to provide visible lines of sight to aid positioning of the targets.

6. A method according to any preceding Claim, including the further steps of inputting the coordinates of the position of each theodolite to a computer having signal connection to each theodolite whereby the computer calculates the coordinates of the desired location position of the optical targets to permit alignment of the theodolites with said positions.

7. Apparatus for use in locating a position in space comprising a support table having a planar upper surface rotatable about an axis, adjustment means for translating said support table about two mutually normal axes in its plane, first location means for locating a first optical target of a remote measuring system on the planar surface at the axis of rotation thereof, and second location means for locating a second optical target of said remote measuring system on the planar surface in known linear relationship with said first location means.

8. Apparatus as claimed in Claim 7, wherein said support table includes a third location means on the planar surface for locating a third optical target of said remote measuring system in known linear and angular relationship with said first and second location means.

9. Apparatus as claimed in Claim 8 and including a second support table having a planar upper surface and three location means at an undersurface thereof and corresponding in linear and angular relationship with the three location means on the first support table so as to facilitate location of said second table on optical targets located by the location means on the first table.

10. Apparatus as claimed in Claim 9 and including adjustment means for adjusting the angular relationship of said second support table with respect to said first support table.

11. Apparatus as claimed in any one of Claims 7 to 10 inclusive and including adjustment means for vertical adjustment of the rotatable support table.

12. Apparatus as claimed in any one of Claims 7 to 11 inclusive, wherein said location means comprise conical indents for locating the optical targets.

13. Apparatus as claimed in any one of Claims 7 to 12 inclusive, wherein said remote measuring system includes at least three theodolites each having signal connection with a computer.

14. Apparatus as claimed in any one of Claims 7 to 13 inclusive and including a camera associated with each theodolite for displaying on a monitor screen having quadrant markings an image of the optical target being sighted by each theodolite.

15. Apparatus as claimed in any one of Claims 7 to 13 inclusive, wherein a laser is associated with each theodolite to provide visible lines of sight to aid positioning of the targets.

16. Apparatus as claimed in Claim 15 and including indicating means associated with each target to facilitate accurate alignment of the theodolites.

17. Apparatus as claimed in Claim 16, wherein said indicating means comprise a photo-electric cell.

18. Every novel feature and every novel combination of features disclosed herein.