HugBot: A soft robot designed to give human-like hugs

Abstract

As robots increasingly enter our daily lives, there is a need to understand how to design robots capable of emotional interaction with humans, especially children, due to their sensitivity and vulnerability. For example, robots that provide children with social and emotional support might be more effective at also helping children develop cognitive abilities, rather than designing robots that focus solely on helping children acquire cognitive skill. In this paper, we examine the design of robots that can provide human-like hugs as a particular form of social and emotional support. We first discuss the need to design robots that can interact emotionally with children. Then, we present the development of a shirt augmented with pressure sensors used to collect data on how humans hug each other. Finally, we detail the design of "Hugbot", a soft robot that could use this data to give human-like hugs, and discuss our planned future work on this system.

Full text

HugBot: A so robot designed to
give human-like hugs
Hooman Hedayati∗
Srinjita Bhaduri∗
hooman.hedayati@colorado.edu
srinjita.bhaduri@colorado.edu
University of Colorado
Boulder, CO
Tamara Sumner
Daniel Szafir
Mark D Gross
sumner@colorado.edu
daniel.szafir@colorado.edu
mdgross@colorado.edu
University of Colorado
Boulder, CO
∗
Both authors contributed equally to this re-
search. ABSTRACT
As robots increasingly enter our daily lives, there is a need to understand how to design robots capable
of emotional interaction with humans, especially children, due to their sensitivity and vulnerability.
For example, robots that provide children with social and emotional support might be more eective
at also helping children develop cognitive abilities, rather than designing robots that focus solely on
helping children acquire cognitive skill. In this paper, we examine the design of robots that can provide
human-like hugs as a particular form of social and emotional support. We first discuss the need to
design robots that can interact emotionally with children. Then, we present the development of a
shirt augmented with pressure sensors used to collect data on how humans hug each other. Finally,
we detail the design of “Hugbot”, a so robot that could use this data to give human-like hugs, and
discuss our planned future work on this system.
Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee
provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full
citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting
with credit is permied. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific
permission and/or a fee. Request permissions from permissions@acm.org.
IDC ’19, June 12–15, 2019, Boise, ID, USA
©2019 Association for Computing Machinery.
ACM ISBN 978-1-4503-6690-8/19/06. . . $15.00
hps://doi.org/10.1145/3311927.3325332
556

HugBot: A so robot designed to give human-like hugs IDC ’19, June 12–15, 2019, Boise, ID, USA
CCS CONCEPTS
•Computer systems organization →Robotics
;
•Human-centered computing →
Interaction
design; Collaborative interaction.
KEYWORDS
So robots; Human-like hugs; Social robots; Child-robot interaction
ACM Reference Format:
Hooman Hedayati, Srinjita Bhaduri, Tamara Sumner, Daniel Szafir, and Mark D Gross. 2019. HugBot: A so
robot designed to give human-like hugs. In Interaction Design and Children (IDC ’19), June 12–15, 2019, Boise, ID,
USA. ACM, New York, NY, USA, 6 pages. hps://doi.org/10.1145/3311927.3325332
INTRODUCTION
The rise in technologies, especially in the area of robotics, is leading to a rise in aordable robots for
families, such as Roomba and Sphero robots. Moreover, there is a trend in developing social home
robots to assist children in a variety of tasks such as developing and improving motor skills, verbal
skills, creativity, etc. Most existing work involving social robots focusew only on the task e.g., ways to
help a child through storytelling [
9
], act as a companion to learn English as a second language [
8
], or
even as informants for young children [
3
]. These eorts are valuable by themselves but we believe
children may learn beer if they can emotionally connect to their tutor or companion. Research shows
that teachers with social-emotional skills have beer influence on their students’ learning [
7
] but
when there is still much to be explored on how robots with such skills impact children’s behavior or
learning. The lack of knowledge in this area is due to the relatively new body of research that looks at
ways to develop robots that can eectively provide social and emotional support. One such area is
the interaction of robots and humans through hugs.
Hugs are a natural and intuitive way of expressing aection and giving a hug is an expression that
comes almost instinctively for some people, while others feel uncomfortable in giving hugs because of
the complex series of interactions involved. First, a “good” hug involves proper positioning of the arms
and hands and torso, then one must be aware of the appropriate amount of force to use, and finally
understand when is the right moment to let go [
2
]. It is a two-way interaction between huggee and
hugger. Researchers have studied how robots could engage in giving hugs, from using a robot-like
design called the “Hug” to give “tele-hugs” [
5
], to acting as a companion inspired by animal therapy to
promote the overall health of an individual [
11
], or even using personal robots to give hugs to adults
for emotional support [
2
]. However, most previous research focuses on the robots instead of the users
i.e., the robot initiates the hugs and opens and closes its arms to give a hug, lacking a consideration of
when the user wants to let go or if the hug is suicient for providing emotional support. More research
557

