samir rawashdeh space systems laboratory university of

Orbital Environment Simulator

Samir Rawashdeh

Space Systems Laboratory

University of Kentucky

2009 Summer CubeSat Developers' Workshop August 9, 2009

2

Overview

Introduction

Implementation Details

Capabilities

KySat-1: Passive Magnetic Stability

RamSat: Aerodynamic Stability

Future Enhancement

August 9th, 2009 CubeSat Developers' Workshop, Logan, UT

3

Introduction

Passive Stability Systems

Aerodynamic

Passive Magnetic

Gravity Gradient

PuTEMP (concept) - Purdue

Magnet Placement in KySat-1

RamSat (concept) –

Kentucky Space

August 9th, 2009 CubeSat Developers' Workshop, Logan, UT

4

Challenges

Determining Pointing Accuracy

Magnetic Hysteresis Damping Behavior

Uncontrolled Axis of Freedom

Behavior in 6DOF

Effect of Gyroscopic “Stiffness”

August 9th, 2009 CubeSat Developers' Workshop, Logan, UT

5

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

August 9th, 2009 CubeSat Developers' Workshop, Logan, UT

6

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.

August 9th, 2009 CubeSat Developers' Workshop, Logan, UT

7

Attitude Propagator

August 9th, 2009 CubeSat Developers' Workshop, Logan, UT

8

Capabilities

Attitude Propagation (Aerodynamic, Gravity

Gradient, Magnetic, and Hysteresis)

Stability System Design Verification

Plotting and Animation (STK)

Case Studies:

KySat-1

RamSat

August 9th, 2009 CubeSat Developers' Workshop, Logan, UT

9

KySat-1: Magnetic Stability

Align with Magnetic Field

Permanent Magnets

Dampen Motion

Hysteresis Material (HyMu80)

August 9th, 2009 CubeSat Developers' Workshop, Logan, UT

10

KySat-1: Simulation

August 9th, 2009 CubeSat Developers' Workshop, Logan, UT

0 2 4 6 8 10 12 14 16 18 20 22140

30

60

90

120

150

180

Time (hours)

Err

or

Angle

(degre

es)

Simulated Time Response of the KySat-1 Passive Magnetic Stability System

Angle to Magnetic Field

Angle to Nadir

11

KySat-1: Animation

12

RamSat: Aerodynamic Stability

Ram-facing

Maximum altitude

No roll control

Simulation:

20cm full width panels

30° deployment angle

August 9th, 2009 CubeSat Developers' Workshop, Logan, UT

13

RamSat: Simulation

0 1 2 3 4 5 6 7 8 90

20

40

60

80

100

120

140

160

180

Time (hours)

Erro

r Ang

le (d

egre

es)

RamSat Time Response: 20cm Panels at 30 degrees

Angle to Velocity Vector

Angle to Nadir

August 9th, 2009 CubeSat Developers' Workshop, Logan, UT

0 2 4 6 8 10 12 14 16 18 20 22140

30

60

90

120

150

180

Time (hours)

Err

or

Angle

(degre

es)

Simulated Time Response of the KySat-1 Passive Magnetic Stability System

Angle to Magnetic Field

Angle to Nadir

0 2 4 6 8 10 12 14 16 18 20 22140

30

60

90

120

150

180

Time (hours)

Err

or

Angle

(degre

es)

Simulated Time Response of the KySat-1 Passive Magnetic Stability System

Angle to Magnetic Field

Angle to Nadir

Simulated Time Response: RamSat with 20cm panels at 30 degrees

14

RamSat: Animation

15

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

August 9th, 2009 CubeSat Developers' Workshop, Logan, UT

Reaction Wheels

sinclairinterplanetary.com

16

Active Control

Translational Forces

Angular RotationMoments

Kentucky Space - Orbital Environment Simulator

Control Torque

Disturbance Torque

[P]

[V]

[A]

[V]

[A]

[P]

[DesiredAttitude]

[P]

[CurrentAttitude]

Position (X)

Attitude (DCM)

Velocity (V)

Torque (N.m)

Environmental Effects

Position ECI (X) Gravitational Force (N)

Earth's Gravity

Desired Attitude

Current Attitude

Torque (N.m)

Controller

Fxyz (N) [ECI]

Mxyz (N.m) [Body-fixed]

X (m) [ECI]

V (m/s) [ECI]

DCMbe (Attitude) [ECI to Body]

6DOF Dynamics

August 9th, 2009 CubeSat Developers' Workshop, Logan, UT

17

Samir Rawashdeh

Space Systems LaboratoryElectrical & Computer EngineeringUniversity of Kentuckysar@ieee.org

Thank You

www.kentuckyspace.com

August 9th, 2009 CubeSat Developers' Workshop, Logan, UT