Steering Device Transition
The PVED-CL allows steering with electric signals from more than one steering device. Every 50 ms, the
PVED sequentially monitors all mapped steering device signals according to their priority.
It selects one of steering devices based on:
•
the amount of signal change detected in the steering signal per time unit and
•
the current in
on page 19. When the steering signal change per time unit exceeds a user-
defined threshold, it is considered as a request to steer the vehicle with that particular steering
device.
The system state is used to ensure:
•
Smooth transition from one to another device by requiring the valve spool to be inside or near the
valve dead-band.
•
Reach-ability of the closed-loop control by demanding the steering actuator to be within the control
region of the closed-loop controller (if closed-loop control is applied).
•
Safe transition to a steering device, and hence program by only allowing this change at vehicle
speeds equal to or lower than the threshold value defined in
on page 19
provided that a vehicle speed signal is present.
When all above criteria are fulfilled, the steering device is selected and the associated steering control
principle is applied. If no steering device fulfils the criteria the previous selected device remains. On
power up, all devices are normally in their rest position, which means that no device is selected. The
magnetic valve is disabled while no device is selected.
Threshold Definition
To determine if a steering device exceeds its defined threshold, two parameters shall be defined for each
applied steering device namely the maximum steering motion speed and the steering motion threshold.
The threshold is defined as a percentage of the maximum steering motion speed.
Define the Maximum Steering Motion Speed
The fastest steering input is defined as the time in ms to change the input signal from its minimum to its
maximum value or visa versa, hence the value corresponding to 100%. This means e.g. the minimum time
required to make one full turn for the steering wheel, one full movement left to right on the joystick, etc.
100
900
time
t1
t2
0.5
4.5
CAN
0
4095
AD
Volt
Example: How the maximum signal change is carried out
Device
Index
Default
Value range
Steering by steering wheel
111
500
500 – 750 (120 to 80 rpm)
Steering by High priority steering device
311
200
150 – 450
Steering by Low priority steering device
411
200
150 – 450
Steering by High priority external set-point controller
511
200
10 – 2000
Changes to parameters of non-present steering devices have no effect.
Operation Manual
PVED-CL Controller for Electro-Hydraulic Steering, Version 1.38
Steering Device Transition
36 |
©
Danfoss | May 2016
11025583 | AQ00000216en-US0302
