Vol.7 No.4 2015

Research paper : Mental fatigue measurement as application software on consumer devices (S. IWAKI et al.)−214−Synthesiology - English edition Vol.7 No.4 (2015) data (Fig. 7). This system accomplished the following:(i)The CCFS (subchapter 3.1) enabled the presentation and control of flickering visual stimuli on the general-purpose display device,(ii)The FCUD-FPT algorithm (subchapter 3.2), which eliminates the subject’s arbitrariness in measuring the flicker perception threshold, is implemented to enable appropriate fatigue measurement without the attendance of the examiner. It also contributes to reducing the overall time required to complete the test, and(iii)Online database was built to manage the measured data, where the fatigue data can be registered and referenced as needed from the application software installed on the terminal devices such as smart phones and PCs (Fig. 7).We conducted actual trials on truck drivers in collaboration with transportation companies that are expected to be our potential users of the system. In the trial, the fatigue measurement was included as part of a dairy routine at the beginning and the end of work. Interview to the safety managers showed that reducing the time needed for testing to less than one minute was a critical factor in its implementation. Therefore, we achieved this goal by reviewing the convergence parameter of the FCUD-FPT algorithm. In the prototype system that was implemented on the personal computer, the time required for measurement was reduced to as short as 40 seconds compared to about 70 seconds with the conventional flicker test (Fig. 8). 5 Effect of realized outcome and new research topicsWe have developed a set of techniques to bring the flicker test, which has been originally used to measure mental fatigue in the laboratory setting using specialized devices, into our dairy life. We confirmed that the results obtained by our method, which is a combination of the CCFS and the FCUD-FPT algorithm, are compatible with those measured by the conventional flicker test. Our prototype system is being used for the long-term data acquisition trial in the business environment including two medium-sized transportation companies and in the R&D division of a major construction company. The above technology is also being commercialized by Flicker Health Management Co., Ltd. (FHM), an AIST Start-up (a venture company aiming to commercialize the AIST research outcomes).[18] Currently, the system is being used mainly to study the continuous changes in fatigue condition, which are originally measured by the conventional flicker test using specialized devices, at R&D division of information appliances companies, automobile companies, and university laboratories. The FHM also distributes free apps with simplified functions and operation for smart phones to be used by the general public, to promote diffusion of the fatigue evaluation technology in daily environment.[19][20]Originally, the flicker test has a long history as a fatigue measurement method for academic purposes at research institutes, and it was used to evaluate the change of fatigue conditions in the time span of several hours to several tens of hours. The results of our research and development on the fatigue measurement provides low-cost alternative to the original flicker test, which has an established reputation for its robustness in tracking the changes of fatigue condition, using readily available devices. This allows not only the easy monitoring of the changes in fatigue condition in short periods that was done conventionally in laboratories, but also allows the continuous measurement over a long term of the daily changes in the degree of fatigue. These techniques can be applied to long-term monitoring of fatigue over a large subject population. There is no precedent research on NetworkFlicker test in daily lifeLong-term fatigue dataReferencing and display of fatigue measurement historyDisplay of fatigue measurement history and warningsFatigue measurement database(Accumulate and search fatigue data, return health management information)Flicker test algorithm to avoid subjects’ arbitrarinessConventional flicker testProposed flicker perception threshold measurement by FCUD algorithmTime (s)p=0.000160102030405060708090Fig. 7 Prototype system of the mental fatigue measurement and management system that can be used in daily lifeFig. 8 Comparison of time required for flicker perception threshold measurement by the conventional method and the FCUD method[17]


page 18