Keep it Clear and Simple; Using Levels of Tactile Alerts for Manned-UnManned Teaming (MUM-T)

Vibro-Tactile interfaces were proposed as an alternative to support situation management and human-machine communication in information-rich domains. Tactile cues can capture the operator's attention in busy environments. However, like the visual and auditory channels, frequent use of tactile alerts may lead to high workload, impaired performance, or neglect. We examined the effectiveness of three levels of tactile alerts when combined with visual alerts. On the 'basic' level, the alert provides easy to interpret binary information with a 'low threshold,' on the 'simple' level the alert provides easy to interpret information about the occurrence of a pre-determined event with a 'high threshold,' in the 'complex' level the alert requires more effort to interpret but includes specific information. Two experiments simulate an operational mission in which participants ride an autonomous ground vehicle patrol while looking for threats and targets in the area and monitoring two supporting unmanned systems (ground and aerial) in a MUM-T (Manned UnManned Teaming) setup. Response times to notifications, threat identification rates, and subjective workload were measured. Results indicate that tactile alerts, in addition to visual alerts in a visually loaded and auditory noisy scene, improve task performance. Moreover, a complex level of tactile alerts does not impair performance or increase the perceived workload compared to the basic and simple levels.