Summary of the results of the LISA-Pathfinder
Test Mass release
Carlo Zanoni1
1
D. Bortoluzzi , J.W. Conklin2 , I. Koeker3 , B. Seutchat1 , S. Vitale1
1 University
of Trento and INFN (Italy)
of Florida (USA)
3 Airbus Defence and Space (Germany)
2 University
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
1 / 13
Outline
Content
Validation of the Release Mechanism performance (= minimize
TM velocity) by means of analytical and experimental studies
on the main phenomena.
1
Intro to Caging and Release Operations
2
Mechanism Physical Model
3
Adhesion Contribution to Final Velocity
4
Simulations and Results
5
What’s next?
6
Conclusion
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
2 / 13
Intro to Caging and Release Operations
Caging Mechanism
CVM: Caging and Vent Mechanism.
1200 N load during launch.
GPRM: Grabbing, Positioning and
Release Mechanism. First centering
and alignment.
Carlo Zanoni, UniTN and INFN
22 May 2014
RT: Release Tip. Small
contact area, high
retraction quickness (40
mm/s). Gold alloy.
LISA Symposium X
3 / 13
Intro to Caging and Release Operations
Caging Mechanism
CVM: Caging and Vent Mechanism.
1200 N load during launch.
GPRM: Grabbing, Positioning and
Release Mechanism. First centering
and alignment.
Carlo Zanoni, UniTN and INFN
22 May 2014
RT: Release Tip. Small
contact area, high
retraction quickness (40
mm/s). Gold alloy.
LISA Symposium X
3 / 13
Intro to Caging and Release Operations
Caging Mechanism
CVM: Caging and Vent Mechanism.
1200 N load during launch.
GPRM: Grabbing, Positioning and
Release Mechanism. First centering
and alignment.
Carlo Zanoni, UniTN and INFN
22 May 2014
RT: Release Tip. Small
contact area, high
retraction quickness (40
mm/s). Gold alloy.
LISA Symposium X
3 / 13
Intro to Caging and Release Operations
Release Procedure [Acrobat Reader needed for the video]
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
4 / 13
Intro to Caging and Release Operations
Requirement and main issues
linear velocity < 5 µm/s
(mission critical)
Approach
requirements on other
states/axes: demanding, but
less challenging
every asymmetry determines
momentum transfer to the TM:
adhesion: limited
repeatability
mechanism actions (e.g.
delay)
Carlo Zanoni, UniTN and INFN
22 May 2014
Collect information on
asymmetry sources.
Extrapolate on ground
data to in-flight conditions.
Estimate the TM velocity
after release.
LISA Symposium X
5 / 13
Intro to Caging and Release Operations
Requirement and main issues
linear velocity < 5 µm/s
(mission critical)
Approach
requirements on other
states/axes: demanding, but
less challenging
every asymmetry determines
momentum transfer to the TM:
adhesion: limited
repeatability
mechanism actions (e.g.
delay)
Carlo Zanoni, UniTN and INFN
22 May 2014
Collect information on
asymmetry sources.
Extrapolate on ground
data to in-flight conditions.
Estimate the TM velocity
after release.
LISA Symposium X
5 / 13
Intro to Caging and Release Operations
Requirement and main issues
linear velocity < 5 µm/s
(mission critical)
Approach
requirements on other
states/axes: demanding, but
less challenging
every asymmetry determines
momentum transfer to the TM:
adhesion: limited
repeatability
mechanism actions (e.g.
delay)
Carlo Zanoni, UniTN and INFN
22 May 2014
Collect information on
asymmetry sources.
Extrapolate on ground
data to in-flight conditions.
Estimate the TM velocity
after release.
LISA Symposium X
5 / 13
Intro to Caging and Release Operations
Requirement and main issues
linear velocity < 5 µm/s
(mission critical)
Approach
requirements on other
states/axes: demanding, but
less challenging
every asymmetry determines
momentum transfer to the TM:
adhesion: limited
repeatability
mechanism actions (e.g.
delay)
Carlo Zanoni, UniTN and INFN
22 May 2014
Collect information on
asymmetry sources.
