Delta RMC151 - Manual (Page 976)

RMC70/150 and RMCTools User Manual
General
This gain helps compensate for changing system dynamics, such as varying loads, and
often aids the axis in rapidly reaching the Command Position or Command Velocity. A low
gain slows the response of the axis to changes and may keep the axis from reaching the
Command Position or Command Velocity. A gain that is too high may make the axis
oscillate.
The Integral Gain controls how much of the Control Output is generated due to the
accumulated Position Error or Velocity Error while in position control or velocity control,
respectively. Position control is defined as when the Current Control Mode is Position PID.
Velocity control is defined as when the Current Control Mode is Velocity PID.
Each gain of the axis contributes to the Control Output. The contribution from the Integral
Gain is called the Integral Output Term. For both PID and I-PD, each control loop, the
Integral Gain is multiplied by the control loop time and Position Error or Velocity Error and
added to the Integral Output Term. The Integral Output term is added to the PFID
Output.
See the Tuning topic for details on how to properly adjust the Integral Gain.
The Integral Gain may be disabled or only be allowed to decrease the Integral output
Term under certain conditions. See below for more details.
Advanced: I-PD
This gain is the most important gain for I-PD control. It must be non-zero in I-PD mode.
If it is zero, it will cause a run-time error. A higher value will increase the response. A
value that is too high will cause oscillation and instability.
Special Conditions
Integrator Hold
The Integral Gain can be disabled by the user by setting the Integrator Mode to Always
Held. The Integrator Output Term will be held at the value at the time it was set.
The Integrator Hold does not apply to Position I-PD or Velocity I-PD, since the integrator
is an important part of the I-PD control.
Integrator Adjust
The Integral Output Term can be manually adjusted with the Integrator Adjust (70)
command. This is useful for clearing it if it has "wound up" for some reason. See the
Integrator Adjust (70) topic for more details.
Integral Gain is Zero
If the Integral Gain is zero, the Integral Output Term will be set to zero.
Output Limiting
When the PFID Output reaches it's maximum value, the Integral Output Term may be
reduced to limit the PFID Output. This helps to avoid overshoot. This applies to all control
modes.
Example:
If the Proportional Output Term is 60%, the Integral Output Term is 10%, the
Differential Output Term is 10%, the Velocity Feed Forward is 25%, and the
Acceleration Feed Forward is 0%, then the total is 105%. This will be limited to
100%, so the Integral Output Term will be set to 5%.
Wind-Down Only
In the Position PID control mode, the Integral Output Term will only be allowed to
decrease in the following conditions:.
• Within Deadband Window
When the target is stopped, and the Position Error is less than the Deadband
Tolerance, the Integral Output Term will only be allowed to wind down. In systems
956 Delta Computer Systems, Inc.