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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 Overview Requirements Environments Development Plan Issues. Overview.

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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 Overview Requirements Environments Development Plan Issues

  3. Overview • ACS creates Magnetic Torques to control CINEMA attitude & spin • Torque = M (coil moment = mnIA) X B (Earth’s magnetic field) • Precession (or pointing) coil is parallel to spin axis (quasi-DC currents) • Spin coil is orthogonal to spin axis (AC current to spin) • SENSORS: Sun Sensor & Magnetometer •ACTUATORS: two onboard coils • Direction of B changes over each orbit (this data is not available on Cinema) • Ground Station will daily uplink direction of B vs. time (ground ephemeris) • ACS MODES • After Launch: B dot de-tumble mode • Operational: Spin Control ; Precession Control; OFF for Science

  4. Overview dsPIC33FJ256GP710 Simulation Satellite Ground Station Development Board PC

  5. Requirements • Mission Requirements: maintain the appropriate attitude for science operations • Spin rate 4RPM • 20 degree cone of pointing accuracy • Each torque coil is required to be operated at a 10% duty cycle for the duration of ACS operations • ACS software is required to use no more than 50% of the available resources. • ACS Requirement on Spacecraft Bus: • Magnetometer data, sun pulses (in real time) • Spacecraft clock,: synchronization with the ground station. • Ground commands: provide B field and adjust controller tasks or parameters • Others( actuator outputs)

  6. Environments Development Hardware: 1.dsPIC33FJ256GP710 2.CubeSat Kit. Development Board (DB) 3.Laptop 4.I/O (DAQ card plug in Laptop,TBD) Development Software: 1.MATLAB 2.Simulink 3. Real-Time Windows Target software 4 MPLAB

  7. Development Plans Development Hand coding the controller from the Simulink model with C code. Incorporating the code and Simulink model Building the ground station block in Simulink Using the same C code of controller implementing in the Pluggable Processor Module (PPM) Comparing the results from the simulation Investigating the internal signal flows from each satellite input

  8. First Step Simulation –PC Simulated Ground Station Simulink - Matlab Simulated Satellite Dynamics Simulated Sensors Sun Sensor & Mag Controller Simulink S function in C Code Simulink - Matlab Simulink - Matlab Simulated Actuators PC Simulink - Matlab

  9. Requirements Ideal conditions, Spin Rate Controller Verification

  10. Requirements Precession Controller Verification

  11. Second Step Simulink (PC) + Board controller (with the same controller code from 1st Step) PC Simulated Ground Station Simulink - Matlab Development Station Simulated Satellite Dynamics Simulated Sensors Sun Sensor & Mag Controller C Code Simulink - Matlab Simulink - Matlab Simulated Actuators Simulink - Matlab DAQ

  12. Second Step • Investigate the way for the DB to communicate with Simulink: • One solution now identified: • National Instruments DAQCard-6024Esupports real-time module in Simulink. • PC/104  connector block cable( 68-pin 0.050 series D-type connector and VHDCI 68-pin connector ) • DAQ card PCMCIA Laptop

  13. Third Step Investigating the real internal control signal between the control and sensors and actuators or other devices. Others Actuators dsPIC33Family Magnetic sensors Sun sensors

  14. CINEMA Integration & Test Phase • The so called “PHASING & POLARITY TESTS” • Inject signals on the CINEMA data bus and monitor coil currents • Compare to PC based simulations • Rotate CINEMA (in Earth’s B field) and also illuminate sun sensors • Monitor coils with a hiking compass or test magnetometer • Compare to PC based simulations

  15. Issues The controller code (c code) from the s-function running in Simulink will need to be verified against the code in the MPLAB IDE (c 30 compiler). Both codes should be as identical as possible. Verify that the Simulink model is not altered by including the DAQ and the necessary Real Time Kernel for data acquisition

  16. Issues • The satellite uses onboard sun sensors to determine angular velocity and sun vector. • Sun sensors alone cannot determine desired attitude, magnetometer data and orbit position are also needed • The satellite communicates with the ground station once every n orbits. The ground station software must determine the satellite attitude and send commands to the satellite to resolve errors in attitude.

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