The “Integral Limit (%)” is the limit for the integral part of a PI or PID controller which is used to eliminate the stationery error (and will manage to do that provided the output of the controller is not saturated).

At the beginning of a motion, where the error is rather large (the reference has started but the motor did not start yet) the output of the controller is given mostly by the proportional part, but as the error gets lower so the proportional part output of the controller, and if we imagine a system with some friction, we can have the situation where the error is rather small (a few encoder counts) and the proportional part output is too small to move the motor to compensate for this error.

If Kp is increased such that even for small errors the output of the controller is high enough to move the motor, then most likely the motor will have continuous oscillations. The integral part on the other side, is slowly increasing the output of the controller, until the motor starts moving – as soon as the error decreases the output of the controller will slowly decrease.

If the Ki is too high then the system will start to oscillate, and if it’s too low it could take too long to reduce the stationery error. The Ki, will control how fast the output of the controller will increase based on the error, while the limit (%) will allow how much to increase in percents of the total controller output.

The TML variable for the integral limit is:

• IMAXP for Position Controller
• IMAXS for Speed Controller

The relation for IMAXP depends on the actual control structure:

• For systems where only the position and current loops are closed then the IMAXP parameter is computed as:
                     IMAXP= 32767 – IPSatP[%]/100 x CrtLimit x 65520 / (2 x ImaxPS)
  where the IPSatP[%] is the integral limit for position controller and is given by the user in the Drive Setup dialog, CrtLimit is the current limit set in the Drive Setup dialog and ImaxPS is the maximum measurable current for a given drive. The ImaxPS can be visualized in the Drive Info dialog
•  For systems where the position, velocity and current loops are closed then the IMAXP parameter is computed as:
  IMAXP= 32767 – IPSatP[%]/100 x SpdLimit x Kvf
  where the IPSatP[%] is the integral limit for position controller and is given by the user in the Drive Setup dialog, SpdLimit is the speed limit set in the Drive Setup dialog and Kvf is the speed scaling factor. The speed scaling factor depends on the speed feedback mounted on the motor. For a given configuration (drive, motor and feedback) the speed scaling factor can be visualized in the on-line help of EasyMotion Studio/EasySetUp with Help | Help Topics | Application Programming | Internal Units and Scaling Factors, respectively Help | Help Topics | Setup Data Management | Internal Units and Scaling factors.

If the integral limit is 0% (meaning that the integral part is disabled) the IMAXP is 32767. Hence, higher values for the integral limit mean smaller values for IMAXP.