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Roughness Feeling Telepresence System with Communication Time-Delay
Shogo Okamoto *Masashi Konyo *Takashi Maeno †Satoshi Tadokoro *(*) Graduate School of Information Sciences, Tohoku University, Japan(†) Department of Mechanical Engineering, Keio University, Japan
E-mail: {okamoto,konyo,tadokoro}@rm.is.tohoku.ac.jp, maeno@mech.keio.ac.jp
Abstract
A framework of tactile telepresence systems will be proposed in the present paper, which enables active touch with
time-delay communication between a tactile sensor sidesystem and a display side system. In the framework, a tactile
display system can apply tactile stimuli to fingers of an operator in syncronization with touch motions based on physicalparameters of objects which are estimated by a tactile sensor. To verify the concepts of the framework, was developed
a roughness feeling telepresence system which produces vibratory stimuli computed by estimated surface wavelengthof objects and rubbing speed of an operator. To implement
the framework, real-time estimation of physical parametersof objects are required as core technology. System implementation and real-time estimation of surface wavelength
will be also proposed.

1. Introduction
Tactile telepresence technology is expected to be applied
to remote robotic manipulation, robotic palpation and soforth. However, conventional studies of tactile telepresence
have not dealt with active touch with time-delay communication because of following two major reasons. First, presentation of tactile stimuli also delays when communication network is delayed. Second, the amount of information
which is transmitted by a tactile sensor to a display sidesystem is huge due to high frequency resolution of tactile
mechanoreceptors and distributed area of stimuli. Therefore, a new framework of tactile telepresence system to realize active touch even with time-delay communication will
be proposed. The framework emphasizes that approximate
tactile stimuli can be reproduced by combining touch motions of operators and representative physical parameters ofobjects to touch. Also, stimuli generation based on touch
motions at the very moment cancels communication timedelay between a slave side system. Implementation and experimental results of a developed roughness feeling telepresence system will be also described to verify the conceptsof the framework.

Second Joint EuroHaptics Conference and Symposium on Haptic
Interfaces for Virtual Environment and Teleoperator Systems (WHC'07)
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2. The Tactile Telepresence System Based on
Physical Parameters of Objects
The proposing tactile telepresence system is explained.
Fig.1 is an example of the system. In the figure, a tactile
sensor is installed on a slave arm, and it estimates physicalparameters of objects. Estimated parameters are transmitted
to a display side system and tactile stimuli are applied to afinger of an operator. The stimuli are produced using thecurrent touch motions sensed by a master arm system so thatthe stimuli should not delay due to communication timedelay.
In the present study, due to psychophisically clear relationships between parameters and touch motions, will be
proposed a roughness feeling telepresence system, in whichmechanical vibration of f is produced as tactile stimuli. fis derived by f = v/λ, where v is rubbing speed of an operator, λ is a surface wavelength of an object.

3. Implementation of A Roughness Feeling
Telepresence System
3.1

Real-time Estimation Method for Surface Wavelengths

Fig.2 shows a picture of the tactile sensor used in thesystem. The sensor emulates the structure of human fingers
and same friction phenomenon are expected to happen intouching objects. Five strain gauges are embedded at theboundary of two layers and designed to acquire vibration inany contact statuses [1].

Figure 1. An example of a master-slave typed
roughness feeling telepresence system

Figure 2. The
human finger
mimetic tactile
sensorFigure 6. Slave sidesystem

Figure 3. An example of sensory outputs
and impulses

Figure 7. Masterside systempresent differences of wavelength 1 ∼ 4[mm] by 1[mm]using limitation methods.

3.3

Figure 4. A
roughness
Samplefor
performance
evaluation :GW=RWFigure 5. Experimental
sensory
outputs
andresult in sliding on 2different samples

Real-time wavelength estimation method will be proposed. The method estimates the vibratory frequency ofthe sensor by accumulating impulses in a certain period
A. Once, the frequency is estimated, surface wavelengthof roughness samples can be derived by λ = v/f . Fig.3 illustrates the basic idea of the proposing estimation method.
The upper plot of Fig.3 shows sensory outputs of a strain
gauge, when the sensor slides on a roughness sample shownin Fig.4. The method puts impulses when high-path filteredsensory outputs of a strain gauge goes over a zero level,
shown in the lower part of Fig.3. A was designed to be
0.08[sec] so that it minimizes the formulation of expected
estimation errors.
The basic performance evaluation clarified that a wavelength difference of 1[mm] can be sufficiently discriminatedby the method.
Fig.5 shows an example of experimental sensory outputs
and estimated wavelengths, where 2 samples of different
wavelength, 1[mm] and 4[mm] were arranged side by sideand the sensor slid on them. At the point B in Fig.5, the sensor just reached the boundary of 2 samples, and estimatedvalue is almost roaming around 4[mm] within 0.08[sec].

3.2

Roughness Feeling Display by ICPF
Tactile Display

ICPF tactile display [2] was employed as a tactile display in the system. ICPF actuators of the display were controlled to vibrate at the set frequency, which was derived by
f = v/λ. It was confirmed that the display method could

Second Joint EuroHaptics Conference and Symposium on Haptic
Interfaces for Virtual Environment and Teleoperator Systems (WHC'07)
0-7695-2738-8/07 $20.00 © 2007

Experimental Setup of Roughness
Feeling Telepresence SystemFig.6 and Fig.7 shows the developed roughness feelingtelepresence system. The sensor was attached to a singleaxis arm in a slave side system. A subject equipped his finger with the tactile display and put his finger on a fingertipof the master arm.

4Experiment and Results

Velocity of the slave single-axis arm was controlled to besame as x-axis velocity of the master arm. Two roughness
samples were arranged beneath the tactile sensor. A subject
answered which wavelength was longer. Four samples 1 ∼4[mm] with 1[mm] interval were tested. The experiment
was conducted by a pairwise comparison method, each pair
was tested 10 times.
As a result, the subject could judge longer samples at therate of more than 0.9 for 4 pairs among 6 pairs, where there
are statistic significance with 95% significant level. For therest 2 pairs, correct answer rates were 0.7.

5Conclusion

The present paper proposed a new framework of tactile
telepresence system for active touch with time-delay communication, in which tactile stimuli are produced based on
physical parameters of objects and touch motions of operators. In the framework, real-time estimation methods ofparameters are inevitable and a method for surface wavelength was proposed. Roughness feeling telepresence system was developed and evaluated, which showed an encouraging performance as a first stage.

References[1] Y.Mukaibo et al., Development of a Texture Sensor Emulating the Tissue Structure and Perceptual Mechanism of HumanFingers, Proc. IEEE Intl. Conf. on Robotics and Automation, pp.
2576-2581, 2005
[2] M.Konyo et al., Tactile Feel Display for Virtual Active Touch,Proc. IEEE/RSJ Intl. Conf. on Intelligent Robots and Systems,
pp.3744-3750, 2003