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
  • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
• • 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

Definitions

• the present invention relates to a system as well as a method to scan the geometry of objects as described in the introduction to claims 1 and 11
• a coordinate measurement machine is complex, inflexible and costly
• An alternative is attaching a scanner to a robot, in such a way that the robot moves the scanner across the object. For each position, a part ofthe surface is scanned. This measurement is registered relative to the position ofthe scanner, and is transformed to a global coordinate system provided by the robot.
• the present invention combines a solution comprising a robot and scanner with use of a position measuring device as described in Norwegian Patent No 303 595
• the scanner and the position measuring device are integrated into one sensor unit
• the position measuring device provides information on the exact position of the scanner
• the robot is only used to move the sensor unit
• Figure 2 shows an alternative configuration
• Figure 3 shows as an example a scanner unit, a triangulation sensor
• Figure 4 shows an example of a position measuring device as described in Norwegian patent No 303 595
• Figure 5 shows a method for determining the internal geometry ofthe sensor unit
• Figure 1 shows an example of a configuration ofthe system. It consists of principally two units, a sensor 1 and a robot 4. The robot is used to position the sensor in relation to the current area 12 on the object 6 The sensor 1 registers the local geometry ofthe object, and measures its own position relative to a global coordinate system 13
• the sensor unit 1 consists of a scanner unit 2 for local scanning of geometry plus position measuring unit 3 to determine the sensor unit's own position relative to the global coordinate system 13.
• the scanner unit 2 e.g. a laser scanner, emits a laser beam 11 which scans a limited region 12
• the position measuring unit 3 registers its own position, and thereby the position ofthe sensor unit 1, relative to a network 8 of reference points 9
• the positions ofthe reference points are known relative to the global coordinate system 13
• the system also includes a computing unit 5 which collects the data from scanner unit 2 and position measuring unit 3 and transforms all information from the scanner unit to the same global coordinate system 13.
• the computing unit 5 also sends data to the robot 4 to control the robot's movement relative to the object.
• FIG. 1 shows an alternative configuration
• the reference points 9 are attached to the object 6
• the position measuring unit 3 is placed to view these reference points.
• the scanner unit 2 can e g be one ofthe following types, but is not limited to this
• Triangulation sensor based on single-axis scanning laser or laser line projection combined with camera (e.g CCD sensor) Such a sensor scans one line from each sensor position
• Triangulation sensor based on dual-axis scanning laser or laser raster projection combined with camera e g CCD sensor
• Sensor based on projection of pattern combined with one or more cameras e g CCD sensor
• Figure 3 shows the principle for a triangulation sensor It contains a laser 14 which emits a laser beam 11 or a laser plane (line projection) The laser projects a point 15 or a line on the object 6
• the point 15 is imaged through a lens 16 onto a sensor 17, e g a CCD array
• the scanner unit 2 is calibrated in such a way that it measures the position ofthe point 15 relative to an internal coordinate system 18
• the laser beam can be aimed at the surface through a two-axis, movable mirror In this way, a region ofthe surface can be scanned from each position ofthe triangulating sensor
• the significant characteristic ofthe scanner is that it registers the local geometry of an object relative to the internal coordinate system ofthe scanner For each scanner position, a registration can be made of a point, points along a line, or points in a two- dimensional pattern
• the position measuring device 3 is of a type described in Norwegian patent No 303 595, as shown in figure 4 Essentially, this comprises one or more cameras mounted together in a unit. Each camera sees a reference pattern in the form of points, lines or other easily recognizable objects. For each position ofthe sensor unit 1, the points 9 in the reference pattern 8 are imaged through the lens 19 onto the sensor 20 The data is transferred to the computing unit 5 Software in the computing unit calculates the position and orientation ofthe position measuring unit 3 relative to the reference pattern 8 The position measuring device in figure 4 is shown with carrying handle 21 and activation switch 22 for manual operation. Also shown is an illumination source 23 for illumination ofthe reference pattern 8, and a mechanical probe 24 for point by point measurement by touching an object, as described in Norwegian patent No 303 595
• the reference pattern 8 is known in the coordinate system of the object, or is a part ofthe object itself as depicted in figure 2 This can be achieved if the object has holes that can be recognized by the position measuring device, or if the reference pattern is attached to the object, e g by mounting easily recognizable targets into holes or depressions in the object These targets may e g be purely passive markers, light sources, light reflectors or similar It is significant that the geometrical relationship between the scanner unit 2 and the unit 3 for measuring position be known and stable This can partly be achieved through a stable, precise and known mechanical construction, and through separate calibration as described below
• the sole purpose ofthe robot 4 is to position the sensor unit 1 in the correct position and o ⁇ entation relative to the object 6
• robot p ⁇ nciples may be used, e g arm robots, Cartesian robots, and robots with one, two, three or more degrees of freedom
• the robot may be controlled by a predefined program, or by using the measured position ofthe sensor unit relative to the object and feed the robot instructions for relative movement in relation to the current position
• Figure 5 illustrates a method for determining this relationship
• the sensor unit 1 is positioned such that at least three ofthe reference points 9 are inside its measurement volume

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Length Measuring Devices By Optical Means (AREA)
• Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
• Mechanical Optical Scanning Systems (AREA)
• Ultra Sonic Daignosis Equipment (AREA)

Applications Claiming Priority (3)

Publications (1)

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ID=19903575

Family Applications (1)

Country Status (5)

Families Citing this family (24)

Family Cites Families (10)

• 1999
  • 1999-07-13 NO NO19993446A patent/NO313113B1/no not_active IP Right Cessation
• 2000
  • 2000-07-10 AU AU74599/00A patent/AU7459900A/en not_active Abandoned
  • 2000-07-10 EP EP00963149A patent/EP1200798A1/en not_active Withdrawn
  • 2000-07-10 JP JP2001512250A patent/JP2003505682A/ja active Pending
  • 2000-07-10 WO PCT/NO2000/000235 patent/WO2001007866A1/en active Application Filing

Non-Patent Citations (1)

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