UBICOMP/ISWC '15 ADJUNCT, SEPTEMBER 7–11, 2015, OSAKA, JAPANTowards Performance Feedback
Through Tactile Displays to Improve
Learning Archery
Heng Gu

Abstract

Keio University

In this paper, we explore a specific case of sensory
augmentation through substitution techniques. We
present an early tactile display prototype designed fornovice archers to provide real time feedback on theirperformance. We evalute the protoype over interviews
with 3 experts. Based on the evaluation, we introduce
improvments on the initial design. We believe that therate skill acquisition could be improved by providing therelevant sensor data to the learner through such atactile interface.

Heng.gu@network.rca.ac.uk
Kai Kunze
Keio Universitykai.kunze@gmail.com
Masashi Takatani
Keio Universitynakatani@iog.u-tokyo.ac.jp
Kouta Minamizawa
Keio University
kouta@kmd.keio.ac.jp

Author Keywords
Wearable; Tactile Display; Archery; Sensory
Augmentation.

ACM Classification Keywords
H.5.m [Information interfaces and presentation (e.g.,HCI)]: H.5.2 User Interfaces, Interaction Style.
__________________________________________________________

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Copyright is held by the owner/author(s).
UbiComp/ISWC'15 Adjunct, September 7-11, 2015, Osaka, Japan
ACM 978-1-4503-3575-1/15/09.
http://dx.doi.org/10.1145/2800835.2800893

141

IntroductionSensory substitution and the use of tactile displays asinterface are not new ideas. However, sensory
substitution projects focus primarily on disabled users;
researchers have explored circumvention of blindness
and deafness through tactile displays. Tactile displays

UBICOMP/ISWC '15 ADJUNCT, SEPTEMBER 7–11, 2015, OSAKA, JAPAN

Figure 1: vibrating motorarray layout

offer a promising noninvasive, natural methodinteraction technique. Specifically for the developmentof motor skills, tactile feedback on the athlete’s
performance creates a closed-loop system for action
modification and preparation. Researches show expert
athletes experience an increased temporal resolution ofvisual perception during action preparation (i.e.
baseball players feel time slow when batting a ball) [5].
The phenomenon could be attributed to the tactile
stimuli experienced, which triggers faster responsethan visual and auditory stimuli [6]. Real time tactile
feedback for sports have been explored in roller derby
through the wrist guard [9] and snowboarding throughdisplays in the torso and legs [7, 8]. Our proposed
tactile display provides tactile cues on the posture of
the bow, to help train motor preparation of the archer,potentially promoting the development of related motor
skills.
The contributions of this paper are as follows: (1) we
discuss our approach to give tactile feedback for acherylearners, (2) we present an initial, functional prototype
of our tactile display, (3) we perform an expert
evaluation and, (4) give lessons learned and future
design improvements for a system that can be tried inlarger experimental setups.

Related Work

Figure 2: Vibration patterns
encoding

Several projects have investigated sensory substitution,
primarily for the use in rehabilitation or overcoming
disabilities (e.g. Versatile Extra-Sensory Transducer[1], Brainport [2]). A promising and most recent
platform is the haptic vest designed by Eagleman Labs;
it is a crowdfunded sensory substitution device thattranslates sound into vibration patterns on the vest toenable hearing in the deaf. The vest was designed to be142

adaptable to other sources of inputs and datasets. The
study shows that deaf only need 2-3 weeks of training
to begin interpreting audio [1]. Other studies also
address tactile interfaces that target disabilities [2,3].
They do not investigate sensory substitution as
augmentation for nondisabled users for improved
learning and skill acquisition. The closest to our work is
the research by Spelmezan and Mareike both looking
into tactile feedback as instructions for snowboarding[7,8]. However their feedback focuses on legs or back.
So far we are unaware of any other research focusing
on the use of tactile displays on the lower arms for skill
acquisition in sports.

Approach
To design this tactile interface, we investigatedvibrotactile stimulation to interface with the body. To
study effect of tactile feedback on skill acquisition, we
proposed designing a tactile display for novice archers.
Archery
issuitablebecauseofits
definitive
measurement of success and improvement, and thetype of relevant data to provide is straightforward:
position and orientation of the bow. Converting thisdata into vibrotactile sensations for the learner mightprovide meaningful feedback on their performance,
allowing immediate adjustment of posture and fasterimprovement. To minimize the effect of the learning
curve for the vibration patterns, we chose an intuitive
correlation
fortheencoding:onetoonecorrespondence between rows of vibrating motors andparameters. With this in mind, we developed an initial
prototype to test before further development of thetactile interface.

