The feasibility of fatigue state monitoring based on eye parameters in virtual reality environment

In human‒machine environments, real-time fatigue monitoring of operators is particularly important. Excessive fatigue will threaten the operation efficiency and even the safety of operators. At present, experimental research methods include simulation experiments, half-physical simulations and real environment tests. The simulation environment experiment has the advantages of low cost, high security, high repeatability and anti-interference from external factors. The virtual reality (VR) environment is a virtual scene based on a 3D virtual model, which is an important development trend of simulation experiment. However, the reliability of various measurement methods in VR simulation environment needs to be verified. In this study, the Varjo XR3 VR device with the best display effect currently on the market is used together with headphones to construct a closed simulation experiment scene and at the same time collect subjective evaluation of monotonous fatigue and eye parameters. Then, the mapping relationship between the two is explored through confirmatory experiments. A total of 10 subjects were recruited in this experiment to induce fatigue by cruising tasks with low load in flight missions. Subjects needed to independently complete the route cruise task for approximately 50 minutes and report their own fatigue subjective evaluation parameters using the Borg scale at the flight turning points every 3 minutes. The data of percentage of eyelid closure over the pupil over time (PERCLOS) and blink rate were obtained by using head display internal camera image and projection vectors algorithm, and the validity of eye data was evaluated by correlation validation with monotonic fatigue subjective evaluation parameters. The results show that the quality of eye parameters collected by VR meets the monitoring requirements, and parameters such as PERCLOS and blink rate have a high correlation with subjective monotonic fatigue evaluation. Eye monitoring has high availability to evaluate operator monotonic fatigue in virtual simulation environment.