Jonathan Abir and James Norman - Cranfield University
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Transcript of Jonathan Abir and James Norman - Cranfield University
From meso scale to metre scale: developments in metrology frame
technologies
Jonathan Abir & James Norman
Jonathan Abir [email protected]
James Norman [email protected]
1
Paul Morantz Stefano Longo
Paul Shore
Xavier Tonnellier Paul Morantz
Future Challenges of Instrumentation and Control in Ultra Precision Manufacturing - 18 May 2016 at Renishaw plc. Organised by the EPSRC Centre for Innovative Manufacturing in Ultra Precision, Cranfield University.
Machine frame
There are two primary functions for a machine frame:
• Transferring forces • Position reference – metrology frame
There are two primary disturbances distorting position measurement and control:
• Processing and servo forces >1 Hz • Thermal forces <<1 Hz
Machine tools and measurement systems alike require precision positioning capability to enable:
• Accurate production of components • Low uncertainty measurement for verification of components
2 Jonathan Abir [email protected]
James Norman [email protected]
Machine frame concepts reducing processing disturbances
Conventional
X
F Carriage
Frame
X
F Carriage
Force frame
Metrology frame
Metrology frame
X
F Carriage
Frame
BM
Balancing Mass
3 Jonathan Abir [email protected]
James Norman [email protected]
Machine frame concepts reducing thermal disturbances
X
F Carriage
Force frame
Metrology frame
Metrology frame
4
Model based compensation technique
1 0
1 0
( )m
m
n
n
b s b s bG s
a s a s a
Jonathan Abir [email protected]
James Norman [email protected]
5
Metrology frame in a machine tool
OAGM 2500 - Off Axis Grinding Machine
Glass reference bars
www.cranfieldprecision.com Shore P. et al. Big OptiX ultra precision grinding/measuring system. 2005.
Jonathan Abir [email protected]
James Norman [email protected]
6
Metrology frame in a CMM
PTB µCMM ~ 250 nm surface measurement uncertainty
Küng A. et al. Ultraprecision micro-CMM using a low force 3D touch probe, 2007.
Jonathan Abir [email protected]
James Norman [email protected]
Virtual Metrology Frame Idea
Virtual Metrology Frame
F Carriage
Frame
7
X X
Jonathan Abir [email protected]
James Norman [email protected]
The advantages of Virtual Metrology Frame
• Enhance machine performance with minimal interference
8
Meso scale machine
Metre scale machine
• Optimal solution
Expandable measurement volume with no extra cost Limited machine size Limited machine cost
Jonathan Abir [email protected]
James Norman [email protected]
Metre scale machine
www.hexagonmi.com
Virtual Metrology Frames in CIM-UP
9 Jonathan Abir [email protected]
James Norman [email protected]
www.eso.org
European Extremely Large Telescope
http://www.jwst.nasa.gov/
James Webb Space Telescope
Off-axis ellipsoidal:
•Non-specular after grinding
•Manufacture difficult
•Metrology is complex
Metrology for large optics
10 Jonathan Abir [email protected]
James Norman [email protected]
~ 1.5 m
11
Metrology Frame for large CMM
• Research aim: To realise a method for low uncertainty probe positioning within large measurement systems.
hexagonmetrology.co.uk/Leitz-Infinity G. N. Peggs, et al. Design for a Compact High-Accuracy CMM. 1999.
Jonathan Abir [email protected]
James Norman [email protected]
± 50 nm over 50 mm3
Virtual Metrology Frame - Multilateration
Unknowns
12
Camboulives M. et al.. Calibration of a 3D working space by multilateration. 2016
Jonathan Abir [email protected]
James Norman [email protected]
Virtual Metrology Frame - Multilateration
10 x 4 sets of equations with 40 unknowns → solvable
No. of retro-reflector positions
No. of interferometer positions
13 Jonathan Abir [email protected]
James Norman [email protected]
14
Probe position measurement
Laser interferometry multilateration Stylus tip on CMM
Jonathan Abir [email protected]
James Norman [email protected]
Stylus tip on CMM
Replace stylus tip
Retro-reflector
15
Probe position measurement
Jonathan Abir [email protected]
James Norman [email protected]
Potentially a trade-off between cost (£) and measurement uncertainty (σ)
LaserTRACER multilateration ~ 400 nm coordinate measurement uncertainty (1 m3)
Enable traceable coordinate measurement of tip centre via HeNe wavelength
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Coordinate measurement - multilateration
Jonathan Abir [email protected]
James Norman [email protected]
System uncertainty assessment
ISO Type B: Monte Carlo style based on analytical model
ISO Type A: Build system and assess via measurement of an artefact (Fizeau interferometric measured optic)
17 17
Further work
R. Jourdain. e al. Design and characterization of an optical test system for metre–scale optics. 2013.
Jonathan Abir [email protected]
James Norman [email protected]
18
Meso scale machine
Virtual Metrology Frames in CIM-UP
Jonathan Abir [email protected]
James Norman [email protected]
Meso scale machine with Virtual Metrology Frame
• Research aim: Improve the dynamic performance of a compact size CNC machine
0.6m 0.6m
1m
Slave side guideway
Master side guideway
Carriage
Encoder
491mm
609mm
215mm
19 Jonathan Abir [email protected]
James Norman [email protected]
Virtual Metrology Frame concept in a meso scale CNC machine
Xc
F
Frame
Xvmf Xf
Xc – Xf = Xvmf
20 Jonathan Abir [email protected]
James Norman [email protected]
Virtual Metrology Frame concept in a meso scale CNC machine - controller
C P +
Frame displacement
sensor
Encoder Xc
Xf
Xvmf
e Xset
+
Controller
21 Jonathan Abir [email protected]
James Norman [email protected]
Requirements of frame displacement sensor
• No reference point – “virtual metrology frame”
• Low delay
• Low noise – compared to the encoder
2( ) ( )a t dt d t
• Measure dynamic displacement of machine frame
22 Jonathan Abir [email protected]
James Norman [email protected]
2
0
2 0[ ( ) ] ( ) ...2
a t dt d ta
a t
Signal processing design of frame displacement sensor
Attenuating Double integrating
23 Jonathan Abir [email protected]
James Norman [email protected]
Results of plant transfer function
Flexible frame
( )( )
( )
X sP s
F s
24 Jonathan Abir [email protected]
James Norman [email protected]
Results of open loop transfer function
fs – Servo bandwidth
φm – Phase margin >45º
40% improvement to servo bandwidth
Flexible frame
Gm – Gain margin >6dB
Notch filter @ 195Hz
25 Jonathan Abir [email protected]
James Norman [email protected]
Summary of Virtual Metrology Frame in a meso scale CNC machine
The virtual metrology frame concept was realised in a meso scale CNC machine:
Improvement to the servo bandwidth by 40% A simple PID control structure Robust solution
26 Jonathan Abir [email protected]
James Norman [email protected]
The advantages of Virtual Metrology Frame
• Enhance machine performance with minimal interference– metre & meso scale • Optimal solution
Expandable measurement volume with no extra cost – metre scale Limited machine size – meso scale Limited machine cost – meso scale
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Meso scale machine
Metre scale machine
Jonathan Abir [email protected]
James Norman [email protected]