aerodynamic attitude control in very low earth orbit · 1.5 1 0-1 100 50 0-50 [deg] 80 40 0-40...
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Aerodynamic Attitude Control in Very Low Earth OrbitPhD Researcher: Miss Sabrina LivadiottiSupervisors: Dr Peter Roberts, Dr Nicholas Crisp
Revolutionizing Earth Observation with sustained operations at lower altitudes than the current state of the art.
Robustness - Inertia matrix Possible applicationsAssumptions
Applied control strategies
Proposed manoeuvres
Geometry - SOAR
Background Results
Aerodynamic Pointing & Trim : Pitch & Yaw
Aerodynamic Momentum Management
Aerodynamic Pointing & Trim : Roll
1. Discrete time domain implementation;2. Environmental disturbances;3. Accommodation coefficients linearly varying with altitude (0.9 to 1) - Sentman model;4. Horizontal thermospheric winds; 5. Panels deflection rates: 30°/s;6. Gyroscopes attitude error knowledge: standard deviation 1σ;7. Disturbance introduced on total angular momentum by rotating panels;8. Software limitations.
1. Small satellites: aerodynamic control to support pointing tasks when the control authority provided by conventional actuators is reduced;2. To perform target acquisition below 250 km, where the control effort required is demanding and RWs saturate quickly;3. To perform the momentum management task without interrupting the pointing task;4. To counteract the perturbation introduced in yaw by atmospheric co-rotation, reducing RWs effort; 5. To achieve aerodynamic rejection of the environmental disturbances affecting the satellite.
Aerodynamic momentum managementAerodynamic pointing & trim
Modified PID & intelligent integrator [1,2] Linear quadratic regulator
1. Aerodynamic roll control combined with reaction wheels (RWs) pitch & yaw control;
2. Aerodynamic pitch & yaw control combined with RWs roll control;
3. Aerodynamic trim;
4. Management of the angular momentum stored in the RWs by means of aerodynamic torques.
1. 3U CubeSat main body;2. Aerostable feathered configuration;3. Aerodynamic control panels extending at the rear of the satellite main body.
The enhanced aerodynamic environment experienced by satellites in VLEO (i.e. below 450 km) offers the opportunity to investigate the feasibility of exotic strategies employing aerodynamic torques to perform attitude control tasks.
Challenges 1. Density & thermospheric winds estimation;2. Gas-surface interaction uncertainties;3. Aerodynamic control authority variations with altitude;4. Control law robustness;5. Hardware & software limitations.
[1] H. Bang, M. J. Tahk, H. D. Choi, "Large angle attitude control of spacecraft with actuator saturation", Control Eng. Pract., vol. 11, no. 9, pp. 989-997, 2003. [2] B. Wie, H. Weiss, A. Arapostathis, "Quaternion feedback regulator for spacecraft eigenaxis rotations", J. Guid. Control Dyn. 12, pp. 375-380, 1989, doi: 10.2514/3.20418.[3] F. L. Markley and J. L. Crassidis, "Fundamentals of spacecraft attitude determination and control", 2014.
[4] D. A. Vallado and W.D. McClain, "Fundamentals of Astrodynamics and Applications", New York, McGraw-Hill Companies Inc., 1997.
[Background] Giacomo Balla, "Mercury passing before the Sun", 1914, 120 x 100 cm, Oil Painting, Peggy Guggenheim Collection (on long-term loan), Venezia
The DISCOVERER project has received funding from the European Union's Horizon 2020 research and innovation programme under agreement No 737183.
Discaimer: this works reflects only the views of the authors. The European Commission is not liable for any use that may be made of the information contained therein.
Body Angular Rates
Reaction Wheels Torque
Y Panels Orientation
[deg
][N
m]
Time [min]
Z Panels Orientation
LVLH Attitude
6 8 10 12 14 16 18 200 2 4
6 8 10 12 14 16 18 200 2 4
6 8 10 12 14 16 18 200 2 4
6 8 10 12 14 16 18 200 2 4
6 8 10 12 14 16 18 200 2 4
100
-100
0
[deg
]
100
-100
0
[deg
]1
0.5
-0.5
-1.5
x10-5[d
eg/s
]
0.2
0
-0.2
-0.4
10
0
-10
0
-1
50
50
-50
-50
Modified PID: Nominal Case Modified PID: Off-Nominal Case
Regular PID: Nominal Case Regular PID: Off-Nominal Case
Time [min]Time [min]
Time [min] Time [min]
[deg
]
[deg
]
[deg
]
[deg
]
20
15
10
5
0
-5
-10
-15
-200 5 10 15 20
20
15
10
5
0
-5
-10
-15
-20
20
15
10
5
0
-5
-10
-15
-200 5 10 15 20
0 5 10 15 20
0 5 10 15 20
200
150
100
50
-50
-100
-150
-200
[
kg m2.I = 0.1275 0.0001 0.0030.0001 0.1266 0 0.003 0 0.1866[
0
[
kg m2.I = 0.057 0 0 0 0.074 0 0 0 0.074[
[
kg m2.I = 0.057 0 0 0 0.074 0 0 0 0.074[ [
kg m2.I = 0.1275 0.0001 0.0030.0001 0.1266 0 0.003 0 0.1866[
0 10 20 30 40 50 60 70
0 10 20 30 40 50 60 70
0 10 20 30 40 50 60 70
[deg
][N
ms]
[deg
/s]
40
20
0
-20
-40
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
2
0
-1
-2
Reaction Wheels Angular Momentum
Body Angular Rates
LVLH Attitude
1
Time [min]
x10-3
No Momentum Management
Reaction Wheels Angular Momentum
LVLH Attitude
Z Panels Orientation
Y Panels Orientation
[deg
][d
eg]
[Nm
s]
100 1200 20 40 60 80
100 1200 20 40 60 80
100 1200 20 40 60 80
100 1200 20 40 60 80
Time [min]
0
10
20
-10
-20
x10-31.5
1
0
-1
100
50
0
-50
[deg
]
80
40
0
-40
0.5
-0.5
-1.5
60
20
-20
With Momentum Management
LVLH Attitude
Body Angular Rates
Reaction Wheels Torque
Y Panels Orientation
Z Panels Orientation
Time [min]
[deg
][d
eg/s
][N
m]
6 8 10 12 14 16 18 200 2 4
0
-40
0.5
0
-0.5
1
0
-1
x10-5
[deg
]
100
0
-100
[deg
]
100
0
-100
6 8 10 12 14 16 18 200 2 4
6 8 10 12 14 16 18 200 2 4
6 8 10 12 14 16 18 200 2 4
6 8 10 12 14 16 18 200 2 4
-20
0.5
-0.5
50
50
-50
-50