Fda - Danfoss PVED-CLS User Manual

ENGINEERING TOMORROW

FDA

FDA – Fault Detection Algorithm is a safety function, which can be used to monitor the system behavior and check if
the steering wheel movements, spool position and the wheel angle changes are consistent with each other. To learn more
about the safety aspect in this functionality, please see the Danfoss document, PVED-CLS Safety Manual.
The FDA functions are only available when both SASA and WAS are present in the system. In a system where the
SASA or WAS are not present, the parameter Safe state upon a failure detection (P3132) must be set to disabled,
otherwise the PVED-CLS will enter safe state. No safety impact.
The FDA evaluation is done in 3 steps:
First step: Sensor validation
The input sensors are evaluated using the thresholds defined by parameters in the FDA sector.
For STW it is determined whether its turning left, not turning or turning right by using parameters P3122 & P3133.
For WAS it is determined whether the vehicle is turning left, not turning or turning right by using parameters P3123 &
P3124.
For the spool position sensor (LVDT) it is determined whether it is outside left dead-band, inside both dead-bands or
outside right dead-band by using the closed loop dead-bands + P3128 & P3130.
The results of these evaluations are found in status message 5, byte 1, bits 8 – 3.
Second step: System evaluation
With the information from the sensors the FDA validates whether the state of the system is OK (Yes) or not OK (No) by
using the following truth table:
Sensor validation
Spool position
Steering wheel direction
WAS direction = Left
WAS direction = Neutral
and cylinder close to left
end-stop (WAS IR < -950)
WAS direction = Neutral
and cylinder not close to end
stop
(|WAS IR| <= 950)
WAS direction = Neutral
and cylinder close to right
end-stop (WAS IR > 950)
WAS direction = Right
Whenever the FDA detects a "not OK" condition, the error condition flag is set. The error condition flag is found in
status message 5, byte 1, bits 2 – 1.
Third step: confidence counter
Whenever the FDA detects an error condition, the confidence counter is incremented by 10ms (the validation is done
every 10ms). If the system is in a good condition, the confidence counter is decremented by 10ms*P3125.
If the confidence counter is greater than equal to P3126, the fault condition flag is set and PVED-CLS enters safe state
(unless disabled by parameter P3132). The fault condition flag is found in status message 5, byte 2, bits 2 – 1.
© Danfoss | August 2018
Left Left Left
Left Neutral Right
Yes Yes No
Yes Yes No
No No No
No No No
No No No
Table 59
Condition
Neutral Neutral Neutral
Left Neutral Right
Yes No No
Yes Yes No
No Yes No
No Yes Yes
No No Yes
AQ00000211 | 133
Right Right Right
Left Neutral Right
No No No
No No No
No No No
No Yes Yes
No Yes Yes