Human-Centered HMI for Crane Teleoperation: Empirical Study on the Operators' Mental Workload

This paper compares the mental workload caused by the traditional machine-centered HMI for crane teleoperation against two new human-centered HMIs: the direction-oriented HMI and the target-oriented HMI. The effect of the HMIs on the operator's mental workload was investigated in a laboratory experiment using a 3D crane simulation in virtual reality with a sample of N = 48 participants, all of them either students or faculty employees. The participants' mental workload was assessed via primary task performance, mean pupil diameters, and RTLX ratings. Additionally, the subjective usability was tested by using the SUS. Comparing the two human-centered HMIs to the machine-centered HMI, participants' average time on task, the total movement distance of the crane's boom tip, the time the boom tip was moved in the wrong direction and the number of caused collisions were significantly reduced. Moreover, participants' mean pupil diameters were significantly smaller and they rated their workload as significantly lower when using the human-centered HMIs, whereas SUS values improved significantly. Comparing the two human-centered HMIs against each other, the target-oriented HMI showed a further reduction of the operator's workload in both pupil diameters and RTLX ratings but not an unequivocal improvement of operating performance.