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On the Discrimination of Stiffness during
Pressing and Pinching of Virtual Springs
Chair of Media Technology
Technische Universität München
IEEE International Symposium on Haptic Audio-Visual Environments
and Games, Dallas, TX
11 October 2014
Giulia [email protected]
Burak [email protected]
Eckehard [email protected]
Technische Universität München
Chair of Media Technology
Teleoperation with perceptual coding
11 October 2014 2Burak Cizmeci: Discrimination of Stiffness during Pressing and Pinching Events
position/velocity
Network
force
operatorteleoperator
force
position/velocity
Hinterseer et al. “Perception-based data reduction and transmission of haptic data in TPTA systems„ IEEE Trans. on Signal
Proc., 2008
Ferrel and Sheridan, “Supervisory Control of Remote Manipulation„ IEEE Spectrum, 1967
stabilitytransparency
Technische Universität München
Chair of Media Technology
3
force force
sensors
Model
Estimator
Local
Rendering
position/velocity position/velocity
Network
operator teleoperator
P. Mitra and G. Niemeyer, “Model mediated telemanipulation”, International Journal of Robotics Research, 2008
Model parameters
Model Parameters
o Object shapes
o Object movement
o Material properties: stiffness, damping and friction
transparency stability
Model-mediated teleoperation
11 October 2014 Burak Cizmeci: Discrimination of Stiffness during Pressing and Pinching Events
Technische Universität München
Chair of Media Technology
Overview
4Burak Cizmeci: Discrimination of Stiffness during Pressing and Pinching Events
• Introduction to stiffness perception
• Experimental conditions and procedure
• Exp. 1: Pressing vs. Pinching
• Exp. 2: WFs for various references
• Conclusion & Future Work
11 October 2014
Technische Universität München
Chair of Media Technology
Introduction to stiffness perception
Discriminating stiffness
5Burak Cizmeci: Discrimination of Stiffness during Pressing and Pinching Events
Deformable
surface
Non-deformable
surface
11 October 2014
by pinchingby pressing with haptic devices
Perception with toolsPerception with direct contact
Technische Universität München
Chair of Media Technology
Stiffness perception with haptic devices
Challenges to utilize previously determined perceptual thresholds:
A wide array of applied methodologies and technologies [1,2,3,4]
□ From custom-designed to commercial haptic devices
□ Different stiffness ranges
□ Different test conditions from real and virtual scenes to augmented reality
A broad range of stiffness thresholds from 0.036 [3] to 0.30 [1]
6Burak Cizmeci: Discrimination of Stiffness during Pressing and Pinching Events11 October 2014
[3] N. Gurari, K.J. Kuchenbecker, and A.M. Okamura. “Stiness discrimination with visual and proprioceptive cues”, EuroHaptics 2009
[1] M.K. O'Malley and M. Goldfarb. “The implications of surface stiffness for size identification and perceived surface hardness in
haptic interfaces”, ICRA 2002
[2]S. Yamakawa, H. Fujimoto, S. Manabe, and Y. Kobayashi “The necessary conditions of the scaling ratio in master-slave systems
based on human difference limen of force sense” IEEE Trans. On Systems, Man and Cybernetics, 2005.
[4] M. Kuschel, M. Di Luca, M. Buss, and R. L. Klatzky, “Combination and integration in the perception of visual-haptic compliance
information”, IEEE Trans. on Haptics, 2010
Technische Universität München
Chair of Media Technology
Research questions
1. Does the exploration event make any difference?
□ Experiment 1: Detection of WFs for pressing and pinching with
respect to a reference stiffness 200 N/m
2. Is there any influence of the reference‘s stiffness on the
differential sensitivity for stiffness?
□ Experiment 2: Detection of WFs for pinching with respect to
reference stiffnesses 50, 135, 220, 305 and 390 N/m
7Burak Cizmeci: Discrimination of Stiffness during Pressing and Pinching Events11 October 2014
Technische Universität München
Chair of Media Technology
Experimental conditions Haptic Device: Force Dimension Sigma 7
Interacting object: Accordion shaped elastic cubes with non
deformable surface rendered with linear model (F=kx).
