ATTITUDE DETERMINATIONAND

CONTROL SUBSYSTEM

SATHYABAMA NANOSATELLITE

ADCS SUBTEAM

ADCS OBJECTIVES

1. Detumbling of satellite after deployment.2. Earth pointing during observation.3. Sun pointing for max power.

SEQUENCE OF OPERATION

STATE DIAGRAM OF DIFFERENTMODES OF OPERATION

•Int- Initialization Mode•FS- Fail safe Mode•DT- Detumbling Mode•PS- Power Safe Mode•Payload- Payload Mode•*- Triggered Externally by OBC or PSU(Power Supply Unit)

REQUIREMENTS

1. Sensors for Attitude Determination2. Control Algorithm for calculating the amount

of current to be given to the Torque Coils3. Actuators to produce torque for positioning

of the satellite

HARDWARE SELECTION

SENSORS SELECTION

Sensors Dimension (mm)

Mass (g)

Power (watts)

Accuracy Temperature (Deg c)

Earth Sensor 160 x 140 x 195 2.95 11 18 Arc sec - 20 to 85

Star Sensor 80 x 100 x 180 1.1 2.5 5 min - 20 to 65

Sun Sensor Depends on Design

0.35 0.5 + 1 deg - 20 to 50

Rate Gyros 26 x 76 x 53 0.1 0.2 + 1 deg - 20 to 50

Magnetometer 25.4 x 36.8 x 11 0.05 0.36 + 30 to + 60 Deg - 20 to 70

SUNSENSOR SELECTION

SUNSENSORSTYPE:- COSINE SUN SENSORS (Single axis)

CONFIGURATION:-No. of sensors = 6No. of photo voltaic cell = 6No. of Amplifier circuit = 12Field of view = 180 deg (each)

Total field of view =360 deg

MAGNETOMETER SELECTION

MAGNETOMETERTYPE:- HMC5843

SPECIFICATIONS:-Operating Temperature=-30 to 85 deg cWeight = 50 mgField of range =-4 to 4 gaussMeasurement Time = 10 ms

ACTUATORS SELECTION

SOFTWARE SELECTION

METHODS OF ATTITUDE DETERMINATON

1. DETERMINISTIC METHOD:- TRIAD,SVD,Q- METHOD,FOAM,QUEST.

2.RECURSIVE METHOD:- KALMAN FILTER, EXTENDED KALMANFILTER

ATTITUDE DETERMINATION ALGORITHM

1. Process Sensor Data2. On- board Sun Model3. On-board orbit Model4. Albedo Correction5. Extended Kalman Filter Algorithm for

attitude determination

FINAL SELECTION LIST

1. SENSORS: MAGNETOMRTER AND SUNSENSORS

2. CONTROL ALGORITHM: RECURSSIVE ALGORITHM

3. ACTUATOR: TORQUE COILS

BLOCK DIAGRAM

INTERACTION OF ADCS

MAGNETOMETER

H-BRIDGE

TEMPERATURE SENSORS

SUNSENSORS

OBCTo TORQUE COILS

From TEMP. SENSORS

From SUN SENSORS

MAGNETIC FIELD

CURRENT

TEMPERATURE

POSITION

MASS BUDGETMAGNETOMETER = 50 gMAGNETORQUERS = 70 g -MOUNTING = 5gSENSORS = 5g -MOUNTING = 10 gPCB+COMPONENTS = 50 gWIRING = 10 g

TOTAL WEIGHT = 200 g

Comparator

SATHYABAMA NANO SATELLITE ADCS SUBTEAM

ATTITUDE DETERMINATION AND CONTROL SYSTEM

SENSOR SIMULATION

SATHYABAMA NANO SATELLITE ADCS SUBTEAM

SENSOR OUTPUT

SATHYABAMA NANO SATELLITE ADCS SUBTEAM

SUN SENSOR SIMULATION

SATHYABAMA NANO SATELLITE ADCS SUBTEAM

SUN SENSOR OUTPUT

SATHYABAMA NANO SATELLITE ADCS SUBTEAM

TORQUE COIL SIMULATION

SATHYABAMA NANO SATELLITE ADCS SUBTEAM

Controller Output Vs Angle Graph

SATHYABAMA NANO SATELLITE ADCS SUBTEAM

SATHYABAMA NANO SATELLITE ADCS SUBTEAM