,This work was supported in
part by the Shenzhen Key Laboratory of Ubiquitous Data Enabling under Grant
ZDSYS20220527171406015, in part by Shenzhen Science and Technology Pro-
gram under Grant JCYJ20220530143013030, in part by Guangdong Innovative
and Entrepreneurial Research Team Program under Grant 2021ZT09L197, in
part by the National Natural Science Foundation of China under Grant 62104125,
and in part by the Tsinghua Shenzhen International Graduate School-Shenzhen
Pengrui Young Faculty Program of Shenzhen Pengrui Foundation under Grant
SZPR2023005

,(Corresponding authors: Wenbo Ding; Qianqian Tong.)
Xiaosa Li, Runze Zhao, Xinyue Chai, and Zimo Wang are with the Tsinghua-
Berkeley Shenzhen Institute, Tsinghua Shenzhen International Graduate
School, Tsinghua University, Shenzhen 518055, China (e-mail: lixs21@mails.
tsinghua.edu.cn; zhao-rz22@mails.tsinghua.edu.cn; chaixy23@mails.tsinghua.
edu.cn; zimo@u.nus.edu).
Qianqian Tong is with the Pengcheng Laboratory, Shenzhen 518055, China
(e-mail: tongqq@pcl.ac.cn).
Wenbo Ding is with the Tsinghua-Berkeley Shenzhen Institute, Tsinghua
Shenzhen International Graduate School, Tsinghua University, Shenzhen
518055, China, and also with the Shenzhen Ubiquitous Data Enabling Key
Lab, Shenzhen International Graduate School, Tsinghua University, Shenzhen
518055, China (e-mail: ding.wenbo@sz.tsinghua.edu.cn).
This letter has supplementary downloadable material available at
https://doi.org/10.1109/LRA.2024.3481828, provided by the authors.
Digital Object Identifier 10.1109/LRA.2024.3481828
Index Terms-Haptics and haptic interfaces, human-centered
robotics, wearable robotics.
I

,The main contributions of this article
are as follows:
· A lightweight vibration feedback bot (VibroBot) is devel-
oped, which is wearable on finger without affecting its sen-
sitivity and flexibility, and can perform the programmable
vibration display wirelessly.
· Six temporally-modulated vibration modes are designed
for VibroBot, which can be quickly and stably recognized
by the number of vibration display periods and the vibration
duration time within one period

 INTRODUCTION
H
UMAN integrates the visual and tactile information in
a statistically optimal fashion, to perceive and under-
stand the properties of interactive objects [1] Among these
sensations, tactile perception based on mechanoreceptors is
distributed throughout the whole body, and is capable of de-
tecting information such as static force, low-frequency skin
deformations, and high-frequency vibrations [2], [3] Cutaneous
tactile perception has an high information bandwidth due to the
different functions of mechanoreceptors, including the spatial
acuity of 1 mm on fingertips, the pressure threshold value of
0.158 g on the palm, as well as the temporal acuity of up to
700 Hz [4] Therefore, researchers tried to encode the data from
high-precision artificial sensors or semantic messages into two-
dimension tactile pattern [5], [6], [7], [8] or temporal vibration
modes [9], [10], [11], which were delivered as recognizable
haptic guidance on the human skin

