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Dr. Steven D. PhillipsDr. Steven D. PhillipsDimensional Metrology Program ManagerDimensional Metrology Program Manager
National Institute of Standards and TechnologyNational Institute of Standards and Technology
Laser Trackers: Laser Trackers: Testing and StandardsTesting and Standards
Large Scale MetrologistsLarge Scale MetrologistsBalaBala MuralikrishnanMuralikrishnan
Dan SawyerDan SawyerChris BlackburnChris BlackburnBruce BorchardtBruce Borchardt
Tyler Tyler EstlerEstlerCraig Craig ShakarjiShakarji
OverviewOverview
Briefly about Laser TrackersBriefly about Laser TrackersB89.4.19 Standard & Tests ResultsB89.4.19 Standard & Tests ResultsVDI/VDE 2617 Draft Standard VDI/VDE 2617 Draft Standard Final RemarksFinal Remarks
X
Y
Z
x
y
z
Horizontal Axis
R
φ
θ
Ver
tical
Axi
s
Laser Trackers:Laser Trackers:Coordinate Measuring Machines Coordinate Measuring Machines Using Spherical CoordinatesUsing Spherical Coordinates
Laser Trackers:Laser Trackers:Optics Link the Workpiece & CMM Optics Link the Workpiece & CMM
•Allows large measurement volumes
•Bring the tracker to the
workpiece
•Lower capital costs than large conventional CMMs
•Factory can be reconfigured
Laser Trackers:Laser Trackers:Type of Ranging Systems Type of Ranging Systems
Laser Radar• Non cooperative target OK
• Moderate accuracy
• More expensive
HeNe Interferometer• Very High Accuracy
• Do NOT break beam during measurement
• Requires cooperative target, e.g. retroreflector
Absolute Distance Measuring System• Good Accuracy
• Can break beam & measure directly to targets
• Requires cooperative target, e.g. retroreflector
ASME B89.4.19 Laser Tracker StandardASME B89.4.19 Laser Tracker Standard
Designed to Test Cooperative Target SystemsDesigned to Test Cooperative Target SystemsFocused on Manufacturing (Indoor) EnvironmentFocused on Manufacturing (Indoor) EnvironmentTests Ranging and Volumetric PerformanceTests Ranging and Volumetric PerformanceDoes not address:Does not address:–– Outdoor EnvironmentsOutdoor Environments
Rain; Fog Rain; Fog
–– NonCooperativeNonCooperative Targets: Targets: Concrete; Wood; DirtConcrete; Wood; Dirt
–– Dynamic effectsDynamic effectsMotion in the field of viewMotion in the field of view
Available At www.ASME.org
(search on B89.4.19)
Ranging Test using 6 Calibrated LengthsRanging Test using 6 Calibrated Lengths
L1 L2
L3 L4
Target Nests
Nest b
Nest a
h
1D Cooperative Target Range Facility1D Cooperative Target Range FacilityNIST System ConfigurationNIST System Configuration
Interferometer
Instrument under test
Carriage can accommodate a variety of targets
11--D Cooperative Target Range FacilityD Cooperative Target Range Facility
Reference retroreflector
Target retroreflector
11--D Cooperative Target Range FacilityD Cooperative Target Range Facility
Range: 60 m (200 feet)
Temperature: 20 ± 0.2 ° C
Sensors:
U(T) = 0.01 °C, spaced @ 10 m
U(P) = 20 Pa
U(RH) = 1 % RH
U(L) = 5 μm + 3 × 10-7
11--D Cooperative Target Range FacilityD Cooperative Target Range FacilityRanging test of an IFM tracker showing vacuum wavelength errorRanging test of an IFM tracker showing vacuum wavelength error
0 1 0 2 0 3 0 4 0 5 0 6 0- 0 . 0 7
- 0 . 0 6
- 0 . 0 5
- 0 . 0 4
- 0 . 0 3
- 0 . 0 2
- 0 . 0 1
0
0 . 0 1
0 . 0 2
D is p la c e m e n t ( m )
Erro
r (m
m)
R u n # 1C o r r e c te d r u n # 1R u n # 2C o r r e c te d r u n # 2E r r o r d u e to i n c o r r e c t w a v e l e n g th
1 x 10-6
Wavelength in instrument = 632.990400 nmCalibrated wavelength (NIST) = 632.991061 nm Difference = 0.6 × 10-3 nmRelative length error = 0.6 × 10-3 nm / 633 nm = 1 × 10-6
