1 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

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

3 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 4 Haptic rendering of the information of contact Use of 6DOF haptic devices Computation of contact force : haptic rendering Collision detection Force feedback

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

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

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

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

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

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

20 First experiment: determining the optimal vibration parameters Objectives 1.Perceptual study : “Is it possible to perceive the contact position in 3D space? Is it possible to perceive the vibration direction ?” 2.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) rad to 0.02 rad 12 Hz to 40 Hz

21 Apparatus Haptic device: Haption Virtuose6D 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 4 frequencies f 12 Hz 18 Hz27 Hz40 Hz

24 Results: Effect of amplitude Average performance : around 80% of correct responses Best performances achieved with high amplitudes 4 amplitudes a 0.02 rad rad0.01 rad0.005 rad

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

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: 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 ? ?

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