POSTERS

Initial Prototype

Figure 3: inital prototype

The arm guard used in archery is necessary equipment,
and a suitable housing for the vibrotactile array (seeFigure 3). We also chose the forearm to interface thedevice for its relative sensitivity and the proximity ofbone to the surface, which allows for stronger vibration
sensations than the torso. It seemed also a natural
positioning to place the actuators on the arm that holds
the bow. The orientation of the bow can be measured
using the accelerometer and gyroscope. Since one axis
is constrained by the wielder’s arm, only 2 axes need tobe considered: front-to-back tilt and side-to-side tilt
about the wrist. Therefore, we chose 2-rows ofvibrating motors, positioned orthogonal to each otheras shown in Figure 1, to encode this information. The
position of the vibration correlates to the tilt of thebow, as shown in Figure 2.

draw. The best stance requires the archer’s body andbow to be on the same plane orthogonal to the ground,as shown in figure 4. To maintain correct angle fromsetup to drawing is a challenge for novices due to thestrain of drawing the string. Training improves themuscle memory and sensing the proper stancethroughout the drawing process. With haptic feedbackon the subtle changes on the stance, the learner canrely less on minute visual cues to know if the drawing
process changed the setup stance. The verticalvibrating motor array would inform the learner if thebow shifted within the center plane of the stance.
Likewise, the horizontal array would inform the learner
if the bow tilted out of the center plane. Both are notideal. So far the haptic feedback is given towards thedirection the user is to adjust the stance.

First Evaluation
HARDWARE

Figure 4: ideal stance

We use a total of 12 vibrating motors [FM34F], 6 forthe front-to-back tilt and 6 for the side-to-side, all ofwhich are controlled by a PWM LED driver. TheTLC5940 driver was suitable for this, with 16 channels
to control the transistor switches. Due to the 120mA
limit of the driver, we need a separate power supply forthe vibrating motor arrays. Figure 3 shows theassembled prototype. The accelerometer and gyroscope
data is collected from a mobile phone directly mounted
onto the handle of the bow over Bluetooth LE. In theteaser Figure on the first page you can see a user
wearing our hardware setup while practicing archery.

We evaluated the prototype with 3 expert archers andstudents at an archery studio in Tokyo. All archers that
tried the system on liked the basic idea and are eager
to see if the tactile feedback can be used to improvetheir skills. We learned that in the next prototype, itwould be beneficial to include a second accelerometeron the forearm, so as to determine the relative angle ofthe bow to the wrist of the wielder. The experts wereinterested in repeating shots with same/similar
inclination. Moreover, providing haptic feedback on thetension of the bowstring to inform successful full drawof the bow would likely also improve learning.

Discussions
INTERACTIONS
For novice archers, the key practice revolves aroundcorrect “setup” or the preliminary action before drawing
the string, then maintaining that stance to the full143

As a result of the design, development and initial testsof the arm guard tactile display, we identified thefollowing design considerations and requirements:

UBICOMP/ISWC '15 ADJUNCT, SEPTEMBER 7–11, 2015, OSAKA, JAPAN• The wearable tactile interface has to be light-weightand portable, and cannot be cumbersome that itaffects the user’s performance and endurance.
• The vibrating motor arrays must be modular, scalable
to larger resolutions• The pattern encoding software must be flexible andscalable to other types and sizes of datasets.
• Instructions to using the device should be minimal ornonexistent, allowing the user to intuitively
understand the haptic feedback
While the tactile display is intended to help novice
archers develop the correct stance for drawing the bow,
it can also be useful for more advanced archers
duplicate shots by informing them of a recorded angle.
The future model of this device would allow advanced
archer reset the recommended angle of the bow as wellas the tension of the string to a shot that they would
like to reproduce.

Conclusion and Future WorkIn this paper, we showed the design and developmentof a tactile display to provide real time performance
feedback and investigate the possibility to improve skill
acquisition for archery. The main contribution of thisposter paper is to present a set of design
considerations
forsensory
augmentation
whiledeveloping a prototype showing a potential application
for tactile displays to expand awareness throughartificial sensors. We plan to conduct a study to assessthe user experience of using the device and measurelearning rate due to the haptic feedback, refining andfurther developing the tactile

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