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Fixed Wing: Compensate minimum sink rate based on weight ratio and air density #22049

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Fixed Wing: Compensate minimum sink rate based on weight ratio and air density #22049

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d6a770a
FixedWingPositionControl: compensate minimum sink rate for weight and…
RomanBapst Sep 6, 2023
f7d7a71
addressed review comments
RomanBapst Sep 11, 2023
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16 changes: 13 additions & 3 deletions src/modules/fw_pos_control/FixedwingPositionControl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -94,16 +94,21 @@ FixedwingPositionControl::init()
return true;
}

float FixedwingPositionControl::getMaximumClimbRate()
float FixedwingPositionControl::getWeightRatio()
{

float weight_factor = 1.0f;

if (_param_weight_base.get() > 0.0f && _param_weight_gross.get() > 0.0f) {
weight_factor = math::constrain(_param_weight_base.get() / _param_weight_gross.get(), MIN_WEIGHT_RATIO,
weight_factor = math::constrain(_param_weight_gross.get() / _param_weight_base.get(), MIN_WEIGHT_RATIO,
MAX_WEIGHT_RATIO);
}

return weight_factor;
}

float FixedwingPositionControl::getMaximumClimbRate()
{
float climbrate_max = _param_fw_t_clmb_max.get();

const float density_min = _param_density_min.get();
Expand All @@ -116,7 +121,12 @@ float FixedwingPositionControl::getMaximumClimbRate()
climbrate_max = _param_fw_t_clmb_max.get() + density_gradient * delta_rho;
}

return climbrate_max * weight_factor;
return climbrate_max / getWeightRatio();
}

float FixedwingPositionControl::getMinimumSinkRate()
{
return _param_fw_t_sink_min.get() * sqrtf(getWeightRatio() * CONSTANTS_AIR_DENSITY_SEA_LEVEL_15C / _air_density);
}

int
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17 changes: 17 additions & 0 deletions src/modules/fw_pos_control/FixedwingPositionControl.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -488,7 +488,24 @@ class FixedwingPositionControl final : public ModuleBase<FixedwingPositionContro
*/
float get_terrain_altitude_takeoff(float takeoff_alt);

/**
* @brief Return the maximum climb rate achievable under the current conditions.
* @return Maximum climbrate.
*/
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thanks for writing a brief - can you list the conditions that are considered, and can you add units to the @return?

float getMaximumClimbRate();

/**
* @brief Return the minimum sink rate achievable under the current conditions.
* @return Minimum sink rate.
*/
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same comment

float getMinimumSinkRate();

/**
* @brief Return the ratio of actual vehicle weight to vehicle base weight.
* @return Weight ratio.
*/
float getWeightRatio();

/**
* @brief Maps the manual control setpoint (pilot sticks) to height rate commands
*
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