Guidance, Navigation and Controls Subsystem Winter 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 Members 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)

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

Guidance, Navigation, and Controls Attitude Estimation Sensors GPS Magnetometer Sun Sensor Horizon Sensor Star Tracker Integrating Rate Gyro

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

Guidance, Navigation, and Controls Control Software Overview Initialize Software Start Standby Mode Look for Command Running Diagnostic Initial Diagnostic Recovery Algorithm Execute Command Attitude/Position Update Attitude Adjustment Check Reaction Wheel momentum 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 Controls Basic Control Modes Standby 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 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 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