What Is a Safety-Rated Monitored Stop? How Robots Remain Stopped Around People.

What Is a Safety-Rated Monitored Stop?

A safety-rated monitored stop, or SRMS, is a safety function historically described in industrial robot standards in which a robot stops hazardous movement and its stopped condition is monitored by a safety-related system.

It has been used in applications where people need access to a robot's collaborative workspace.

For example, a robotic assembly cell may stop its robot before a worker enters a shared area to inspect a component. The safety system monitors the stopped condition while access is permitted.

The terminology has evolved: ISO 10218:2025 no longer lists safety-rated monitored stop as a separate collaborative application technique. The updated standard instead describes the relevant stopping and monitored-standstill functions.

Key Takeaways

• A safety-rated monitored stop involves bringing a robot to a stop and monitoring its stopped condition through a safety function.
• It is different from simply pausing a robot program.
• ISO 10218:2025 updated the terminology, so engineers should use the requirements of the applicable standard edition.

How Does a Safety-Rated Monitored Stop Work?

Imagine a robot that places components into an assembly fixture.

A worker needs to enter the shared workspace to inspect a product.

The safety-related system detects the relevant access condition.

The robot is brought to a defined stop.

Its stopped condition is monitored through an appropriate safety function.

While the worker is present, the system must prevent hazardous unintended movement according to the safety design.

When the worker leaves, operation may resume only under the conditions established for the application.

The implementation must account for the complete machine, including its tools, loads, and surrounding equipment.

SRMS vs. Ordinary Program Pause

A normal program pause changes the robot's operating sequence.

It does not automatically provide safety-related monitoring or fault-handling capability.

A safety-rated stop function is designed and evaluated according to defined safety requirements.

For example, a robot program might pause while waiting for a sensor.

That pause should not be assumed to provide adequate protection for someone entering a hazardous workspace.

The required protective function must be deliberately engineered.

SRMS vs. Safe Torque Off

These functions are different.

Safety-rated monitored stop: Historically described a stopped condition monitored by a safety function.

Safe torque off (STO): Prevents a compatible motor drive from generating torque through a safety-related function.

A monitored stop may maintain motor control to hold position.

STO removes torque-producing capability, which may allow motion under gravity or other external forces.

The correct stopping method depends on the risk assessment.

What Changed in ISO 10218:2025?

Earlier industrial robot standards identified safety-rated monitored stop as one of the collaborative operation techniques.

The 2025 revision changed this framework.

The updated requirements describe a Category 2 stop followed by a monitored-standstill safety function where applicable.

The 2025 collaborative application capabilities are organized around hand-guided controls, speed and separation monitoring, and power and force limiting.

This distinction matters when reading older technical documents or evaluating newly designed installations.

Frequently Asked Questions

Can a robot automatically restart after a monitored stop?

Restart behavior depends on the applicable standards, risk assessment, and protective conditions. Resuming operation must not create a hazardous situation.

Does SRMS mean a robot's electrical power is removed?

Not necessarily. The function may maintain control power and monitor that the robot remains stopped.

The Bottom Line

A safety-rated monitored stop is an established term for a monitored protective stopping condition. Its underlying safety principles remain important, but engineers should use the updated terminology and requirements of ISO 10218:2025 when applicable.