Poster: MR Telepresence System with Inertial Force Sensation
Using a Motion Platform and an Immersive Display
Maiya Hori∗

Masayuki Kanbara†

Naokazu Yokoya‡

Nara Institute of Science and Technology

A BSTRACTThis paper presents a telepresence system for a ride, such as on aroller coaster, using a motion platform that can provide a seateduser with the sensation of inertial force. Most conventional studies using a motion platform with a few degrees of freedom havenot generated an inertial force when a ride accelerates, because amotion platform cannot simulate the same motion of a real rollercoaster. We propose a new telepresence system that can provide auser with an inertial force sensation using a motion platform with afew degrees of freedom and an immersive display. In our research,
the inertial force sensation is generated by acceleration of gravity
produced by inclining the motion platform. The inclination of theseated user is estimated from an image sequence captured using anomnidirectional camera placed on an actual running roller coaster.
In our experiments, the inertial force sensation is realized using amotion platform and an immersive display.
Index Terms: H.5.1 [Information Interfaces and Presentation]:
Multimedia Information Systems—Artificial, augmented, and virtual realities; H.5.2 [Information Interfaces and Presentation]: User
Interfaces—Prototyping;
1I NTRODUCTION

Telepresence is a technology that enables users to feel as if they areat a remote site. This study presents a telepresence system for a ride,such as on a roller coaster, using a motion platform and an immersive display as one of the entertainment contents. Information provided to a user in telepresence includes motion information, suchas of a vibration or an inclination, generally presented by a motion
platform. In a roller coaster simulation, the motion platform plays
an important role and requires many degrees of freedom to simulate the motion of a real roller coaster [1]. However, such a motion
platform is very expensive, requires a large amount of space, andis complicated to control. Therefore, in recent years, roller coaster
simulation using a motion platform with a few degrees of freedom
has been developed [2]. This motion platform is easy to control andis cheaper than a motion platform with many degrees of freedom.
However, there is one drawback: a motion platform with only a few
degrees of freedom cannot produce the inertial force that is generated when a ride moves. Therefore, a motion platform with a few
degrees of freedom cannot generate the same motion as a real roller
coaster.
This paper presents a new telepresence system that can provide
a user with a sensation of the inertial force produced when an actual ride is accelerating. In our telepresence system, we employ an
immersive display and a motion platform that can incline the user’s
seating. Figure 1 shows an example of the telepresence system using a motion platform with a few degrees of freedom. In general, as∗ e-mail:maiya-h@is.naist.jp† e-mail:kanbara@is.naist.jp‡ e-mail:yokoya@is.naist.jp

Figure 1: Experimental environment using motion platform with a few
degrees of freedom

the motion platform has limited degrees of freedom and a narrow
range of motion, it is difficult to precisely simulate an inertial force
for the user. In our research, the inertial force sensation is generated by acceleration of gravity obtained by inclining the motion
platform. The amount of inertial force is estimated using an image sequence that has been captured from the viewpoint of a user
actually riding on a roller coaster.
2 R EALIZATION OF I NERTIAL F ORCE S ENSATIONIn this study, the inertial force sensation is achieved by inclining
the motion platform. Figure 2(a) illustrates the forces that a userexperiences in a real environment. The user experiences a resultant
force that is the resolution of an acceleration of gravity and an inertial force. Figure 2(b) illustrates the forces that a user feels in anexperimental environment. The resultant force in real world is generated by acceleration of gravity in the experimental environment.
Because the inertial forces work in the same direction as in an actual environment the user experiences a sensation of inertial force.
2.1 Estimation of the motion of roller coasterIn our experimental environment, an inertial force is generated byinclining the motion platform according to the amount of inertial
force in a real environment. In order to estimate the amount of thisforce, the acceleration of the roller coaster needs to be known. In
our study, the motion of the roller coaster is estimated from theimage sequence, which is captured from viewpoints of the user actually riding on a roller coaster.
We use an existing method [3] for estimating the camera position and posture from multiple image sequences obtained using anomnidirectional multi-camera unit. This method uses the structurefrom-motion technique which is based on tracking natural features,and the perspective n-point problem (PnP) techniques. The camera
parameters are estimated by tracking natural features automaticallyand by making use of a robust approach, RANSAC. Figure 3, theresult of estimated camera parameters, confirms that the camera parameters can be recovered smoothly. The acceleration of the roller
coaster is estimated by using extrinsic camera parameters, and theinertial force is estimated by this acceleration.

