Example; Danfoss | May - Danfoss pved-cl Operation Manual

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

Danfoss | May 2016

Qr, Qramp
1000
YsetFr, fast ramp down range
750
500
250
0
Tfr
Tro
-250
Tfo
-500
-YsetFr
-750
-1000
Sr Selects the ramp type. The ramp function can be disabled, fixed or related to vehicle speed. Set Sr to 1
to select fixed ramps.
Lr Sets the linearity of the ramp-up curve. The default value is a linear ramp.
Lf Sets the linearity of the slow ramp-down curve. The default value is a linear ramp.
Tro Sets the ramp-up time to open the valve from zero to max port flow. The time applies for both ports.
To gain the best performance, the ramp-up time shall be set larger than the inherent ramp up time of the
main spool. See Technical Data
Tfo Sets the ramp-down time to close the valve from max to zero port flow. The time applies for both
ports. It has most effect when the ramp-up time is set larger than the inherent ramp down time of the
main spool. See Technical Data
YsetFr Experience shows that ramping down from maximum flow towards medium flows do not cause
as much jerk as ramping down from medium flows towards no flow (close to the valve dead-bands). In
order to "expedite" the ramping at large flows, a flow range can be set up where the spool can move
faster down to a flow range, where the slow down ramp is active. The overall goal with the parameter is
too optimize steering response time without degrading the anti-jerk performance. Set up fast ramp down
time Tfr before tuning this parameter. Setting YsetFr to 1000 eliminates the effect of the fast ramp down.
Typical settings are 500-800. Use trial and error.

Example:

A value of 800 can be interpreted as allowing the spool to ramp down with a fast ramp for flow requests
between maximum flow (1000) and 800/1000 of maximum flow.
Tfr This time defines the applied ramp time in the fast ramp-down range. It is defined as the ramp time
from maximum flow to no flow. This means that in practice, the actual fast ramp-down time is
proportional to the fast ramp-down range divided by 1000.
Use this optimization criterion: Ramp down as fast as possible for flow ranges, where jerks are not
significant. Typical values are 1-50 ms. The fast ramp down time shall always be less than the slow ramp-
down time. Once the value is set, it should not be adjusted anymore during further ramp parameter
optimization.
YAbortDownRamp To come around the problem of slow steering response for large down-ramp times,
especially if a sudden emergency change of direction is needed, a slow down-ramp can be aborted by
requesting a flow in the opposite direction. Once a slow down-ramp is aborted, an abort down-ramp
time, Tra is applied. Obviously Tra shall be significantly smaller than the slow down-ramp to get any
effect.
Tra is the ramp-down time applied when the slow down-ramp is aborted. This rampdown time shall
typically be much lower than the slow ramp-down time, Tfo, in order to gain any increased steering
responsiveness. Typical value is half the value of Tfo or Tfh time if vehicle speed dependency is applied
(Sr=2). Use trail and error.
Qr Requested port flow
Qramp ramp port flow
YsetFr
YAbortDownRamp
Up ramp
slow ramp down range
Slow down ramp
}
YAbortDownRamp
Abort down ramp
}
Slow down ramp
}
Fast down ramp
on page 22 for these ramp times.
on page 22 for these ramp times.
time
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