Beyond Physical Safety in Human–Robot Collaboration: Investigating Speed and Proximity Effects in Mental Workload

Abstract

Human–robot collaboration (HRC) has improved flexibility and productivity in industrial environments; however, current safety standards primarily address physical risks, overlooking operators’ mental workload. This study adopts a neuroergonomic approach to examine how robot speed and human–robot proximity influence mental workload during collaborative tasks. Participants (N=25, n=21) performed a shelf-replenishment task with a collaborative robot under six experimental conditions combining three speed levels and two proximity levels. Mental workload was assessed using subjective ratings, performance indicators (error rate), and functional near-infrared spectroscopy (fNIRS) of pre-frontal cortical activity. Speed emerged as the primary determinant of mental workload. High speed significantly increased perceived demand and error rates, particularly under near proximity. Proximity alone did not produce significant global effects but amplified demand under high operational intensity. Physiological measures confirmed pre-frontal engagement during task execution compared to baseline; however, differentiation among graded task conditions was modest. These findings suggest that excessive operational intensity may compromise performance stability before strong neural amplitude differences emerge. Regulating robot speed may therefore represent an effective mechanism for maintaining mental workload within functional limits in collaborative environments. The integration of subjective, performance, and physiological indicators contributes to a more comprehensive neuroergonomic assessment of human–robot collaboration.

Keywords: Proxemics, Neuroergonomics, Human Systems Integration, Adaptive Control, Physiological Monitoring, Performance Variability

DOI: 10.54941/ahfe1007393