(a) Roller coasterFigure 3: Result of estimated camera motion(b) Motion platform

Figure 2: Realization of inertial force sensation(a) X-axis(b) Y-axis(c) Z-axis

Figure 4: Result of estimated inertial force

2.2 Estimation of Inclination of Motion Platform andgeneration of user’s view
The proposed method generates an approximation of the inertial
force from acceleration of gravity by inclining the motion platform
to an inclination that is different from that of a real roller coaster. In
our research, the resultant force that a user experiences in the realworld is substituted by acceleration of gravity in telepresence. The
motion platform is inclined so as to fix the direction of a resultant
force vector to a user’s body as shown in Figure 2.
The inertial force cannot be reproduced only by inclining a motion platform, because there is inconsistency between the visual aspect and the physical inclination of the user. Because the motion
platform inclines in a different direction from the body of the roller
coaster in an actual environment, it is necessary to change the image shown to the user appropriately. The image is presented to theuser so as to fix the relationship between the position of the roller
coaster and the user. The image can be easily made because theimage sequence is captured using the omnidirectional camera unit.
Since the user cannot distinguish the inclination of the motion platform from visual information, the user experiences the sensation ofinertial force. In order to achieve this effect, it is necessary to cover
the user’s field of view with an immersive display.
3C ONSTRUCTION OF T ELEPRESENCE S YSTEM

Figure 1 shows a prototype telepresence system with a HMD(Daeyang, i-visor FX601) and a motion platform (Kawada Industries, JoyChair). In this system, the user sees an image made froma panoramic sequence captured using a multi-camera unit (PointGreyResearch, Ladybug2). The user sees 800 × 600 resolution images at 30 fps on the HMD. The motion platform can rotate on rolland pitch axes, and each axis has a movable range of ± 15 degrees.
Figure 4 shows comparisons between a target value and theamount of estimated inertial force using the proposed method. As
shown in this figure the user can experience an inertial force sensation that is proportional to the actual inertial force.

4 C ONCLUSION
This paper presents a telepresence system for a ride, such as on aroller coaster, using a motion platform and an immersive display.
The important contribution of this research is the construction of a
new telepresence system that can provide a user with the sensationof an inertial force similar to that generated when an actual ride isaccelerating. The inertial force is estimated automatically by recovering the camera motion from the omnidirectional image sequence.
The inertial force sensation is approximated by an acceleration ofgravity. In our experiments, we have confirmed that the user canfeel an inertial force sensation using the prototype system.
Our future work includes verification of the validity of the proposed method by conducting a subjective evaluation experiment. In
particular, it is necessary to consider the amount of virtual inertial
force that is different from the amount of actual inertial force.
ACKNOWLEDGEMENTS
This research was partially supported by the Ministry of Education,Culture, Sports, Science and Technology, Grant-in-Aid for Scientific Research (A), 19200016.
R EFERENCES[1] K. C. Cheok, J. L. Overholt, and R. R. Beck. Exact Methods for Determining the Kinematics of a Stewart Platform Using Additional Displacement Sensors. In Journal of Robotic systems, Vol. 10, Iss. 5, pp.
689–707, 1993.
[2] Z. C. Shih, Y. S. Jaw, and M. L. Hsu. Virtual Roller Coaster. In Proceedings of the IEEE Virtual Reality 2000 Conference, pp. 225–232,
2000.
[3] T. Sato, S. Ikeda, and N. Yokoya. Extrinsic Camera Parameter Recovery from Multiple Image Sequences Captured by an Omni-directional
Multi-camera System. In Proceedings of European Conference on
Computer Vision, Vol. 2, pp. 326–340, 2004.