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MC rate controller: add I term reduction factor #12296

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Jun 22, 2019
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MC rate controller: add I term reduction factor #12296

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bea54d7
mc rate controller: add I term reduction factor
bkueng Apr 17, 2019
8487830
mc airframes: increase I gains a bit
bkueng Jun 17, 2019
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2 changes: 1 addition & 1 deletion ROMFS/px4fmu_common/init.d/airframes/4041_beta75x
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Expand Up @@ -31,7 +31,7 @@ then

param set MC_AIRMODE 2
param set MC_PITCHRATE_D 0.0010
param set MC_PITCHRATE_I 0.4
param set MC_PITCHRATE_I 0.5
param set MC_PITCHRATE_MAX 600
param set MC_PITCHRATE_P 0.0750
param set MC_PITCH_P 6
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2 changes: 1 addition & 1 deletion ROMFS/px4fmu_common/init.d/airframes/4050_generic_250
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Expand Up @@ -17,7 +17,7 @@ if [ $AUTOCNF = yes ]
then
param set MC_ROLL_P 8
param set MC_ROLLRATE_P 0.08
param set MC_ROLLRATE_I 0.2
param set MC_ROLLRATE_I 0.25
param set MC_ROLLRATE_D 0.001
param set MC_PITCH_P 8
param set MC_PITCHRATE_P 0.08
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4 changes: 2 additions & 2 deletions ROMFS/px4fmu_common/init.d/airframes/4052_holybro_qav250
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Expand Up @@ -26,12 +26,12 @@ then

param set MC_AIRMODE 1
param set MC_PITCHRATE_D 0.0012
param set MC_PITCHRATE_I 0.25
param set MC_PITCHRATE_I 0.35
param set MC_PITCHRATE_MAX 1200
param set MC_PITCHRATE_P 0.082
param set MC_PITCH_P 8
param set MC_ROLLRATE_D 0.0012
param set MC_ROLLRATE_I 0.2
param set MC_ROLLRATE_I 0.3
param set MC_ROLLRATE_MAX 1200
param set MC_ROLLRATE_P 0.076
param set MC_ROLL_P 8
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11 changes: 10 additions & 1 deletion src/modules/mc_att_control/mc_att_control_main.cpp
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Expand Up @@ -481,8 +481,17 @@ MulticopterAttitudeControl::control_attitude_rates(float dt)

}

// I term factor: reduce the I gain with increasing rate error.
// This counteracts a non-linear effect where the integral builds up quickly upon a large setpoint
// change (noticeable in a bounce-back effect after a flip).
// The formula leads to a gradual decrease w/o steps, while only affecting the cases where it should:
// with the parameter set to 400 degrees, up to 100 deg rate error, i_factor is almost 1 (having no effect),
// and up to 200 deg error leads to <25% reduction of I.
float i_factor = rates_err(i) / math::radians(400.f);
i_factor = math::max(0.0f, 1.f - i_factor * i_factor);

// Perform the integration using a first order method and do not propagate the result if out of range or invalid
float rate_i = _rates_int(i) + rates_i_scaled(i) * rates_err(i) * dt;
float rate_i = _rates_int(i) + i_factor * rates_i_scaled(i) * rates_err(i) * dt;

if (PX4_ISFINITE(rate_i) && rate_i > -_rate_int_lim(i) && rate_i < _rate_int_lim(i)) {
_rates_int(i) = rate_i;
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