EP1190207A1 - Appareil de mesure servant a mesurer la position et l'orientation d'une premiere piece destinee a etre usinee, controlee et deplacee - Google Patents

Appareil de mesure servant a mesurer la position et l'orientation d'une premiere piece destinee a etre usinee, controlee et deplacee

Info

Publication number
EP1190207A1
EP1190207A1 EP00937085A EP00937085A EP1190207A1 EP 1190207 A1 EP1190207 A1 EP 1190207A1 EP 00937085 A EP00937085 A EP 00937085A EP 00937085 A EP00937085 A EP 00937085A EP 1190207 A1 EP1190207 A1 EP 1190207A1
Authority
EP
European Patent Office
Prior art keywords
light
imaging devices
light sources
distribution
orientation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00937085A
Other languages
German (de)
English (en)
Inventor
Richard Michael Gooch
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BAE Systems PLC
Original Assignee
BAE Systems PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by BAE Systems PLC filed Critical BAE Systems PLC
Publication of EP1190207A1 publication Critical patent/EP1190207A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes

Definitions

  • This invention relates to measurement apparatus for measuring the position and orientation of a first part to be worked, inspected or moved.
  • a variety of contact measurement devices have been developed having a touch probe device at one end to register contact with a feature or object on a part, and having a number of pin-jointed angled connections along its length. The number of connections determines the degrees of measurement, and there are typically six. Each joint is precision machined to a specified tolerance, each of which in combination provides a discrete overall system accuracy. The obvious limitation with such systems is that the touch probe is required to contact the part to be measured, limiting its range of application.
  • Laser trackers which are non-contact polar devices utilising an interferometer, are commonly used to measure the angles of elevation and azimuth as well as the range of a single retro-reflective target.
  • Typical systems require positioning of corner cubes (tooling-balls) to re-direct the incoming laser beam at various positions on the part.
  • corner cubes toolsing-balls
  • the most important limitation of this type of system is that it only measures position to three degrees, and thus provides no information on orientation of the part.
  • CCD Charge Couple Device
  • the measurement equipment For measurements of this type, the measurement equipment is typically set up in a 'workcell' area, and the part to be worked, tested or inspected is brought into the workcell for measurements to be made.
  • a photogrammetry system has been developed which positions the imaging devices (may be CCD cameras) on a robot body, which brings them closer to the part to be worked by the robot than if they were mounted remotely therefrom, as described above. Nevertheless, this still constrains the part to be worked to be brought to the cell where the robot is mounted, as these are typically substantial objects.
  • apparatus for measuring the position and orientation of a first part to be worked, inspected or moved, which first part is to be carried by the apparatus or is separate therefrom including an end-effector, at least two imaging devices, O 01/01068 _ 4 _ PCT/GBOO/02236
  • first light sources each attachable to the end-effector and each configurable to image a first face of the first part, a plurality of first light sources, which first light sources include active light sources and/or illuminable reflecting points and are positionable on said first part, so that when light is projected or reflected from each of the first light sources when positioned on the first surface of the first part, a distribution of light is generated at each of said at least two imaging devices, each of which at least two imaging devices is operable to output signals indicative of the distribution of light received by the respective imaging device, a processor for receiving and processing the output signals indicative of the distribution of light from each of said imaging devices, and calibrating means in operative association with the processor for calibrating the output signals indicative of the distribution of light processed by the processor so as to define the position and orientation of the first part.
  • the end-effector includes means for mounting a second part thereon.
  • each of the at least two imaging devices is a metrology sensor operable to create digitisable images.
  • the plurality of first light sources is a plurality of reflective targets, each positionable on the first part.
  • each of the plurality of reflective targets is fabricated from retro-reflective material. O 01/01068 c _ PCT/GBOO/02236
  • the plurality of reflective targets includes at least six reflective targets, each of which is non-planar and non-linearly spaced with respect to each other.
  • communication links between the imaging devices and the processor for transmitting the output signals indicative of the distribution of light at each of the operating positions which links include coaxial cables and framegrabber ports.
  • the calibrating means includes a sensor co-ordinate frame of reference, which sensor co-ordinate frame of reference is a co-ordinate frame of the at least two imaging devices, combining means for combining the output signals from the at least two imaging devices so as to define first light positions of said first light sources in the sensor co-ordinate frame, and transformation means for locating said first light positions on the first part in the sensor coordinate frame.
  • the means for mounting the second part is a drill mount.
  • the second part is a drill.
  • the means for mounting the second part is a jig having a plurality of suction devices removably attachable thereto, which suction devices are operatively associated with pneumatic means.
  • imaging devices substantially equi- spaced about a central axis of the jig. O 01/01068 _ g _ PCT/GBOO/02236
  • a method for measuring the position and orientation of a first part to be worked, inspected or moved, which first part is to be carried by the apparatus or is separate therefrom including the steps of imaging on at least two imaging devices a distribution of light projected or reflected from a plurality of first light sources, which first light sources include active light sources and/or illuminable reflecting points, transmitting signals indicative of the distribution of light from each of the at least two imaging devices to a processor, processing the signals, and calibrating from the processed signal the distribution of light using calibrating means so as to determine the position and orientation of the first part.
  • the calibration of the distribution of light includes the steps of identifying each active light source and/or illuminable reflecting point comprising the plurality of first light sources from the output signals from the at least two imaging devices so as to define a first position thereof in a sensor co-ordinate frame, which sensor co-ordinate frame is a co-ordinate frame of the at least two imaging devices, combining each of the first positions to generate a plurality of first positions in the sensor co-ordinate frame, and transforming the plurality of first positions into locations with respect to the first part, so as to define the position and orientation of the first part in the sensor co-ordinate frame.
  • Figure 1 is a schematic perspective representation of apparatus for measuring the position and orientation of a first part to be worked, inspected or moved according to a first embodiment of the present invention
  • Figure 2 is a schematic perspective representation of apparatus for measuring the position and orientation of a first part to be worked, inspected or moved according to a second embodiment of the present invention
  • Figure 3 is a schematic block diagram of the apparatus of Figures 1 or 2 showing calibrating means.
