Development of a Multimodal, Universal Human-Machine-Interface for Hypovigilance-Management-Systems (IPA-IAO Forschung und Praxis; 462) Zugl.: Stuttgart, Univ., Dissertation, 2007

The development and evaluation of a universal, multimodal HMI for Hypovigilance-Management-Systems (HVMSs) is described. In principles, Hypovigilance-Management- Systems measure the state of vigilance of the respective user and take according measures if a critical state of hypovigilance with respect to the work task of the user is reached, i.e., warn the user on different levels of urgency and might try to keep the user awake for a short period.
Hypovigilance is a key cause for severe accidents in various application scenarios, among them the transportation sector and the shift working industry. Clearly, countermeasures are to be considered. Primary measures, such as the proper design of shift cycles, intend to prevent the creation of hypovigilance itself. Where this is not possible, technical countermeasures, so called HVMSs can support the user and increase safety.
The main influencing factors for hypovigilance were discussed and it was concluded that HVMSs should cause the user to stop his/her dangerous work task and go to sleep or, at least, take a power nap.
A requirements analysis with respect to HVMS has been conducted. It was concluded that a universal HVMS needs to be mobile, should have predictive warning capabilities and aim for a high compliance of the user with the system.
Then, general requirements for the interaction strategy, i.e., the warning strategy, as well as its implication in physical HMI-elements were deduced.
Basic design guidelines were summarized on the basis of the current psychological and human factors literature. In the same way, usability and personalization issues were discussed and the benefit of designing a most universal system was pointed out.
On the basis of the requirements for a HVMS, 18 existing HVMS were investigated. It was concluded that none of these systems fulfils the requirements both for the warning strategy and the HMI-elements. However, it was claimed that it is principally possible to generate a HVMS setup that fulfils all of the requirements. Furthermore, it was claimed that, by fulfilling these requirements, this system would effective in terms of the reduction of errors and the enhancement of performance in real working tasks.
Consequently, the development of such a system was pursued and a new hybrid, multi-tiered-development approach was followed.
A detailed warning strategy resulted which features three warning modes, a normal mode in which the actual vigilance state is displayed, a cautionary mode in which the user is warned early before dangerous vigilance degradations occur, and an imminent mode in which the user is intensively warned that a very dangerous vigilance level has been reached. The latter mode is augmented by a vigilance maintenance mode.
In the same way, according HMI-elements were developed. The center of the physical HMI-setup is represented by a watch-like device. The border ring of the "clock-face" is used as a status indicator; it is lighted green, yellow or red, according to the detected user state. The center of the "clock-face" flashes white in case of an imminent alarm and acts as a push-button for the user feedback at the same time. In addition, a vibration device was developed to present haptic stimuli. Finally, a specific headphone was chosen to display audio signals.
By the way of methodological construction, the developed HVMS inherently fulfils the requirements defined above, proving that it is indeed possible to construct a system which fulfills these requirements. Usability testing showed that the system, overall, was well designed.
The HVMS constructed was tested in a practical experiment for effectiveness. An industrial work task was analyzed and mapped to a practical laboratory task in order to control most influencing factors. A homogeneous sample was chosen and randomly divided into three groups, a control group with no intervention, a treatment group using the system developed and a positive control group using a system with random output. The experiments included a training session, a baseline measurement in the evening, and, after a night of sleep deprivation, the actual data measurement in the morning.
It could be shown that the dependent variables were chosen meaningfully, and that the experimental design was well done, resulting in a valid test set-up. By the results, an increase in safety by HVMSs was assumed to be reached twofold: On the one hand, the system could help the user to learn to better judge his/her own level of sleepiness by getting objective vigilance feedback. On the other hand, if the user complies with the system (which is very likely by the above results), and stops his/her dangerous work task such as working on a dangerous machine or driving a car, obviously, the risk of an accident would be reduced.

Fraunhofer IAO
Lorenz Hagenmeyer
2007
Heimsheim
Jost-Jetter
180 Seiten
ISBN 3-939890-17-0


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