Fatigue is an important issue of concern for aircraft pilots. A high level of fatigue may well result in accidents, leading to loss of precious lives and resources. Hence, detection of the level of fatigue just before a flight can prevent a possible accident. Evidently, this problem needs to be seriously addressed.
Fatigue can be assessed using different measures such as electroencephalogram (EEG) signals, ocular features, blood samples, speech and others. EEG in particular has been reported to be highly authentic for estimating the state of drowsiness. However, measurement of EEG signals needs time and cooperation and may cause inconvenience to the pilot. Since the task of assessing the state of go/no-go for a pilot should be completed within a short duration of time, preferably within a couple of minutes, an appropriate and sensitive measure could be eye saccades.
Eye saccades are fast movements of both the eyes in the same direction. It has been widely established that the peak saccadic velocity is a valid indicator of the level of alertness of a person. Higher the peak saccadic velocity, more alert is the person.
A research team from the Department of electrical engineering at IIT Kharagpur with professor Aurobinda Routray (team leader), Dr Rajlakshmi Guha (psychologist) along with PhD scholars Anirban Dasgupta, Aritra Chaudhuri, Suvodip Chakroborty, and Punyashlok Dash, in conjunction with the Defence Institute of Physiology and Allied Sciences, DRDO, New Delhi, has developed a fatigue monitoring system (FMS) for pre-flight assessment of Indian Air Force pilots.
Prof Routray read about a bus accident in 2005 caused because the bus driver slept due to fatigue. Hence he ventured to find a solution. Gradually, he moved to prepare a solution for fatigue monitoring of pilots. There is a similar model being developed for fatigue monitoring of doctors at operation theatres. The research and development (R & D) was done at the department of electrical engineering at IIT Kharagpur. Idea and initial R&D took about seven years. Developing test model took about two years.
The equipment is based upon a physiological measure and a psychological measure. The physiological measure is electrooculogram (EOG), while the psychological measure is the performance of the pilot in a psychomotor vigilance test. EOG is a record of the standing electrical potential between the cornea and the retina, and is an indicator of eye movements. From the recorded EOG data, an algorithm has been developed for finding peak saccadic velocity.
In the FMS design, the EOG acquisition unit is specially designed by embedding the Ag-AgCl sensors inside the frame of a spectacle, for ease of acquisition of the signal. The frame of the spectacle has three electrodes – one located on the forehead and two on distal ends on the eyes.
The team has also utilised the concept of a psychomotor vigilance test (PVT) to designa game both for a PC as well as an Android device. The game has two independent metrics which are used to obtain the alertness level of the pilot: the number of correct responses and the mean response time for the correct responses.
The main application has three sub-applications or activities for the concerned task. The first two sub-apps are the attention game and the EOG recording, and execute in parallel. The third and final sub-app performs the classification using a decision level fusion.
This system has been tested with EEG and Epworth Sleepiness Scale (ESS) which are standard measures of sleepiness and alertness. The findings demonstrate that the FMS was effective in more than 90% cases for the prediction of the Go/ No-go status for pre-flight assessment of IAF pilots.
The FMS has been evaluated in studies carried out at 1AMTC, HINDON and Institute of Aerospace Medicine, Bengaluru on Indian Air Force pilots and aircrew. At present the team is working on converting the wired system into a wireless module.
Prototype development and testing costed Rs 30 lakh. When commercialised the product will cost Rs 10000 or even less. Patent has been filed at IIT Kharagpur two weeks back. Collaboration is awaited for commercialisation.
How does the FMS work?
1. The pilot is seated and asked to wear the spectacles. Instructions are provided regarding the game. The application is started on the PC/Android tablet and the user starts playing the game. Simultaneous acquisition of EOG signals are carried out on the PC/Android tablet.
2. Once the game is over, the third sub-app is executed for making the decision on the ‘Go’ or ‘No-go’ condition of the pilot.
3. The decision is made considering the game scores (reaction time and number of correct responses) as well as the value of peak saccadic velocity.
The author is project associate, institutional development programme, IIT Kharagpur