Sail attitude evolution under disturbances. No orbit dynamics.

Combines a CAD model with the disturbance model and a simple RHS. The sail
starts out in a sun-pointing attitude with an offset and nonzero body rates.

Functions demonstrated:
   FlatPlate.m / FlatSail.mat, the CAD model
   SailDisturbance.m, the full disturbance model
   SailEnvironment.m, the environment model
   FRB.m, rigid body dynamics integrated with RK4

Since version 7.
------------------------------------------------------------------------
See also DrawSCPlanPlugIn, AU2Q, QMult, Constant, Plot2D, RK4, Unit,
JD2000, RARP2A, RARP2E, El2RV, CEcl2Eq, QSail, DisturbanceStruct,
EnvironmentStruct, ProfileStruct, SailDisturbance, SailEnvironment
------------------------------------------------------------------------

Contents

%-------------------------------------------------------------------------------
%	  Copyright (c) 2006 Princeton Satellite Systems, Inc.
%   All rights reserved.
%-------------------------------------------------------------------------------

%-----------------------------

Load and view the sail model

%-----------------------------
g = load('FlatSail.mat');
DrawSCPlanPlugIn('initialize',g);
view(3); axis equal; axis square;
clear SailDisturbance

%-----------------------------------------------

Hold at a single point in interplanetary orbit

%-----------------------------------------------
aU            = Constant('au');
mu            = Constant('mu sun');
rP            = 0.25*aU;
rA            = aU;
a             = RARP2A( rA, rP );
e             = RARP2E( rA, rP );

Profile is stored in p for disturbance function

%------------------------------------------------
p             = ProfileStruct;
[p.r, p.v]    = El2RV([a,0,0,0,e,0], [], mu );
p.jD          = JD2000;

Vectors must be in ECI so transform from the ecliptic

%------------------------------------------------------
c    = CEcl2Eq;
p.r  = c*p.r;
p.v  = c*p.v;

Quaternion (sun pointing with an offset)

%-----------------------------------------
q0  = QMult(QSail( -Unit(p.r), p.r, p.v ), AU2Q(0.05,[0;1;0]) );

Initial body rate (rad/s)

%--------------------------
w0 = [0.001;0.0005;-0.001]/100;

%--------------------------

Create the data structure

%--------------------------

d = DisturbanceStruct;
d = EnvironmentStruct( d );

Turn off unwanted disturbances

%-------------------------------
d.aeroOn   = 0.0;
d.albedoOn = 0.0;
d.magOn    = 0.0;
d.radOn    = 0.0;
d.ggOn     = 0.0;

Turn on solar

%--------------
d.solarOn  = 1.0;

Orbiting the sun

%-----------------
d.planet   = 'Sun';

Simulation loop

%----------------
t  = 0;
dT = 100;
x  = [q0;w0];

Store mass properties for speed

%--------------------------------
inr    = g.mass.inertia;
invInr = inv(inr);

Set up plotting arrays

%-----------------------
nPts  = 100;
xPlot = zeros(7,nPts+1);
tPlot = zeros(1,nPts+1);
fPlot = zeros(3,nPts);
tqPlot = zeros(3,nPts);

xPlot(:,1) = x;

for k = 1:nPts

  % Store quaternion in p for disturbances
  %---------------------------------------
  p.q = x(1:4);

  % Compute the disturbances.
  % The inputs are ( cad model, profile structure, function control structure )
  %----------------------------------------------------------------------------
  e       = SailEnvironment( d.planet, p, d );
  [fS,tS] = SailDisturbance( g, p, e, d );
  fPlot(:,k) = fS.total;
  tqPlot(:,k) = tS.total;

  % Integrate the rigid body dynamics
  %----------------------------------
  x = RK4( 'FRB', x, dT, t, inr, invInr, tS.total );
  t = t+dT;

  % Store
  %------
  xPlot(:,k+1) = x;
  tPlot(:,k+1) = t;

end

Create plots

%-------------
Plot2D(tPlot,xPlot(1:4,:),'Time (s)','Quaternion');
Plot2D(tPlot,xPlot(5:7,:),'Time (s)','Rates');
Plot2D(tPlot(1:end-1),fPlot,'Time (s)','Solar Force');
Plot2D(tPlot(1:end-1),tqPlot,'Time (s)','Solar Torque');


%--------------------------------------
% PSS internal file version information
%--------------------------------------

Published with MATLAB® R2020a