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improve comments in PID tuning

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David P Hilton
2018-11-09 07:45:06 -07:00
parent f4e2de4608
commit ad4569fc4b
2 changed files with 9 additions and 5 deletions
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10
workspace/TS100/src/main.cpp
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@@ -954,11 +954,13 @@ void startPIDTask(void const *argument __unused) {
// P term - total power needed to hit target temp next cycle. // P term - total power needed to hit target temp next cycle.
// thermal mass = 1690 milliJ/*C for my tip. // thermal mass = 1690 milliJ/*C for my tip.
// = Watts*Seconds to raise Temp from room temp to +100*C, divided by 100*C. // = Watts*Seconds to raise Temp from room temp to +100*C, divided by 100*C.
// divided by 20 to let I term dominate near set point. // we divide milliWattsNeeded by 20 to let the I term dominate near the set point.
// I should retune this, but don't want to do it until // This is necessary because of the temp noise and thermal lag in the system.
// the feed-forward temp adjustment is in place. // Once we have feed-forward temp estimation we should be able to better tune this.
const uint16_t mass = 1690 / 20; const uint16_t mass = 1690 / 20; // divide here so division is compile-time.
int32_t milliWattsNeeded = tempToMilliWatts(tempError.average(), mass, rawC); int32_t milliWattsNeeded = tempToMilliWatts(tempError.average(), mass, rawC);
// note that milliWattsNeeded is sometimes negative, this counters overshoot
// from I term's inertia.
milliWattsOut += milliWattsNeeded; milliWattsOut += milliWattsNeeded;
// I term - energy needed to compensate for heat loss. // I term - energy needed to compensate for heat loss.

4
workspace/TS100/src/power.cpp
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@@ -16,7 +16,9 @@ history<uint16_t, oscillationPeriod> milliWattHistory = {{0}, 0, 0};
int32_t tempToMilliWatts(int32_t rawTemp, uint16_t mass, uint8_t rawC) { int32_t tempToMilliWatts(int32_t rawTemp, uint16_t mass, uint8_t rawC) {
// mass is in milliJ/*C, rawC is raw per degree C // mass is in milliJ/*C, rawC is raw per degree C
// returns milliWatts needed to raise/lower a mass by rawTemp
// degrees in one cycle.
int32_t milliJoules = mass * rawTemp / rawC; int32_t milliJoules = mass * rawTemp / rawC;
return milliJoules * hz; return milliJoules * hz;
} }