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ACS Dave Auslander, Dave Pankow, Sandhu Jaikarn, Yao-Ting Mao,

ACS Dave Auslander, Dave Pankow, Sandhu Jaikarn, Yao-Ting Mao, UC Berkeley Space Sciences Laboratory University of California, Berkeley February 8, 2010. ACS Agenda. AGENDA Hardware Requirements Software Requirements Control Design Model Issues. Requirements. ACS Hardware.

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ACS Dave Auslander, Dave Pankow, Sandhu Jaikarn, Yao-Ting Mao,

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  1. ACS • Dave Auslander, • Dave Pankow, • Sandhu Jaikarn, • Yao-Ting Mao, • UC Berkeley Space Sciences Laboratory • University of California, Berkeley • February 8, 2010

  2. ACS Agenda • AGENDA Hardware Requirements Software Requirements Control Design Model Issues

  3. Requirements ACS Hardware • Actuators • Torque Coils: • 1.23 Am2 (62 turns copper wire 26 inch gauge) at 5.2W • 10% Duty  5.3 x 10-5 N-m at 650km orbit altitude • Orientation perpendicular to spin axis : Pointing • Orientation parallel to spin axis: Spin • Sensors: • Sun Sensor • V-Slit sun sensor oriented looking up at the spin plane • Contains two collimated photodiode devices with a • 5° x 80° FOV • Magnetometer • 25 nT resolution in engineering mode • Cadence: 1 vector/s at 0.1W • Note: Torque coils and magnetometer can be active simultaneously.

  4. Requirements Software Modes • Detumble Mode • Detumble maneuver using B-Dot control • Initialization Mode • Acquire attitude using currents in solar panels • Spin-up and initialize sun sensors. • Spin-Up/Precession Modes • Establish desired spin rate of 4 RPM • Establish sun normal orientation (Spin axis normal to sun vector) • Nominal Mode • Idle mode. ACS OFF.

  5. Design ACS Control Laws • Detumble • B-Dot controller from magnetometer data to reduce angular velocities from launch vehicle separations .

  6. Design ACS Control Laws • Spin/Precession Controller • Same laws apply in ground based control • Spin Controller • Precession Controller E = hf - h (hf is desired final angular momentum) E = kB - k (kB is desired final orientation)

  7. Issues Sun Sensor Model kss is a constant derived geometrically and through simulations.

  8. Issues Sun Sensor Model Non-Linear! Need to investigate sun sensor activation model

  9. Issues Sun Sensor Model • Must rely on uplinked data, system clock, and magnetometer data when the sun is outside the range of the sun sensors or the satellite is in shadow. • Multiple pulses (glint) and/or lack of pulses from failed sensor may affect satellite behavior. This behavior is difficult to predict and design for

  10. End

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