Power and Force Limiting

功率与力限制PFLAdvanced

A collaborative-safety mode that lets a robot touch a person but caps contact force and pressure below injury thresholds.

PFL is one of several collaborative operating modes defined by the ISO 10218 series and ISO/TS 15066 (the others are safety-rated monitored stop, hand guiding, and speed and separation monitoring), and it is the main way collaborative robots work alongside people without safety fencing. Rather than avoiding contact, it limits the consequences of contact: TS 15066 specifies allowable force and pressure by body region, distinguishing transient contact (the person can be pushed away) from quasi-static contact (the body part is pinned), which gets a lower threshold. In practice this relies on a lightweight, slow-moving robot body, or on safety functions such as joint torque sensors that slow or stop the robot when limits are exceeded. TS 15066 gives a simplified formula for allowed speed: v ≤ F_max/√k · √(1/m_R + 1/m_H), where F_max is the maximum allowed force for that body region, k is its equivalent stiffness, and m_R and m_H are the equivalent masses of the robot and the human body part. According to Universal Robots' own materials, the 2025 edition of ISO 10218 has absorbed most of TS 15066's content.

ExampleUnder TS 15066, a pinched back of the hand (quasi-static contact) allows up to 140 N, while unconstrained transient contact allows up to 280 N. A 2021 ICRA paper used this formula to calculate that, where pinching risk exists, a UR10e end-effector's speed must be capped at about 0.13 m/s.

Also called: PFL, PFL Collaborative Mode
Related: Collaborative Robot · ISO/TS 15066 Robots and Robotic Devices — Collaborative Robots · Speed and Separation Monitoring · Protective Stop · Collision Detection (Robot Safety) · Physical Human-Robot Interaction
Sources: OSHA Technical Manual, Section IV Chapter 4: Industrial Robot Systems and Industrial Robot System Safety
3D Collision-Force-Map for Safe Human-Robot Collaboration (arXiv:2009.01036, ICRA 2021)
Universal Robots: Safety FAQ
As of: 2026-05