HugBot: A so robot designed to give human-like hugs IDC ’19, June 12–15, 2019, Boise, ID, USA
is needed to explore ways to train a robot to understand these challenges and provide emotional
support to children. Children are sensitive to hugs and by learning how to give a good hug they might
learn an important social skill from a robot and be more socially engaged with their parents and peers
[
12
]. Bearing in mind the process of a “good” hug, we designed HugBot: a so-robot that can give
human-like hugs to users, especially children. In this paper, we describe background research and our
approach for designing the HugBot. First, we lay out the steps to design a custom sensory t-shirt to
measure how humans hug each other, e.g., how to initiate hug, aachment-detachment time, etc.
Then, we discuss the design of HugBot (see Figure 1), and finally, we share our findings and elaborate
our future plans to collect data to train the HugBot to give human-like hugs.
Figure 1: A child geing hugged by the
HugBot
RELATED WORK
We designed the HugBot in consideration of prior work in two research areas: robots as social agents
and the need for designing so robots to provide more human-like interactions.
Robots as social agents
Research has shown that children tend to perceive robots as life-like characters and with extended
interaction the relationship evolves to the point that children see robots as their peers [
6
]. As a result,
researchers have suggested the need to create robots that are engaging and interact continuously
with humans. In the case of children, robots serve as tutors, therapeutic assistants, or toys [
6
]. In
exploring these use cases, researchers have developed robots that express emotions in a variety of
ways, for example through eye gaze or gestures [
3
]. Although dierent social-emotional interactions of
robots have been studied, comparatively less work has explored the impact of the robot on children’s
learning to actively engage in such interactions. Researchers have postulated that this could advance
the field of child-robot interaction [
1
]. In this work, we are interested in supporting children’s learning
of social and emotional skills, such as giving and receiving hugs, and ways to use this learning in
other aspects of day-to-day interactions.
Figure 2: Design of sensory shirt: contains
a shirt with 8 pressure sensors that uses
velostat to measure the pressure and alu-
minium foil to make the sensors conduc-
tive
So robots to support human-like interactions
Interactive robots are being used in providing physical, educational and therapeutic assistance in
schools, homes, and hospitals [
5
]. Robots with animal-like appearances, such as the robotic dog AIBO,
can be an important factor in providing tangible interactions and developing a sense of emotional
aachment [
13
]. PARO, a robotic baby harp seal, has been used to help reduce agitation and improve
mood states in people with dementia [
4
]. Others have designed so robots that react to touch, like
the Huggable [
11
], which can motivate children, or like the HuggieBot [
2
], which can engage adults in
aectionate behavior such as cuddling or hugging. Additionally, Disney plush toys or stued animals
are being used by researchers to study the amount of pressure children can exert while giving hugs,
558