  • Apparatus for measuring the position and orientation of a first part to be worked, inspected or moved, according to the present invention, as shown in Figures 1 to 3 is intended for use in situations where non-contact, accurate measurements are required, and where the working volume of the apparatus should overlap with the working volume of additional parts, for example a robot, which are used to control the position and orientation of the first part.
  • the apparatus is thus suited for use with a variety of robots and machine tools.
  • Figure 1 of the accompanying drawings shows apparatus according to a first embodiment of the present invention for measuring the position and orientation of a first part 1 to be worked, inspected or moved, which first part 1 is to be carried by the apparatus or is separate therefrom, includes an end- effector 2, at least two imaging devices 3a, 3b, each attachable to the end- effector 2 and each configurable to image a first face 4 of the first part 1 , and a plurality of first light sources 5.
  • the first light sources 5 include active light sources and/or illuminable reflecting points and are positionable on said first O 01/01068 _ o _ PCT/GBOO/02236
  • each of the imaging devices 3a, 3b is operable to output signals 6a, 6b indicative of the distribution of light, and a processor 7 is provided for receiving and processing the output signals 6a, 6b, which processor is in operative association with calibrating means 12, shown in Figure 3.
  • the calibrating means 12 calibrates the output signals 6a, 6b processed by the processor 7 so as to define the position and orientation of the first part 1.
  • the end effector 2 includes means 2a for mounting a second part 8 thereon, where the means 2a for mounting a second part is a drill mount 13 and the second part 8 is a drill.
  • the apparatus includes at least two second light sources 9a, 9b, each associated with a respective imaging device 3a, 3b.
  • the plurality of first light sources 5 in the Figure 1 embodiment is a plurality of reflective targets, each positionable on the first part 1 , and each fabricated from retro-reflective material such that light projected by each of the second light sources 9a, 9b is reflected back therefrom in the exact direction of the incident ray.
  • at least six such targets each of which is non-planar and non-linearly spaced with respect to each other, require to be placed on the first part 1.
  • a minimum of three is required. O 01/01068 _ g _ PCT/GBOO/02236
  • Each of the at least two imaging devices 3a, 3b is preferably a metrology sensor operable to create digitisable images, such that the light projected or reflected from each of the first light sources 5 is reproduced as an image of white pixels against a dark background, which white pixels define a two dimensional spatial location of the first light sources 5 on each of the imaging devices 3a, 3b.
  • These images are communicated as output signals 6a, 6b by means of communication links 11 , which are preferably coaxial cables or twisted pairs, to the processor 7 through framegrabber ports 11a, 11b.
  • the output signals 6a, 6b contain video data in a format such as International Radio Consultative Committee (CCIR).
  • CCIR International Radio Consultative Committee
  • the calibrating means 12 operates upon this data, using a sensor co-ordinate frame of reference 12a, typically determined off-line by standard stereo triangulation techniques, which sensor co-ordinate frame of reference 12a defines a single co-ordinate frame of reference corresponding to the at least two imaging devices 3a, 3b.
  • the calibrating means 12 further includes combining means 12b for combining the output signals 6a, 6b in the form of bitmap images corresponding to the at least two imaging devices 3a, 3b so as to define first light positions 12c of the first light sources 5 in the sensor co-ordinate frame 12a, and transformation means 12d for locating the first light positions 12c on the first part 1 in the sensor coordinate frame 12a.
  • Figure 2 of the accompanying drawings shows apparatus according to a second embodiment of the present invention for measuring the position and orientation of a first part to be worked, inspected or moved, generally similar to O 01/01068 _ .
  • the end effector 2 includes means 2a for mounting a second part 8 thereon, where the means 2a for mounting a second part is a jig 14 having a plurality of suction devices 15 removably attachable thereto and the second part 8 is the first part 1.
  • the means 2a may alternatively be provided by magnetic or mechanical gripping means.
  • the apparatus of the invention is operable to measure a position and orientation of a first part 1 to be worked, inspected or moved by implementing a method of the invention, which method is identically applicable to both embodiments.
  • the method will be described with reference to the first embodiment, illustrated in Figure 1 , and includes the steps of imaging on at least two imaging devices 3a, 3b a distribution of light projected or reflected from a plurality of first light sources, then transmitting signals 6a, 6b indicative of the distribution of light from each of the imaging devices 3a, 3b to a processor 7.
  • These signals 6a, 6b are analogue signals that are digitised by a framegrabber in the processor 7 and are stored in memory as bitmaps 16a, 16b for further processing.
  • the further processing includes identifying each of the first light sources 5 from the bitmaps 16a, 16b corresponding to the output signals 6a, 6b so as to define positions thereof in a sensor co-ordinate frame 12a, shown schematically in Figure 3. This therefore requires determination of the sensor co-ordinate O 01/01068sky-offsets of the sensor co-ordinate O 01/01068sky-offsets of the sensor co-ordinate frame 12a, shown schematically in Figure 3.
  • sensor co-ordinate frame 12a conveniently defines a single co-ordinate frame of reference, to which measurements taken by either of the imaging devices 3a, 3b can be related. This is typically performed off-line, and there are several methods known in the art to achieve this.
  • One such method includes taking measurements of active light sources which are positioned at pre-specified locations in a known co-ordinate frame from numerous imaging positions, and mathematically optimising the measurements so as to derive a transformation describing the relationship between each of the imaging devices
  • the distribution of light stored in the bitmaps 16a, 16b are calibrated so as to determine the position and orientation of the first part.
  • the bitmaps 16a, 16b are stored in memory, contain a two dimensional array of pixel light intensity values corresponding to a sampling of the output signals 6a, 6b, and are each analysed by the processor 7 to locate, in two dimensional space, and in the sensor co-ordinate system 12a, a plurality of bright dots 17a, 17b. These bright dots 17a, 17b are assumed to correspond with first light sources 5 recorded by the imaging devices 3a, 3b.
  • the calibration is performed by the processor 7, which performs calculations to project rays from each of the plurality of bright dots 17a, 17b into three dimensional space, using a focal length characteristic of the respective imaging device 3a, 3b.
  • each of the plurality of dots 17a, 17b have corresponding lines 18a, 18b projecting therefrom, and the intersection of each of these lines defines a plurality of first positions 12c in the sensor co-ordinate frame 12a.
  • first positions 12c require transforming into locations 12d with respect to the first part 1 , so as to define the position and orientation of the first part 1 in the sensor co-ordinate frame 12a.
  • This can be achieved by following one of several techniques known in the art, for example by positioning at least three of the first light sources 5 at a datum location specified in a corresponding CAD model of the first part 1.
  • the locations 12d of the remaining first light sources 5 are then readily calibrated relative thereto.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

