Speed and Separation Monitoring

A collaborative-robot safeguard that tracks human-robot distance in real time and slows or stops the robot once it gets too close.

Speed and separation monitoring is one of the collaborative operating modes defined by ISO 10218 and ISO/TS 15066 (the others are safety-rated monitored stop, hand guiding, and power and force limiting). External sensors — safety laser scanners, 3D cameras, and the like — continuously track both the person and the robot, and the system computes a protective separation distance in real time: S = S_h + S_r + S_s + C + Z_S + Z_R. Here S_h is the distance the person covers during the robot's reaction and braking time (the person's approach speed toward the robot is usually taken as 1.6 m/s), S_r and S_s are the distances the robot itself travels during its reaction time and while braking, C is an allowance for how far a person's hand might reach in, and Z_S and Z_R are the position-measurement uncertainties for the person and the robot. If the actual distance drops below S, a safety-rated monitored stop is triggered — the slower the robot moves, the smaller S becomes, letting the person approach closer. The difference from power and force limiting is that PFL tolerates limited contact, while SSM aims to avoid contact altogether.

ExampleSuppose the robot's reaction time is 0.1 s and its braking time is 0.3 s, and a person approaches at 1.6 m/s. The S_h term alone is 1.6 × (0.1 + 0.3) = 0.64 m; adding the robot's own travel distance, the hand-reach allowance, and measurement error gives the minimum distance that must be maintained. Once the robot slows down, it brakes faster and travels less, so the person can stand closer.

Also called

SSM

Related

ISO/TS 15066 Robots and Robotic Devices — Collaborative Robots · Power and Force Limiting · Collaborative Robot · Protective Stop · Safety Laser Scanner / Safety Light Curtain · Human-Robot Collaboration

Sources

Implementing Speed and Separation Monitoring in Collaborative Robot Workcells (Marvel & Norcross, NIST, Robot Comput Integr Manuf 2017)
NIST 出版物页面：Implementing Speed and Separation Monitoring in Collaborative Robot Workcells (Chinese)