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Update autotune comments, defaults and functional description. Add

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reference to sources.
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Dominic Clifton 2014-05-28 20:36:53 +01:00
parent 7ec0df8abe
commit 5913266ce0
1 changed files with 48 additions and 11 deletions
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59
src/flight_autotune.c
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@ -12,14 +12,51 @@
extern int16_t debug[4];
// To adjust how aggressive the tuning is, adjust the AUTOTUNEMAXOSCILLATION value. A larger
// value will result in more aggressive tuning. A lower value will result in softer tuning.
// It will rock back and forth between -AUTOTUNE_TARGET_ANGLE and AUTOTUNE_TARGET_ANGLE degrees
// AUTOTUNE_D_MULTIPLIER is a multiplier that puts in a little extra D when autotuning is done. This helps damp
// the wobbles after a quick angle change.
// Always autotune on a full battery.
/*
* Authors
* Brad Quick - initial implementation in BradWii
* Dominic Clifton - baseflight port & cleanup.
*
* Autotune in BradWii thread here: http://www.rcgroups.com/forums/showthread.php?t=1922423
*
* We start with two input parameters. The first is our target angle. By default it's 20 degrees, so we will bank to 20 degrees,
* see how the system reacts, then bank to -20 degrees and evaluate again. We repeat this over and over. The second input is
* how much oscillation we can tolerate. This can range from 2 degrees to 5 or more degrees. This defaults to 4 degrees. The
* higher this value is, the more agressive the result of the tuning will be.
*
* First, we turn the I gain down to zero so that we don't have to try to figure out how much overshoot is caused by the I term
* vs. the P term.
*
* Then, we move to the target of 20 degrees and analyze the results. Our goal is to have no overshoot and to keep the bounce
* back within the 4 degrees. By working to get zero overshoot, we can isolate the effects of the P and D terms. If we don't
* overshoot, then the P term never works in the opposite direction, so we know that any bounce we get is caused by the D term.
*
* If we overshoot the target 20 degrees, then we know our P term is too high or our D term is too low. We can determine
* which one to change by looking at how much bounce back (or the amplitude of the oscillation) we get. If it bounces back
* more than the 4 degrees, then our D is already too high, so we can't increase it, so instead we decrease P.
*
* If we undershoot, then either our P is too low or our D is too high. Again, we can determine which to change by looking at
* how much bounce we get.
*
* Once we have the P and D terms set, we then set the I term by repeating the same test above and measuring the overshoot.
* If our maximum oscillation is set to 4 degrees, then we keep increasing the I until we get an overshoot of 2 degrees, so
* that our oscillations are now centered around our target (in theory).
*
* In the BradWii software, it alternates between doing the P and D step and doing the I step so you can quit whenever you
* want without having to tell it specifically to do the I term. The sequence is actually P&D, P&D, I, P&D, P&D, I...
*
* Note: The 4 degrees mentioned above is the value of AUTOTUNE_MAX_OSCILLATION. In the BradWii code at the time of writing
* the default value was 1.0f instead of 4.0f.
*
* To adjust how aggressive the tuning is, adjust the AUTOTUNEMAXOSCILLATION value. A larger value will result in more
* aggressive tuning. A lower value will result in softer tuning. It will rock back and forth between -AUTOTUNE_TARGET_ANGLE
* and AUTOTUNE_TARGET_ANGLE degrees
* AUTOTUNE_D_MULTIPLIER is a multiplier that puts in a little extra D when autotuning is done. This helps damp the wobbles
* after a quick angle change.
* Always autotune on a full battery.
*/
#define AUTOTUNE_MAX_OSCILLATION 1.0f
#define AUTOTUNE_MAX_OSCILLATION_ANGLE 4.0f
#define AUTOTUNE_TARGET_ANGLE 20.0f
#define AUTOTUNE_D_MULTIPLIER 1.2f
#define AUTOTUNE_SETTLING_DELAY_MS 250 // 1/4 of a second.
@ -154,7 +191,7 @@ float autotune(angle_index_t angleIndex, const rollAndPitchInclination_t *inclin
} else if (secondPeakAngle > 0) {
if (cycleCount == 0) {
// when checking the I value, we would like to overshoot the target position by half of the max oscillation.
if (currentAngle - targetAngle < AUTOTUNE_MAX_OSCILLATION / 2) {
if (currentAngle - targetAngle < AUTOTUNE_MAX_OSCILLATION_ANGLE / 2) {
pid.i *= AUTOTUNE_INCREASE_MULTIPLIER;
} else {
pid.i *= AUTOTUNE_DECREASE_MULTIPLIER;
@ -189,7 +226,7 @@ float autotune(angle_index_t angleIndex, const rollAndPitchInclination_t *inclin
bool timedOut = signedDiff >= 0L;
// stop looking for the 2nd peak if we time out or if we change direction again after moving by more than half the maximum oscillation
if (timedOut || (oscillationAmplitude > AUTOTUNE_MAX_OSCILLATION / 2 && currentAngle > firstPeakAngle)) {
if (timedOut || (oscillationAmplitude > AUTOTUNE_MAX_OSCILLATION_ANGLE / 2 && currentAngle > firstPeakAngle)) {
// analyze the data
// Our goal is to have zero overshoot and to have AUTOTUNEMAXOSCILLATION amplitude
@ -198,7 +235,7 @@ float autotune(angle_index_t angleIndex, const rollAndPitchInclination_t *inclin
debug[0] = 1;
#ifdef PREFER_HIGH_GAIN_SOLUTION
if (oscillationAmplitude > AUTOTUNE_MAX_OSCILLATION) {
if (oscillationAmplitude > AUTOTUNE_MAX_OSCILLATION_ANGLE) {
// we have too much oscillation, so we can't increase D, so decrease P
#endif
pid.p *= AUTOTUNE_DECREASE_MULTIPLIER;
@ -214,7 +251,7 @@ float autotune(angle_index_t angleIndex, const rollAndPitchInclination_t *inclin
// undershot
debug[0] = 2;
if (oscillationAmplitude > AUTOTUNE_MAX_OSCILLATION) {
if (oscillationAmplitude > AUTOTUNE_MAX_OSCILLATION_ANGLE) {
// we have too much oscillation
pid.d *= AUTOTUNE_DECREASE_MULTIPLIER;
} else {