Rockwell Automation 1336T Master/Slave Parallel AC Drv - Manual (Page 36)

1336 FORCE-5.19 – August, 2000
3-18 Startup
12. Adjust Ki (P139), Kp (P140), and Kf (P141) to obtain desired
response. Reduce kf if needed to control overshoots or help
achieve stability.
Note: P141 (Kf) must equal 65535 for web handling systems
that require the drive to accurately track a change in
reference or in any section that has an outer loop such as a
tension loop.
Set the Torque Step Response of the drive as follows:
1. Run the motor RPM up to
1
/
2
of base speed.
a. Enter a 5-10% torque step into Parameter 166 [Ext Torque
Step]. Verify that the speed regulator recovers quickly and
is stable. Adjust Ki (P139), if needed to get the desired
response.
b.When an acceptable response is achieved, the plot should
be saved with all pertinent tuning parameter information
recorded on the chart recording. Pertinent information
includes speed reference, velocity regulator gains, amount
of step, amount of filtering used, section name and date.
c. Write parameters to EEPROM and to a disk file.
Typically, in the paper industry, a minimum of 1 radian response
is desired. It is acheived when, after a step input, the speed
feedback rises to 63% of the speed step value in a one (1) second
duration. Radian = 1/rise time (sec.). The velocity regulator’s
integral gain may be raised by increasing KI (P139). As this is
accomplished, the rise time will decrease and overshoot will be
seen.
If Parameter 139 is set too small, the regulator will be sluggish to
load changes. If it is set too large, the regulator will be
underdamped, and possibly unstable. Overshoot can be reduced
by increasing the proportional gain (P140) or by using feed
forward gain (P141). A coordinated drive system should use a
value of Kf = 65535, which is a gain of one.
Remember if any gain values are changed, the response
(bandwidth) will change. It is best to tune each section of process
equipment to get the fastest response from that section without
the danger of being close to unstable. The chattering of the
gearbox and twisting of the shaft should also be considered. You
should NOT detune a section just to get a desired radian
response if the section can mechanically handle the faster
response. The drive system’s overall response to a change in
reference is limited by the response of the slowest section, but it
will not hurt the system to have sections with different bandwidth
responses.
2. If oscillations occur upon the removal of the speed step, a
velocity feedback filter select (P152) may be used. If filtering
is used, you may want to increase the velocity bandwidth
slightly for a faster response.