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Guidance, Navigation and Guidance, Navigation and Controls SubsystemControls Subsystem
Winter 1999 Semester ReviewWinter 1999 Semester Review
Guidance, Navigation, and Controls
Outline
• Team Overview (Greg Chatel)
• Attitude Determination (David Faulkner)
• Attitude Control (Brian Shucker)
• Simulations (Barry Goeree)
Guidance, Navigation, and Controls
Team MembersTeam Mentor:• Dr. Fasse (AME)
Team Members:• Matt Angiulo (AME)• Greg Chatel (AME)• David Faulkner (AME)• Marc Geuzebroek (Phys)• Barry Goeree (AME)• James Harader (AME)
• Marissa Herron (AME)• Steve Hoell (Phys)• Brian Ibbotson (AME)• Martin Lebl (CSC)• Adam Mahan (ECE) • Brian Shucker (Phys/Math)• Daniel Stone (AME)
Guidance, Navigation, and Controls
Generalized GNC System
KalmanMeasurement
Update
StateUpdate
&Covariance
Update
DynamicSystem Model
StatePropagation
&CovariancePropagation
ControlSoftware
StandbyStar Pointing
Horizon TrackGround TrackPower Gen.Emergency
Instruments
MagnetometerSun SensorsRate Gyros
Horizon Sensor
ExternalReferences Measurement
SatelliteMotion
AttitudeEstimation
Update
Attitude Estimation
ControlHardware
React. WheelsTorque Rods
AttitudeEstimation
Control System
ControlCommands
Guidance, Navigation, and Controls
Attitude Estimation Sensors
• GPS• Magnetometer• Sun Sensor• Horizon Sensor• Star Tracker• Integrating Rate Gyro
Guidance, Navigation, and Controls
i.c.
kt
ut
t
k
i.c.
GainUpdate
(1)
StateUpdate
(2)
CovarianceUpdate
(3)
StateModel
(4)
ut
CovarianceModel
(5)
$&P
$&x kx$
kP$
kP$ ( )+
kx$( )+
kKkx$( )−
kx$( )−
kx$( )−
kP$ ( )−
kP$ ( )−
z
kP$ ( )+
kx$( )+
Extended Kalman Filter Block Diagram-- Discrete Measurement Updates-- Continuous Dynamic Propagation Models
In from instruments
Out to controller
Guidance, Navigation, and ControlsControl Software Overview
Initialize Software
Start Standby Mode
Look for Command
Running DiagnosticInitial Diagnostic
Recovery Algorithm
Execute Command
Attitude/Position Update
Attitude Adjustment
Check Reaction Wheelmomentum
Momentum handling
Determine Desired State
OK
Problem
Command given
No command
Problem
Output to Reaction Wheels
Output to Magneto-torquers
Input from Attitude Estimation
Main Control Loop
Startup
Interface
Guidance, Navigation, and ControlsBasic Control Modes
Standby
Max Power Generation
Position satellite foroptimum solar panelperformance
Photometry Experiment
Inertial pointing at star
Lightning/Sprite Experiment
Point at limb of the earth
Laser Experiment
Track ground stationin Tucson
Error Recovery
Detumbling
Momentum Management
Deployment
Acquire Satellite Error Detection
Guidance, Navigation, and Controls
Attitude Control Simulation
• What is simulated?– Torques acting on satellite determine how attitude
changes with time. These equations of motion are integrated in time.
– This is different then what STK does!
• What are we trying to achieve?– Obtain accurate estimates for important design
parameters like max torque and momentum storage.
– Analysis and verification of control and attitude estimation algorithms.
Guidance, Navigation, and Controls
Attitude Control Simulation
• What’s included in the simulation?– aerodynamic drag torques
– magnetic field models
– sun sensor model
– dynamics of satellite, orbital kinematics
– control algorithms
– simple visualization
– kinematics of ground station tracking
Guidance, Navigation, and Controls
Attitude Control Simulation
• What needs to be done?– solar pressure
– gravity gradient
– attitude estimation algorithms
– models of all other sensors (magnetometer, horizon sensor)
– continue work on control algorithms
– kinematics of other control modes
– more realistic visualizations
Guidance, Navigation, and Controls
Attitude Control Devices
• Dynacon Mini Reaction Wheels– Size: 80 x 80 x 100 mm
– Power: 2.5 W ea @ 2000 RPM
• Optional integrated rate sensor: 1 W
– Angular Momentum Capacity: 0.3 N-m-s
• Student Designed Torque Rods– lost our Space Grant student
– found a detailed paper on designing torque rods
