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 High Priority Steering Device – Open Loop
Symbol Index
YAbortDownRamp 3y34
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

Soft (Cushion) End-stop

© Danfoss | May 2016
Default
0
Tuning the parameters is an iterative process. The following sequence may be useful when tuning a
vehicle:
1. Initial setting: Set Tro to 1. Tfr to 1. 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.
This functionality can be applied only in open-loop control mode, but requires that a steered wheel
feedback sensor is mapped and mounted on either the steered wheel or cylinder, to indicate the motion-
range.
In the figure below the red line shows how the actuator is slowed down near the end lock position, and
the black line shows how port flow is reduced. The steering actuator signal must be present in the PVED
for this functionality to work.
Value range
0 to 500 (1 unit = 0.1% of max. flow).
The default value will force an down-ramp abort at a slight reverse port flow
request.
Typically YAbortDownRamp needs be increased to avoid unintentional
down-ramp aborts as this will infer a jerk on the driver.
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