Steering by Steering wheel – Closed Loop
Closed loop steering by wheel steering is chosen when:
•
The knob of the steering wheel must return in the same position for straight forward driving
•
Accurate steering sensitivity is required
•
Steering motion is required at extreme low steering wheel speeds
•
Hold the steering actuator at a fixed position when steering wheel speed is zero.
W
Warning
Steering by steering wheel in closed loop mode shall only applied in systems with a PVED-CL and an
EHPS valve. Using an OSP and an EH valve in closed-loop is not a valid configuration and will lead to
unpredictable closed loop performance.
Functionality Tree
The tree below illustrates the functionality available in the PVED-CL for closed-loop steering wheel
steering. The manufacturing default is found by following the red line. Following the instructions in this
chapter can of course modify it. The switches in the tree are used to select the functionality required. In
case different functionalities are required, the EHPS software provides multiple programs for each
steering device.
Open loop, fixed sensisitivity, with´no ramps
applied.
Closed loop, fixed sensisitivity
Closed loop
Cp=255
Related to
vehicle speed
Sse=3
Fixed
Sse=1
Open loop, fixed sensisitivity, with fixed ramp times,
Fixed
Sse=1
Related to
position of
steering actuator
Sse=2
Related to
vehicle speed
Sse=3
Open loop, sensisitivity related to steering actuator
position, with fixed ramp times
Open loop, sensisitivity related to steering actuator
position, no ramps applied
Open loop, sensisitivity related to vehicle speed,
with fixed ramp times
Open loop, sensisitivity related to vehicle speed,
no ramp times applied
Open loop
Cp=0
Fixed
Sr=1
Var
Sr=2
C
on
tr
ol pr
inciple swit
ch
Sensitivit
y swit
ch
R
amp swit
ch
Open loop, fixed sensisitivity, with variable ramp
times as function to vehicle speed,
Open loop, sensisitivity as function to steering actuator
position, with variable ramp times related to vehicle
speed,
Open loop, sensisitivity related to vehicle speed,
with ramp times related to vehicle speed
Closed loop, sensisitivity related to vehicle speed,
switches
No signal (0)
CAN (255)
C
hannel mapping swit
ch
Cp
Sse
Sr
No,
Sr=0
default
Fixed
Sr=1
Var
Sr=2
No,
Sr=0
Fixed
Sr=1
Var
Sr=2
No,
Sr=0
* Sensitivity means: number of revolutions on steering wheel from lock to lock
*
Y=0
1
2
3
4
Program number: Y
For safety reasons, an anti wind up function prevents the steering actuator to lag behind the drivers
steering intends. The function is typically needed when not enough flow is supplied to the steering
system at high steering wheel speeds combined with a low steering ratio or when not enough pressure is
provided when the driver steers against a high resistance. Under these conditions and without effective
measures it might significantly reduce the ability to steer the vehicle at higher speeds. The anti wind up
function operates continuously and will limit the set point when commanded port flow exceeds the max
flow capacity of the valve. These events always increase the number of steering wheel turn from lock to
lock.
Operation Manual
PVED-CL Controller for Electro-Hydraulic Steering, Version 1.38
Steering by Steering Wheel – Closed Loop
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©
Danfoss | May 2016
11025583 | AQ00000216en-US0302