Calibration - Danfoss PVED-CLS User Manual

ENGINEERING TOMORROW

Calibration

A PVED-CLS shall always be calibrated to the valve it is controlling (OSPE, EHPS or EHI). This allows cancellation of
mechanical, electrical and environmental dependent tolerances. Spool calibration also compensates for the
mechanical dead-bands designed into the EH spool. Spool calibration is only required at first installation or after PVED-
CLS replacement.
When using PVED-CLS for quick-steering, correctly calibrated dead-bands values (P1 and P2) are important.
If P1 and P2 are too-close-to-neutral (conservative values), no EH flow will be added at low steering wheel RPM,
causing understeer. If P1 and P2 are further away from neutral than they should be (aggressive values), EH-flow
contribution will be higher than expected at low RPM.
For AUX mini-wheel steering, having P1 and P2 too-close-to-neutral (conservative values) causes no steering at low
mini-wheel steering RPM. If P1 and P2 are too far away from neutral (aggressive values) jerky mini-wheel steering,
when steering motion starts.
For open loop joystick, having P1 and P2 too-close-to-neutral (conservative values) causes extra perceived dead-
band in the joystick. If P1 and P2 are too far away from neutral (aggressive values) makes it impossible to steer small
amounts of flow, potentially leading to jerk.
For closed loop joystick having P1 and P2 too-close-to-neutral (conservative values), will cause slight increase in
possible steady state error. If P1 and P2 are too far away from neutral (aggressive values) could cause the wheels
never to settle at a position (oscillation around the set point).
(P3162)
Flow range
Closed loop dead-bands for auto-guidance are placed further away from neutral. They should be placed where
definite, yet small oil output of the EH spool is achieved.
This is to eliminate steady state error between wheel angle and its set point. The PVED-CLS will potentially oscillate a
bit around steady state, but in auto guidance there is never a steady state set point.
Closed-loop mode
(P3166)
Open-loop mode
P1
L Hydraulic deadband
P1: (P3166 + P3170)
P2: (P3168 - P3170)
Flow, Q
(L/min)
(P3088)
Maximum flow
(P3168)
P2
R
Figure 14
(P3164)
Spool displacement
Flow range