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When performing the application risk assessment, it is necessary to take into account the motion

of the robot after a stop has been initiated. In order to ease this process, the safety functions

Stopping Time Limit and Stopping Distance Limit can be used.

These safety functions dynamically reduces the speed of the robot motion such that it can always

be stopped within the limits. The joint position limits, the safety planes and the tool/end effector

orientation limits take the expected stopping distance travel into account i.e. the robot motion will

slow down before the limit is reached.

The functional safety can be summarized as:

Safety Function Accuracy Performance Level Category

Emergency Stop – d 3

Safeguard Stop – d 3

Joint Position Limit 5° d 3

Joint Speed Limit 1.15°/s d 3

Safety Planes 40mm d 3

Tool Orientation 3° d 3

Speed Limit 50mm/s d 3

Force Limit 25N d 3

Momentum Limit 3kg m/s d 3

Power Limit 10W d 3

Stopping Time Limit 50ms d 3

Stopping Distance Limit 40mm d 3

Safe Home 1.7° d 3

WARNING

There are two exceptions to the force limiting function that are important when

designing an application (Figure Due to the physical properties of the robot arm,

certain workspace areas require attention regarding pinching hazards. One area

(left) is defined for radial motions when the wrist 1 joint is at least mm from the

base of the robot. The other area (right) is within mm of the base of the robot,

when moving tangentially.). As the robot stretches out, the knee-joint effect can

give high forces in the radial direction (away from the base) at low speeds.

Similarly, the short leverage arm, when the tool/end effector is close to the base

and moving around the base, can cause high forces at low speeds. Pinching

hazards can be avoided by removing obstacles in these areas, placing the robot

differently, or by using a combination of safety planes and joint limits to eliminate

the hazard by preventing the robot moving into this region of its workspace.

Hardware Manual 17 UR5e

2.Safety-related Functions and Interfaces

Universal Robots UR e Series Hardware Manual

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