Speed and separation monitoring keeps a robot and a person at a safe distance by watching where the human is and slowing or stopping as they get closer — one of the four collaborative-robot safety methods that let robots and people share space.
Speed and separation monitoring lets a robot keep working near people by tracking how close a person is: as someone approaches, the robot slows down, and if they get too close, it stops — then speeds back up when they move away.
🎯 Quick challenge
Under speed and separation monitoring, as a person gets closer the robot…
How can a robot keep working productively while a person walks right up to it? One of the four collaborative-safety methods answers this by watching the distance and adjusting: speed and separation monitoring (SSM).
The idea
SSM continuously monitors where humans are relative to the robot (via laser area scanners, 3D cameras, or safety mats) and maintains a protective separation distance. The rule is graduated:
Person far away → robot runs at full speed.
Person approaching → robot slows down, so it could stop before contact.
Person too close (minimum distance breached) → robot stops.
Person retreats → robot resumes and speeds back up.
The minimum safe distance isn't fixed — it depends on the robot's speed, its stopping time, and the person's approach speed, all computed live so the robot can always halt before contact.
Distance sets the speed
The robot's speed scales with how much room there is to stop safely. It keeps working when it's safe and slows or halts only when a person is close.
Why it's valuable
Productivity + safety together. The robot doesn't have to crawl or stop just because a person is somewhere in the area — only when they're genuinely close. It runs fast when the space is clear.
No cage, no constant stops. People can share the workspace and approach as needed, and the robot recovers automatically.
It's especially suited to larger or faster robots that can't rely on being inherently gentle.
The four collaborative methods
ISO/TS 15066 defines four ways robots and humans safely share space:
Speed and separation monitoring is a key enabler of human-robot collaboration — letting capable robots keep working while people move freely around them, by trading speed for distance in real time. It's central to modern flexible manufacturing where fences are giving way to shared, sensed spaces.