Extrapolate on ground
data to in-flight conditions.
Estimate the TM velocity
after release.
LISA Symposium X
5 / 13
Intro to Caging and Release Operations
Requirement and main issues
linear velocity < 5 µm/s
(mission critical)
Approach
requirements on other
states/axes: demanding, but
less challenging
every asymmetry determines
momentum transfer to the TM:
adhesion: limited
repeatability
mechanism actions (e.g.
delay)
Carlo Zanoni, UniTN and INFN
22 May 2014
Collect information on
asymmetry sources.
Extrapolate on ground
data to in-flight conditions.
Estimate the TM velocity
after release.
LISA Symposium X
5 / 13
Mechanism Physical Model
Release Tip model & Identification
RT model required because of mechanism-adhesion mutual
interaction
RT moved by a piezo-stack
preloaded by washer springs.
lumped-element model.
10 parameters, no hysteresis.
identified with unloaded
retractions of the FMs.
nominal input: 120 V step.
improvement of previous
versions1 .
1
D. Bortoluzzi, J.W. Conklin, and C. Zanoni, Prediction of the LISA Pathfinder release mechanism in-flight
performance, Advances in Space Research, 2013.
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
6 / 13
Mechanism Physical Model
Release Tip model & Identification
RT model required because of mechanism-adhesion mutual
interaction
RT moved by a piezo-stack
preloaded by washer springs.
lumped-element model.
10 parameters, no hysteresis.
identified with unloaded
retractions of the FMs.
nominal input: 120 V step.
improvement of previous
versions1 .
1
D. Bortoluzzi, J.W. Conklin, and C. Zanoni, Prediction of the LISA Pathfinder release mechanism in-flight
performance, Advances in Space Research, 2013.
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
6 / 13
Mechanism Physical Model
Release Tip model & Identification
RT model required because of mechanism-adhesion mutual
interaction
RT moved by a piezo-stack
preloaded by washer springs.
lumped-element model.
10 parameters, no hysteresis.
identified with unloaded
retractions of the FMs.
nominal input: 120 V step.
improvement of previous
versions1 .
1
D. Bortoluzzi, J.W. Conklin, and C. Zanoni, Prediction of the LISA Pathfinder release mechanism in-flight
performance, Advances in Space Research, 2013.
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
6 / 13
Mechanism Physical Model
Release Tip model & Identification
RT model required because of mechanism-adhesion mutual
interaction
RT moved by a piezo-stack
preloaded by washer springs.
lumped-element model.
10 parameters, no hysteresis.
identified with unloaded
retractions of the FMs.
nominal input: 120 V step.
improvement of previous
versions1 .
1
D. Bortoluzzi, J.W. Conklin, and C. Zanoni, Prediction of the LISA Pathfinder release mechanism in-flight
performance, Advances in Space Research, 2013.
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
6 / 13
Mechanism Physical Model
Release Tip model & Identification
RT model required because of mechanism-adhesion mutual
interaction
RT moved by a piezo-stack
preloaded by washer springs.
lumped-element model.
10 parameters, no hysteresis.
identified with unloaded
retractions of the FMs.
nominal input: 120 V step.
improvement of previous
versions1 .
1
D. Bortoluzzi, J.W. Conklin, and C. Zanoni, Prediction of the LISA Pathfinder release mechanism in-flight
performance, Advances in Space Research, 2013.
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
6 / 13
Mechanism Physical Model
Release Tip model & Identification
RT model required because of mechanism-adhesion mutual
interaction
RT moved by a piezo-stack
preloaded by washer springs.
lumped-element model.
10 parameters, no hysteresis.
identified with unloaded
retractions of the FMs.
nominal input: 120 V step.
improvement of previous
versions1 .
