If you find that you have turned the Derivative Gain to maximum, and overshoot is still occurring,
then you have set the Proportional Gain too high. If this occurs, turn the Derivative Gain BACK TO
MINIMUM, then decrease the Proportional Gain a bit and try Step 6 again.
7. When overshoot has been eliminated, measure the response time once again. You should see a
marked improvement, as shown in Figure 7.
8. When the overshoot is corrected, try to increase the Proportional Gain some more, until a slight
overshoot occurs. The see if additional Derivative Gain will correct it. You should soon reach a point
where response time cannot be improved any further.
9. Cycle the system several times, using the step input, to see whether the adjustments are stable. If
occasional overshoot is noted, decrease the Proportional Gain SLIGHTLY, until this stops occurring.
10. When the Derivative Gain is set satisfactorily, you can then attempt to set the Integral Gain to
eliminate any steady state error.
Remember that you want the Integral Gain to be disabled (RESET) during the dynamic part of the
motion cycle.
If Integral Gain is improperly timed, the overshoots will return. This is usually caused by the
interaction between the Derivative and Integral terms, as they "fight" each other for control.
If Integral Gain is set too high, you may even lose control of the system as it oscillates out of control. If
this occurs, shut down the amplifier, turn the Integral Gain back to minimum, and start again.
When in doubt, set the Integral Gain on the LOW side, since it tends to LESSEN THE STABILITY of a
closed loop system.
11. Watch the system carefully through the first few days of operation, to ensure that you have not set
the gains too high. Some performance "drift" can be expected as the hydraulic fluid changes
temperature or as new mechanical components "wear-in," producing the need for some "fine tuning"
later on.
Figure 2. Set-up command signal
Figure 3. Increasing Proportional Gain.
Installation Guide
Servo Amplifier
PID Set-Up Procedure
©
Danfoss | August 2023
BC459665217198en-000101 | 15
