Power and force limiting makes a robot inherently gentle — capped in speed and force so that even if it touches a person, it can't hurt them — the collaborative-safety method behind fenceless cobots that share a workbench with people.
Power and force limiting means a robot is built and controlled to be gentle enough that bumping into a person can't injure them. It moves slowly and softly, and stops or gives way at the first sign of contact — so no fence is needed.
Most collaborative-safety methods keep a robot away from people. Power and force limiting (PFL) takes the opposite approach: make the robot so inherently gentle that touching a person is safe — so it can share a workbench with no fence at all.
The idea
A PFL robot is designed and controlled so its speed, force, and contact pressure stay below the levels that would injure a human. If it does bump into someone, the contact is limited to a harmless push, and the robot detects the collision and stops or backs off immediately. Safety comes from the robot's own limits, not from keeping distance — which is why these are the true "collaborative" robots you see working elbow-to-elbow with people.
Gentle by design
Because force and speed are kept below injury thresholds and contact is detected instantly, incidental touch causes no harm — no barrier required.
How it's achieved
Limited speed and force in software, monitored by safety-rated systems.
Collision detection — the robot senses unexpected resistance (force-torque or motor-current sensing) and reacts in milliseconds.
Physical gentleness — rounded edges, no pinch points, low inertia, and sometimes compliant actuation (series-elastic actuators) that cushion contact.
Validated against biomechanical limits.ISO/TS 15066 specifies pain/injury thresholds for each body region; a PFL robot's contact forces must stay under them (verified by testing).
The trade-off
Inherent gentleness has a cost: PFL robots are slower and weaker than caged industrial arms. Keeping forces safe limits payload and speed, so they're used where light, delicate, collaborative tasks matter more than raw throughput. For heavier or faster work near people, speed and separation monitoring (keep distance) is used instead — and many cells blend both.
Where you'll see it
The classic collaborative "cobots" (Universal Robots, Franka, and kin) on assembly benches, machine tending, light packaging, and lab automation — working directly alongside people without fencing.
Why it matters
Power and force limiting is the method that most fully realizes the collaborative-robot vision: a robot safe enough to touch, sharing a person's workspace with no barrier. It reframes safety from "separate the human" to "make the machine harmless," and it's central to flexible, human-centered automation.
