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ramp in curvature dependent lower period bound

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This commit is contained in:
Thomas Stastny
2021-09-10 17:27:36 +02:00
committed by JaeyoungLim
parent b0dc3a4f51
commit 78d7ddbec7
1 changed files with 43 additions and 26 deletions
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src/lib/npfg/npfg.cpp
+43 -26
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@@ -158,38 +158,55 @@ float NPFG::adaptPeriod(const float ground_speed, const float airspeed, const fl
const float wind_factor = windFactor(airspeed, wind_speed); const float wind_factor = windFactor(airspeed, wind_speed);
if (en_period_lb_) { if (en_period_lb_) {
// lower bound the period for stability w.r.t. roll time constant and current flight condition // lower bound for period not considering path curvature
const float period_lb = periodLB(air_turn_rate, wind_factor, feas_on_track); const float period_lb_zero_curvature = periodLB(0.0f, wind_factor, feas_on_track) * PERIOD_SAFETY_FACTOR;
period = math::max(period_lb * PERIOD_SAFETY_FACTOR, period);
// lower bound for period *considering path curvature
float period_lb = periodLB(air_turn_rate, wind_factor, feas_on_track) * PERIOD_SAFETY_FACTOR;
// recalculate the time constant and track error bound considering the zero
// curvature, lower-bounded period and subsequently recalculate the normalized
// track error
const float time_const = timeConst(period_lb_zero_curvature, damping_);
const float track_error_bound = trackErrorBound(ground_speed, time_const);
const float normalized_track_error = normalizedTrackError(track_error, track_error_bound);
// calculate nominal track proximity with lower bounded time constant
// (only a numerical solution can find corresponding track proximity
// and adapted gains simultaneously)
const float look_ahead_ang = lookAheadAngle(normalized_track_error);
const float track_proximity = trackProximity(look_ahead_ang);
// ramp in curvature dependent lower bound
period_lb = (ramp_in_adapted_period_) ? period_lb * track_proximity + (1.0f - track_proximity) *
period_lb_zero_curvature :
period_lb;
// lower bounded period
period = math::max(period_lb, period);
// only allow upper bounding ONLY if lower bounding is enabled (is otherwise // only allow upper bounding ONLY if lower bounding is enabled (is otherwise
// dangerous to allow period decrements without stability checks) // dangerous to allow period decrements without stability checks).
const float period_ub = periodUB(air_turn_rate, wind_factor, feas_on_track); // NOTE: if the roll time constant is not accurately known, lower-bound
// checks may be too optimistic and reducing the period can still destabilize
// the system! enable this feature at your own risk.
if (en_period_ub_) {
if (en_period_ub_ && PX4_ISFINITE(period_ub) && period > period_ub) { const float period_ub = periodUB(air_turn_rate, wind_factor, feas_on_track);
// NOTE: if the roll time constant is not accurately known, reducing
// the period here can destabilize the system!
// enable this feature at your own risk!
// upper bound the period (for track keeping stability), prefer lower bound if violated if (en_period_ub_ && PX4_ISFINITE(period_ub) && period > period_ub) {
const float period_adapted = math::max(period_lb * PERIOD_SAFETY_FACTOR, period_ub); // NOTE: if the roll time constant is not accurately known, reducing
// the period here can destabilize the system!
// enable this feature at your own risk!
// recalculate time constant and track error bound for lower-bounded // upper bound the period (for track keeping stability), prefer lower bound if violated
// period for normalized track error calculation const float period_adapted = math::max(period_lb, period_ub);
const float time_const = timeConst(period, damping_);
const float track_error_bound = trackErrorBound(ground_speed, time_const);
const float normalized_track_error = normalizedTrackError(track_error, track_error_bound);
// calculate nominal track proximity with lower bounded time constant // transition from the nominal period to the adapted period as we get
// (only a numerical solution can find corresponding track proximity // closer to the track
// and adapted gains simultaneously) period = (ramp_in_adapted_period_) ? period_adapted * track_proximity + (1.0f - track_proximity) * period :
const float look_ahead_ang = lookAheadAngle(normalized_track_error); period_adapted;
const float track_proximity = trackProximity(look_ahead_ang); }
// transition from the nominal period to the adapted period as we get
// closer to the track
period = (ramp_in_adapted_period_) ? period_adapted * track_proximity + (1.0f - track_proximity) * period :
period_adapted;
} }
} }