Spool Dead-Band Hold Control Function; Dead-Band Jump Control; Dead-Band Hold And Proportional Control; Responding To Flow Requests After Tolsout - Danfoss pved-cl Operation Manual

Operation Manual
PVED-CL Controller for Electro-Hydraulic Steering, Version 1.38
Steering by Low Priority Steering Device – Open Loop
Symbol Index Default
YR 4y07 1000
YL 4y08 -1000
Off 4y28 50
Cf 4y29 333
See chapter Mapping steering signals, Steering actuator Sensor (feedback from vehicle wheels) and Steering actuator position to acquire "steering
actuator position".

Spool Dead-band Hold Control Function

© Danfoss | May 2016
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.
Off This parameter sets the permitted actuation speed when hitting the end lock defined by YR or YL.
When the steering actuator passed YR or YL, actuation speed will decay to zero.
The default sets a speed that allows building up pressure when the actuator is located at YR or YL.
Value range
-1000 – 1000, Values smaller than 0 will be set equal to the positive equivalent
-1000 – 1000, Values greater than 0 will be set equal to the negative equivalent
0 to 1000 (0.0 - 100.0% of max port flow)
1 to 1000
Tolsout Maximum time where the main spool is allowed to be operated proportionally within the valve
dead-bands. The main spool control range for this function can be seen on the
page 24. This function is useful to eliminate frequent spool relocating events from its neutral to its dead-
band position and back (so called jumps) at small flow requests.
The flow request is 0 while moving the high priority steering device within the steering device dead-
band, db (see Set-point Transfer Function

Dead-band Jump Control

Set Tolsout lower than 21 (ms) to momentarily set the main spool in neutral as soon as the flow request is
0, No proportional spool movement will take place. The spool will jump from neutral to either of the valve
dead-bands depending on a flow request. The steering device dead-band, db, has no impact for these
Tolsout values.

Dead-band Hold and Proportional Control

Setting Tolsout between 21 and 30000 (ms) defines the maximum time where the main spool is either set
on the valve dead-band or controlled proportionally within the valve dead-band (granted that the flow
request is 0 during this time).
After a flow request to either left or right port, the main spool will be set on the respective left or right
valve dead-band. Any steering device movement within the defined steering device dead-band, db, will
result in proportional main spool movement. Proportional control will be allowed for Tolsout ms.
If the flow request has been 0 for Tolsout ms, the main spool will be set in neutral and any steering device
movements within db will be ignored.
To utilize proportional control, a steering device dead-band, db, needs to be created. If db is set a low
value, the main spool will effectively be operated as dead-band jump control.

Responding to Flow Requests after Tolsout

If the main spool has been set in neutral after Tolsout ms, any flow request will cause the spool to
immediately jump to the relevant spool position with no initial proportional dead-band control.
on page 78).
11025583 | AQ00000216en-US0302 | 87
Dead-band crossing on