 3 Using the VibroBot to guide the finger bending status by temporal vibration modes (a) Wearing position of VibroBot on finger, and knuckle angles of
finger joints including MCP PIP, DIP joints (b) The variation of vibration amplitudes and copper coil temperature within a continuous working time of 20 minutes.
(c) The vibration time part and the gap time part in one vibration display period, and the time-varying waves of six temporal vibration modes for guiding the flexion
or extension of three joints respectively (d) Confusion matrix of recognition results of six vibration modes (e) The mean time taken for correct recognition of the
six vibration modes (f) The correct recognition rate and time variation as the testing epochs increased.
collisions with the drive circuitry at the bottom of the coil When
the cantilever beam angle is larger than 120°, the displacement of
the permanent magnet decays quickly with the increasing angle.
Therefore, an angle of 120° has been chosen as the design angle
for VibroBot for the optimal vibration display strength.
C Vibration Display Performance
To measure the VibroBot vibration performance accurately
under wearable conditions, we use a piezoelectric accelerometer
(SAED0005B, Wuxi Shiao) to capture its vibration output at a
frequency of 128 kHz in direct contacting (Fig 2(d)) With a
PWM square wave input at the 50% duty cycle, the measured
vibration wave of VibroBot approximates the sine wave shape,
due to the coil inductive resistance to changes in excitation
current We try to assess the VibroBot output to all the input
PWM waves under the constant driving voltage of 3V, in the
frequency range from 0 to 700 Hz perceivable by the human
skin [4], and plot the vibration amplitude responses in Fig 2(e).
The results show that in 370 Hz, VibroBot can achieve the max
vibration response amplitude of 0.929 m/s2  Besides, another
smaller peak in the frequency-amplitude curve occurs at 120 Hz.
We plot the amplitudes at two peak frequencies under different
duty cycles of input waves (shown in Fig 2(f)) At 120 Hz,
the relationship between vibration amplitude and duty cycle
is indescribable, and it shows three peaks as the duty cycle
increases At 370 Hz, the measured vibration amplitude exhibits
an ideal inverted U-shaped relationship with the duty cycle The
maximum vibration amplitude appears at a 55% duty cycle rather
than 50%, and this is because the magnet on the cantilever beam's
free-end needs to overcome the gravity for vibrating.
Furthermore, since all four modules of VibroBot are rigidly
connected, the vibration from coil actuator propagates with
a negligible attenuation across the solid VibroBot body We
measured the vibration amplitudes in different areas of VibroBot
contacting with the accelerometer The mean amplitudes for
vibration coil contacting (used in this work), MCU board con-
tacting, and bot side contacting are 0.79± 0.04 m/s2, 1.66±
0.05 m/s2, and 0.78± 0.24 m/s2 respectively, and all contacting
methods maintains the enough vibration strength for wearable
tactile feedback It means that users can choose any comfortable
way to wear the VibroBot, without worrying about perceptual
failures in the programmed vibration waves The design details
and performance assessment establish VibroBot's capability to
provide programmable and effective vibration feedback, and
ensure the device's suitability for haptic guidance of various
application scenes.
III METHODOLOGY
A Vibration Mode Design
The vibration guidance of VibroBot on each finger is achieved
by adjusting the angles of finger joints, as shown in Fig 3(a).
When worn on finger for a continuous vibration display use in 20
minutes, the vibration amplitudes of VibroBot decreased as the
battery power was consumed, with a peak-to-peak value ranging
in (0.45, 0.76) m/s2 (shown in Fig 3(b)) Besides, the maximum
temperature achieved by the copper coils was 36.9 ℃  The
vibration amplitudes of VibroBot maintained within the range of
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LI et al .: VIBROBOT: A LIGHTWEIGHT AND WIRELESSLY PROGRAMMABLE VIBRATION BOT FOR HAPTIC GUIDANCE
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occupying the visual channel The implementation of our haptic
guidance system based on VibroBots emphasizes the role of
haptics in expanding human-machine interfaces By translating
subtle gesture information that is hard to quantify visually into
distinguishable vibration modes, the VibroBot enables more
intuitive and precise user interactions This capability is ben-
eficial for complex or precision-demanding tasks, and holds
promise for improving remote accessibility and virtual training
in various fields, where haptic devices can bridge the gap be-
tween human capabilities and machine functionalities However,
when vibration feedback is used to guide the completion of
gestures without any prior knowledge, it can take a significant
amount of time to complete the process, far exceeding the 10-20
seconds required to accurately perform common gestures as
trained in this paper Our future work will focus on refining
the design of the VibroBot to enhance its wearing comfort
and functions on gesture sensing via magnetic field location.
Vibration modes that can be identified more effectively need
to be developed, to address some real-time operational guid-
ance requirements Also, the deeper integration with virtual and
augmented reality technologies should be explored, to enrich
user experiences and broaden the scope of haptic guidance
applications.
REFERENCES
[1] M O Ernst and M S Banks, "Humans integrate visual and haptic
information in a statistically optimal fashion," Nat., vol 415, no 6870,
pp 429-433, 2002.
[2] K O Johnson, "The roles and functions of cutaneous mechanoreceptors,"
Curr Opin Neurobiol., vol 11, no 4, pp 455-461, 2001.
[3] R S Johansson and J R Flanagan, "Coding and use of tactile signals from
the fingertips in object manipulation tasks," Nat Rev Neurosci., vol 10,
no 5, pp 345-359, 2009.
[4] R S Dahiya, G Metta, M Valle, and G Sandini, "Tactile sensing-from
humans to humanoids," IEEE Trans Robot., vol 26, no 1, pp 1-20,
Feb 2010.
[5] Y Guo, Q Tong, P Zhao, Y Zhang, and D Wang, "Electromagnetic-
