PID Feedback Control

1. This plug-in relies on the simple-pid (v2+) library. Install it (don’t forget to conda activate scopefoundry if necessary):

   pip install simple-pid
   

2. Add PIDFeedbackControl to your app:

   # fancy_app.py
   from ScopeFoundry import BaseMicroscopeApp
   
   
   class FancyApp(BaseMicroscopeApp):
   
       name = "fancy_app"
   
       def setup(self):
   
           from ScopeFoundry.controlling import PIDFeedbackControl
           self.add_measurement(PIDFeedbackControl)
   

3. Refer to the following figure to define the control:
   

   a) The system used in this example: a laser beam from the OPO is controlled by a motorized ND filter wheel (“Plant”). The power of the laser beam is monitored at a pickoff location using a power meter (“Sensor”). (Ignore the rest of figure a).)

   b) Control loop diagram. It is a standart PID feeback control except that the range of input to the plant are constrained (min/max block).

   c) The GUI of PIDFeedbackControl:

   • Define the setpoint.
   • plant_input (position of the motor of the ND filter wheel, side_beam_power_wheel).
   • sensor is the power readout of a power meter (thorlabs_powermeter as a sensor) by moving an ND density filter wheel (as the plant).
   • The PID controller with the usual 3 parameters.
   • Note that the input to the plant can be constrained by (min_plant_input, max_plant_input).
   • Lastly, you can define when the measurement terminates.