HugBot: A so robot designed to give human-like hugs IDC ’19, June 12–15, 2019, Boise, ID, USA
in order to design interactive robots [
10
]. Our work contributes to this area through the design of a
human-size so robot that supports opportunities for social and emotional skill enhancement.
Figure 3: Prototype of a 3D printed arm
with 3 joints and a fixed part on which the
other joints rest
SYSTEM DESIGN
Our system consists of 3 components: 1) a sensory shirt to study hugs, 2) robotic arms to manipulate
the hug, and 3) a panda-like stued animal, which hosts all the sensors and actuators.
Design of a sensory shirt
To execute a realistic hug, it is necessary to study how people give and get hugs. It is also important
to describe a hug by features or aributes so that it can measured and emulated. We identify two
features to describe a hug. First, “engaged body parts”, a vector of n bits where n is the number of
sensors, and each bit represents whether the relevant sensor is sensing pressure. Second, “duration”, is
the total aachment-detachment time, starting when one of the sensors show a number more than
the threshold (e.g. in our application it is 0.12) and ending when all the “engaged body parts” vectors
are less than the same threshold. We designed a custom sensor shirt, consisting of 8 pressure sensors
(4 on the chest and 2 on each arm) that can record the amount of pressure exerted to dierent parts
of the chest and arm, the aachment-detachment time, and which parts of body are involved during
the hug (see Figure 2). A preliminary study with volunteers provided an initial understanding of the
data. We used these data to control and actuate the robotic arm to imitate a hug. In the future, we
plan to collaborate with local primary schools to complete a formal user study with children. We
used the gathered data in two ways, first for classifying the dierent type of hugs, and second for
reinforcement learning, to control the robot arm so that it can give realistic hugs.
Design of a so-robotic arm
To design a proof-of-concept arm, we used cardboard to develop arms with dierent degrees of
freedom (DOF) to determine a design that supports a flexible arm that can bend freely around an
object. These parts are still being developed and we need more data to accurately classify hugs.The
Figure 4: Design of HugBot’s arm using
foam sponge and strings
robotic arm should be able to completely grasp the chest and back with an adjustable pressure similar
to human arms when humans hug each other. Aer several iterations, we found that an arm with
3 joints provides a suitable trade-o between arm complexity and flexibility. Next, we 3D printed a
variety of joints for the arms to test possible shapes (see Figure 3). Through this process, we determined
that each joint should have a curvature of at least 30 degrees. From the 3D printed joints we observed
that for safety, it was essential to make the material for the arms soer, as we did not want HugBot
to exert an uncomfortable amount of pressure on the person it was hugging. In the final design, the
arms were made using foam sponge. As shown in Figure 4, it consisted of 6 identical pieces roughly
quarter-circle shape (15cm x 10cm x 5cm). Strings were used to keep the arms straight, with one end
559

HugBot: A so robot designed to give human-like hugs IDC ’19, June 12–15, 2019, Boise, ID, USA
fixed to the end of the arm, while the other side was connected to a servo motor. Rubber bands were
Figure 5: The T-shape structure used for
making the backbone of HugBot
used to keep the arms open by default. The arms were aached to a T-shaped wooden structure,
which acted as a backbone for the robot (Figure 5). The actuation of the arms were such that the
entire arms bend on the pulling and releasing of two strings aached to a pulley that go all the way
through both the arms. To automate this process, a stepper motor was added to the T-shape structure
and it completed majority of the Hugbot design.
Figure 6: A panda shaped stued toy we
used for creating the HugBot
Choice of so robot
There are multiple challenges to choose the right robot body for this project. It is essential that the
appearance of the robot be acceptable to children. No maer how well the hugging part of the robot
works, if the robot itself is not appealing (e.g., scary, too big, etc.), children will not use it. We opted
for a zoomorphic appearance, rather than a humanoid morphology to avoid uncanny valley eects.
As we wanted to put the arm and actuators inside the body, the choice of using a stued animal
was promising. We decided to use a panda stued animal that is visually appealing and mimics the
common notion of a stued bear with which many children are familiar (Figure 6). As elementary
school children are the main target of this research, we decided to use a stued animal with 1 meter
height, roughly mimicking the height of the children.
DESIGN IMPLICATIONS AND FUTURE WORK
This paper presents ongoing work on HugBot, a hugging robot that gives human-like hugs. The aim
of designing such a robot is to teach social skills to children through emotional interactions like hugs.
To test the feasibility of our design we pilot tested it with dierent users. The sensor-shirt was tested
by members from our research group and we noted changes necessary in order to eectively collect
data, such as increasing the surface area of the 8 pressure points and making the pressure points
more continuous instead of separating them from one another. We presented our work at a research
expo where child visitors interacted with the HugBot (see Figure 1). From our observations we saw
that robots with zoomorphic appearance keep children more engaged, and that HugBot could be used
as a means to teach social skills to children. Our system design and initial tests suggest that there are
dierent types of hugs (e.g., between two friends, or between a parent and a child). To design a robust
system that mimics these types of human hugs, intensive user studies need to be conducted with
children to train the robot. As part of our future work, we will test the sensor-shirt and the robotic
arms with children and their parents and peers, and record types of hugs. Using these data, we plan
on implementing machine learning techniques to train the robot to give dierent hugs and enable
more social interaction with children. Thus, we envision all the parts of our system to be integrated
into a HugBot design that can help children learn about social skills like hugs and it comfortable for
them to interact with family and peers.
560