11--D Cooperative Target Range FacilityD Cooperative Target Range Facility
0 5 1 0 1 5 2 0 2 5 3 0 3 5-0 . 0 4
-0 . 0 3
-0 . 0 2
-0 . 0 1
0
0 . 0 1
0 . 0 2
0 . 0 3
0 . 0 4
D is p la c e m e n t (m )
Erro
r (m
m)
R u n # 1R u n # 2R u n # 3M P E
Ranging test of an IFM tracker; passing specificationsRanging test of an IFM tracker; passing specifications
+MPE
−MPE
11--D Cooperative Target Range FacilityD Cooperative Target Range FacilityRanging test of an ADM tracker passing specificationsRanging test of an ADM tracker passing specifications
0 1 0 2 0 3 0 4 0 5 0 6 0-0 . 0 8
-0 . 0 6
-0 . 0 4
-0 . 0 2
0
0 . 0 2
0 . 0 4
0 . 0 6
0 . 0 8
D is p la c e m e n t (m )
Erro
r (m
m)
R u n # 1R u n # 2R u n # 3M P E
+MPE
−MPE
Significantly morepoints sampled than required by B89.4.19
Ranging System Test on ADM #2-2
0.000
0.100
0.200
0.300
0.400
0 5 10 15 20 25
Length, m
Erro
r, m
m
11--D Cooperative Target Range FacilityD Cooperative Target Range FacilityRanging test of an ADM tracker showing complex Ranging test of an ADM tracker showing complex range errors before compensation & small errors range errors before compensation & small errors after compensationafter compensation
Before Cal
After Cal
Volumetric System Tests:Volumetric System Tests:Check OpticalCheck Optical--Mechanical AlignmentsMechanical Alignments
Volumetric System TestsVolumetric System Tests
b
a
A
D h
Target stands
Standing axis
a
bh
D
Target nestsA
Standing axis
Horizontal Positions Vertical Positions
Volumetric System TestsVolumetric System Tests
Right Diagonal Position Left Diagonal Position
45 degrees0.7A
h
a
b Target nests
D
0.7A
Standing axis A
45 degrees
h
0.7A
D
a
b
Target nests
0.7A
Standing axis
A
Large Scale Volumetric Test FacilityLarge Scale Volumetric Test Facility
B89.4.19 Volumetric System TestsB89.4.19 Volumetric System Tests(Horizontal Tests)(Horizontal Tests)
Back to back target SMRs
LaserInterferometer
B89.4.19 Volumetric System TestsB89.4.19 Volumetric System Tests(Horizontal Tests (Horizontal Tests –– Physical Artifact)Physical Artifact)
B89.4.19 Volumetric System TestsB89.4.19 Volumetric System Tests(Diagonal Tests)(Diagonal Tests)
Volumetric Performance Test on ADM #6
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
Erro
r, m
m
1st reading
2nd reading
3rd reading
+MPE
-MPE
Vertical Right DiagonalHorizontal Left Diagonal User
All readings in ADM mode unless otherw ise indicated
3m
6m
3m
6m
3m
6m
3m
6m
1m
3m5m
0 9 0 18 0 2 7 0 0 9 0 18 0 2 7 0 0 9 0 18 0 2 7 0 0 9 0 18 0 2 7 0 0 9 0 18 0 2 7 0 0 9 0 18 0 2 7 0 0 9 0 18 0 2 7 0 0 9 0 18 0 2 7 0
B89.4.19 Volumetric System TestsB89.4.19 Volumetric System TestsVolumetric test of an ADM, passing MPE specificationsVolumetric test of an ADM, passing MPE specifications
B89.4.19 Volumetric System TestsB89.4.19 Volumetric System Tests
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
Erro
r (m
m)
1st reading2nd reading3rd readingMPE
3m 6m 3m 6m 3m 6m 3m 6m0 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270
3 m 6 m
3 m6 m
3 m6 m
3 m6 m
1 m
Horizontal Vertical Right Diagonal Left Diagonal
Volumetric test of an IFM tracker, failing MPE specificationsVolumetric test of an IFM tracker, failing MPE specifications
B89.4.19 Volumetric System TestsB89.4.19 Volumetric System Tests
H o r 3 m
H o r 6 m
V e r 3 m
V e r 6 m
R D 3 m
R D 6 m
L D 3 m
L D 6 m
0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0
Erro
r
Beam Tilt (X)
Beam Tilt (Y)
Horizontal Angle Encoder Eccentricity (Y)
Horizontal Angle Encoder Eccentricity (X)
0 5 1 0 1 5 2 0 2 5 3 0 3 5-0 .4
-0 .2
0
0 .2
0 .4
Erro
r (m
m)
