4 4
OEM6250 Installation Guide
Tuning Scenario
This example shows how to obtain the highest possible
proportional feedback (
SGP
) and velocity feedback (
SGV
)
gains experimentally by using the flow diagram illustrated
earlier in Step 4 of the Tuning Procedure.
N O T E
The steps shown below (steps 1 - 11) represent the
major steps of the process; the actual progression
between these steps usually requires several iterations.
The motion command used for this example is a step
command with a step size of 100. The plots shown are as
they might appear on a scope (X axis = time, Y axis =
position).
Step 1
For a starting trial, we set the proportional feedback gain
(
SGP
) to 2. As you can see by the plot, the response is slow.
In the next step, we should increase
SGP
until the response is
slightly underdamped.
SGP = 2
Commanded Position
Actual Position
Step 2
With
SGP
equal to 15, the response becomes slightly
underdamped (see plot).
Therefore, we should introduce the velocity feedback gain
(
SGV
) to damp out the oscillation.
SGP = 15
Step 3
With
SGV
equal to 2, the response turns out fairly well
damped (see plot).
At this point, the
SGP
should be raised again until
oscillation or excessive overshoot appears.
SGP = 15
SGV = 2
Step 4
As we iteratively increase
SGP
to 105, overshoot and
chattering becomes significant (see plot). This means either
the
SGV
gain is too low and/or the
SGP
is too high.
Next, we should try raising the
SGV
gain to see if it could
damp out the overshoot and chattering.
SGP = 105
SGV = 2
Step 5
After the
SGV
gain is raised to 2.6, the overshoot was reduced
but chattering is still quite pronounced. This means either
one or both of the gains is too high.
The next step should be to lower the
SGV
gain first.
SGP = 105
SGV = 2.6
Step 6
Lowering the
SGV
gain to 2.3 does not help reduce the
chattering by much.
Therefore, we should lower the
SGP
gain until chattering
stops.
SGP = 105
SGV = 2.3
Step 7
Chattering stops after reducing the
SGP
gain to 85.
However, the overshoot is still a little too high.
The next step should be to try raising the
SGV
to damp out
the overshoot.
SGP = 85
SGV = 2.3
