Parker Hannifin SERVO CONTROLLER OEM6250 - Manual (Page 50)

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