actuated soft tactile device using a pull-push latch structure," IEEE Trans.
Ind Electron., vol 70, no 10, pp 10344-10352, Oct 2023.
[6] Y Liu et al., "Electronic skin as wireless human-machine interfaces for
robotic VR," Sci Adv., vol 8, no 2, 2022, Art no eab16700.
[7] D Li et al., "Touch IoT enabled by wireless self-sensing and
haptic-reproducing electronic skin," Sci Adv., vol 8, no 51, 2022,
Art no eade2450.
[8] K Yao et al., "Encoding of tactile information in hand via skin-integrated
wireless haptic interface," Nat Mach Intell., vol 4, no 10, pp 893-903,
2022.
[9] A Kawazoe, M D Luca, and Y Visell, "Tactile echoes: A wearable system
for tactile augmentation of objects," in Proc IEEE World Haptics Conf.,
Tokyo, Japan, Jul 2019, pp 359-364.
[10] A Kawazoe, G Reardon, E Woo, M Di Luca, and Y Visell, "Tactile
echoes: Multisensory augmented reality for the hand," IEEE Trans Hap-
tics, vol 14, no 4, pp 835-848, Fourth Quarter 2021.
[11] X Li, S Yuan, and Z Yuan, "Electromagnetic vibration tactile feedback
for biological and artificial wave signals," in Proc ACM Int Joint Conf.
Pervasive Ubiquitous Comput., Sep 2021, pp 649-654.
[12] N Thomas, F Fazlollahi, J D Brown, and K J Kuchenbecker,
"Sensorimotor-inspired tactile feedback and control improve consis-
tency of prosthesis manipulation in the absence of direct vision," in
Proc IEEE/RSJ Int Conf Intell Robots Syst., Prague, Czech Republic,
Sep 2021, pp 6174-6181.
[13] L Vargas, H Huang, Y Zhu, and X Hu, "Evoked tactile feedback and
control scheme on functional utility of prosthetic hand," IEEE Robot.
Autom Lett., vol 7, no 2, pp 1308-1315, Apr 2022.
[14] F Barontini et al., "Tactile feedback in upper limb prosthetics: A pilot
study on trans-radial amputees comparing different haptic modalities,"
IEEE Trans Haptics., vol 16, no 4, pp 760-769, Fourth Quarter 2023.
[15] A V Zakharov, V A Bulanov, E V Khivintseva, A V Kolsanov, Y V.
Bushkova, and G E Ivanova, "Stroke affected lower limbs rehabilitation
combining virtual reality with tactile feedback," Front Robot AI, vol 7,
2020, Art no 81.
[16] Y Abbass, L Seminara, M Saleh, and M Valle, "Novel wearable tactile
feedback system for post-stroke rehabilitation," in Proc IEEE Biomed.
Circuits Syst Conf., Oct 2021, pp 1-6.
[17] H Nagano, H Takenouchi, N Cao, M Konyo, and S Tadokoro, "Tactile
feedback system of high-frequency vibration signals for supporting del-
icate teleoperation of construction robots," Adv Robot., vol 34, no 11,
pp 730-743, 2020.
[18] Y Luo, J Wang, R Shi, H .- N Liang, and S Luo, "In-device feedback
in immersive head-mounted displays for distance perception during tele-
operation of unmanned ground vehicles," IEEE Trans Haptics., vol 15,
no 1, pp 79-84, First Quarter 2022.
[19] Y Liu, Y .- Y Tsai, B Huang, and J Guo, "Virtual reality based tactile
sensing enhancements for bilateral teleoperation system with in-hand
manipulation," IEEE Robot Autom Lett., vol 7, no 3, pp 6998-7005,
Jul 2022.
[20] C Pacchierotti and D Prattichizzo, "Cutaneous/tactile haptic feedback in
robotic teleoperation: Motivation, survey, and perspectives," IEEE Trans.
Robot., vol 40, pp 978-998, 2023.
[21] T Maeno, K Kobayashi, and N Yamazaki, "Relationship between the
structure of human finger tissue and the location of tactile receptors," JSME
Int J Ser C Mech Syst Mach Elem Manuf., vol 41, no 1, pp 94-100,
1998.
[22] H Ando, E Kusachi, and J Watanabe, "Nail-mounted tactile display
for boundary/texture augmentation," in Proc Int Conf Adv Comput.
Entertain Technol., Salzburg, Austria, Jun 2007, pp 292-293.
[23] S V Salazar, C Pacchierotti, X de Tinguy, A Maciel, and M Marchal,
"Altering the stiffness, friction, and shape perception of tangible objects
in virtual reality using wearable haptics," IEEE Trans Haptics., vol 13,
no 1, pp 167-174, First Quarter 2020.
[24] P Preechayasomboon and E Rombokas, "Haplets: Finger-worn wireless
and low-encumbrance vibrotactile haptic feedback for virtual and aug-
mented reality," Front Virtual Real., vol 2, 2021, Art no 738613.
[25] M Malvezzi, F Chinello, D Prattichizzo, and C Pacchierotti, “Design of
personalized wearable haptic interfaces to account for fingertip size and
shape," IEEE Trans Haptics., vol 14, no 2, pp 266-272, Second Quarter
2021.
[26] S Costrell, M Alam, R L Klatzky, M E McHenry, L M Walker, and
M O Martinez, "A magnetic soft device for tactile haptic actuation of
the fingertip," in Proc IEEE World Haptics Conf., Delft, Netherlands,
Jul 2023, pp 48-55.
[27] O Ozioko and R Dahiya, "Smart tactile gloves for haptic interaction,
communication, and rehabilitation," Adv Intell Syst., vol 4, no 2, 2022,
Art no 2100091.
[28] Y Huang et al., "A skin-integrated multimodal haptic interface for im-
mersive tactile feedback," Nat Electron., vol 6, no 12, pp 1020-1031,
2023.
[29] Y Luo et al., "Adaptive tactile interaction transfer via digitally embroidered
smart gloves," Nat Commun., vol 15, no 1, 2024, Art no 868.
[30] C Pacchierotti, S Sinclair, M Solazzi, A Frisoli, V Hayward, and D.
Prattichizzo, "Wearable haptic systems for the fingertip and the hand:
Taxonomy, review, and perspectives," IEEE Trans Haptics., vol 10, no 4,
pp 580-600, Fourth Quarter 2017.
[31] X Li, Z Yuan, J Zhao, and X Liao, "Dynamic and accurate force feedback
for electromagnetic haptic display," in Proc IEEE Int Conf Smart Internet
Things), Beijing, China, Aug 2020, pp 132-139.
[32] J Landsmeer, "The coordination of finger-joint motions," J Bone Joint
Surg., vol 45, no 8, pp 1654-1662, 1963.
[33] I R Summers, P G Cooper, P Wright, D A Gratton, P Milnes, and B.
H Brown, "Information from time-varying vibrotactile stimuli," J Acoust.
Soc Amer., vol 102, no 6, pp 3686-3696, 1997.
[34] P Cerveri, E D Momi, N Lopomo, G Baud-Bovy, R Barros, and G Fer-
rigno, "Finger kinematic modeling and real-time hand motion estimation,"
Ann Biomed Eng., vol 35, pp 1989-2002, 2007.
[35] C Lugaresi et al., "MediaPipe: A framework for perceiving and processing
reality," in Proc IEEE Conf Comput Vis Pattern Recognit., Long Beach,
USA, Jun 2019, pp 1-9.
Authorized licensed use limited to: Tsinghua University Downloaded on March 12,2025 at 13:17:28 UTC from IEEE Xplore Restrictions apply.

