Automatic tuning

[romainbrette]

We need some methods to automatically adjust bridge and voltage-clamp tunings.

[romainbrette]

What can be automated:

• Capacitance neutralization (current-clamp or I=0)
• TEVC: loop gain, loop lag ()

First step:

• Increase capacitance
• Measure voltage trace
• Look at what changes: increased variance? or oscillations?

[romainbrette]

For the TEVC, there's a PID autotuning library we might be able to use. A classic rule is Ziegler-Nichols. It's based on increasing the gain until we see an oscillation, ie just before it becomes unstable. In fact perhaps we can even use the amplifier oscillation detector.

[romainbrette]

The Z-N rule is the following: measure the gain G at oscillation and the period T of the oscillation. The tunings are: gain = 0.8*G; phase lag = T/8.

[romainbrette]

I have implemented it with pyautogui. It works simply by using the oscillation detection feature, and bisection. Then selects 0.8*C, where C is the critical capacitance. This should be fine in the bath, maybe not so much in the cell.