Method 3: Valve Auto-Calibration; Preconditions; Valve Auto-Calibration Command Parameters - Danfoss pved-cl Operation Manual

Operation Manual
PVED-CL Controller for Electro-Hydraulic Steering, Version 1.38
Installation

Valve auto-calibration command parameters

Command Description
XspStartSearch Sets the starting main spool set-point. Values close to 0 will include more of the hydraulic dead-band in the search and thus
consume more time. Setting the value closer to a main spool position where flow is expected, will speed up the calibration
time.
The starting main spool set-point is used for both the left and right direction.
XspIncrementSize The main spool set-point increment size defines the step that the algorithm is using in each iteration. As a consequence, it
defines the resolution of the calibration result. A small value < 5 could potentially produce a more accurate calibration result
at the expense of calibration time. However, repeatability of the calibration result may be poor. A step size > 5 will speed up
the calibration time at the expense of calibration accuracy.
© Danfoss | May 2016
3. The closed-loop dead-band values are calculated as the detected hydraulic dead-band values plus
some margin depending on the desired minimum correction flow. Typical values are 20-30 fur-ther
out than the hydraulic dead-band values.
4. Xspl_1000 and Xspr_1000 are set to the respective maximum stroke for the valve (see valves types
overview).
The applied values are example values. The optimum values are vehicle specific.
The result that can be achieved with manual calibration is also operator sensitive. Manual valve
calibration depends on visual confirmation of wheel movement. Differing perception of wheel
movement will affect the final steering performance.

Method 3: Valve auto-calibration

A third alternative is to utilize a build-in valve auto-calibration algorithm which can automate the valve
calibration and produce deterministic results. The algorithm utilizes the wheel angle sensor and can be
regarded as an automated manual calibration procedure.
See section StartValveAutoCalibration in PVED-CL Communication Protocol, 11079551 on how to
invoke the valve auto-calibration.
During the calibration procedure, the actuator position/steered wheel angle (Yact) change is measured in
a pre-defined time interval (dt) to derive a steering velocity representation. Exceeding a defined Yact/dt is
used as an "output flow detected" criterion. The principle in valve auto-calibration is to search for the
main spool set-point Xsp, where output flow is detected and then derive the software open-loop dead-
bands by applying a fixed rule . This is done for both left and right direction.

Preconditions:

1. The PVED to valve auto-calibration is available only when PVED is in the calibration mode. See section
EnterCalibrationMode in PVED-CL Communication Protocol, 11079551 on how to set the PVED-CL in
calibration mode.
2. The valve auto-calibration command shall be sent from the MMI controller.
3. A wheel angle sensor shall be installed, mapped and calibrated.
4. A steering wheel sensor (SASA) shall be installed and mapped.
5. The wheels shall be positioned in the straight ahead position ± 25% of the max angle in one direction
prior to invoking valve auto-calibration.
6. Auto-calibration shall be performed while the wheels are on an even and solid surface. No front load
or front attachment shall be mounted.
7. Parameter configuration is not possible during the auto-calibration procedures. Any attempt to read
or write parameters is ignored.
Valve auto-calibration command parameters
See section StartValveAutoCalibration in PVED-CL Communication Protocol, 11079551 on how to
format the command and for detailed status/error code information.
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