Design of automation for telerobots and the effect on performance, operator situation awareness, and subjective workload

In this article we review and assess human-centered level of automation (LO A), an alternate approach to traditional, technology-centered design of aut omation in dynamic-control systems. The objective of human-controlled LOA i s to improve human-machine performance by taking into account both operator and technological capabilities. Automation literature has shown that tradi tional automation can lead to problems in operator situation awareness (SA) due to the out-of-the (control) loop performance problem, which may lead t o a negative impact on overall systems performance. Herein we address a sta nding paucity of research into LOA to deal with these problems. Various sch emes of generic control system function allocations were developed to estab lish a LOA taxonomy. The functions allocated to a human operator, a compute r, or both, included monitoring system variables, generating process plans, selecting an "optimal" plan and implementing the plan. Five different func tion allocation schemes, or LOAs, were empirically investigated as to their usefulness for enhancing telerobot system performance and operator SA, as well as reducing workload. Human participants participated in experimental trials involving a high fidelity, interactive simulation of a telerobot per forming nuclear materials handling at the various LOAs. Automation failures were attributed to various simulated system deficiencies necessitating ope rator detection and correction to return to functioning at an automated mod e. Operator performance at each LOA, and during the failure periods, was ev aluated. Operator SA was measured using the Situation Awareness Global Asse ssment Technique, and perceived workload was measured using the NASA-Task L oad Index. Results demonstrated improvements in human-machine system perfor mance at higher LOAs (levels involving greater computer control of system f unctions) along with lower operator subjective workload. However, under the same conditions, operator SA was reduced for certain types of system probl ems and reaction time to, and performance during, automation failures was s ubstantially lower. Performance during automation failure was best when par ticipants had been functioning at lower, intermediate LOAs (levels involvin g greater human control of system functions). (C) 2000 John Wiley & Sons, I nc.