PolyMAX Algorithm

[RhynoOC]

I am attempting to implement the PolyMAX algorithm for output only vibration data. What is the best constraint to apply to the least squares problem of solving the reduced normal equations?
Right now my version of the algorithm does not provide me with the clear stabilisation diagrams I expected.

 

[mkoijn9]

Have a glance at this:

http://mech.vub.ac.be/avrg/PhD/phd_parloo.pdf

 

[RhynoOC]

I have applied a constraint of alpha(1) = Identity, which resulted in negative damping on many poles. A constraint of alpha(k) = Identity resulted in positive damping on all poles. Based on the above thesis I expected alpha(k) = Identity to be the better constraint, however these results contradict this. Any suggestions?