Robot arm position affects how close people let it get
CALM: Configuration-Aware Human Intervention Boundaries During Robot Approach
RoboticsHuman-Computer Interaction
Summary
People feel differently about how close a robot can come based on how it holds its arms. The study found that when a humanoid robot's arms were fully extended forward, people stopped it from coming as close compared to when its arms were down by its sides. The researchers created a model called CALM that predicts how close people will allow a robot to get based on its arm position. This helps robots plan their movements to avoid making people uncomfortable or feeling unsafe.
What this means in practice
- •For robotics engineers: Design robot approach behaviors by adjusting arm positions to improve human comfort and reduce intervention.
- •For industrial automation teams: Configure robots in shared workspaces to dynamically change posture for safer human proximity during collaborative tasks.
Authors
Xinting Gao, Sipu Zhu, Weimin Zhuang
Abstract
How robot body configuration shapes human intervention during approach remains underexplored. We conducted a within-participants study with 41 participants, measuring final stopping distance, subjective comfort, and exploratory eye-tracking responses across four humanoid arm configurations and two spatial scales. Full forward arm extension increased stopping distance by approximately 31-36 cm relative to arms-down. Spatial scale primarily affected comfort and pupil responses without a detectable stopping-distance shift. We introduce the Configuration-Aware Limit Model (CALM), which translates stopping-distance distributions into configuration-dependent population-coverage boundaries. Estimated boundaries at 80% coverage ranged from 0.88 to 1.47 m. In an illustrative one-dimensional planning analysis, reconfiguration enabled a 1.10 m approach goal that was unreachable with arms remaining fully extended under the same nominal pointwise 20% intervention-probability constraint. These findings support treating body configuration as a planning variable while distinguishing physical safety, behavioral intervention, and subjective cost.