Safety Configuration

Description

The safety system limits are defined in the Safety Configuration. The safety system receives values from the input fields and detects any violation if any the values are exceeded. The robot controller prevents violations by making a robot stop or by reducing the speed.

 

Use of Safety Configuration parameters different from those defined by the risk assessment can result in hazards that are not reasonably eliminated or risks that are not sufficiently reduced.

 

 

Safety Related Functions and Interfaces

Description

Universal Robots robots are equipped with a range of built-in safety functions as well as safety I/O, digital and analog control signals to or from the electrical interface, to connect to other machines and additional protective devices. Each safety function and I/O is constructed according to EN ISO 13849-1 with Performance Level d (PLd) using a Category 3 architecture.

 

The use of safety configuration parameters different from those determined as necessary for risk reduction can result in hazards that are not reasonably eliminated, or risks that are not sufficiently reduced.

  • Ensure tools and grippers are connected correctly to avoid hazards due to interruption of power.

Programmer and/or wiring errors can cause the voltage to change from 12 V to 24 V leading to fire damage to equipment.

  • Verify the use of 12 V and proceed with caution.

  • The use and configuration of safety functions and interfaces must follow the risk assessment procedures for each robot application.

  • The stopping time should be taken into account as part of the application risk assessment.

  • If the robot detects a fault or violation in the safety system (e.g. if one of the wires in the Emergency Stop circuit is cut or a safety limit is exceeded), then a Stop Category 0 is initiated.

The end effector is not protected by the UR safety system. The functioning of the end effector and/or connection cable is not monitored.

 

Stop Categories

Depending on the circumstances, the robot can initiate three types of stop categories defined according to IEC 60204-1. These categories are defined in the following table.

Stop Category Description Stop Function
0 Stop the robot by immediate removal of power.  
1 Stop the robot in an orderly, controlled manner. Power is removed once the robot is stopped. Emergency Stop
2 *Stop the robot with power available to the drives, while maintaining the trajectory. Drive power is maintained after the robot is stopped. Safeguard Stop

 

*Universal Robots’ Category 2 stops are further described as SS1 or SS2 type stops according to IEC 61800-5-2.

 

Configurable Safety Functions

Description

Universal Robots robot safety functions, as listed in the table below, are in the robot but are meant to control the robot system, i.e., the robot with its attached tool/end effector. The robot safety functions are used to reduce robot system risks determined by the risk assessment. Positions and speeds are relative to the base of the robot.
Safety Functions
Safety Function Description

Joint Position Limit

Sets upper and lower limits for the allowed joint positions.

Joint Speed Limit

Sets an upper limit for joint speed.

Safety Planes

Defines planes in space that limit robot position. Safety planes limit either the tool/end effector alone or both the tool/end effector and the elbow.

Tool Orientation

Defines allowable orientation limits for the tool.

Speed Limit

Limits maximum robot speed. The speed is limited at the elbow, at the tool/end effector flange, and at the center of the user-defined tool/end effector positions.

Force Limit

Limits maximum force exerted by the robot tool/end effector and elbow in clamping situations. The force is limited at the tool/end effector, elbow flange, and center of the user-defined tool/end effector positions.

Momentum Limit

Limits maximum momentum of the robot.

Power Limit

Limits mechanical work performed by the robot.

Stopping Time Limit

Limits maximum time the robot uses for stopping after a protective stop is initiated.

Stopping Distance Limit

Limits maximum distance travelled by the robot after a protective stop is initiated.

 

 

Safety Mode

When no protective stops are active, the safety system operates in a Safety Mode associated with a set of safety limits:

Safety mode Effect
Normal

This configuration is active by default.
Reduced

This configuration activates when the Tool Center Point (TCP) is positioned beyond a Trigger Reduced mode plane, or when triggered using a configurable input.

 
Description

Robot Limits restrict general robot movements.

  • Change the values in robot limits (Normal and Reduced) and apply to see the applied changes in safety checksum.

  • Verify the values of reduced should be always less than the values in Normal.

The safety limits restrict forces and motions at the tool flange and the center of the two user-defined tool positions