 These vibration modes
allow the simultaneous recognition on multiple fingers'
bending adjustment.
· Five VibroBots are equipped on fingers to guide users to
adjust their hand gestures Virtual training experiments
demonstrate that VibroBots can help users overcome the
visual and muscle memory gesture mismatch and achieve
precise operations with less joint errors.
II SYSTEM DESIGN
A Device Configuration
Aimed at wearable tactile feedback device, the design of
VibroBot is depicted in Fig 1(a) Five VibroBots are respectively
attached to the second joint of each finger using elastic threads,
for guiding the bending states corresponding to each finger.
Each VibroBot has a cylinder-like shape with a diameter of
16 mm and a height of 8 mm, consisting of the MCU board, a
vibration coil, the power board, and a button cell (Fig 1(b))

,Cutaneous tactile feedback
can compensate for or enhance users' perception of self-body
state and interactive objects, making it highly significant in appli-
cations such as prosthetic limbs [12], [13], [14], rehabilitation
training [15], [16], and robotic teleoperation [17], [18], [19],
[20].
Human hand is the most important medium for human-
machine interaction and tactile perception, and it is highly sen-
sitive due to its dense concentration of mechanoreceptors [21].
Finger-worn actuation devices [22], [23], [24], [25], [26] and
tactile gloves [27], [28], [29], integrated with cutaneous feed-
back, can provide the intuitive two-way haptic interfaces for
Virtual/Augmented Reality (VR/AR) applications [30], allow-
ing users to enjoy the full characteristic benefits of interac-
tion, immersion, and imagination

