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Using vibration patterns to provide impact position information in haptic manipulation of virtual objects
13/06/2008
Jean SrengAnatole LécuyerClaude [email protected]
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Outline
• Introduction
• Vibration patterns
• Evaluation
• Conclusion
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Introduction
• The impact between “rigid” objects :• A low-frequency reaction force of contact (simplified model)• A high-frequency force transient (more complex model)
• This high-frequency force transient can be used in haptic rendering of impact (open-loop haptic) :
• Improve the realism• Convey some information about the object’s material
• Is-it possible to convey position information using this transient ?
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Vibrations and impact position
• Chosen approach : • The impact generates vibrations depending on the impact position
• Vibration model, a first approximation• Euler-Bernouilli cantilever beam
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Vibrations and impact position
• General solution :
Impact position
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Simplified vibration patterns
• Simplified patterns based on the physical behavior• Simplified computation• Maybe easier perception ?
• Chosen model : exponentially damped sinusoid• Amplitude changes with impact position• Frequency changes with impact position• Both amplitude and frequency changes
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Simplified vibration patterns
Am
Fr
AmFr (Consistent)
AmCFr (Conflicting)
Near impact Far impact
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Evaluation
• Preliminary evaluation :• Quantitative : “Between these two impacts which one was the closest
one from the hand ?”• Qualitative : Subjective rating of the impact realism
• Conducted on 15 subjects
• Apparatus :• Virtuose6D device• Sound blocking noise headphones
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Quantitative evaluation
• Quantitative evaluation : “Between these two impacts which one was the closest one from the hand ?”
• 6 models– 2 realistic models (Euler-Bernoulli) (EB1, EB2)– 4 simplified models (Am, Fr, AmFr, AmCFr)
• 4 locations• 8 random repetitions• Total of 576 trials (40 min)
ERRATUM Page 7 § 4.3EB1: 10Hz, 64HzEB2: 5Hz, 25HzOther: 15Hz to 45Hz
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Quantitative evaluation : results
• The ratio of “good answers” was evaluated : “How well the user was able to associate a vibration and an impact location ?”
0.5 0.750.25No association
Inverted association
association
• The value was used to represent the overall performance
0 0.25 0.5
association
No association
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Quantitative evaluation : results
• Overall performance :• ANOVA Significant (p < 0.007)• Paired t-tests (p < 0.05) :
– Am -– EB1– EB2– AmCFr
– Fr -– EB1– EB2
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Quantitative evaluation : results
• Inversion ratio : The ratio of users who inverted the association between the vibration pattern and the position
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Qualitative evaluation : results
• Rate the impact realism :• Paired t-tests :
– Am– EB1– EB2– Fr– AmFr
– EB2– Fr– AmCFr
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Discussion
• Global weak inter – subject correlation : • Each subject seems to have his/her own interpretation (inversion or not)
• Strong intra – subject consistency :• Subjects seem to be very consistent within his/her interpretation
• Several strong inter – subject correlation between models :• Fr and AmCFr strongly correlated
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Conclusion
• We proposed several vibration patterns to convey impact position information
• We conducted a preliminary evaluation :• The user is able to use the vibration pattern to get an impact position
information• The simplified models Am and Fr seems to perform better
• Future work :• Evaluate the role of the hand impedance and the haptic device
bandwidth to elaborated more effective feedback• Deeper analysis of the data• New models
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Questions ? ?