Protective Stop

A safety function that brings a robot to an automatic, controlled halt as soon as it detects an overload or hazard.

Protective stop is a basic safety function defined in the ISO 10218 industrial and collaborative robot safety standards: when collision detection fires, force or speed exceeds a configured safety limit, a safety gate opens, or a light curtain is broken, the controller brings the robot to an orderly stop. It differs from an emergency stop (E-stop): an E-stop is a person hitting the red button and is reserved for real emergencies — Universal Robots' E-stop first performs a controlled stop and then cuts power to the drives — whereas a protective stop is usually triggered automatically by the system itself. IEC 60204-1 defines three stop categories: category 0 removes power immediately, category 1 performs a controlled stop before removing power, and category 2 stops and then holds position without removing power, which resumes fastest. A related concept is 'safety-rated monitored stop' in collaborative mode, where the robot halts and waits when a person enters the collaborative workspace and resumes automatically once they leave; per Universal Robots' documentation, ISO 10218-1:2025 has renamed this ‘monitored standstill’.

ExampleA UR collaborative arm running into an obstacle will automatically trigger a protective stop the moment any force or torque parameter exceeds its safety settings; an operator must clear the cause and confirm before the robot can resume.

Also called

Safety Stop

Related

Emergency Stop · Functional Safety · Collision Detection (Robot Safety) · Collision Reaction · Power and Force Limiting · Speed and Separation Monitoring

Sources

Universal Robots: Safety FAQ（stop categories, protective stop, monitored standstill）
OSHA Technical Manual, Section IV Chapter 4: Industrial Robot Systems and Industrial Robot System Safety

As of

2026-05