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StratoBlimp - changes to SITL code with focus on lift #26920

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StratoBlimp - changes to SITL code with focus on lift #26920

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9e7deb6
Update param.py
Dan-field Apr 29, 2024
26bf26b
Added side drag, modified lift simulation
Dan-field Apr 29, 2024
46256aa
Update SIM_StratoBlimp.h
Dan-field Apr 29, 2024
fddfdfe
Update SIM_StratoBlimp.cpp
Dan-field Apr 29, 2024
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15 changes: 8 additions & 7 deletions Tools/autotest/param_metadata/param.py
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Expand Up @@ -115,24 +115,25 @@ def has_param(self, pname):
'dB' : 'decibel' ,
# compound

'kB' : 'kilobytes' ,
'MB' : 'megabyte' ,
'kB' : 'kilobytes' ,
'MB' : 'megabyte' ,
'm.m/s/s' : 'square meter per square second',
'deg/m/s' : 'degrees per meter per second' ,
'm/s/m' : 'meters per second per meter' , # Why not use Hz here ????
'mGauss/A': 'milligauss per ampere' ,
'mAh' : 'milliampere hour' ,
'mAh' : 'milliampere hour' ,
'A/V' : 'ampere per volt' ,
'm/V' : 'meters per volt' ,
'gravities': 'standard acceleration due to gravity' , # g_n would be a more correct unit, but IMHO no one understands what g_n means
'octal' : 'octal' ,
'RPM' : 'Revolutions Per Minute',
'kg' : 'kilograms',
'kg' : 'kilograms' ,
'kg/m/m' : 'kilograms per square meter', # metre is the SI unit name, meter is the american spelling of it
'kg/m/m/m': 'kilograms per cubic meter',
'litres' : 'litres',
'Ohm' : 'Ohm',
'N' : 'Newtons',
'm^3' : 'cubic meters' , # metre is the SI unit name, meter is the american spelling of it
'litres' : 'litres' ,
'Ohm' : 'Ohm' ,
'N' : 'Newtons' ,
}

required_param_fields = [
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43 changes: 30 additions & 13 deletions libraries/SITL/SIM_StratoBlimp.cpp
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Expand Up @@ -60,10 +60,15 @@ const AP_Param::GroupInfo StratoBlimp::var_info[] = {
// @Description: drag on X axis
AP_GROUPINFO("DRAG_FWD", 5, StratoBlimp, drag_fwd, 0.27),

// @Param: DRAG_SIDE
// @DisplayName: drag in sidewards direction
// @Description: drag on Y axis
AP_GROUPINFO("DRAG_SIDE", 16, StratoBlimp, drag_side, 0.5),

// @Param: DRAG_UP
// @DisplayName: drag in upward direction
// @Description: drag on Z axis
AP_GROUPINFO("DRAG_UP", 6, StratoBlimp, drag_up, 0.1),
AP_GROUPINFO("DRAG_UP", 6, StratoBlimp, drag_up, 0.4),

// @Param: MOI_YAW
// @DisplayName: moment of inertia in yaw
Expand All @@ -87,10 +92,10 @@ const AP_Param::GroupInfo StratoBlimp::var_info[] = {
AP_GROUPINFO("ALT_TARG", 10, StratoBlimp, altitude_target, 20000),

// @Param: CLMB_RT
// @DisplayName: climb rate
// @Description: climb rate
// @DisplayName: target climb rate
// @Description: target climb rate
// @Units: m/s
AP_GROUPINFO("CLMB_RT", 11, StratoBlimp, climb_rate, 5),
AP_GROUPINFO("CLMB_RT", 11, StratoBlimp, target_climb_rate, 5),

// @Param: YAW_RT
// @DisplayName: yaw rate
Expand All @@ -114,7 +119,18 @@ const AP_Param::GroupInfo StratoBlimp::var_info[] = {
// @DisplayName: weathervaning offset
// @Description: center of drag for weathervaning
// @Units: m
AP_GROUPINFO("WVANE", 15, StratoBlimp, center_of_drag, 2),
AP_GROUPINFO("WVANE", 15, StratoBlimp, center_of_drag, 0.3),

// @Param: ENV_VOL
// @DisplayName: envelope volume
// @Description: volume of the envelope when full
// @Units: m^3
AP_GROUPINFO("ENV_VOL", 17, StratoBlimp, envelope_volume, 1545),

// @Param: FLR
// @DisplayName: free lift ratio
// @Description: amount of free lift generated by helper balloons, as a proportion of vehicle mass
AP_GROUPINFO("FLR", 18, StratoBlimp, free_lift_ratio, 0.12),

AP_GROUPEND
};
Expand Down Expand Up @@ -201,14 +217,15 @@ float StratoBlimp::get_lift(float altitude)
// start with neutral buoyancy
float lift_accel = GRAVITY_MSS;

// assume lift will equal drag at the given climb rate
float climb_accel = 0.5 * air_density * sq(climb_rate) * drag_up;

// ramp down lift as we approach target alt
lift_accel += linear_interpolate(climb_accel, 0,
altitude,
altitude_target-1000, altitude_target);

// add helper balloon if it's still attached
if (helper_balloon_attached) {
// the helper balloon adds an amount of lift based on free lift ratio
lift_accel += GRAVITY_MSS*free_lift_ratio;
// detach helper balloon if the target altitude has been reached
if (altitude >= altitude_target) {
helper_balloon_attached = false;
}
}
return mass * lift_accel;
}

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6 changes: 5 additions & 1 deletion libraries/SITL/SIM_StratoBlimp.h
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Expand Up @@ -61,15 +61,17 @@ class StratoBlimp : public Aircraft {
float EAS2TAS;
float drag_yaw;
bool released;
bool helper_balloon_attached = true;

AP_Float mass;
AP_Float helium_mass;
AP_Float arm_length;
AP_Float motor_thrust;
AP_Float drag_fwd;
AP_Float drag_side;
AP_Float drag_up;
AP_Float altitude_target;
AP_Float climb_rate;
AP_Float target_climb_rate;
AP_Float turn_rate;
AP_Float motor_angle;
AP_Float yaw_rate_max;
Expand All @@ -78,6 +80,8 @@ class StratoBlimp : public Aircraft {
AP_Float moi_pitch;
AP_Float center_of_lift;
AP_Float center_of_drag;
AP_Float envelope_volume;
AP_Float free_lift_ratio;
};

}
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