Our new 2W Mephisto has a pretty zippy "SLOW" temperature input. Tuning the perl PID servo, I found that the best response came from setting
the "P" and "D" terms to zero. This is because the internal temperature stabilization servo has a fairly high UGF. In the attached
image you can see how the open loop step response looks (loop is open then the "KI" parameter is set to zero). The internal servo
really has too little damping. There is a 30% overshoot when it gets a temperature step. For this kind of servo Innolight would have done better
to back off on the gain until they got back some phase margin.
New SLOW parameters:
timestep = 1.9 s
KP = 0
KI = 0.035
KD = 0
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