Orbital Environment Simulator Samir Rawashdeh Space Systems Laboratory University of Kentucky 2009 Summer CubeSat Developers' Workshop August 9, 2009
Overview Introduction Implementation Details Capabilities KySat-1: Passive Magnetic Stability RamSat: Aerodynamic Stability Future Enhancement 2
Introduction Passive Stability Systems Aerodynamic Passive Magnetic Gravity Gradient RamSat (concept) Kentucky Space Magnet Placement in KySat-1 PuTEMP (concept) - Purdue 3
Challenges Determining Pointing Accuracy Magnetic Hysteresis Damping Behavior Uncontrolled Axis of Freedom Behavior in 6DOF Effect of Gyroscopic Stiffness 4
Orbital Environment Simulator Adjustable Spacecraft Description and Orbit Mass and Inertia Matrix Magnets and Hysteresis Material Geometry (Aerodynamics) Orbital Elements Simulate Effect of Orbital Environment on Satellite Attitude (in 6DOF): Gravity Gradient Magnetic Torques Magnetic Hysteresis Material Aerodynamic Torque 5
Simulink Modeling Model-based Design Graphical description of dynamics Definition of initial state Solve differential equations and propagate the systems state over time Hit play and watch events unfold. 6
Attitude Propagator 7
Capabilities Attitude Propagation (Aerodynamic, Gravity Gradient, Magnetic, and Hysteresis) Stability System Design Verification Plotting and Animation (STK) Case Studies: KySat-1 RamSat 8
KySat-1: Magnetic Stability Align with Magnetic Field Permanent Magnets Dampen Motion Hysteresis Material (HyMu80) 9
Error Angle (degrees) KySat-1: Simulation Simulated Time Response of the KySat-1 Passive Magnetic Stability System 180 150 Angle to Magnetic Field Angle to Nadir 120 90 60 30 0 0 2 4 6 8 10 12 14 16 18 20 22 Time (hours) 10
KySat-1: Animation 11
RamSat: Aerodynamic Stability Ram-facing Maximum altitude No roll control Simulation: 20cm full width panels 30 deployment angle 12
Error Angle (degrees) Error Angle (degrees) Error Angle (degrees) RamSat: Simulation Simulated Simulated Time Time Response Response of the of KySat-1 the KySat-1 Passive Passive Magnetic Magnetic Stability Stability System System Simulated Time Response: RamSat Time Response: RamSat 20cm with Panels 20cm at 30 panels degrees at 30 degrees 180 180 160 150 150 140 Angle to Angle Magnetic to Magnetic Field Field Angle to Nadir Angle to Angle Nadir to Nadir Angle to Velocity Vector 120 120 120 100 90 90 80 60 60 60 40 30 30 20 0 0 0 20 42 64 86 108 12 10 14 12 16 14 18 16 20 18 22 20 22 0 1 2 3 4 5 6 7 8 9 Time (hours) Time (hours) Time (hours) 13
RamSat: Animation 14
Future Enhancements Active Attitude Control Systems Torque Coils Reaction Wheels Momentum Wheels Thrusters System Design Choices (e.g. reaction wheel size, torque coil strength) Control Logic Development Danjon (concept) Kentucky Space Reaction Wheels sinclairinterplanetary.com 15
Active Control Kentucky Space - Orbital Environment Simulator [P] [A] [P] [V] Position ECI (X) Position (X) Attitude (DCM) Velocity (V) Torque (N.m) Environmental Effects Gravitational Force (N) Earth's Gravity Translational Forces Angular Rotation Moments Disturbance Torque Fxyz (N) [ECI] Mxyz (N.m) [Body-fixed] X (m) [ECI] V (m/s) [ECI] DCMbe (Attitude) [ECI to Body] 6DOF Dynamics [P] [V] [A] [DesiredAttitude] [CurrentAttitude] Desired Attitude Torque (N.m) Current Attitude Controller Control Torque 16
Thank You Samir Rawashdeh Space Systems Laboratory Electrical & Computer Engineering University of Kentucky sar@ieee.org www.kentuckyspace.com 17