function [ssc]=StateSpaceControlDesign(mot)
  % !!! first it need to run: [mot1,mot2]=identifyFxFyStage() to build a motor object !!!
  %
  % builds a state space controller designed for the plant.
  % shows step answers of open and closed loop, also for the observer controller and the final discrete observer
  %
  % the matchich simulink model is: 'observer'

  %References:
  %http://ctms.engin.umich.edu/CTMS/index.php?example=Introduction&section=ControlStateSpace
  %space state controller:
  % web(fullfile(docroot, 'simulink/examples.html'))
  % web(fullfile(docroot, 'simulink/examples/inverted-pendulum-with-animation.html'))
  % web(fullfile(docroot, 'simulink/examples/double-spring-mass-system.html'))
  %
  % https://www.youtube.com/watch?v=Lax3etc837U

  %mPlt: mode to select plant
  %0 real plant (model of real plant)
  %1 current, mechanic, no resonance
  %2 no current current, mechanic, no resonance
  %3 no current current, mechanic, first resonance



  %mMdl: mode to select model for observer
  %0 real plant (NOT RECOMANDED, because not observab,econtrolable)
  %1 current, mechanic, no resonance
  %2 no current current, mechanic, no resonance
  %3 no current current, mechanic, first resonance

  %mPrefilt:prefilter mode
  %0 no filter
  %1 inverse resonance filter
  %2 manual setup filter


  %mShow: mode(bits) to plot/simulate
  % 0: 1: bode plots of open loop
  % 1: 2: step answer on open loop
  % 2: 4: step answer on closed loop with space state controller
  % 3: 8: step answer on closed loop with observer controller
  % 4:16: step answer on closed loop with disctrete observer controller
  % 5:32: plot all closed loop bode and pole-zero diagrams of desPos->actPos
  % 6:64:


  %use_lqr: use lqr instead of pole placement

  mPlt=0;
  mMdl=1;
  mPrefilt=2;
  mShow=32+64;
  use_lqr=0;

  switch mPlt
    case 0
      ssPlt=mot.ssPlt;%real plant (model of real plant)
    case 1
      ssPlt=mot.ssMdl_c1;%current, mechanic, no resonance
    case 2
      ssPlt=mot.ssMdl_1;%no current current, mechanic, no resonance
    case 3
      ssPlt=mot.ssMdl_12;%no current current, mechanic, first resonance
  end
  ssPlt.Name='open loop plant';

  switch mMdl
    case 0
      ssMdl=mot.ssPlt;%real plant (model of real plant)
    case 1
      ssMdl=mot.ssMdl_c1;%current, mechanic, no resonance
    case 2
      ssMdl=mot.ssMdl_1;%no current current, mechanic, no resonance
    case 3
      ssMdl=mot.ssMdl_12;%no current current, mechanic, first resonance
  end
  ssMdl.Name='open loop model'; %model for observer


  [Ap,Bp,Cp,Dp]=ssdata(ssPlt);
  [Am,Bm,Cm,Dm]=ssdata(ssMdl);

  if bitand(mShow,1)
    figure();h=bodeplot(ssPlt,ssMdl);
    setoptions(h,'IOGrouping','all')
  end

  xp0 = zeros(1,length(Ap));
  xm0 = zeros(1,length(Am));

  if bitand(mShow,2)
    % step answer on open loop:
    t = 0:1E-4:.5;
    u = ones(size(t));
    [yp,t,x] = lsim(ssPlt,u,t,xp0);
    [ym,t,x] = lsim(ssMdl,u,t,xm0);
    figure();plot(t,yp,t,ym,'--');title('step on open loop (plant and model)');
    legend('plt.iqMeas','plt.iqVolts','plt.actPos','mdl.iqMeas','mdl.iqVolts','mdl.actPos')
  end
  poles = eig(Am);
  %w0=abs(poles);
  %ang=angle(-poles);
  %-------------------
  %p=w0.*exp(j.*ang)