HugBot: A so robot designed to give human-like hugs IDC ’19, June 12–15, 2019, Boise, ID, USA
REFERENCES
[1]
Tony Belpaeme, Paul Baxter, Robin Read, Rachel Wood, Heriberto Cuayáhuitl, Bernd Kiefer, Stefania Racioppa, Ivana
Kruij-Korbayová, Georgios Athanasopoulos, Valentin Enescu, et al. 2013. Multimodal child-robot interaction: Building
social bonds. Journal of Human-Robot Interaction 1, 2 (2013), 33–53.
[2]
Alexis E Block and Katherine J Kuchenbecker. 2018. Emotionally Supporting Humans Through Robot Hugs. In Companion
of the 2018 ACM/IEEE International Conference on Human-Robot Interaction. ACM, 293–294.
[3]
Cynthia Breazeal. 2003. Emotion and sociable humanoid robots. International journal of human-computer studies 59, 1-2
(2003), 119–155.
[4]
Adrian Burton. 2013. Dolphins, dogs, and robot seals for the treatment of neurological disease. The Lancet Neurology 12, 9
(2013), 851–852.
[5]
Carl DiSalvo, Francine Gemperle, Jodi Forlizzi, and Ellio Montgomery. 2003. The hug: an exploration of robotic form for
intimate communication. In The 12th IEEE International Workshop on Robot and Human Interactive Communication, 2003.
Proceedings. ROMAN 2003. IEEE, 403–408.
[6]
Yasemin Dönmez, Naz AGZ Börekçi, and Mathieu Gielen. 2018. Wow he is talking!: a study on intrinsic motivations
for child-robotic toy interactions. In Proceedings of the 17th ACM Conference on Interaction Design and Children. ACM,
349–356.
[7]
Stephen N Ellio, Christine K Malecki, and Michelle K Demaray. 2001. New directions in social skills assessment and
intervention for elementary and middle school students. Exceptionality 9, 1-2 (2001), 19–32.
[8]
Goren Gordon, Samuel Spaulding, Jacqueline Kory Westlund, Jin Joo Lee, Luke Plummer, Marayna Martinez, Madhurima
Das, and Cynthia Breazeal. 2016. Aective personalization of a social robot tutor for children’s second language skills. In
Thirtieth AAAI Conference on Artificial Intelligence.
[9]
Layne Jackson Hubbard, Boskin Erkocevic, Dylan Cassady, Chen Hao Cheng, Andrea Chamorro, and Tom Yeh. 2018.
MindScribe: Toward Intelligently Augmented Interactions in Highly Variable Early Childhood Environments. In Proceedings
of the 23rd International Conference on Intelligent User Interfaces Companion (IUI ’18 Companion). ACM, New York, NY,
USA, Article 11, 2 pages. hps://doi.org/10.1145/3180308.3180319
[10]
Joohyung Kim, Alexander Alspach, Iolanda Leite, and Katsu Yamane. 2016. Study of children’s hugging for interactive
robot design. In 2016 25th IEEE International Symposium on Robot and Human Interactive Communication (RO-MAN). IEEE,
557–561.
[11]
Walter Dan Stiehl, Cynthia Breazeal, Kuk-Hyun Han, Je Lieberman, Levi Lalla, Allan Maymin, Jonathan Salinas, Daniel
Fuentes, Robert Toscano, Cheng Hau Tong, et al
.
2006. The huggable: a therapeutic robotic companion for relational,
aective touch. In ACM SIGGRAPH 2006 emerging technologies. ACM, 15.
[12]
James Keng Soon Teh, Adrian David Cheok, Roshan L. Peiris, Yongsoon Choi, Vuong Thuong, and Sha Lai. 2008. Huggy
Pajama: A Mobile Parent and Child Hugging Communication System. In Proceedings of the 7th International Conference
on Interaction Design and Children (IDC ’08). ACM, New York, NY, USA, 250–257. hps://doi.org/10.1145/1463689.1463763
[13]
Astrid Weiss, Daniela Wurhofer, and Manfred Tscheligi. 2009. “I love this dog”-children’s emotional aachment to the
robotic dog AIBO. International Journal of Social Robotics 1, 3 (2009), 243–248.
561