 For example, Preechayasom-
boon et al introduced the finger-worn wireless haptic device
that provides vibrotactile feedback for hand tracking applica-
tions in VR/AR scenes [24] Huang et al used the palm-form
skin-integrated haptic interface to reproduce tactile information
of fine or macro roughness, slipperiness, force and temperature
of virtual objects [28] Luo et al developed the digitally embroi-
dered tactile glove to record and reproduce tactile interactions,
thus alleviating the tactile occlusion and guiding people to learn
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LI et al .: VIBROBOT: A LIGHTWEIGHT AND WIRELESSLY PROGRAMMABLE VIBRATION BOT FOR HAPTIC GUIDANCE
10883
physical skills of piano playing, rhythmic gaming and racing
gaming in the virtual world [29] However, wearing a tactile
glove can cover the sensitive palm and fingers greatly, thus re-
ducing the tactile information from interactive objects in the real
world [24] Besides, tight and weighty wearable devices impair
the hand's motion capabilities and gesture habits, leading to the
inconsistency between virtual training and practical operation
scenarios.
In this study, we develop a lightweight wearable Vibration
Bot (VibroBot) to implement multi-finger recognizable haptic
guidance on the hand VibroBot integrates the power battery,
a wireless microcontroller unit (MCU), the voltage amplifier
board, and a coil actuator Single VibroBot features the point-
wise tactile feedback programmed wirelessly, to display the
modulated vibration wave on the finger skin with a low net-
work latency We design six vibration modes by modulating
the vibration duration time and cycle count, which can be
recognized quickly and accurately for guiding the flexion or
extension movement of three finger joints Five VibroBots can
work collaboratively for the hand gesture adjustment In virtual
scenes, finger joint angle errors are calculated between the
visually-captured and target gestures, and then vibration modes
corresponding to the angle errors are displayed on VibroBots
for the gesture correction During the haptic guidance process,
VibroBots convert the imperceptible hand gesture information
into easily identifiable vibration modes by the numerical com-
puter vision, for the close-loop gesture adjustment and better
operation performance

 How-
ever, wearable tactile gloves cover the palm and fingers greatly,
thus reducing the tactile information from interactive objects and
causing the inconsistency between virtual and practical operations.
In this work, we design a lightweight finger-worn vibration bot,
named VibroBot, to provide the individual vibrotactile feedback
to each finger without compromising the hand dexterity Each
VibroBot, weighing only 2.9 grams, integrates components of the
power, a wireless chip and a coil actuator, to receive programmable
waveform signals and perform the real-time vibration feedback
wirelessly on finger Our design features six rapidly distinguishable
vibration modes with the 96.4% recognition rate in 2.0 s, each
guiding one of three finger joints for flexing or extending to a
specified angular range When worn on all five fingers, VibroBots
can collaboratively guide the user with multi-dimension semantics,
to adjust five fingers for target hand gestures at the same time.
In virtual gesture training experiments, VibroBots were used to
correct users' muscle memory bias for common gestures, and
reduced the average gesture error from about 30° to less than
15° Haptic guidance by VibroBots shows its potential in various
Tactile Internet scenarios that require a large number of pretrained
hand operations, such as robotic teleoperation and virtual surgical
training.
Received 5 June 2024; accepted 29 September 2024 Date of publication
16 October 2024; date of current version 24 October 2024 This article was
recommended for publication by Associate Editor H Kajimoto and Editor J .- H.
Ryu upon evaluation of the reviewers' comments

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