27
Electronic for proportional DC valves
Series PWDXXA-40X
Operation Manual
PWDXXA-40X_20 5715-677 UK.indd 26.01.17
Parker Hannifin Corporation
Hydraulics Group
Parker Hannifin Corporation
Hydraulics Group
2. Check once more to be sure that P17 and P18
are set to zero.
3. Adjust P16 to a low value, i.e. 10 %, and try the
system on the test profile.
Observe the result of the test. There are three
possible outcomes:
The drive oscillates continuously
• Stop the system quickly. Reduce the P16-
value to ½ of the initial guess, and try again.
The drive overshoots, but stops after one or
two oscillations
• Reduce the P16-value to ¾ of the initial guess,
and try again.
The drive reaches the commanded position
with no overshoot
• The system is usable with the estimated value
of P-gain. You should experiment with stepwise
increasing of the P16-value to see how high a
value the system will tolerate. Accuracy and
response are improved by high values, but do
not allow permanent oscillation!
4. You have now completed the basic tuning for
your control loop. The next step is to test the
performance of the system to see if it meets
your requirements. If not, the electronic has ad-
ditional control features you can use to improve
performance, as explained below.
Guarantee of control functionality
Before the tuning of the control loop may be com-
menced, the functionality of the control circuit must
be ensured. As previously mentioned, the control-
ler compares command and feedback signal and
adjusts the electrical input to the valve amplifier
to move the drive to the commanded position. To
ensure this functionality, the polarities of command
and feedback signal must be equal.
How can the functionality of the control loop
be achieved?
At first you should set off the control loop (set
parameter E2 to value 0 = open loop and transmit
to the electronic) and cause the drive via manual
control to the middle of the cylinder stroke. After-
wards adjust at first the control coefficients as
described in chapter “Simple tuning of a position
control loop” (P16 at 10 %) as well as the parameter
E2 at 2 = external closed loop and transmit to the
electronic. If this results in a rapid movement of the
drive to an end position, the polarities are incorrect.
Access now the parameter P12 = feedback signal
polarity, change the value and transmit the data.
The drive should be adjustable and remain in its
position when you switch on the closed loop control
via parameter E2. Now you should preset position
commands and supervise the drive movement. If
the drive even tough is running in closed loop mode,
but the direction of the movement is not as required,
you have to change the polarities of both command
and feedback signal via the parameters P11 and
P12. After that the drive is running as desired, you
can continue with tuning of the loop.
Tuning of the closed loop control
1. Create a suitable tuning test profile – otherwise
it may be difficult for you to tell how good the
system response is (the test profile may also be
generated by an upstreamed electronic module
PZD00A-40X). The test profile should so pro-
grammed to causing the drive to move from the
start position with the desired maximum accel-
eration and velocity to the required final position.
In the final position the drive should be com-
manded to dwell, that will give you enough time
to watch the load position to see if it oscillates
or remains stationary. This should be followed by
returning of the drive to the start position, where
the dwell in position may also be evaluated.
Summary of Contents for PWD Series
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