Sto Standards; Sto Functional Description - Aerotech XR3 Hardware Manual

XR3 Hardware Manual
2.11.1. STO Standards
Table 2-48 describes and specifies the safety requirements at the system level for the Safe Torque Off
(STO) feature of the XSP3-10, -20, -30 and XSL3-10-40 products. This assumes that diagnostic testing is
performed according to Section 2.11.4.
Table 2-48: STO Standards
Standard
EN/IEC 61800-5- 2:2016
EN/IEC 61508-1:2010
EN/IEC 61508-2:2010
EN ISO 13849-1:2015
EN/IEC 62061:2005 with Amendments
Table 2-49: STO Standards Data
Standard
EN ISO 13849-1:2015
EN ISO 13849-1:2015
EN/IEC 61508
EN/IEC 61508

2.11.2. STO Functional Description

The motor can only be activated when voltage is applied to both STO 1 and STO 2 inputs. The STO state will
be entered if power is removed from either the STO 1 or the STO 2 inputs. When the STO state is entered,
the motor cannot generate torque or force and is therefore considered safe.
The STO function is implemented with two redundant channels in order to meet stated performance and SIL
levels. STO 1 disconnects the high side power amplifier transistors and STO 2 disconnects the low side
power amplifier transistors. Disconnecting either set of transistors effectively prevents the XR3 from being
able to produce motion.
The XR3 software monitors each STO channel and will generate an Emergency Stop software fault when
either channel signals the stop state. Each STO channel contains a fixed delay which allows the XR3 to
perform a controlled stop before the power amplifier transistors are turned off.
A typical configuration requiring a controlled stop has the Emergency Stop Fault mask bit set in the
FaultMask, FaultMaskDecel, and FaultMaskDisable parameters. This stops the axis using the rate
specified by the AbortDecelRate parameter. The software will disable the axis as soon as the deceleration
ramp is complete. This is typically configured to occur before the STO channel turns off the power amplifier
transistors.
www.aerotech.com
Chapter 2: Installation and Configuration
and Table 2-49.
Value
MTTF > 1000 years,
D
DC 99%
AVG
Maximum PL e, Category 4
Lifetime = 20 years
No proof test required
Interval for manual STO test:
Once per year for SIL2/PL d/category 3
l
Once per three months for SIL3/PL e/category 3
l
Once per day for SIL3/PL e/category 4
l
SIL3
PFH < 3 FIT
SFF > 99%
Maximum Achievable Safety
SIL 3
SIL 3
SIL 3
Category 4, PL e
SIL 3
77