Prepared by: Shelley Rounds Dept. of Electrical and Computer Engineering Utah State University

1. ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: Torque Coil Actuators Prepared by: Shelley Rounds Dept. of Electrical and Computer Engineering Utah State University E: shelleyr@cc.usu.edu T: (801)884-9235 3/9/2007

2. Outline • Reference List • To probe further • Applications • Attitude Control • Operational Interface • Parameters • Basic working principle • Sample Configuration • Specifications • Limitations • Cost ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

3. Reference List • http://www.oss.goodrich.com/datasheets/oss/Goodrich_TRSeries_TorqueRods.pdf • http://cosmos.ssol.iastate.edu/cysat/Docs/Fall%2003/Controls/Control%20overview.pdf • M. J. Sidi, “Spacecraft Dynamics and Control” Cambridge University Press, 2005. • http://en.wikipedia.org/wiki/Spacecraft • http://einstein.stanford.edu/highlights/hl_102805.html • http://ocw.mit.edu/NR/rdonlyres/Mechanical-Engineering/2-141Fall-2002/4706270A-4F69-4020-958A-F5172054F35F/0/dcpmm_basics.pdf • http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magmom.html • http://www.st.northropgrumman.com/capabilities/SiteFiles/technicallibrary/aiaa_1369.pdf ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

4. To explore further (survival pointers of web references etc) • http://staff.ee.sun.ac.za/whsteyn/Papers/Magsat.pdf • http://ocw.mit.edu/NR/rdonlyres/Aeronautics-and-Astronautics/16-358JSystem-SafetySpring2003/B169A368-9DCC-4916-8897-12B0DE4DC855/0/hete.pdf • http://ocw.mit.edu/NR/rdonlyres/Mechanical-Engineering/2-141Fall-2002/4706270A-4F69-4020-958A-F5172054F35F/0/dcpmm_basics.pdf • http://www.sti.nasa.gov/tto/spinoff1997/t3.html • http://www.nasa.gov/centers/ames/research/technology-onepagers/advanced_min_wheel.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

5. Applications “Satellites are increasingly used in telecommunications, scientific research, surveillence, and meteorology. These satellites rely heavily on the effectiveness of complex onboard control systems.” From “Spacecraft Dynamics and Control” CySat Model Torque coils are used in a spacecraft to accurately control its orientation. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

6. Attitude Control • Attitude control • Control of the position and rotation of the spacecraft • Relative to the object that it is orbiting, or relative to sun and stars • Orientation described by roll, pitch and yaw angles www.st.northropgrumman.com UofU CubeSat ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

7. Attitude Control • Attitude control system must react to external torques • External torques: • Aerodynamic • Solar • Magnetic • Gravity Gradient ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

8. Operational Interface The attitude control system consists of: • Sensors (gyroscopes, magnetometers etc.) • Actuators (torque coils, momentum wheels etc.) • Controlling Algorithms (Control laws from torque equations etc.) From ECE 5320 class slides ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

9. Attitude Control Parameters From Goodrich ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

10. Basic Working Principle • Torque Rods • Act as electromagnets • Interacts with Earth’s magnetic field • Creates controlled torque to reorient spacecraft • Magnetic moment depends on amount of current through the coil • Direction of current determines repelling or attracting force Torque Rods (Goodrich) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

11. Basic Working Principle Torque coils take advantage of the Earth’s Magnetic Field to control the position of the spacecraft. Three orthogonal coils can control the x, y, and z-axis. einstein.stanford.edu ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

12. Basic Working Principle ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

13. Basic Working Principle • The equation for magnetic moment in the current-carrying loop, with current    and area vector      is given by: • Where •    is the magnetic moment, a vector measured in ampere–square meters •    is the current, a scalar measured in amperes, and •    is the loop area vector ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

14. Basic Working Principle • The magnetictorque of an object is given by: • Where is the torque, measured in Newton-meters, is the magnetic moment, measured in ampere-square meters, and is the magnetic field, measured in Newtons per (ampere-meter). ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

15. Basic Working Principle • Dipole moment linearly proportional (±4%) to input current • Saturation • Point where dipole moment deviates from approximation by ±30% Typical performance curve of Torque Coil From “Spacecraft Dynamics and Control” ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

16. Sample Configuration From CySat project ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

17. Sample Configuration • Configuration Procedure • Magnetometer and gyros send information to the microcontroller. • Microcontroller sends current to the torque coils. • Spacecraft moves in the desired direction. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

18. Specifications From “Spacecraft Dynamics and Control” ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

19. Limitations • Creates stray magnetic fields • Affects magnetometer readings • Applied torques extremely small • Magnetic moment proportional to 1/(Distance from earth)3 B = m/R3 • Torque coils cannot be used if too far away from earth • Moments are direction-dependant ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

20. Cost • Ithaco • Hughes • Lockheed • McDonnell Douglas • cost approx. $2000 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators