Performs a covariance analysis of different gyros.

------------------------------------------------------------------------
See also C2DZOH, Plot2D, RW2SDev
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Measurement noise
the final attitude stand. dev.

------------------------------------------------------------------------- Copyright 1999 Princeton Satellite Systems, Inc. All rights reserved. -------------------------------------------------------------------------

radToDeg      = 180/pi;
degToRad      = pi/180;
perHrToPerSec = 1/3600;
gyroType      = 'HRG';

switch gyroType
  case 'HRG'
    sigmaBias  = RW2SDev(0.005*perHrToPerSec);
    sigmaNoise = RW2SDev(0.0003);

  case 'IFOG'
    sigmaBias  = RW2SDev(0.015*perHrToPerSec); % 8.0964e-9; %
    sigmaNoise = RW2SDev(0.005);

  otherwise
    error([gyroType, ' not supported.']);
end

q11   = sigmaNoise^2*ones(1,3);
q22   = sigmaBias^2*ones(1,3);

dT = 10;

qK = diag([q11 q22])*dT;

Measurement noise

%------------------
r    = (0.001*degToRad)^2; %*eye(2);
rK   = r/dT;
h    = [1 0 0 0 0 0];

nSim = 18*3600/dT;
p    = zeros(6); % start with perfect knowledge

t    = zeros(1,nSim);
pDg  = zeros(6,nSim);

w0       = -7.291e-5;
b        = [eye(3);zeros(3,3)];
a        = [ 0    0  w0   -1  0  0;...
             0    0  0     0 -1  0;...
            -w0   0  0     0  0 -1;...
             zeros(3,6)];
[phi,gam] = C2DZOH(a,b,dT);


for k = 2:nSim
  t(k) = t(k-1) + dT;

  % Compute the Kalman Gain & update the covariance
  kG = p*h'*inv(h*p*h' + rK);

  iKH = (eye(size(p)) - kG*h);
  p   = iKH*p*iKH' + kG*r*kG';

  p  = 0.5*(p + p');  % Make p symmetric

  % Propagate the covariance matrix
  p = phi*p*phi' + qK;
  p = 0.5*(p + p');  % Make p symmetric

  pDg(:,k) = diag(p);

end

Plot2D(t/3600,[sqrt(pDg(1,:))*radToDeg;sqrt(pDg(4,:))*3600*radToDeg],'Time (hours) ',strvcat('theta (deg)','bias (deg/hr)'),'Roll Sigma')
Plot2D(t/3600,[sqrt(pDg(2,:))*radToDeg;sqrt(pDg(5,:))*3600*radToDeg],'Time (hours) ',strvcat('theta (deg)','bias (deg/hr)'),'Pitch Sigma')
Plot2D(t/3600,[sqrt(pDg(3,:))*radToDeg;sqrt(pDg(6,:))*3600*radToDeg],'Time (hours) ',strvcat('theta (deg)','bias (deg/hr)'),'Yaw Sigma')

the final attitude stand. dev.

pSig = sqrt(diag(p(1:3,1:3)))*radToDeg


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

Performs a covariance analysis of different gyros.

Contents

Measurement noise

the final attitude stand. dev.