Safety parameter
Specification
Description
CCF analysis
75
ISO 13849:2014/2015
ISO 25119:2018/2019
Software Requirement Level
SIL2 / SRL3
IEC 61508:2010
ISO 13849:2014/2015
ISO 25119:2018/2019
Source: JS1-SBW Component FMEDA and Lifetime Test.
Functional safety system integration
As shown in the steering system overview, JS1-H Steer by Wire requires an EHD as steering controller to
be present on both available CAN busses. The entireness of Functional Safety can only be obtained by
following the given system architecture.
It is strongly recommended that the system integrator performs a System-Level Failure Mode Effects
Analysis (FMEA) for installation of the steering-by-wire system to the vehicle.
Environmental control measures
Generally, JS1-H Steer by Wire does not monitor its temperature. Therefore, exceeding the allowed
ambient temperature could cause permanent damage of the joystick.
Force feedback over-temperature shut-down
The joystick JS1-H Steer by Wire implements over-temperature security mechanisms for its Force
Feedback components. In the unlikely occurrence of exceeding the allowed temperature threshold inside
the joystick housing, Force Feedback will immediately be disabled. This will also send the joystick into
safe state and send out Force feedback error, meaning it will remain operable at limited performance
until the next power-down.
DC power supply
JS1-H Steer by Wire is designed to reliably operate at battery voltages between 5.5V and 16V. Internal
protection circuitry ensure that the joystick’s electronics can withstand absolute maximum voltage peaks
of 26V for 5 minutes. Polarity protection withstands voltages down to -16V.
During engine cranking, the joystick will remain functional, even though the supply voltage may reach
excessively low levels, especially in cold conditions.
If the general power supply goes below 5.5V, JS1-H Steer by Wire will shut down without sending any
warning.
Force Feedback is supplied separately. The allowed operating range is 11V to 16V; additional load dump
protection is in place and reverse polarity protection secures the joystick down to -16V. However, Force
Feedback will not be functional during engine cranking!
If the Force Feedback’s supply voltage dips below 11V, Force Feedback can not be expected to be
functional. Between 10V and 11V it will not be comfortable and the noise level increases. Below 10V there
will be no Force Feedback.
User and Safety Manual
PLUS+1® JS1-H Steer by Wire
Functional Safety
©
Danfoss | December 2022
AX436683569858en-000101 | 19
