Attitude Determination and Control System

Team: Daniel Crane, Jaydon Pierson, Ben Willard

Sponsor: USU Get Away Special Student Satellite Team

Project

model
  • Get Away Special Student Satellite Team has a new mission that involves a directional patch antenna
  • To accurately test the patch antenna, that satellite must be able to control its attitude (or orientation) to aim the antenna towards the earth
  • Upon deployment, the satellite rotates with random angular velocity and first “detumbles” or reduces its angular velocity to near zero
  • The satellite also determines its current attitude and “nadir points,” or orients the antenna towards the center of the earth
  • The Attitude Determination and Control System (ADCS) performs the Detumble and Nadir Point functions

System

System diagram

Methods

prototype
  • The ADCS uses data from coarse sun sensors, magnetometers, and rate gyros
  • Magnetorquers generate a magnetic moment, which interacts with the earth’s magnetic field to create a torque on the satellite
  • The ADCS uses a B-Dot control algorithm to determine the required magnetic field the magnetorquers must generate to detumble
  • To estimate the satellite’s attitude, the system uses ephemeris and magnetic field models compared to measured sun and magnetic field vectors (TRIAD method)
  • The ADCS calculates the required torques to rotate the satellite to the desired nadir-pointing attitude

Conclusion

graph
  • Detumble control working and verified using Systems Tool Kit
    • Satellite can detumble in a minimum of approximately 2 hours
    • Slower detumble time can be chosen to limit power draw
  • TRIAD attitude determination working properly and verified using Simulink
  • Nadir pointing control in progress, further testing on magnetorquer control authority required