Parker PWD Series, Руководство по эксплуатации

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PWDXXA-40X_20 5715-677 UK.indd 26.01.17
Electronic for proportional DC valves
Series PWDXXA-40X
Operation Manual
Parker Hannifin Corporation
Hydraulics Group
Parker Hannifin Corporation
Hydraulics Group
The table below gives information, which approaches may be embarked if typical problems with pres-
sure control loops appear.
Problem Solution
Variation error too large, when pressure
command remains constant
Use parameter
P17 = I-gain
(only effective for P26 >0)
Repeatable deviation by using a valve
with overlap/hysteresis
Use deadband compensation feature
P7 = MIN channel A
Sequence error too large when following
pressure command profile
Use parameter P13 = bypass gain
Disappointingly low P-gain
Check the frequency response of valve
and pressure transducer, and the system
resonant frequency (s. items below)
Response too slow
Be sure P16 = p-gain is adjusted high enough
(s. also previous items) and check the flow
capacity of the valve
In explainable problems Check the setting of all parameters
Improving system performance
Using the parameter P17 = I-gain
The integrator gain (abbreviated I) can be ad-
justed to reduce or eliminate the error between the
commanded pressure and the feedback pressure
measured by the transducer, when the command is
constant. Higher values of I-gain will cause a better
error reduction while the response will be longer.
This parameter is only effective if a window (>0) is
defined via P26.
Eliminating a slow, small amplitude oscillation
in stationary condition
Due to the possible effects of friction and or other
application variables, use of the I-gain sometimes
causes a slow, small amplitude oscillation in the
stationary condition. This is a different problem
from the vigorous oscillations that occur when the
P-gain is set too high. The electronics provide a
“Window” feature (sometimes called “in-position-
window”) to solve this problem. In this case the
integrator operates only within this window. Select
this option via parameter P26. Step increases of the
window size will eliminate the oscillation.
Increasing load stiffness
“Load stiffness” is the term for the resistance of the
servo loop characteristics to deflection by external
forces. Adjusting P16 to the highest practical value
is important.
Disappointing control loop function
The higher the value of P-gain that can be used,
the better is the static and dynamic performance
of the system. You may not have any direct need
for fast response, but may still need a high value
of P to reduce static error, reduce following error
or increase load stiffness. High values of P cause
faster system response, whether you need it or not.
As the system frequency response gets too close
to the frequency response of one of your compo-
nents, the system response becomes oscillatory.