Sensors for orientation and control of satellites and space probes

Transcription

1 Sensors for orientation and control of satellites and space probes Ing. Ondrej Závodský GOSPACE s.r.o. ESA Contract No /16NL/NDe Specialized lectures

2 Content 1) How to determine the orientation of the satellite? Sensors Calibration Sensor fusion 2) How to control the orientation of the satellite? Passive systems Magnetorquers B-dot algorithm Testing with 3D helmholtz coils system Reaction wheel

3 Gyroscope Measure angular velocity Types MEMS vibrating structure Optical gyroscopes Sensors

4 MEMS vibrating gyroscope Uses Coriolis force Hurricanes Toilets Sensors

5 MEMS vibrating gyroscope Uses Coriolis force Sensors

6 Optical gyroscope Sensors Developed soon after the discovery of laser technology Operate under the principle of the Sagnac effect 6

7 Optical gyroscope Polarised light interference Sensors 7

8 Gyroscope main parameters Sensitivity [deg/s] Noise [deg/s] Bandwidth [Hz] Full-scale [deg/s] Zero drift and temperature drift [deg/s] Sensitivity drift Cross-axis Sensors 8

9 Magnetometer Measure three-axis magnetic field Possible detect position relative to the Earth IGRF or WMM2015 model Types Fluxgate AMR Hall-effect Sensors

10 Fluxgate magnetometer Uses saturation of high permeable core Very high sensitivity (up to 1nT) Sensors 10

11 Fluxgate magnetometer Sensors 11

12 Fluxgate magnetometer Sensors 12

13 Sensors 13

14 AMR (Anisotropic Magnetoresistance) Sensors Changes the value of its electrical resistance in an externally-applied magnetic field. 14

15 AMR (Anisotropic Magnetoresistance) Sensors 15

16 AMR (Anisotropic Magnetoresistance) Null-field offsets Sensors 16

17 AMR (Anisotropic Magnetoresistance) Temperature drift Sensors 17

18 AMR (Anisotropic Magnetoresistance) Set/reset procedure Sensors Reduces null-field offset and temperature drift offset 18

19 Magnetometer main parameters Sensitivity [ut or Gauss] (1gauss = 100uT) Noise [ut] Bandwidth [Hz] Full-scale [ut] Zero drift [ut] Temperature drift [ut/ C] Sensitivity drift [%/ C] Cross-axis [%] Sensors 19

20 Earth sensor 16x4 px thermopile Sensors Detects earth-space horizon based on the temperature difference

21 Sun sensor Detects position of the Sun Types: PSD detector QUAD detector Sensors

22 PSD detector measure a position of a light spot in one or two-dimensions on a sensor surface High precision Sensors

23 Quad photodiode detector Incoming light is focused on the detector as a spot Comparing of the output currents received from each of the four quadrants = position of light source 23

24 Calibration 24

25 VÝSTUP SNÍMAČA 1) Attitude Determination Sun-sensors orthogonality Calibration Sun-sensors y = x UHOL VZHĽADOM K ZDROJU SVETLA [ ] X- X+ Y+ Y- X- polo X+ polo Y+ polo Y- polo Linear (Y-) 25

26 Star tracker Sensors Optical device that measures the position(s) of star(s) using photocell(s) or a camera. 26

27 Sensors 27

28 Sensor fusion Gyroscope Drift Low-pass noise Poor response Magnetometer Noisy low-drift Sensor fusion 28

29 2) Attitude control Passive systems Magnetic stabilization B-dot algorithm Testing with 3D helmholtz coils system Reaction wheel 29

30 2) Attitude control Passive magnetic stabilization Uses permanent magnet 2-axis stabilization Passive systems 30

31 2) Attitude control Gravitation Gradient Stabilization Passive systems Different distance of the two masses m1 and m2 to the center of gravity -> F1 > F2 Centrifugal forces Fz1 and Fz2 also different 31

32 2) Attitude control Gravitation Gradient Stabilization Example of a Gravitational Stabilized Satellite (UoSat-12) Passive systems 32

33 2) Attitude control Spin-Stabilization Rotating mass has an inherent stability (just like a spintop) Long duration stability around the spinning axis Antenna and instruments are rotating Solar arrays must be body mounted Examples: INTELSAT I, II und III, METEOSAT, MSG Passive systems 33

34 2) Attitude control Reaction wheels Implemented as special electric motors Reaction wheels rotation speed is changed - counter-rotate proportionately through conservation of angular momentum 34

35 2) Attitude control Reaction wheels 35

36 2) Attitude control Active magnetic stabilization Complexity (Actuators, Sensors, Software) Magnetic stabilization Not for interplanetary missions (require external magnetic field)

37 2) Attitude control Magnetorquer Small coercivity is required Higher permeability = lower energy Magnetic stabilization

38 2) Attitude control Magnetic stabilization 38

39 2) Attitude control B-dotequation m = k B Magnetic stabilization Commanded magnetic dipole moment Proportional gain Derivation of the magnetic field 39

40 2) Attitude control B-dot algorithm Magnetic stabilization Magnetorquers 40

41 2) Attitude control Testing of ADCS 3D hemholtz coils system Generates an external magnetic field Air bearing Creates conditions of microgravity Testing

42 2) Attitude control Magnetic stabilization 42

43 2) Attitude control Magnetic stabilization 43

44 ANGULAR VELOCITY [ /SEC] 2) Attitude control Magnetic stabilization B-dot axis Y-Z y = e x y = e x ČAS bez b-dot z b-dot z-os Expon. (bez b-dot z) Expon. (b-dot z-os) 44

45 Thank you for your attention 45