La présente invention concerne un appareil de mesure servant à mesurer la position et l'orientation d'une première pièce (1) destinée à être usinée, contrôlée et déplacée, ladite première pièce (1) étant portée par l'appareil ou séparée de celui-ci. L'appareil comprend: un effecteur terminal (2); au moins deux dispositifs d'imagerie (3a, 3b) pouvant être chacun fixés à l'effecteur terminal (2) et pouvant être chacun configurés pour donner une image d'une première face (4) de la première pièce (1); une pluralité de premières sources de lumière (5) comprenant des sources de lumière actives et/ou des points de réflexion pouvant être éclairés, et pouvant être placées sur ladite première pièce (1) de sorte que lorsque de la lumière est projetée ou réfléchi à partir de chacune des premières sources de lumière (5) étant placées sur la première face (4) de la première pièce (1), une distribution de lumière est produite au niveau de chacun des deux ou plus dispositifs d'imagerie (3a, 3b) pouvant chacun produire des signaux (6a, 6b) représentant la distribution de lumière reçue par le dispositif d'imagerie respectif; un processeur (7) destiné à recevoir et à traiter les signaux produits (6a, 6b) représentant la distribution de lumière reçue par chaque dispositif d'imagerie (3a, 3b); et des éléments de calibrage (12) qui coopèrent avec le processeur (7) pour calibrer les signaux produits (6a, 6b) représentant la distribution de lumière traitée par le processeur (7) afin de définir la position et l'orientation de la première pièce (1).
EP00937085A 1999-06-26 2000-06-08 Appareil de mesure servant a mesurer la position et l'orientation d'une premiere piece destinee a etre usinee, controlee et deplacee Withdrawn EP1190207A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB9914914 1999-06-26
GBGB9914914.8A GB9914914D0 (en) 1999-06-26 1999-06-26 Measurement apparatus for measuring the position and orientation of a first part to be worked, inspected or moved
PCT/GB2000/002236 WO2001001068A1 (fr) 1999-06-26 2000-06-08 Appareil de mesure servant a mesurer la position et l'orientation d'une premiere piece destinee a etre usinee, controlee et deplacee

