Harness Mechanisms for Full-Body Motions in Virtual Environments

Roger E. KaufmanThe George Washington University

Mechanical and Aerospace Engineering DepartmentWashington, DC

kaufman1@gwu.edu

ABSTRACT

Natural motions such as twisting, turning, jogging in place, drop-ping to the knees or moving to a prone position are permitted by the virtual reality harness mechanisms presented in this poster. They constrain an immersed user within the field of view of a virtual lo-comotion sensing system. Unwanted rotational inertial loads felt by the user are minimized while compliant constraints provide natural feedback forces. These ergonomic forces enhance the experience of virtual motion by partially substituting for the missing real-world dynamic loads encountered in locomotion. They also aid the user in remaining centered in the field of view of the camera system by providing subtle, natural cues to the immersed user. Unlike some other virtual locomotion systems these passive harness devices have a stationary floor and are relatively low-cost, easy and natu-ral to use. This makes them minimally intrusive on the process of learning the simulated task.

Keywords: 3D interaction, haptics, non-visual interfaces, tracking, harness mechanisms, immersion, input devices locomotion, human factors, full-body, prone,

Index Terms: H.5.2 [User Interfaces]; Haptic I/O; H.1.2 [User/Machine Systems]; Human factors; I.3.6 [Methodology and Tech-niques]; Interaction Techniques; Tracking, Motion;

1 INTRODUCTION

This poster presents several new full-body harness devices de-veloped to constrain a user as unobtrusively as possible in an im-mersive environment. (Reference 3 expands on this discussion and provides much more details about these devices.) These harness mechanisms provide a cost-effective compromise between simula-tion realism and practicality, since they are passive and don’t in-volve any servomotors, actuators, or moving floors.

Motions such as dropping to a prone position or sudden twists and turns are permitted by these harness mechanisms, making them more useful as real-world training devices than technologies whose dynamics limit the user’s ability to make sudden motions. They are ergonomically designed so as to be natural to use and require a minimal amount of mental mapping by the user to correlate what is happening in the simulator to what is intended in the real world. The user is freed to concentrate on learning the task at hand without needing to concentrate on distracting irrelevant issues such as how to balance on a slippery moving surface or how to operate the har-ness mechanism.

2 PEDEDSTAL-STYLE INVERTED HARNESS SYSTEMS

Figures 1 and 2 show a small low-profile harness that uses an ap-proximate straight-line vertical motion four-bar linkage to permit a user to drop to the knees, jog in place, twist, turn and so forth. No overhead structure interferes with the camera sight lines or with

Figure 1 Inverted small harness

Figure 2 Inverted small har-ness in kneeling position

the motions of the user’s arms. Slip rings permit unlimited turning without tangling the headmount cables and allow higher bandwidth than would be obtained in a wireless system.

An inverted system that permits full go-prone capability is shown in Figures 3 and 4. These mechanisms accomplish the ap-proximate straight-line vertical motion needed for “go-prone” mo-tion by making use of long radius swinging arms. The vertical arcs described by the pair of swinging arms provide a close approxima-tion to a vertical straight line chord of the arc and compliance in the

Figure 3 Inverted full “go-prone” system with a single composite strut arm

Figure 4 Inverted full “go-prone” system with a dual composite carbon fiber arm

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IEEE Virtual Reality Conference 2007March 10 - 14, Charlotte, North Carolina, USA1-4244-0906-3/07/$20.00 ©2007 IEEE

Figure 5 A common backpack system is used in all the new harness systems. It re-

sists inertial effects during sudden motions, acting like an exoskeleton mechanically

supporting and stabilizing the harness on the user.

Figure 7 Latest dual diagonal arm overhead harness system offers full go-prone capability, strength, minimal inertia, and

superior centering control

Figure 8 Integrated backpack is part of the cable manage-ment, compliance,

and human restraint subsystems

Figure 9 Immersed user can tug against flexural hip supports to enhance simulation of running

in place

Figure 10 Immersed Army Ranger using the new overhead harness in the NRL’s Gaiter Lab

arms compensates for any minor differences.3 BACKPACK MAN/MACHINE INTERFACE

Each of these harness mechanisms interfaces with the user through an ergonomically designed belt/backpack system. (Figures 5 and 6.) Ball joints at the level of the user’s hip joints couple telescop-ing compliant swinging arms to a leaf spring system on the belt. Flexural couplings between the belt and the backpack distribute static or inertial loads imposed by the user or the harness via mul-tiple attachment points on the user’s waist and torso. This increases comfort, helps keep the backpack/marker system in position and provides better control for the harness.

The backpack also provides a calibrated mounting surface for the reference markers used by the cameras and a covered mount for the low-voltage head mount display electronics needed to carry the high bandwidth signals through the slip rings.

Figure 6 The backpack also provides a calibrated mounting surface for the vi-sion marker system and a case for the headmount video and audio electron-ics whose high bandwidth signals are

transmitted through the slip rings. The purpose of this poster was to provide a brief description of several new low cost full body virtual reality harness systems which permit jogging in place, dropping prone or to a kneeling position, and unlimited twisting and turning. None of the devices described in this paper has been previously published in the technical litera-ture. Due to space limitations no effort has been made to discuss other harness systems or the results of user studies.

12 ACKNOWLEDGMENTS

The author would like to express his appreciation to Dr. Jim Temple-man of the NRL for his many ideas and support of this project and to Mr. Carl Behnke, of The George Washington University’s Me-chanical and Aerospace Engineering Department, for his invaluable help with the construction of these devices. He is also appreciative of the support of this work through the VIRTE (Virtual Technolo-gies and Environments) Future Manpower Capability Program of the Office of Naval Research, grant number N00014-04-1-0068, and by the NRL through contract number N00173-05-P-0983.

REFERERNCES

[1] Templeman, J.N., Denbrook, P.S., and Sibert, L.E. Virtual Lo-comotion: Walking in Place Through Virtual Environments, Pres-ence: Teleoperators [2] Kaufman, R.E, Virtual Reality Simulator Harness Systems, In-ternational PCT Patent Application, Pending[3] Kaufman, R.E, A Family of New Ergonomic Harness Mecha-nisms for Full-Body Natural Constrained Motions in Virtual Envi-ronments, 3DUI 2007

4 GO-PRONE OVERHEAD HARNESS SYSTEMS

Figures 5 through 10 show the latest overhead system we have de-veloped. It utilizes an overhead pivot with slip rings and diagonal composite carbon fiber arms for strength and minimal rotational inertia. It also incorporates the long radius vertical motion system used in the large inverted go-prone harnesss. In a permanent instal-lation the central overhead pivot could be ceiling mounted, low-ering production costs and freeing up sight lines for the camera system.

5 SUMMARY

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