8Burak Cizmeci: Discrimination of Stiffness during Pressing and Pinching Events11 October 2014
Technische Universität München
Chair of Media Technology
Experimental procedure
9Burak Cizmeci: Discrimination of Stiffness during Pressing and Pinching Events
1-up 4-down adaptive double staircase detection is applied.
2-IFC (interval forced choice) procedure:
□ 500 ms pause between each stimuli
□ 1600 ms pause between each trial
□ After the second interval, the subject inputs his/her answer
□ A break of 30 sec after 20 trials
□ 5 min break in the middle
Training session with 40 trials
11 October 2014
H. Levitt, “Transformed up-down methods in psychoacoustics” , The Journal of Acoustical society of America, 1971
Technische Universität München
Chair of Media Technology
Experiment 1: Pressing vs. Pinching
10Burak Cizmeci: Discrimination of Stiffness during Pressing and Pinching Events11 October 2014
Group Pressing
Starting stiffness value
Pinching
Starting stiffness value
202.5 N/m (below threshold) 202.5 N/m (below threshold)
262.5 N/m (above threshold) 262.5 N/m (above threshold)
197.5 N/m (below threshold) 197.5 N/m (below threshold)
137.5 N/m (above threshold) 137.5 N/m (above threshold)
Group Bbelow reference
Group Aabove reference
Reference stiffness value 200 N/m compared with harder and softer
stimuli
10 male and 4 female (7 subjects per group), aged between 22 and 30
Technische Universität München
Chair of Media Technology
Experiment 1: Results
Groups Pressing
(WF±σ)
Pinching
(WF±σ)
Group A 0.147±0.047 0.166±0.032
Group B 0.134±0.032 0.143±0.041
11
ANOVA factors F(1,12) p-value significant
pressing vs. pinching 1.93 0.19 No
above vs. below reference 0.97 0.34 No
Interaction between event
and group
0.28 0.60 No
11 October 2014 Burak Cizmeci: Discrimination of Stiffness during Pressing and Pinching Events
Technische Universität München
Chair of Media Technology
Experiment 2 : WFs for various references
12Burak Cizmeci: Discrimination of Stiffness during Pressing and Pinching Events
Pinch the object using the gripper fingers
Reference stiffness values 50, 135, 220, 305, 390 N/m compared
with harder and softer stimuli
13 new participants (5 female) aged between 23 and 28
Reference Starting point
above threshold
Starting point
below threshold
50 N/m 47.5 N/m 7.5 N/m
135 N/m 132.5 N/m 92.5 N/m
220 N/m 217.5 N/m 177.5 N/m
305 N/m 302.5 N/m 242.5 N/m
390 N/m 387.5 N/m 287.5 N/m
11 October 2014
Technische Universität München
Chair of Media Technology
Experiment 2 : Results
13Burak Cizmeci: Discrimination of Stiffness during Pressing and Pinching Events
Reference 50 N/m 135 N/m 220 N/m 305 N/m 390 N/m
WF±σ 0.281±0.127 0.151±0.05 0.143±0.032 0.127±0.038 0.132±0.034
Significant difference is detected between softest reference 50 N/m
and the other reference values. F(4,48)=15.94, p=0
No statistical difference between 135, 220, 305 and 390 N/m
11 October 2014
Technische Universität München
Chair of Media Technology
Conclusion
We studied stiffness perception of virtual springs
We analyzed two events: pressing and pinching
Observation 1:
□ No significant difference between pressing and pinching
Observation 2:
□ No statistical perceptual difference between stimuli (135 – 390 N/m) for
pinching
1411 October 2014 Burak Cizmeci: Discrimination of Stiffness during Pressing and Pinching Events
Technische Universität München
Chair of Media Technology
Future Work
15
• Further investigation for the stiffness range (50 - 135 N/m )
Perform experiments on deformable surface compliant objects
Perform experiments on incongruent visual-haptic information
o Under delay conditions
Validation of results on a real physical interaction
Usage of these thresholds in stiffness data reduction for model-
mediated teleoperation
11 October 2014 Burak Cizmeci: Discrimination of Stiffness during Pressing and Pinching Events
Technische Universität München
Chair of Media Technology
Thank you for your attention!
16Burak Cizmeci: Discrimination of Stiffness during Pressing and Pinching Events11 October 2014