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FW raise min airspeed based on commanded bank (#7575)

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This commit is contained in:
Daniel Agar
2017-09-19 11:06:40 -04:00
committed by GitHub
parent 3498fe0c6f
commit 9cd915949a
1 changed files with 24 additions and 1 deletions
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src/modules/fw_pos_control_l1/FixedwingPositionControl.cpp
+24 -1
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@@ -405,9 +405,32 @@ FixedwingPositionControl::get_demanded_airspeed()
float
FixedwingPositionControl::calculate_target_airspeed(float airspeed_demand)
{
/*
* Calculate accelerated stall airspeed factor from commanded bank angle and use it to increase minimum airspeed.
*
* We don't know the stall speed of the aircraft, but assuming user defined
* minimum airspeed (FW_AIRSPD_MIN) is slightly larger than stall speed
* this is close enough.
*
* increase lift vector to balance additional weight in bank
* cos(bank angle) = W/L = 1/n
* n is the load factor
*
* lift is proportional to airspeed^2 so the increase in stall speed is
* Vsacc = Vs * sqrt(n)
*
*/
float adjusted_min_airspeed = _parameters.airspeed_min;
if (_airspeed_valid && PX4_ISFINITE(_att_sp.roll_body)) {
adjusted_min_airspeed = constrain(_parameters.airspeed_min / sqrtf(cosf(_att_sp.roll_body)), _parameters.airspeed_min,
_parameters.airspeed_max);
}
// add minimum ground speed undershoot (only non-zero in presence of sufficient wind)
// sanity check: limit to range
return constrain(airspeed_demand + _groundspeed_undershoot, _parameters.airspeed_min, _parameters.airspeed_max);
return constrain(airspeed_demand + _groundspeed_undershoot, adjusted_min_airspeed, _parameters.airspeed_max);
}
void