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Guidance, Navigation and Controls Subsystem

Guidance, Navigation and Controls Subsystem. Winter 1999 Semester Review. Outline. Team Overview (Greg Chatel) Attitude Determination (David Faulkner) Attitude Control (Brian Shucker) Simulations (Barry Goeree). Team Mentor : Dr. Fasse (AME) Team Members : Matt Angiulo (AME)

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Guidance, Navigation and Controls Subsystem

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  1. Guidance, Navigation and Controls Subsystem Winter 1999 Semester Review

  2. Outline • Team Overview (Greg Chatel) • Attitude Determination (David Faulkner) • Attitude Control (Brian Shucker) • Simulations (Barry Goeree)

  3. Team 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) Team Members

  4. Generalized GNC System Kalman Measurement Update State Update & Covariance Update Dynamic System Model State Propagation & Covariance Propagation Instruments Magnetometer Sun Sensors Rate Gyros Horizon Sensor Control Software Standby Star Pointing Horizon Track Ground Track Power Gen. Emergency Control Hardware React. Wheels Torque Rods External References Satellite Motion Attitude Estimation Update Attitude Estimation Measurement Control Commands Attitude Estimation Control System

  5. Attitude Estimation Sensors • GPS • Magnetometer • Sun Sensor • Horizon Sensor • Star Tracker • Integrating Rate Gyro

  6. Extended Kalman Filter Block Diagram -- Discrete Measurement Updates -- Continuous Dynamic Propagation Models t k Out to controller In from instruments State Model (4) u State Update (2) t i.c. Gain Update (1) Covariance Update (3) t k Covariance Model (5) u t i.c.

  7. Control Software Overview Command given Initialize Software Look for Command Execute Command No command Initial Diagnostic Running Diagnostic Determine Desired State OK Start Standby Mode Attitude/Position Update Input from Attitude Estimation Startup Attitude Adjustment Output to Reaction Wheels Problem Problem Check Reaction Wheel momentum Output to Magneto-torquers Recovery Algorithm Interface Momentum handling Main Control Loop

  8. Basic Control Modes Deployment Detumbling Acquire Satellite Error Detection Standby Error Recovery Momentum Management Max Power Generation Position satellite for optimum solar panel performance Photometry Experiment Inertial pointing at star Lightning/Sprite Experiment Point at limb of the earth Laser Experiment Track ground station in Tucson

  9. 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.

  10. 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

  11. 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

  12. 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

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