1 Using vibration patterns to provide impact position

1 Using vibration patterns to provide impact position information in haptic manipulation of virtual objects 13/06/2008 Jean Sreng Anatole Lécuyer Claude Andriot jean. sreng@inria. fr

2 Outline • Introduction • Vibration patterns • Evaluation • Conclusion

3 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 ?

4 Vibrations and impact position • Chosen approach : • The impact generates vibrations depending on the impact position • Vibration model, a first approximation • Euler-Bernouilli cantilever beam

5 Vibrations and impact position • General solution : Impact position

6 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

7 Simplified vibration patterns Near impact Am Fr Am. Fr (Consistent) Am. CFr (Conflicting) Far impact

8 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 : • • Virtuose 6 D device Sound blocking noise headphones

9 Quantitative evaluation ERRATUM Page 7 § 4. 3 EB 1: 10 Hz, 64 Hz EB 2: 5 Hz, 25 Hz Other: 15 Hz to 45 Hz • Quantitative evaluation : “Between these two impacts which one was the closest one from the hand ? ” • • 6 models – 2 realistic models (Euler-Bernoulli) (EB 1, EB 2) – 4 simplified models (Am, Fr, Am. CFr) 4 locations 8 random repetitions Total of 576 trials (40 min)

10 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. 25 0. 75 No association Inverted association • The value performance was used to represent the overall 0 0. 25 No association 0. 5

11 Quantitative evaluation : results • Overall performance : • • ANOVA Significant (p < 0. 007) Paired t-tests (p < 0. 05) : – Am – EB 1 – EB 2 – Am. CFr – EB 1 – EB 2

12 Quantitative evaluation : results • Inversion ratio : The ratio of users who inverted the association between the vibration pattern and the position

13 Qualitative evaluation : results • Rate the impact realism : • Paired t-tests : – Am – EB 1 – EB 2 – Fr – Am. Fr – EB 2 – Fr – Am. CFr

14 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 Am. CFr strongly correlated

15 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

16 Questions ? ?