User Manual

4–9
Publication 1746-6.19 March 1998
It is usually desirable to have some INTEGRAL GAIN (5 to 50 counts)
to help compensate for valve null drift or changes in system dynamics.
Some systems may require larger
INTEGRAL GAIN, in particular if
they are moving a large mass or are nonlinear. Too much
INTEGRAL
GAIN
will cause oscillations. On the other hand, some hydraulic
systems do not require
INTEGRAL GAIN.
DIFFERENTIAL GAIN is used mainly on systems which have a
tendency to oscillate. This happens when heavy loads are moved
with relatively small cylinders.
DIFFERENTIAL GAIN will tend to
dampen out oscillations and help the axis track during acceleration
and deceleration. If you use
DIFFERENTIAL GAIN, you may be able
to increase the
PROPORTIONAL GAIN somewhat without causing the
system to oscillate.
A disadvantage to
DIFFERENTIAL GAIN is that it amplifies position
measurement noise which can cause the system to chatter or
oscillate if the gain is too high or there is too much noise.
The
DEAD BAND ELIMINATOR compensates for valve overlap.
Typically it is required if the valve has relatively:
• large overlap (up to 20%)
• slow speed (less than 40 Hz)
• large capacity for its application
(For a description of how Dead Band Eliminator affects the system,
refer that subject under Hydraulic Configurator Help Topics.)
Important: Use this procedure only if your valve needs the
DEAD
BAND ELIMINATOR. If not, go to the next section, Saving Parameters.
This procedure requires operating the module in open-loop mode with
drive outputs connected to the amplifier. In this procedure, you will
increase the drive output until the axis just moves in one direction, then
in the other.
1. Select the axis and enter a small positive value (such as 200 mV)
in the
COMMAND V ALUE number field.
2. Issue the open-loop output command “O”.
3. Look for axis motion.
4. Important: If necessary, be prepared to stop axis motion. To stop:
– Enter zero in the
COMMAND V ALUE number field.
– Issue the open-loop output command “O”.
5. Slowly increase the value that you entered in the
COMMAND V ALUE
number field, and repeat steps 2 and 3 until the axis just starts to move.
Important: Observe if the axis moved in the intended direction.
If in the wrong direction, check drive wiring polarity and hydraulic
plumbing before reversing the drive mode in the Config word.
Finding the Value of the
Dead Band Eliminator