attitude final)
DESCRIPTION
get to know abt satellites 2TRANSCRIPT
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