9/12/2008

1. Spatialized Haptic Rendering: Providing Impact Position Information in 6DOF Haptic Simulations Using Vibrations 9/12/2008 Jean Sreng, Anatole Lécuyer, Claude Andriot, Bruno Arnaldi Jean.sreng@cea.fr

2. Introduction • Context: Manipulation of solid objects in Virtual Reality • Applications: Industrial virtual assembly / disassembly / maintenance

3. Enhancement of the information of contact • Use of visual cues of contact (Sreng, Lécuyer, et al., IEEE TVCG 2006) • Use of auditory cues of contact (Sreng, Lécuyer et al., ACM VRST 2007)

4. Haptic rendering of the information of contact • Use of 6DOF haptic devices • Computation of contact force : haptic rendering • Collision detection • Force feedback

5. Limits of haptic rendering ? • Importance of contact information • In a real world • In a virtual world

6. Spatialized haptic rendering • We propose to superimpose the vibrations corresponding to the 3D contact position to the classical haptic rendering

7. Outline • Spatialized haptic rendering • First experiment: Determining the optimal vibration parameters • Second experiment: Preliminary evaluation • Conclusion OUTLINE

8. Haptic rendering of contact position • The impact between objects: • A reaction force • A high-frequency transcient vibrations • This high frequency transcient vibrations depends on: • The object material(Okamura et al. 1998) • The object geometry • The impact position

9. Haptic rendering of contact position • How can we use vibrations to convey impact position information ? • Different vibration models can be used (Sreng, Lécuyer, et al., EH 2008) • Realistic model of a vibrating cantilevel beam • Simplified model

10. Simulation of vibrations: Realistic model • Realistic simulation based on the Euler-Bernouilli model • General solution

11. Simulation of vibrations: Simplified model • Simplified patterns based on the physical behavior based on an exponentially damped sinusoid: • Amplitude changes with the impact position • Frequency changes with the impact position • Both Amplitude and frequency changes • Main benefits: • Easier perception • Simplified computation

12. Simplified vibration patterns Am Fr AmFr (Consistent) Far impact Near impact

13. 6DOF Spatialized haptic rendering • Generalizing the previous approach for 6DOF manipulation: • Virtual beam model

14. 6DOF Spatialized haptic rendering • Two types of information can be conveyed: • A distance of impact • A direction providing the orientation of the impact

15. 6DOF Spatialized haptic rendering • The impact force • The wrench sensed by the hand

16. 6DOF Spatialized haptic rendering • The wrench is then modulated by the vibration model: • In particular the vibration torque can be expressed: Vibration pattern Vibration orientation

17. Manipulation point and circle of confusion • Different impact positions can generate the same haptic feedback Manipulation point Manipulation point

18. 6DOF Spatialized haptic rendering • The total torque applied to the device is obtained by superimposing: • The classic torque obtained with closed-loop rendering method • The impact vibrations torque

19. Outline Spatialized haptic rendering First experiment: Determining the optimal vibration parameters Second experiment: Preliminary evaluation Conclusion OUTLINE

20. First experiment: determining the optimal vibration parameters • Objectives • Perceptual study : “Is it possible to perceive the contact position in 3D space? Is it possible to perceive the vibration direction ?” • Technological aspect : Determine the optimal range of amplitude / frequency parameters • Tests among: ( 4 amplitudes a) x( 4 frequencies f) • Population: 10 male subjects (22 – 27 years old) 0.005 rad to 0.02 rad 12 Hz to 40 Hz

21. Apparatus • Haptic device: Haption Virtuose6D 35-45 • Vibrations applied around the 3 axes • Update rate of 1kHz

22. Procedure • “On which axis is the vibration applied ? Where is the impact located ?” ●●● (3AFC) • 15 blocks of 4 x 4 x 3 = 48 vibrations: total of 720 trials (35min) ● ● ●

23. Results: Effect of frequency • Average performance : around 80% of correct responses • Best performances achieved with low frequencies 18 Hz 27 Hz 40 Hz 12 Hz 4 frequencies f

24. Results: Effect of amplitude • Average performance : around 80% of correct responses • Best performances achieved with high amplitudes 0.015 rad 0.01 rad 0.005 rad 0.02 rad 4 amplitudes a

25. Discussion • Participants were able to perceive the vibration directions among the three axes • Most participants reported that they did not use a particular strategy • Best performances were achieved with low frequencies • Suggest the importance of kinesthetic cues over tactile cues • However some participants reported that they relied on tactile cues for small amplitudes • Best performances were achieved with high amplitudes • However some participants reported that high amplitudes made their perception more difficult

26. Outline Spatialized haptic rendering First experiment: Determining the optimal vibration parameters Second experiment: Preliminary evaluation Conclusion OUTLINE

27. Second experiment: perliminary user evaluation • Objective: Subjective evaluation of Spatialized Haptic Rendering in a real case • Population: 11 naive subjects (8M, 3F) (25 – 43 years old) • Task: 6DOF manipulation of 3D object • Subjective ratings • Realism of the impact • Feeling of impact position • Overall comfort of the manipulation • Procedure: Participants were asked to test the two rendering techniques successively (without and with vibrations) in a random order

28. Procedure • Virtual scene: two 3D objects • Spatialized Haptic Rendering parameters: 0.005 rad 0.02 rad 40 Hz 15 Hz Manipulation point

29. Results • Mean ratings from 1 (worst) to 6 (best) without and with superimposed vibration

30. Discussion • Better feeling of impact position obtained with Spatialized Haptic Rendering • Several participants spontaneously reported that the vibrations enabled them to perceive the impact position • Most participants pointed out that they perceived different materials between the two conditions • A « crisper » or « harder » feeling with vibrations (Okamura et al. 1998, Kuchenbecker et al. 2006) • A feeling of « vibrating metal » • Most participants enjoyed the manipulation using the vibrations • Two participants (familiar with haptic rendering) reported that they associated the vibration with an unstable, an potentially harmfull rendering algorithm

31. Conclusion • We proposed a 6DOF spatialized haptic rendering method to provide impact position directly on the haptic channel • using vibrations based on a vibrating beam • We conducted two experiments to evaluate this method • Experimental study on the perception of vibration direction • Participants can identify the vibration direction, i.e., the position of contact in 3D space • Optimal range of model parameters: Low frequencies / High amplitudes have better results • Subjective study on a 6DOF case • Better subjective perception of impact position • Further work • Investigate more deeply the perceptive characteristics of vibrations • Conduct an objective evaluation on a virtual prototyping context

32. Thank you. Questions ? ?