  % *** space state controller ***
  %
  %place poles for the controller feedback
  if use_lqr %use the lqr controller
    Q=eye(length(ssMdl.A));
    R=1;
    [K,P,E]=lqr(ssMdl,Q,R,0);
  else
    if mot.id==1
      %2500rad/s = 397Hz -> locate poles here
      %6300rad/s = 1027Hz -> locate poles here
      switch mMdl
        case 0
          p1=-3300+2800i;  p2=-2700+500i;  p3=-2500+10i;
          P=[p1 p1' p2 p2' p3 p3'];
        case 1
          %p1=-6300+280i;    p2=-6200+150i;
          %P=[p1 p1' p2 p2'];
          P=[-4100 -4000 -1500+10j -1500-10j];
        case 2
          %p1=-6300+280i;    p2=-6200+150i;
          %P=[p1 p1' p2 p2'];
          P=[-1500+10j -1500-10j];
        case 3
          %p1=-6300+280i;    p2=-6200+150i;
          %P=[p1 p1' p2 p2'];
          P=[-1500+10j -1500-10j -1400 -1300];
      end
    else
      %2500rad/s = 397Hz -> locate poles here
      %6300rad/s = 1027Hz -> locate poles here
      switch mMdl
        case 0
          p1=-3300+2800i;    p2=-1900+130i;       p3=-2900+80i;
          p4=-2300+450i;     p5=-2000+20i;        p6=-1500+10i;
          P=[p1 p1' p2 p2' p3 p3' p4 p4' p5 p5' p6 p6'];
        case 1
          %p1=-6300+2800i;   p2=-6200+1500i;
          %P=[p1 p1' p2 p2'];
          P=[-2500 -2800 -1500+10j -1500-10j];
        case 2
          %p1=-6300+2800i;   p2=-6200+1500i;
          %P=[p1 p1' p2 p2'];
          P=[-2500 -2800 -1500+10j -1500-10j];
      end
    end
    K = place(Am,Bm,P);
    %K = acker(Am,Bm,Pm);
  end %if lqr

  V=-1./(Cm*(Am-Bm*K)^-1*Bm); %(from Lineare Regelsysteme2 (Glattfelder) page:173 )
  %Nbar(2)=1; %the voltage stuff is crap for now
  if length(V)>1
    V=V(3); % only the position scaling needed
  end

  ss_cl = ss(Am-Bm*K,Bm*V,Cm,0,'Name','space state controller','InputName',ssMdl.InputName,'OutputName',ssMdl.OutputName);
  if bitand(mShow,4)
    % step answer on closed loop with space state controller:
    t = 0:1E-4:.5;
    [y,t,x]=lsim(ss_cl,V*u,t,xm0);
    figure();plot(t,y);title('step on closed loop');
  end

  % *** observer controller ***
  %
  %observer poles-> 5 times farther left than system poles
  OP=2*P;
  L=place(Am',Cm',OP)';
  %L=acker(A',C',OP)';

  At = [ Am-Bm*K             Bm*K
         zeros(size(Am))    Am-L*Cm ];
  Bt = [    Bm*V
         zeros(size(Bm)) ];
  Ct = [ Cm    zeros(size(Cm)) ];

  Dt=0;
  ss_t = ss(At,Bt,Ct,Dt,'Name','observer controller','InputName',{'desPos'},'OutputName',ssMdl.OutputName);
  if bitand(mShow,8)
    % step answer on closed loop with observer controller:
    figure();lsim(ss_t,ones(size(t)),t,[xm0 xm0]);title('step on closed loop with observer');
  end

  % *** disctrete observer controller ***
  %
  Ts=1/5000; % 5kHz
  ss_tz = c2d(ss_t,Ts);
  [Atz,Btz,Ctz,Dtz]=ssdata(ss_tz );
  ss_tz.Name='discrete obsvr ctrl';

  if bitand(mShow,16)
    % step answer on closed loop with disctrete observer controller:
    t = 0:Ts:.05;
    figure();lsim(ss_tz ,ones(size(t)),t,[xm0 xm0]);title('step on closed loop with observer discrete');
  end

  if bitand(mShow,32)
    %plot all bode diagrams of desPos->actPos
    figure();
    if mMdl==2 || mMdl==3
      idx=1;
    else
      idx=3;
    end
    h=bodeplot(ss_cl(idx),ss_t(idx),ss_tz(idx));
    setoptions(h,'FreqUnits','Hz','Grid','on');legend('location','sw');

    figure();
    h=pzplot(ss_cl(idx),ss_t(idx));
    setoptions(h,'FreqUnits','Hz','Grid','on');legend('location','sw');
    figure();
    h=pzplot(ss_tz(idx));
    setoptions(h,'FreqUnits','Hz','Grid','on');legend('location','sw');
  end

  %calculate matrices for the simulink system
  Ao=Am-L*Cm;
  Bo=[Bm L];
  Co=K;
  Do=zeros(size(Co,1),size(Bo,2));
  
  if mMdl==2 || mMdl==3
    ss_o = ss(Ao,Bo,Co,Do,'Name','observer controller','InputName',{'desPos','actPos'},'OutputName',{'k*xt'});
  else
    ss_o = ss(Ao,Bo,Co,Do,'Name','observer controller','InputName',{'desPos','iqMeas','iqVolts','actPos'},'OutputName',{'k*xt'});
  end
  
