ACS Dave Auslander Dave Pankow Sandhu Jaikarn YaoTing
- Slides: 16
ACS Dave Auslander, Dave Pankow, Sandhu Jaikarn, Yao-Ting Mao, UC Berkeley Space Sciences Laboratory University of California, Berkeley February 8, 2010 TRIO-CINEMA 1 UCB, 2/08/2010
ACS Agenda AGENDA Overview Requirements Environments Development Plan Issues TRIO-CINEMA 2 UCB, 2/08/2010
Overview ACS creates Magnetic Torques to control CINEMA attitude & spin • Torque = M (coil moment = mn. IA) 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; TRIO-CINEMA 3 OFF for Science UCB, 2/08/2010
Overview ds. PIC 33 FJ 256 GP 710 Ground Station Simulation Satellite Development Board PC TRIO-CINEMA 4 UCB, 2/08/2010
Requirements Mission Requirements: maintain the appropriate attitude for science operations • Spin rate 4 RPM • 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) TRIO-CINEMA 5 UCB, 2/08/2010
Environments Development Hardware: 1. ds. PIC 33 FJ 256 GP 710 2. Cube. Sat 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 TRIO-CINEMA 6 UCB, 2/08/2010
Development Plans Development 1. Hand coding the controller from the Simulink model with C code. 2. Incorporating the code and Simulink model 3. Building the ground station block in Simulink 4. Using the same C code of controller implementing in the Pluggable Processor Module (PPM) 5. Comparing the results from the simulation 6. Investigating the internal signal flows from each satellite input TRIO-CINEMA 7 UCB, 2/08/2010
First Step Simulation –PC Simulated Ground Station Simulink - Matlab Simulated Satellite Dynamics Simulink - Matlab Simulated Sensors Sun Sensor & Mag Simulink - Matlab Controller Simulink S function in C Code Simulated Actuators Simulink - Matlab TRIO-CINEMA 8 PC UCB, 2/08/2010
Requirements Ideal conditions, Spin Rate Controller Verification TRIO-CINEMA 9 UCB, 2/08/2010
Requirements Precession Controller Verification TRIO-CINEMA 10 UCB, 2/08/2010
Second Step Simulink (PC) + Board controller (with the same controller code from 1 st Step) PC Simulated Ground Station Simulink - Matlab Development Station Simulated Satellite Dynamics Simulink - Matlab Simulated Sensors Sun Sensor & Mag Controller C Code Simulink - Matlab Simulated Actuators Simulink - Matlab DAQ TRIO-CINEMA 11 UCB, 2/08/2010
Second Step Investigate the way for the DB to communicate with Simulink: One solution now identified: • National Instruments DAQCard-6024 E supports 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 TRIO-CINEMA 12 UCB, 2/08/2010
Third Step Investigating the real internal control signal between the control and sensors and actuators or other devices. Others Actuators ds. PIC 33 Family Magnetic sensors Sun sensors TRIO-CINEMA 13 UCB, 2/08/2010
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 TRIO-CINEMA 14 UCB, 2/08/2010
Issues 1. 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. 2. Verify that the Simulink model is not altered by including the DAQ and the necessary Real Time Kernel for data acquisition TRIO-CINEMA 15 UCB, 2/08/2010
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. TRIO-CINEMA 16 UCB, 2/08/2010
