Idle, executing, and failed states must be externally distinguishable
Aliases: state legibility · visible operating mode · external status display
What it is
An externally legible robot state lets people without an operator console distinguish idle, executing, paused, waiting for help, and failed. Visibility is not a dump of internal logs; it answers whether motion may occur, input is accepted, avoidance is needed, or intervention is requested.
Why it happens
The same still body can mean completion, temporary waiting, emergency stop, lost localisation, or power loss. People fill this missing state from recent behaviour and may wait unnecessarily or assume a failed machine will resume. Stable mappings from control state to external cues reduce the gap between system state and the on-site mental model.
Studying it
Operators and bystanders can classify state, next action, and appropriate response from fragments of real operation. Accuracy, confidence, response time, and wrong intervention are relevant. Transitions matter more than screenshots, especially pause-to-resume. Sensor, network, and display failures should be inserted to reveal false-normal presentation.
Where it stops holding
Roles need different granularity: a passer-by needs passage safety, while maintenance needs subsystem and isolation detail. Excess data increases search and may expose sensitive information. A powered-off robot cannot rely on active lights; braking and passive indicators remain necessary.
Applying it
- Define an external state machine mapping each visible state to motion possibility, input acceptance, and responsible actor.
- Update mode cues atomically; when the display chain is unreliable, show a recognisable failed state rather than freezing the last state.
- Blind-test full-task recordings with different roles, prioritising confident errors and unsafe approaches.