M e a s u re d e rro rsS im u la te d e rro rs
H o r 3 m
H o r 6 m
V e r 3 m
V e r 6 m
R D 3 m
R D 6 m
L D 3 m
L D 6 m
0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0
(0 5 1 0 1 5 2 0 2 5 3 0 3 5
-0 .4
-0 .2
0
0 .2
0 .4
Erro
r (m
m)
M e a s u re d e rro rsS im u la te d e rro rs
0 5 1 0 1 5 2 0 2 5 3 0 3 5-0 .4
-0 .2
0
0 .2
0 .4
Erro
r (m
m)
M e a s u re d e rro rsS im u la te d e rro rs
H o r 3 m
H o r 6 m
V e r 3 m
V e r 6 m
R D 3 m
R D 6 m
L D 3 m
L D 6 m
0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0
(
Simulated and actual errors for the volumetric testSimulated and actual errors for the volumetric test
B89.4.19 Two Face TestB89.4.19 Two Face Test
B89.4.19 Two Face TestsB89.4.19 Two Face Tests
0
0.05
0.1
Erro
r (m
m)
1st reading2nd reading3rd readingMPE
0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270
D minimum 3 m 6 m
Low Mid High Low Mid High Low Mid High
Two face test of an ADM tracker, passing MPE specificationsTwo face test of an ADM tracker, passing MPE specifications
B89.4.19 B89.4.19 Two Face Two Face TestsTests
0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270
D minimum 3 m 6 m
Low Mid High Low Mid High Low Mid High
0
0.1
0.2
0.3
0.4
0.5
Erro
r (m
m)
1st reading2nd reading3rd readingMPE
Two face test of an ADM tracker, failing MPE specificationsTwo face test of an ADM tracker, failing MPE specifications
B89.4.19 B89.4.19 Two Face Two Face TestsTests
0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270
D minimum 3 m 6 m
Low Mid High Low Mid High Low Mid High (Kz)
Erro
r
Horizontal angle encoder eccentricity (X) Horizontal angle encoder eccentricity (Y)
0 5 10 15 20 25 30 350
0.1
0.2
0.3
0.4
0.5
Erro
r (m
m) Measured errors
Simulated errors
Simulated and actual errors for the two face testSimulated and actual errors for the two face test
VDI / VDE Tracker Draft
Use a measurement volume ≈ 3 x 6 x 10 m with multiple calibrated lengths created via distances between fixed mounts
Evaluate the observed errors against the manufacture's MPE specification
VDI / VDE Tracker Draft
Projecting the lengths onto a wall and moving the tracker makes the set up easier
VDI / VDE Tracker Draft
“Probe Test” to check the SMR size and form
Similar to the ISO CMM probe test
25 measurement points on a calibrated test sphere:
Report: Size and Form error
Final Thoughts On Laser TrackersFinal Thoughts On Laser TrackersLarge Measurement Volumes; range Large Measurement Volumes; range > 30 m> 30 m–– Very Low Cost Compared to Large CMMsVery Low Cost Compared to Large CMMs
Portable, Bring the Tracker to the WorkpiecePortable, Bring the Tracker to the Workpiece–– Allows Factory Floor to be Easily ReconfiguredAllows Factory Floor to be Easily Reconfigured
ADM Systems Yield Direct MeasurementsADM Systems Yield Direct Measurements–– No Issue with Beam Breakage or No Issue with Beam Breakage or ““WalkoutWalkout””
Standardized Tracker Tests AllowTracker Tests Allow– For manufacturers to specify performance– For users to test performance – Detection of most tracker errors
– Test results that are metrologically traceable(e.g., per ASME B89.7.5)
Final Thoughts On Laser Trackers
ISO Working Draft for Trackers– Combines B89 & VDI work– Improves sensitivity to errors– Includes SMR probe test– Includes workpiece CTE compensation test
Laser Trackers: Laser Trackers: Testing and StandardsTesting and Standards
Q & AQ & A
Disclaimer:
Data on commercial products are only provided for the sake of describing experimental results. NIST does not endorse or recommend any commercial products or imply that this equipment is the best for any particular application.