Document reverse acting control using simple_pid

[kjkoster]

Dear All,

Really more of a support question, but can the documentation be enhanced to show how to use simple_pid for reverse acting control?

To add colour: I have a temperature control (aiming for 70°C) for which I control the motor speed (PWM). Lower flow means higher temperatures, higher flow means lower temperatures.

Kees Jan

[juan11iguel]

You need to use negatives gains for all the control actions that you use (proportional, integral, derivative)

I agree that maybe in the README there could be a bit more documentation about the structure of the controller and so on but since it's a classical control strategy you can find a lot of information on Google

Wikipedia, related question in stackoverflow

[juan11iguel]

Checking the README it actually appears to be documented:

To use the PID in reverse mode, meaning that an increase in the input leads to a decrease in the output (like when cooling for example), you can set the tunings to negative values:
pid.tunings = (-1.0, -0.1, 0)
Note that all the tunings should have the same sign.

[kjkoster]

Oh, it is! You are right. Sorry to cause you work.