Run a formation flying simulation with "DFFSim".

A reconfiguration is performed using decentralized formation flying (DFF) guidance and control algorithms developed by PSS under NASA SBIR contracts.

This demo is initially set up to do a 4-satellite reconfiguration maneuver from an out-of-plane leader follower (repeated groundtrack) formation to a dual-plane projected circle formation with the reference on one circle.

Several parameters may be modified by the user, including the number of satellites, the simulation time-step, and the initial and final states of the cluster.

Since version 7.
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See also WrapPhase, DFFSim, RotateState, GenerateTeamGoals,
Goals2DeltaElem, M2Nu
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Contents

%---------------------------------------------------------------------------
%  Copyright (c) 2003 Princeton Satellite Systems, Inc.
%  All rights reserved.
%---------------------------------------------------------------------------


disp('... initializing demo parameters');
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% THE FOLLOWING DATA MAY BE MODIFIED BY THE USER

... initializing demo parameters

demo parameters

%----------------
nSC      = 4;           % number of spacecraft
dT       = 20;          % integration time step        [sec]
useJ2    = 0;           % use J2 or not?
planTime = 0;           % when to plan?                [orbits]
nOrbits  = 6;           % number of orbits to simulate [orbits]

initial state of the cluster (may be changed by user, see GenerateTeamGoals for more info)

%-----------------------------
fType_Init = 2;
fSize_Init = 0.3;

desired state of the cluster (may be changed by user, see GenerateTeamGoals for more info)

%--------------------------------------------------------------------------------------------
fType_Des = 10;
fSize_Des = 1.0;

Reference Orbit

%----------------
a   = 7000;    % semi-major axis [km]
i   = 60;      % inclination     [deg]
W   = 45;      % right ascension [deg]
w   = 120;     % arg of perigee  [deg]
e   = 1e-5;    % eccentricity
M   = 30;      % mean anomaly    [deg]

% END OF USER-MODIFIABLE DATA
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

reference orbital element set

%------------------------------
i   = i*pi/180;
W   = W*pi/180;
w   = w*pi/180;
M   = M*pi/180;
th  = WrapPhase( M2Nu( e, M ) + w );
q1  = e*cos(w);
q2  = e*sin(w);
el0 = [a, th, i, q1, q2, W];

Geometric Goals of the Cluster

%-------------------------------
disp('... computing the geometric goals of the cluster');
teamID    = 99;
angRes    = 5*pi/180;
teamGoals = GenerateTeamGoals( el0, fType_Des, fSize_Des, nSC, teamID, angRes );

... computing the geometric goals of the cluster

Compute the original state of the cluster

%------------------------------------------
disp('... computing the initial state of the cluster');
tG0 = GenerateTeamGoals( el0, fType_Init, fSize_Init, nSC, teamID, angRes );
clear cG0;
k = 0;
for i=1:tG0.nU,
    k = k+1;
    cG0(k) = tG0.geometry(i);
    u = k;
    for j=1:tG0.constraints(i).nDuplicates,
        k = k + 1;
        cG0(k) = RotateState( cG(u), tG0(i).phi(j) );
    end
end

... computing the initial state of the cluster

compute initial orbital elements

%---------------------------------
dEl0 = zeros(nSC,6);
for i=1:nSC
   dEl0(i,:) = Goals2DeltaElem( el0, cG0(i) );
end

run the simulation

%-------------------
disp('... running the simulation');
[t,el,fH,xH,dEl,dElDes] = DFFSim( el0, dEl0, teamGoals, dT, planTime, nOrbits, useJ2 );

clear sc;
for i=1:nSC+1,
    sc(i).r = xH{i}(1:3,:);
    sc(i).v = xH{i}(4:6,:);
    sc(i).t = t;
end


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

... running the simulation
*** 1 orbit complete ***
*** 2 orbits complete ***
*** 3 orbits complete ***
*** 4 orbits complete ***
*** 5 orbits complete ***
Elapsed time is 15.685375 seconds.

Published with MATLAB® R2014b