Universal Robots provides reliability data for the safety of control components as a SISTEMA Parameter list in order to assist customer's with their Performance Level (PL) calculation.

 

What is SISTEMA?

SISTEMA is a software tool to calculate PL, for the implementation of EN ISO 13849-1. Provided by IFA, SISTEMA is a free software and is widely recognized within the industry.

You can download SISTEMA software and its instruction manual via the following link.

 

Download SISTEMA

 

PFHd calculation, UR Robots, Safety System 3.1

The following safety functions (1-15) are tested and certified by TÜV NORD CERT GmbH. Performance Level (PL) and Probability of a dangerous Failure per Hour (PFHd) is calculated for each safety function.

Safety function		According to ISO 13849-1
		PL	PFHd UR3	PFHd UR5	PFHd UR10
1	Emergency Stop (Monitoring of the emergency stop)	d	4.27E-07	4.27E-07	4.27E-07
2	Safeguard Stop (Monitoring of the safeguard stop)	d	3.15E-07	3.15E-07	3.15E-07
3	Joint Position Limit (Monitoring of the joint position limit)	d	3.15E-07	3.15E-07	3.15E-07
4	Joint Speed Limit (Monitoring of the joint speed limit)	d	3.15E-07	3.15E-07	3.15E-07
5	Joint Torque Limit (Monitoring of the joint force limit)	d	2.72E-07	2.72E-07	2.72E-07
6	TCP Pose Limit (Monitoring of the TCP position limit)	d	3.15E-07	3.15E-07	3.15E-07
7	TCP Speed Limit (Monitoring of the TCP speed limit)	d	3.15E-07	3.15E-07	3.15E-07
8	TCP Force Limit (Monitoring of the TCP force limit)	d	3.15E-07	3.15E-07	3.15E-07
9	Momentum Limit (Monitoring of the momentum limit)	d	3.15E-07	3.15E-07	3.15E-07
10	Power Limit (Monitoring of the power limit)	d	3.15E-07	3.15E-07	3.15E-07
11	System Emergency Stop Output (Monitoring of the System Emergency Stop Output)	d	1.56E-07	1.56E-07	1.56E-07
12	Robot Moving Digital Output (Monitoring of the Robot Moving Digital Output)	d	3.15E-07	3.15E-07	3.15E-07
13	Robot Not Stopping Digital Output (Monitoring of the Robot Not Stopping Digital Output)	d	3.15E-07	3.15E-07	3.15E-07
14	Reduced Mode Digital Output (Monitoring of the Reduced Mode Digital Output)	d	3.15E-07	3.15E-07	3.15E-07
15	Not Reduced Mode Digital Output (Monitoring of the Not Reduced Mode Digital Output)	d	3.15E-07	3.15E-07	3.15E-07

 

The PFHd calculations are based on the conservative assumption that all potential faults of any component in the safety-related parts of the control system are dangerous.

The version number of the UR safety system is found in the TÜV certificate in the specific robot user manual.

 

Heterogeneous architecture

The complete safety system and each safety function is based on a heterogeneous category architecture, where a Category 3 system monitors a Category 2 system with high Diagnostics Coverage (DC). Hence, the design of the safety system cannot be comprehensively explained using the traditional category terminology. A comprehensive risk assessment done together with TÜV NORD CERT GmbH has determined that the heterogeneous system is indeed warranted for the intended use of the robots.

Category combinations are calculated using the software SISTEMA, which is designed and published by the German institute of occupational health (IFA, DGUV).