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Consolidating Computer Operation and Wheelchair Control [Demo Proposal] Torsten Felzer and Rainer Nordmann Department of Mechatronics in Mechanical Engineering Darmstadt University of Technology, Petersenstr. 30, D-64287 Darmstadt, Germany

{felzer,nordmann}@mim.tu-darmstadt.de ABSTRACT

that person has to apply an alternative interface, if using the hands is not possible. The same is true for an electric wheelchair (in lieu of a PC). Someone who is unable to walk needs a wheelchair to get around, and if that someone does not have the physical strength to drive alone in a mechanic wheelchair, she or he needs an electrically powered wheelchair. However, the standard interface here involves a manual joystick, which complicates usage if the disability causing the user to be in need of an electric wheelchair also keeps him or her from controlling the hands at all.

The HAnds-free Mouse COntrol System HaMCoS is a software kit designed for persons with severe physical disabilities, allowing its users to fully operate a PC using intentional contractions of a single dedicated muscle only. The system’s theoretical concept has originally been developed for a wheelchair control system, a revised and enhanced version of which – comprising a stand-alone realization plus a software-based simulator – has been introduced just recently. Since it is very likely that someone who needs the kind of assistance offered by HaMCoS is also obliged to use a wheelchair, the idea to interface the simulator with the computer tool really suggested itself. This demo presents the outcome of that idea. It will be shown how both systems work individually and how they interact with each other.

Categories and Subject Descriptors K.4.2 [Computers and Society]: Social Issues—Assistive technologies for persons with disabilities; H.5.2 [Information Interfaces and Presentation]: User Interfaces—Input devices and strategies

General Terms Experimentation, Human Factors

Keywords Human-computer interaction, intentional muscle contractions

1.

INTRODUCTION

Severely motor impaired persons often have problems using common computer equipment. The reason is that operating a PC usually requires reliable control of the hands, because the standard interface involves manual keyboard and mouse. Since a computer can considerably help someone with a physical disability in leading an independent life, Figure 1: Controlling a wheelchair hands-free The HAnds-free Mouse COntrol System HaMCoS [1, 3] represents an application of an alternative input interface based on intentional muscle contractions. The system allows its user to completely operate a PC without using the hands. The exact same interface has been applied to a wheelchair control system [2, 4] which merely demands intentional contractions of a single muscle of choice (e.g., raising the eye-

Copyright is held by the author/owner(s). ASSETS’07, October 15–17, 2007, Tempe, Arizona, USA.. ACM 978-1-59593-573-1/07/0010.

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brow) to navigate the vehicle to any arbitrary (accessible) destination (see fig. 1, the manual joystick is not needed). Both applications have been introduced before, while the innovation to be presented here is some sort of a ’plugin’ for HaMCoS bringing them together. The outcome is a comprehensive system enabling a severely impaired person to operate a laptop and to change his or her physical location (e.g., by navigating to a different room) with one set of hardware (laptop and input sensor) only. The next section contains a short description of the underlying architecture, while section 3 briefly outlines the implementation. The contents of the intended demo is detailed in section 4.

the stand-alone hardware with a standard laptop (relying on the non-standard input interface described above).

3. IMPLEMENTATION DETAILS

The basic idea in HaMCoS is to monitor the muscular activity originating from an arbitrary muscle and to analyze this input stream in order to filter out intentional muscle contractions. The temporal sequence of the contraction events is translated into mouse cursor movement and click actions, so that the system can emulate a two-button mouse. Furthermore, HaMCoS comes with a comprehensive set of framework applications which are optimized for this kind of input interface in the sense that they render any other input device unnecessary.

Since both, HaMCoS and the above mentioned simulator, R XP (and Microsoft R have been developed under Windows Visual C++), trying to ’mobilize’ a HaMCoS user by interfacing the applications appeared to be a pretty logical step (especially since the target populations are quite similar). It was decided to leave both tools as two separate (independent) processes – with only one process being active (and showing a visible window) at any given time. However, both applications originally ’listen’ to the standard microphone input for muscle-based input signals which is not possible when they are running at the same time. To resolve this issue, the HaMCoS main module was chosen as the ’listener’ process, either handling the input signals directly or passing them on to the wheelchair control module (making use R of inter-process communication with the help of Windows messages). Finally, switching between the two processes is done by deactivating the ’visible’ process (i.e., hiding its window and disabling its output) and sending a corresponding message to the other process which then activates itself.

2.1 Closed-loop Control

4. DEMO CONTENTS

Since the user receives visual feedback from her/his input via the computer screen, HaMCoS operation can be interpreted as an instance of closed-loop control (see fig. 2, left half).

This demo illustrates how HaMCoS is used to operate a computer hands-free and how the same input principle is applied for controlling a wheelchair. The main focus of this demonstration is on the option of switching back and forth between the two target applications. In particular, it is shown that the help of a second person (e.g., a family member or a caregiver) is only necessary at the beginning (for setting the system up). The presented combination therefore tremendously increases the amount of independence perceived by someone with a severe physical disability. The entire hardware (laptop, wheelchair, ...) is provided by the author. The only thing requested from the conference organizers is a little empty space (probably 50 or 60 sq. ft.), so that at least some wheelchair movement without jeopardizing anything (or anyone) is possible.

2.

ARCHITECTURE

5. ACKNOWLEDGMENTS This work is supported by DFG grant FE 936/3-1 ”The AID package – An Alternative Input Device based on intentional muscle contractions”. Figure 2: Control loops characterizing the two target applications: mouse (left) and wheelchair (right) control

6. REFERENCES

[1] T. Felzer, R. Fischer, T. Gr¨ onsfelder, and R. Nordmann. Alternative control system for operating a PC using intentional muscle contractions only. In Online-Proc. CSUN Conf. 2005. [2] T. Felzer and B. Freisleben. HaWCoS: The “Hands-free” Wheelchair Control System. In Proc. ASSETS 2002, pages 127–134. ACM Press, 2002. [3] T. Felzer and R. Nordmann. Poster Proposal: How To Operate a PC Without Using the Hands. In Proc. ASSETS 2005, pages 198–199. ACM Press, 2005. [4] T. Felzer and R. Nordmann. Alternative wheelchair control. In Proc. RAT’07, pages 67–74. IEEE Computer Society, 2007.

In the case of wheelchair control, the visual feedback associated with the control software is supplemented by other feedback the user experiences in response to movements of the wheelchair (in fig. 2 simply called ’environment’).

2.2 Stand-alone vs. Simulator The newest version of the wheelchair control system has been realized as two distinct variants: a stand-alone device – composed of a micro-controller and a monochrome display – and a software-based simulator. The software tool offers various simulation levels, and one of them allows replacing

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