1
D. Bortoluzzi, J.W. Conklin, and C. Zanoni, Prediction of the LISA Pathfinder release mechanism in-flight
performance, Advances in Space Research, 2013.
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
6 / 13
Adhesion Contribution to Final Velocity
Adhesion: experimental facility
limited repeatability.
worst-case: adhesion acts on
one TM side only.
experimental facility to study
dynamic adhesion:
pendulum in space-like
environm. (10−7 mbar)
representative surfaces
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
7 / 13
Adhesion Contribution to Final Velocity
Adhesion: measurements
TM motion measured by a SIOS interferometer
Tip motion measured with DOSS sensor
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
8 / 13
Adhesion Contribution to Final Velocity
Adhesion: results
Rough Extrapolation:
Fine Extrapolation (Fit):
F (∆) = X1 ∆l e−∆l/X2
peak force < 50 mN.
peak duration ∼ 1 ms.
flight mechanism speed 10×
ground actuator.
extrap. impulse <50% req.
Carlo Zanoni, UniTN and INFN
22 May 2014
fit the acceleration time
profile
simulation requires analytical
expression.
LISA Symposium X
9 / 13
Simulations and Results
Montecarlo Simulation
Randomization of:
mechanism parameters
(identification).
contact geometries (design
tolerances).
input voltage time profile
(measurements).
adhesion (experimental
campaigns).
99.73 % worst case velocity: 1.50 µm/s
Adhesion contribution: 1.36 µm/s
Mechanism contributions: 0.24 µm/s
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
10 / 13
Simulations and Results
Numerical analysis of contact (preliminary)
Motivation:
validation of experimental
data (avoid
underestimation)
estimation of compression
behavior (used Hertz, so
far)
F (∆l) in rough contact
sum of forces computed
with JKR/DMT/ductile
models for single asperity
local plasticity hard to model
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
11 / 13
What’s next?
What’s next?
GPRM testing:
LISA-Pathfinder → eLISA
optimization example (radius)
worst-case momentum:
∝ contact depth (push time)
∝ contact area (adhesion
strength)
further margin possible
maximize representativeness.
learn GPRM functioning for
mission support.
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
12 / 13
What’s next?
What’s next?
GPRM testing:
LISA-Pathfinder → eLISA
optimization example (radius)
worst-case momentum:
∝ contact depth (push time)
∝ contact area (adhesion
strength)
further margin possible
maximize representativeness.
learn GPRM functioning for
mission support.
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
12 / 13
What’s next?
What’s next?
GPRM testing:
LISA-Pathfinder → eLISA
optimization example (radius)
worst-case momentum:
∝ contact depth (push time)
∝ contact area (adhesion
strength)
further margin possible
maximize representativeness.
learn GPRM functioning for
mission support.
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
12 / 13
Conclusion
Conclusion
validation activity of requirement for the TM release.
experimental assessment of the most important
phenomena.
modeling and Montecarlo simulation of the release.
estimated worst-case velocity compliant with the
requirement.
(but not 100% representativeness).
direct testing with GPRM to be started in June (this year).
Contacts:
carlo.zanoni@unitn.it
daniele.bortoluzzi@unitn.it
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
13 / 13
Conclusion
Conclusion
validation activity of requirement for the TM release.
experimental assessment of the most important
phenomena.
modeling and Montecarlo simulation of the release.
estimated worst-case velocity compliant with the
requirement.
(but not 100% representativeness).
direct testing with GPRM to be started in June (this year).
Contacts:
carlo.zanoni@unitn.it
daniele.bortoluzzi@unitn.it
Carlo Zanoni, UniTN and INFN
22 May 2014
LISA Symposium X
13 / 13
Full Requirement
State
offset
linear velocity
angle
angular rate
Carlo Zanoni, UniTN and INFN
Value
± 200 µm
± 5 µm/s
± 2 mrad
± 100 µrad/s
22 May 2014
LISA Symposium X
1/3