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PowerBroker2 / ArduPID

PID library for Arduinos with greater accuracy than the legacy Arduino PID library
MIT License
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Zero I term if I coefficient set to zero #11

Closed ptapping closed 1 year ago

ptapping commented 1 year ago

Currently, when setting a finite integral coefficient, the iOut term will reach some value. If the coefficient is then set to zero, the iOut term keeps its last value.

I don't think this is a bug as such, but is unexpected behaviour. For example, if at some point we call setCoefficients(0.0, 0.0, 0.0) we would expect the output to become zero. Instead, the output changes to some non-zero value equal to the current value of iOut. Calling reset() will set iOut to zero and "fix" the problem, but also resets everything else, so isn't a great solution.

This change modifies the line:

double iTemp = iOut + (ki * ((curError + lastError) / 2.0));

to

double iTemp = (iIn == 0.0) ? 0.0 : iOut + (ki * ((curError + lastError) / 2.0));

so that setting the integral coefficient to zero instantly removes its effect from the output. Note that the integral windup limits are still respected in case the integral windup minimum is set > 0 for some reason.

PowerBroker2 commented 1 year ago

This makes sense - thank you!