Unconstrained Neck: Omnidirectional Observation from an
Extra Robotic Neck
Lichao Shen, MHD Yamen Saraji, Kai Kunze and Kouta Minamizawa
Keio University, Graduate School of Media DesignYokohama, Japan{shenlc,yamen,kai,kouta}@kmd.keio.ac.jp

ABSTRACT
Humans are born with physiological limitations in terms of thesensory and motor abilities. Due to the narrow range of motion ofthe neck and the small visual field of the eyes, the human visual
sense is limited in terms of the spatial range. We address this visual
limitation by proposing a programmable neck that can leverage therange of motion limits. Unconstrained Neck, a head-mounted robotic
neck, is a substitution neck system which provides a wider rangeof motion enabling humans to overcome the physical constraintsof the neck. Using this robotic neck, it is possible to control thevisual/motor gain which allows the user to thus control the range
and speed of his effective neck motion or visual motion.

VisionYaw Z-axis

CCS CONCEPTS• Computing methodologies → Graphics systems and interfaces; • Human-centered computing → Human computer interaction (HCI); Interaction design; • Hardware → Sensor devices
and platforms;

KEYWORDS
robotic neck, vision expansion, human augmentation, biomimetics
ACM Reference Format:
Lichao Shen, MHD Yamen Saraji, Kai Kunze and Kouta Minamizawa. 2018.
Unconstrained Neck: Omnidirectional Observation from an Extra RoboticNeck. In AH2018: The 9th Augmented Human International Conference, February 7–9, 2018, Seoul, Republic of Korea. ACM, New York, NY, USA, 2 pages.
https://doi.org/10.1145/3174910.3174955

1

SYSTEM OVERVIEW

We utilize an extra robotic neck to achieve the Unconstrained Neck.
The prototype consists of a stereo camera, helmet-based robotic
neck with 3 degrees of freedom (DOF), and head-mounted display(HMD) as shown in Figure 1. The motorized camera is mounted
at the endpoint of the robotic neck, allowing the camera and its
vision direction to operate 3-axis rotations: yaw, pitch, and roll.
The resulting motion of the rotation is thus a combination of thehuman neck and the robotic neck movements. For this system,
the maximum range of motion is −180° to 180° about the threeaxes, which is almost twice the range of the human neck. ThePermission to make digital or hard copies of part or all of this work for personal orclassroom use is granted without fee provided that copies are not made or distributedfor profit or commercial advantage and that copies bear this notice and the full citationon the first page. Copyrights for third-party components of this work must be honored.
For all other uses, contact the owner/author(s).
AH2018, February 7–9, 2018, Seoul, Republic of Korea© 2018 Copyright held by the owner/author(s).
ACM ISBN 978-1-4503-5415-8/18/02.
https://doi.org/10.1145/3174910.3174955

ψaxisll X-Roψ

HeadVision(projected)

Pitc
hY-ax
isFigure 1: The Unconstrained Neck

Unconstrained Neck is driven by user’s neck orientation, and themotion mapping is defined by the software. Previous work [1, 2]
addressed the possibility of human visual/motor system adaptation
to different gain values in the virtual environment. We apply asimilar approach for this system. The visual/motor gain (g) for eachaxis of the system is controlled in the software side, with positivevalues (g>0) to amplify the speed of motion, or negative values(-1<g<0) to result in slower operation of the neck. For example,
as shown in Figure 1, the gain value used g=1, the user’s humanhead (neck) is at a yaw angle of ψ , and the resulting system vision(camera) is at a yaw angle equivalent to 2ψ (calculated by ψ +ψ ∗ д).
Depending on the application or scenario, this gain value can bealtered to make the movements of the vision faster with a wider
range of motion. Or it can be slower with a limited range of motion.
This approach can be viewed as programming our body’s motorsystem.
The system operates by wearing the helmet, with the robotic
neck being mounted at the center top of the user’s head maintainsimilar perspective (with a vertical offset of approximately 450 mm
from user’s eyes). The camera streams stereo images to the HMD,
creating a see-through experience. The camera is configured withAH2018, February 7–9, 2018, Seoul, Republic of Korea
an interpupillary distance of 65 mm, and a horizontal field of viewequivalent to 110° matching the used HMD settings (Oculus DK2).
The coherence in vision can ease the user’s incompatibility andoptimize this augmented experience.

2USER EXPERIENCE

When using this prototype, the users can have full omnidirectionalview covering 360° surroundings with the neck action only. The
users are also able to re-program their neck motion to achieve avarying values of the range of motion. When scanning, the system
can substitute the movements of the torso and spine, and this makes
the operation swifter and more agile. It is especially fit for people
who have stiffness or disability in lower body or spine, but also
can be used by health people to augment the neck motion andthe spatial range of the vision. The overall experience is smoothand immersive, and naive users are able to adapt to the new visualaugmentation experience within a short time.

REFERENCES[1] Shunichi Kasahara, Keina Konno, Richi Owaki, Tsubasa Nishi, Akiko Takeshita,
Takayuki Ito, Shoko Kasuga, and Junichi Ushiba. 2017. Malleable Embodiment:
Changing Sense of Embodiment by Spatial-Temporal Deformation of Virtual
Human Body. In Proceedings of the 2017 CHI Conference on Human Factors in
Computing Systems. ACM, 6438–6448.
[2] Michiteru Kitazaki. 2013. Human Adaptation, Plasticity and Learning for a New
Sensory-Motor World in Virtual Reality. In International Conference on Virtual,
Augmented and Mixed Reality. Springer, 184–191.

L. Shen et al.