Symbol
Index
Default
Value range
Tra
4y35
1
1 to 1000 ms
Ramp-down time for canceled down-ramp
The discontinuities in the progressive characteristic are located at 50, 120 and 333 ([5.0;T at 25], [12,0;T at 50] and [33.3;T at 75] of max port flow
capacity)
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 Tfr to Set YsetFr to 1000. Set Tra to 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.
Soft (Cushion) End-stop
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.
This functionality can be applied only in open-loop control mode, but requires that Steered wheel
feedback sensor is mapped and mounted on either the steered wheel or cylinder, to indicate the motion-
range.
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.
time
1000
-1000
750
500
250
0
-250
-500
-750
Yac
t - st
eer
ing ac
tua
tor p
osition
Q - p
or
t flo
w c
ommand
Right end lock
Left end lock
250 ms
Port flow
command
Defaults
Yl=-1000
Yr=1000
Off=50
Cf=350
Steering actuator position
Cf
Yr, Software end lock position
Yl, Software end lock position
O
ff
P005 221E
Operation Manual
PVED-CL Controller for Electro-Hydraulic Steering, Version 1.38
Steering by Low Priority Steering Device – Open Loop
86 |
©
Danfoss | May 2016
11025583 | AQ00000216en-US0302