Installation guide

246 Servo Drive
Velocity feed forward
This term is multiplied by the commanded velocity to
contribute to the output torque command. It has no
effect on general stability, and may be set to as high
as 100% to reduce position error during motion. Too
high a Kvff causes undue motor heating. Generally,
Kvff should be set between 50 and 100
.
Integral limit
Limits the contribution of the integral term to the
servo loop’s output. This limit is imposed on the in-
ternal calculation within the controller, and is used to
prevent excessive buildup of the integrator output
which can occur if a constant error is allowed to exist
for extended periods of time. Too low an integral
limit may reduce the effectiveness of the integrator
by limiting its contribution to the output torque
command. This would cause a constant steady state
error. Too high an integral limit may allow the inte-
grator to build up a large error stored in the controller
memory. This error would then be “unwound” at the
end of a move causing excessive overshoot and a
long settling time. The limit can be set between 0 and
319 volts. A setting of 100 is a good midrange start-
ing point, and this parameter rarely needs adjustment.
Following error
Defines the maximum error allowed during motion in
units. If this limit is exceeded the servo drive shuts
down. The default setting is a good starting point.
Sample time
Determines how often the servo loop output is up-
dated. The possible settings are .256 milliseconds to
2.048 milliseconds in .256 millisecond increments. A
setting of 1.024 is a good starting point.
Integration during motion
This feature allows you to select whether the integra-
tion gain is used during the profile motion. Enabling
the integrator during motion will reduce your error at
speed, but may cause some unacceptable overshoot in
the response. Some controllers allow you to set this
parameter in the servo tuning screen, while others re-
quire that you change it in the Servo folder in the
program configuration (be sure to compile and
download the project each time you change the con-
figuration or the change will not take effect).
Note: A program does not have to be written
in the task in order to tune the servomotor.
9.1.1.4 – Servo Tuning Environment
The servo-tuning Environment allows a servo drive to be
manually tuned, auto-tuned and testing the results of the
tuning.
Clicking on the
Servo Tuning
command button can ac-
cess the servo-tuning Environment. The project in the
controller must match the project in the PC. If necessary
compile and download the project at this time.
The servo gains, Integration Limit, Sample Time, Inte-
gration during motion parameters can be modified for an
individual axis on the opening screen. The four steps for
tuning a servo can be executed from this screen as well.
Command Buttons
Zoom
toggles between displaying the graph between
cursors and the full screen view. The two vertical
lines in the display window are the cursors.
Save Graph
saves the currently displayed graph and
appears as an item on the drop list.
Freeze scale
freezes the current logged scale value.
UnFreeze
allows the next commanded motion graph
to be auto scaled.
Graph setup
allows for the selection of color and
style for each logged item.
Print
prints the current graph.
Quit
exits the Servo Tuning environment.
Shutdown
disables the servo drive and outputs a
torque command of 0 volts. The
Update controller
gains
command button will re-enable the servo out-
put voltage.
Apply voltage
Measure
system gain
!! Motor may turn !!
Execute move
using updated
controller gains
SHUTDOWN
Update controller
with calculated
servo gains
2
0.0 %Kvff
100.0 voltsIntLim
1.024 ms
Sample
time
Step 3: Update
0.0 volts
30 hertz
Calculate servo gains
based on measured
system gain
0.0 revs/sec /v
2
System Gain
System Bandwidth
Step 2: Calculation
2.048 secs
Display
time
Disable integrator during motion
TrapezoidalProfile
0.0 mv/cntKp
0.0 msKi
10.0 msKd
0.0 v/cnt/msKaff
100.0Accel
100.0Decel
10.0 units/secSpeed
10.0 unitsMove
units/sec
2
units/sec
2
Step 1: Measure Step 4: Response
0.0 ms 1024.00 ms 2048.0 ms
Freeze scale
Print
Graph setup
Save graph
Zoom
0.0
0.0
0.0
Left cursor
0.000 ms
Right cursor
2048.000 ms
View Logged Data
_ X
5.0
Distance Limit - units
10.0
Speed - units/sec
2.0
Output - volts
1Servo axis
Servo Tuning environment
Quit