TRIO-CINEMA 1 UCB, 2/08/2010 ACS Dave Auslander, Dave Pankow, Han Chen, Yao-Ting Mao, UC Berkeley Space Sciences Laboratory University of California, Berkeley August 10, 2010

TRIO-CINEMA 2 UCB, 2/08/2010 ACS creates Magnetic Torques to control CINEMA attitude & spin Torque = M (coil moment =  nIA) 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 (has limit function) Operational: Spin Control ; Precession Control; OFF for Science Overview

TRIO-CINEMA 3 UCB, 2/08/2010 The Goal of ACS Desired direction (elliptical normal) parallel 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)

TRIO-CINEMA 4 UCB, 2/08/2010 ECI ecuator Body Boom Yard SimMechanics toolbox: 1 design a simple geometry 2 design for each component’s mass center, inertia of moment Simulink: SimMechanics

TRIO-CINEMA 5 UCB, 2/08/2010 Spin rate Attitude of the cinema Elliptical normal Before summer With prefect sensors, no estimators, sample time 0.1 second

TRIO-CINEMA 6 UCB, 2/08/2010 dsPIC33FJ256GP710 Development Board Laptop ok Serial signal RS232 ok ?? (real-time) ?? Simlink/simple model Simulink/satellite (complicated) Before summer

TRIO-CINEMA 7 UCB, 2/08/2010 This summer Simulations of simulink ACS in PIC, Environment of space and sensors in PC Test communication of ACS and sensor and ground station Evaluation the results

TRIO-CINEMA 8 UCB, 2/08/2010 Desired attitude estimator omega x,y,z estimator t s This summer Bang-bang control S>0, current >0 S<0, current <0

TRIO-CINEMA 9 UCB, 2/08/2010 Sun ECI estimator ECI Desired attitude B field Body frame ? The cinema knows the B field (ECI) and B field (body), sun attitude (body) Now, using three vector, computing desired attitude (body) sun B R

TRIO-CINEMA 10 UCB, 2/08/2010 θ Desired attitude cone θ ECIBody frame θ Sun Desired attitude vector plane cone Over a little bit Desired attitude vector Correct direction Desired attitude vector Desired attitude estimator

TRIO-CINEMA 11 UCB, 2/08/2010 Sun ECI estimator omega attitude

TRIO-CINEMA 12 UCB, 2/08/2010 Sun sensor estimator X Y Z elevation X Y Z X Y

TRIO-CINEMA 13 UCB, 2/08/2010 Precession mode Real sun position Estimate sun position Spin up mode Error From sun sensor

TRIO-CINEMA 14 UCB, 2/08/2010 Solar Panel model 10 degree 30 Sun sensor Solar panel Elevation determination for sun sensor and solar panel Unable degree

TRIO-CINEMA 15 UCB, 2/08/2010 Note: We can also get spin rate from this computation Result from previous computation for desired attitude Want to know Bonus Omega estimator

TRIO-CINEMA 16 UCB, 2/08/2010 Gravity Disturbance Gravity of disturbance x1 x2 m2 m1

TRIO-CINEMA 17 UCB, 2/08/2010 Real inertia of moment Inertia of moment in controller Effect of inertia of moment Due to derivation in inertia of moment Final attitude: 1.4 degree

TRIO-CINEMA 18 UCB, 2/08/2010 Effect of the sample time of the controller Sample time 0.5 second Sample time 1.5 second Attitude of the cinema limitation for sample time precession(1.4 sec)< speed up (2.5 sec)< detumble(5 sec)

TRIO-CINEMA 19 UCB, 2/08/2010 Instrument control toolbox (simulink) Interfaces from COM and simulink 1 Timeout: waiting time for serial port signals 2 Block sample time: time for sample (a big effect to the simulation model )

TRIO-CINEMA 20 UCB, 2/08/2010 Protocol design and tasks ….. Serial data Begin byte Data set data1data Each variable (total 17) is float, each float includes 4 bytes (17x4=68) Begin byte ….. 1 separate each variable (float->byte) 2 transmit them in the serial port of Simulink 3 receive them in the serial buffer of PIC 4 combine them in the PIC (byte-float)

TRIO-CINEMA 21 UCB, 2/08/2010 Simulink Interface betweeen COM and simulink Serial Receiver (decode) Serial Receiver Serial send block PIC Serial send (encode) ACS code B field Body Spin rate from sun sensor Solar Panel current Sun elevation from sun sensor Flag from sun sensor Timer B field ECI (just 2) Ground station command CINEMA, Ground torque Sensor, command Data flow

TRIO-CINEMA 22 UCB, 2/08/2010 PIC Simulink Comparing results of Simulink and PIC Gravity disturbance Simulink PIC

TRIO-CINEMA 23 UCB, 2/08/2010 Current of coil 1: coil off 0: coil on off Gravity disturbance On/off off on

TRIO-CINEMA 24 UCB, 2/08/2010 Control logic Coil on, off, negative on Review Control logic I/O Sun ECI initial value B field Body Spin rate from sun sensor Solar Panel current Sun elevation from sun sensor Flag from sun sensor Timer B field ECI Ground station command Desired attitude ECI Spin rate Mode: detumble, spin up, precession, auto,off, sun normal(yet) Shadow (on or off) Sun sensor and solar panel switcher Sun ECI estimator Rotation matrix Desired attitude of body frame Sun position estimator (for sun sensor) Omega X,Y,Z estimator Lyapunov function

TRIO-CINEMA 25 UCB, 2/08/2010 Dynamics of the satellite (c code, *exe) Sun sensor model (update each revolution) Data sets of magnetic field and sun (c code,*exe) Gravity Disturbance Actuator *magnetometer Ground Station *Solar panel model (Area, unable 10 degree) Physical body of the satellite * Magnetometer assume prefect model *Color text box means finish Shadow analysis Control logic Serial send block Serial Receiver Review the full structure

TRIO-CINEMA 26 UCB, 2/08/2010 Sun sensor simulation form Prof. Auslander and Han Chen Nonlinear region Maybe due to the number of the data (Least square ) Elevation degree Time degree * period rotation

TRIO-CINEMA 27 UCB, 2/08/2010 Q & A