  %discrete plant
  ssPltz = c2d(ssPlt,Ts);
  [Apz,Bpz,Cpz,Dpz]=ssdata(ssPltz);

  %discrete observer controller
  ss_oz = c2d(ss_o,Ts);
  [Aoz,Boz,Coz,Doz]=ssdata(ss_oz);
  %mdlName='observer';
  %open(mdlName);


  %prefilter to compensate non observable resonance frequencies
  prefilt=Prefilt(mot,mPrefilt);

  numV=prefilt.Numerator{1};
  denV=prefilt.Denominator{1};

  %discrete prefilter
  prefiltz=c2d(prefilt,Ts);
  numVz=prefiltz.Numerator{1};
  denVz=prefiltz.Denominator{1};

  if bitand(mShow,64)
    h=bodeplot(prefilt,prefiltz);
    setoptions(h,'FreqUnits','Hz','Grid','on');legend('location','sw');
  end

  %state space controller
  ssc=struct();
  for k=["Ts","At","Bt","Ct","Dt","Atz","Btz","Ctz","Dtz","Ap","Bp","Cp","Dp","Am","Bm","Cm","Dm","Ao","Bo","Co","Do","Apz","Bpz","Cpz","Dpz","Aoz","Boz","Coz","Doz","V","K","L","ss_cl","ss_o","ss_oz","numV","denV","numVz","denVz"]
    ssc=setfield(ssc,k,eval(k));
  end
  save(sprintf('/tmp/ssc%d.mat',mot.id),'-struct','ssc');
end

function pf=Prefilt(mot,mode)
  switch mode
    case 0 %no filter
        pf=tf(1,1);
    case 1 %inverse resonance
      if mot.id==1
        den=mot.mdl.num2;%num=1;
        num=mot.mdl.den2;%den=[1 0 0];
        pf=tf(num,den);
      else
        den=conv(conv(conv(mot.mdl.num2,mot.mdl.num3),mot.mdl.num4),mot.mdl.num5);%num=1;
        num=conv(conv(conv(mot.mdl.den2,mot.mdl.den3),mot.mdl.den4),mot.mdl.den5);%den=[1 0 0];
        pf=tf(num,den);
      end
    case 2
      if mot.id==1
        f=200;w0=f*2*pi;  num1=[1 300 w0^2]; den1=[1 200 w0^2];
        numV=num1;
        denV=den1;
        pf=tf(numV,denV);
      else
        f=277;w0=f*2*pi;  num1=[1 20 w0^2];  den1=[1 500 w0^2];
        f=138;w0=f*2*pi;  num2=[1 300 w0^2]; den2=[1 100 w0^2];
        f=60;w0=f*2*pi;   num3=[1 33 w0^2];  den3=[1 20 w0^2];
        numV=conv(num1,num2);
        denV=conv(den1,den2);
        numV=conv(conv(num1,num2),num3);
        denV=conv(conv(den1,den2),den3) ;
        pf=tf(numV,denV);
      end
  end
  %controlSystemDesigner('bode',1,pf);    % <<<<<<<<< This opens a transferfunction that can be edited
end


%code snipplets from an example on youtube (see reference at top)
function SCRATCH()
%import numpy as np
%fh=np.load('mode1.npz')
%import scipy.io
%scipy.io.savemat('mode1.mat',fh,do_compression=True)

%matlab:
  load('mode1.mat');
  plot(pts(:,1),pts(:,2),'.');hold on;
  plot(rec(:,5),rec(:,6),'-');%despos
  plot(rec(:,2),rec(:,3),'-');%actPos

  %sig.time = [0 1 1 5 5 8 8 10];
  %sig.signals.values = [0 0 2 2 2 3 3 3]';
  %sig.signals.dimensions = 1;
  sig.time=0:2E-4:(length(rec)-1)*2E-4;
  sig.signals.values=rec(:,5);
  sig.signals.dimensions = 1;

  sum(desPos_actPos.Data(:,1)-desPos_actPos.Data(:,2))

  A = [ 0   1   0
       980  0  -2.8
        0   0  -100 ];

  B = [ 0
        0
        100 ];

  C = [ 1 0 0 ];

  poles = eig(A)

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

  sys = ss(A,B,C,0);

  [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)')

  p1 = -20 + 20i;
  p2 = -20 - 20i;
  p3 = -100;

  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])

  Nbar = rscale(sys,K)

  lsim(sys_cl,Nbar*u,t)
  title('Linear Simulation Results (with Nbar)')
  xlabel('Time (sec)')
  ylabel('Ball Position (m)')
  axis([0 2 0 1.2*10^-3])
end