What constitutes a 'safe state' in a robot safety system?

• A. A configuration where no dangerous energy states or motion can occur; typically power-off or controlled safe mode.
• B. A state where the robot operates at maximum speed.
• C. A state where all sensors are bypassed.
• D. A state used only during testing.

Answer: (A)

A safe state in a robot safety system is a configuration where no dangerous energy states or motion can occur. In practice, this means energy sources are isolated or de-energized and actuators are held in a non-moving, controlled condition—often a power-off or a controlled safe mode with safety interlocks engaged. This state is designed so that even if faults or unexpected inputs appear, the machine cannot release energy or move into a hazardous situation.

This is the best answer because it captures the essential purpose of a safe state: to eliminate the possibility of harm by eliminating the pathways to energy release and motion. The other scenarios fail safety: operating at maximum speed creates the potential for harm; bypassing sensors removes critical fault detection and safe-quiesce behavior; and a state used only during testing isn’t a guaranteed, persistent safe condition for normal operation.