Anti-Jerk Ramp Parameter Tuning Guide; Soft (Cushion) End-Stop - Danfoss pved-cl Operation Manual

Operation Manual
PVED-CL Controller for Electro-Hydraulic Steering, Version 1.38
Steering by Steering Wheel – Open Loop

Soft (Cushion) End-stop

© Danfoss | May 2016

Anti-jerk Ramp Parameter Tuning Guide

Tuning the parameters is an iterative process. The following sequence may be useful when tuning a
vehicle:
1. Initial setting: Set Tro to Set Tfr to Set YsetFr to 1000. Set Tra to 1. Set YabortThreshold to 500.
2. Set the ramp-down time , Tfo, to a start value e.g. 500.
3. Decrease YsetFr from 1000 towards a smaller number. Observe which value of YsetFr where the level
of jerks starts to get worse to find the flow request range, where ramping has an effect. Optionally
increase Tfr to optimize on the fast ramp-down operation. Tfr should not exceed 150 ms and always
be smaller than Tfo.
4. Adjust the ramp-down time, Tfo, until at good anti-jerk performance is achieved.
5. Increase the ramp-up time, Tro, to further improve the anti-jerk performance. Tro is typically smaller
than Tfo.
6. Fine-tune the performance by experimenting with Tfr, Tra, and YsetFr. Note that the largest jerks shall
be tuned away with the ramp-up time, Tro, and ramp-down time, Tfo.
7. Finally the YAbortThrehold and Tra may be adjusted. Consider how many steering wheel RPM is
needed to abort the down-ramp. Secondly, adjust Tra to reduce the jerk when aborting the down-
ramp. Obviously, Tra needs to be less than the down-ramp time, Tfo to get a faster steering response.
Typical values for Tra is 50 – 100 ms.
The above typical parameter settings may vary from vehicle to vehicle.
To prevent the steering actuator to hit the mechanical end lock with great speed, the PVED is able to slow
down the actuator speed when approaching the end lock electronically. The red line in the figure below
shows how the actuator is slowed down near the end lock position. The black line in the figure below
shows how port flow is reduced. The steering actuator signal must be present in the PVED for this
functionality to work.
Right end lock
1000
750
Port flow
command
500
250
0
-250
-500
-750
-1000
Left end lock
Yr, Yl The difference between the values of both parameter set the freedom of the steering actuator.
Normally, Yr is set equal at the right mechanical end lock. Yl is normally set equal to the left mechanical
end lock. For example, setting Yr at 500 and Yl at –500 reduces the freedom of the actuator by 50%.
The default values for Yr and Yl are set equal to position of the mechanically end locks.
Cf Sets the region where actuation speed is slowed down. This region starts from the position defined by
Yr and Yl. Making this region to small reduces or can eliminate the effect of soft stop. The default value for
Cf ensures the valve is closed proportionally with actuator position.
In order to slow down in a controlled manner, the inherent shortest time for the PVED to move the spool
from max open to be fully closed has to be considered. This ramp down time can be found in
Data on page 22.
Yr, Software end lock position
Steering actuator position
250 ms
Defaults
Yl=-1000
Yr=1000
Off=50
Cf=350
Yl, Software end lock position
time
P005 221E
Technical
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