Gateway docking simulation

Loads the stored MassProps.mat.

See also: PID3Axis, PIDMIMO, RHSSGCMG, RK4, TimeHistory

Contents

%--------------------------------------------------------------------------
%   Copyright (c) 2022 Princeton Satellite Systems, Inc.
%   All rights reserved.
%--------------------------------------------------------------------------
%   Since 2023.1
%--------------------------------------------------------------------------

User inputs

tEnd      = 500; % s
dT        = 0.1; % s

% Disturbance torque
tD        = [0.02;0;0]; % Nm
kD        = [100 200 300]; % Doublet times

% Docking
kDock    = 500;

% Target quaternion and Orion residual angular rates
qTarget    = [1;0;0;0];
omegaOrion = [1;1;1]*1e-6;

printFigs = false; % create PDFs of figures

Script control

if( printFigs )
  close all
end

Read in the Gateway and Orion inertia

s = load('MassProps.mat');

nSim   = floor(tEnd/dT);
x      = [1;zeros(12,1)];
xP     = zeros(length(x)+6,nSim);

Design the controller

dC = PID3Axis;
dC.q_desired_state = qTarget;
dC.inertia = s.inrG;
dC.dT = dT;
[dC.a, dC.b, dC.c, dC.d] = PIDMIMO(1,1,0.01,200,0.05,dT);

Simulation

Default data structure

dRHS     = RHSSGCMG;
dRHS.inr = s.inrG;

for k = 1:nSim
  % Attitude control
  [tC, dC] = PID3Axis( x(1:4), dC );
  if( k > kD(1) && k < kD(2))
    dRHS.torque = tD;
  elseif( k > kD(2) && k < kD(3))
    dRHS.torque = -tD;
  else
    dRHS.torque = [0;0;0];
  end

  if( k == kDock )
    [x(5:7),inr] = Docking(x(5:7),s,omegaOrion);
    dRHS.inr     = inr;
    dC.inertia   = inr;
  end

  dRHS.tC  = -tC;

  xP(:,k)  = [x;dRHS.tC;dRHS.torque];
  x        = RK4(@RHSSGCMG,x,dT,0,dRHS);
end

Plot

yL = {'q_s' 'q_x' 'q_y' 'q_z' '\omega_x' '\omega_y' '\omega_z'...
      '\Omega_{1_y}' '\Omega_{1_z}' '\Omega_{2_y}' '\Omega_{2_z}'...
      '\Omega_{3_y}' '\Omega_{3_z}' 't_{C_1}' 't_{C_2}' 't_{C_3}'...
      't_{D_x}' 't_{D_y}' 't_{D_z}'};

t = (0:nSim-1)*dT;

k = 1:4;
TimeHistory(t,xP(k,:),yL(k),'Quaternion'); k = 5:7;
TimeHistory(t,xP(k,:),yL(k),'Body Rates'); k = 8:13;
TimeHistory(t,xP(k,:),yL(k),'CMG Rates'); k = 14:19;
TimeHistory(t,xP(k,:),yL(k),'Torques');

Print to file

if( printFigs )
  for k = 1:4
    PrintFig(1,4,k,sprintf('DS%d',k));
  end
end

function [omega,inr] = Docking( omegaOld, s, omegaOrion )

Docking

rO = [-4;0;0];
rG = [ 7;0;0];
mO = 33446;
mG = 40000;

c     = (mO*rO + mG*rG)/(mO+mG);
inr   = s.inrG + s.inrO - mO*SkewSq(rO-c) - mG*SkewSq(rG-c);
omega = inr\(s.inrG*omegaOld + s.inrO*omegaOrion);

end


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% $Id: e062aedbc41ada792d3afd9f1bf6243e0164dc43 $

Published with MATLAB® R2024a