Cannot Find Acceptable PID Design in Simulated Model
When you run your Simulink® model using the PID gains computed by PID Tuner, the simulation output may not meet your design requirements.
How to Fix It
Sometimes, PID control is not adequate to meet the control requirements for your plant. If you cannot find a design that meets your requirements when you simulate your model, consider designing a more complex controller using Control System Designer.
If you have enabled saturation limits in the PID Controller block without antiwindup circuitry, enable antiwindup circuitry. You can enable antiwindup circuitry in two ways:
Activate the PID Controller block antiwindup circuitry on the PID Advanced tab of the block dialog box.
Use the PID Controller block tracking mode to implement your own antiwindup circuitry external to the block. Activate the PID Controller block tracking mode on the PID Advanced tab of the block dialog box.
To learn more about both ways of implementing antiwindup circuitry, see Anti-Windup Control Using PID Controller Block.
After enabling antiwindup circuitry, run the simulation again to see whether controller performance is acceptable.
If the loop response is still unacceptable, try slowing the response of the PID controller. To do so, reduce the response time or the bandwidth in PID Tuner. See Refine the Design.
You can also try implementing gain-scheduled PID control to help account for nonlinearities in your system. See Design Family of PID Controllers for Multiple Operating Points and Implement Gain-Scheduled PID Controllers.
If you still cannot get acceptable performance with PID control, consider using a more complex controller. See Control System Designer.