function [ssc]=testObserver()
  %http://ctms.engin.umich.edu/CTMS/index.php?example=Introduction&section=ControlStateSpace
  mdl=1; % 0:hovering ball  1:fast stage
  A = [ 0   1   0
       980  0  -2.8
        0   0  -100 ];

  B = [ 0
        0
       100 ];

  C = [ 1 0 0 ];
  D=0;
  
  Ap=A;Am=A;
  Bp=B;Bm=B;
  Cp=C;Cm=C;
  Dp=D;Dm=D;Dt=D;

  poles = eig(A);
  poles

  
  t = 0:0.01:2;
  u = zeros(size(t));
  x0 = [0.01 0 0];

  sys = ss(A,B,C,D);

  [y,t,x] = lsim(sys,u,t,x0);
  plot(t,y)
  title('Open-Loop Response to Non-Zero Initial Condition')
  xlabel('Time (sec)')
  ylabel('Ball Position (m)')

  p1 = -10 + 10i;  p2 = -10 - 10i; p3 = -50;
  K = place(A,B,[p1 p2 p3]);
  sys_cl = ss(A-B*K,B,C,0);
  lsim(sys_cl,u,t,x0);
  xlabel('Time (sec)')
  ylabel('Ball Position (m)')

  t = 0:0.01:2;
  u = 0.001*ones(size(t));

  sys_cl = ss(A-B*K,B,C,0);

  lsim(sys_cl,u,t);
  xlabel('Time (sec)')
  ylabel('Ball Position (m)')
  axis([0 2 -4E-6 0])

  V=-1./(Cm*(Am-Bm*K)^-1*Bm); %(from Lineare Regelsysteme2 (Glattfelder) page:173 )
  lsim(sys_cl,V*u,t)
  title('Linear Simulation Results (with Nbar)')
  xlabel('Time (sec)')
  ylabel('Ball Position (m)')
  axis([0 2 0 1.2*10^-3])     

  op1 = -100;
  op2 = -101;
  op3 = -102;
  OP=[op1,op2,op3];
  %OP=P*2;
  L = place(A',C',OP)';
  At = [ A-B*K             B*K
         zeros(size(A))    A-L*C ];
  Bt = [    B*V
         zeros(size(B)) ];
  Ct = [ C    zeros(size(C)) ];

  sys = ss(At,Bt,Ct,0);
  %lsim(sys,zeros(size(t)),t,[x0 x0]);
  lsim(sys,u,t,[x0 x0]);
  title('Linear Simulation Results (with observer)')
  xlabel('Time (sec)')
  ylabel('Ball Position (m)')

  t = 0:1E-6:0.1;
  x0 = [0.01 0.5 -5];
  [y,t,x] = lsim(sys,zeros(size(t)),t,[x0 x0]);

  n = 3;
  e = x(:,n+1:end);
  x = x(:,1:n);
  x_est = x - e;

  % Save state variables explicitly to aid in plotting
  h = x(:,1); h_dot = x(:,2); i = x(:,3);
  h_est = x_est(:,1); h_dot_est = x_est(:,2); i_est = x_est(:,3);

  plot(t,h,'-r',t,h_est,':r',t,h_dot,'-b',t,h_dot_est,':b',t,i,'-g',t,i_est,':g')
  legend('h','h_{est}','hdot','hdot_{est}','i','i_{est}')
  xlabel('Time (sec)')
  K,L,V
end