What is the function of a Safe Torque Off (STO) in robot safety?

• A. It safely disables torque from the robot drive to stop movement during fault or emergency without requiring de-energization of control power.
• B. It increases torque to overcome stuck joints during operation.
• C. It reboots the controller when a fault is detected.
• D. It provides manual override for power to all axes.

Answer: (D)

Safe Torque Off is a safety function that immediately disables the motor’s ability to produce torque, so the robot stops moving in fault or emergency situations. It does this by interrupting the torque output from the drive while keeping the control electronics powered so safety monitoring can continue. The goal is to rapidly eliminate motion without shutting down the entire control system. This is different from rebooting the controller, providing a manual power override, or increasing torque to force a movement; those actions don’t achieve a safe, torque-free state.