Publications (1)

Publication Number Publication Date
EP1190207A1 true EP1190207A1 (fr) 2002-03-27

Family

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Application Number Title Priority Date Filing Date
EP00937085A Withdrawn EP1190207A1 (fr) 1999-06-26 2000-06-08 Appareil de mesure servant a mesurer la position et l'orientation d'une premiere piece destinee a etre usinee, controlee et deplacee

Country Status (5)

Country Link
EP (1) EP1190207A1 (fr)
JP (1) JP2003503684A (fr)
AU (1) AU5237600A (fr)
GB (1) GB9914914D0 (fr)
WO (1) WO2001001068A1 (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20010056574A1 (en) * 2000-06-26 2001-12-27 Richards Angus Duncan VTV system
US7480037B2 (en) * 2005-12-02 2009-01-20 The Boeing Company System for projecting flaws and inspection locations and associated method
EP2131146A1 (fr) * 2008-06-02 2009-12-09 Saab Ab Positionnement d'un objet réfléchissant la lumière utilisant des faisceaux lumineux en forme de ligne
US8899535B2 (en) * 2012-04-05 2014-12-02 The Boeing Company Mount for a calibration standard
US11648677B2 (en) * 2019-05-28 2023-05-16 Vehicle Service Group, Llc Automatic wheel changer robot

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4654949A (en) * 1982-02-16 1987-04-07 Diffracto Ltd. Method for automatically handling, assembling and working on objects
JPS6212483A (ja) * 1985-05-30 1987-01-21 Nachi Fujikoshi Corp 自動車窓ガラスの自動取付装置
NO164946C (no) * 1988-04-12 1990-11-28 Metronor As Opto-elektronisk system for punktvis oppmaaling av en flates geometri.

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO0101068A1 *

Also Published As

Publication number Publication date
AU5237600A (en) 2001-01-31
GB9914914D0 (en) 1999-08-25
JP2003503684A (ja) 2003-01-28
WO2001001068A1 (fr) 2001-01-04

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